publications

Journal Articles (2024)

1. A&A

   Do not forget the electrons: Extending moderately-sized nuclear networks for multidimensional hydrodynamic codes

   D. García-Senz, R. M. Cabezón, M. Reichert, A. S. Lechuga, J. A. Escartín, A. Psaltis, A. Arcones, and F.-K. Thielemann

   Astronomy & Astrophysics (2024)

   Abstract Bib

   Context. Nuclear networks are widely used coupled with hydrodynamical simulations of explosive scenarios to account for the change of nuclear species and energy generation rate due to nuclear reactions. In this way, there is a feedback mechanism between the hydrodynamical state and the nuclear processes. Unfortunately, the timescale of nuclear reactions is orders of magnitude smaller than the dynamical timescale that drives hydrodynamical simulations. Therefore, these nuclear networks are usually very small, reduced in most cases to a dozen elements, especially when simulations are carried out in more than one dimension. Aims. We present here an extended nuclear network, with 90 species, designed for being coupled with hydrodynamic simulations, which includes neutrons, protons, electrons, positrons, and the corresponding neutrino and anti-neutrino emission. This network is also coupled with temperature, making it extremely robust and, together with its size, unique of its kind. The inclusion of electron captures on free protons makes the network very appropriate for multidimensional studies of Type Ia supernova explosions, especially when the exploding object is a massive white dwarf. Methods. We perform several tests that are relevant to simulate explosive scenarios, such as Type Ia supernovae and core-collapse supernovae. We compare the results of the 90 nuclei network with a standard α-chain network with 14 elements to evaluate the differences in the energy generation rate. We also evaluate the relevance of including the electrons in the network in terms of generated yields and how it affects the pressure of a degenerate fluid such as that of white dwarfs. The results obtained with the 90-nuclei network have been verified with a much larger 2000-nuclei network built from REACLIB (WinNet), in terms of nuclear energy generation rate, pressure, and produced yields. Results. The results obtained with the proposed medium-sized network compare fairly well, to a few percent, with those computed with WinNet in scenarios reproducing the gross physical conditions of current Type Ia supernova explosion models. In those cases where the carbon and oxygen fuel ignites at high density, the high-temperature plateau typical of the nuclear statistical equilibrium regime is well defined and stable, allowing large integration time steps. We show that the inclusion of electron captures on free protons substantially improves the estimation of the electron fraction of the mixture. Therefore, the pressure is better determined than in networks where electron captures are excluded, which will ultimately lead to more reliable hydrodynamic models. Explosive combustion of helium at low density, occurring near the surface layer of a white dwarf, is also better described with the proposed network, which gives nuclear energy generation rates much closer to WinNet than typical reduced alpha networks. Conclusions. A nuclear network with N = 90 species, including electrons, aimed at multidimensional calculations of supernova explosions is described and verified. The proposed network is suitable for the study of Type Ia supernova explosions because it provides better values of pressure and electron abundance than other existing networks with smaller or even a similar size but without including electron capture processes.

   @article{GarcaSenzAA2024,
     volume = {688},
     issn = {1432-0746},
     doi = {10.1051/0004-6361/202449863},
     journal = {Astronomy & Astrophysics},
     publisher = {EDP Sciences},
     author = {García-Senz, D and Cabezón, R. M and Reichert, M and Lechuga, A. S and Escartín, J. A and Psaltis, A and Arcones, A and Thielemann, F.-K},
     year = {2024},
     month = aug,
     pages = {A218},
   }

      
   
   
2. EPJA

   The first in-beam reaction measurement at CRYRING@ESR using the CARME array

   J. J. Marsh, C. G. Bruno, T. Davinson, P. J. Woods, Z. Andelkovic, A. Bräuning-Demian, R.-J. Chen, S. F. Dellmann, P. Erbacher, S. Fedotova, and 22 more authors

   The European Physical Journal A (2024)

   Abstract Bib

   In the last decade nuclear reaction measurements using heavy ion storage rings became an important tool for nuclear astrophysics studies. The new CRYRING Array for Reaction MEasurements (CARME), recently commissioned at the low energy CRYRING@ESR storage ring (GSI/FAIR), is designed to take this novel approach one step further and perform direct nuclear reaction measurements at stellar energies, as well as indirect studies of nuclear properties of interest for nuclear astrophysics. CRYRING is unique worldwide in being able to store high quality, isotopically pure, radioactive beams produced in-flight at the low energies required for nuclear astrophysics. This paper describes the first in-beam reaction measurement with CARME at CRYRING, the first beam on (conventional) target measurement for FAIR Phase-0, and the data analysis approach required by this unprecedented, unique experimental approach.

   @article{MarshEPJA2024,
     title = {The first in-beam reaction measurement at CRYRING@ESR using the CARME array},
     volume = {60},
     issn = {1434-601X},
     doi = {10.1140/epja/s10050-024-01318-2},
     number = {4},
     journal = {The European Physical Journal A},
     publisher = {Springer Science and Business Media LLC},
     author = {Marsh, J. J and Bruno, C. G and Davinson, T and Woods, P. J and Andelkovic, Z and Br\"{a}uning-Demian, A and Chen, R.-J and Dellmann, S. F and Erbacher, P and Fedotova, S and Forstner, O and Freire-Fernandez, D and Glorius, J and Gumberidze, A and Hall, O and Hillenbrand, P.-M and Herfurth, F and Hudson-Chang, G and Kalinin, A and Lestinsky, M and Litvinov, Y. A and Menz, E. B and Nociforo, C and Petridis, N and Psaltis, A and Sanjari, S and Selina, M and Spillman, U and Sidhu, R. S and St\"{o}hlker, T and Varga, L and Vorobjev, G},
     year = {2024},
     month = apr
   }

      
   
   
3. ApJ

   Neutrino-driven Outflows and the Elemental Abundance Patterns of Very Metal-poor Stars

   A. Psaltis, M. Jacobi, F. Montes, A. Arcones, C. J. Hansen, and H. Schatz

   The Astrophysical Journal (2024)

   Abstract Bib

   The elemental abundances between strontium and silver (Z = 38–47) observed in the atmospheres of very metal- poor stars in the Galaxy may contain the fingerprint of the weak r-process and νp-process occurring in early core- collapse supernovae explosions. In this work, we combine various astrophysical conditions based on a steady-state model to cover the richness of the supernova ejecta in terms of entropy, expansion timescale, and electron fraction. The calculated abundances based on different combinations of conditions are compared with stellar observations, with the aim of constraining supernova ejecta conditions. We find that some conditions of the neutrino-driven outflows consistently reproduce the observed abundances of our sample. In addition, from the successful combinations, the neutron-rich trajectories better reproduce the observed abundances of Sr–Zr (Z = 38–40), while the proton-rich ones, Mo–Pd (Z = 42–47)

   @article{PsaltisApJ2024,
     title = {Neutrino-driven Outflows and the Elemental Abundance Patterns of Very Metal-poor Stars},
     volume = {966},
     issn = {1538-4357},
     doi = {10.3847/1538-4357/ad2dfb},
     number = {1},
     journal = {The Astrophysical Journal},
     publisher = {American Astronomical Society},
     author = {Psaltis, A and Jacobi, M and Montes, F and Arcones, A and Hansen, C. J and Schatz, H},
     year = {2024},
     month = apr,
     pages = {11},
   }

      
   
   

Conference Proceedings (2024)

Journal Articles (2023)

1. PRL

   Study of the 22Mg Waiting Point Relevant for X-Ray Burst Nucleosynthesis via the 22Mg(α,p)25Al Reaction

   H. Jayatissa, M. L. Avila, K. E. Rehm, P. Mohr, Z. Meisel, J. Chen, C. R. Hoffman, J. Liang, C. Müller-Gatermann, D. Neto, and 6 more authors

   Physical Review Letters (2023)

   Abstract Bib

   The 22Mg(α,p)25Al reaction rate has been identified as a major source of uncertainty for understanding the nucleosynthesis flow in Type-I x-ray bursts. We report a direct measurement of the energy- and angle-integrated cross sections of this reaction in a 3.3–6.9 MeV center-of-mass energy range using the MUlti-Sampling Ionization Chamber (MUSIC). The new 22Mg(α,p)25Al reaction rate is a factor of ∼4 higher than the previous direct measurement of this reaction within temperatures relevant for x-ray bursts, resulting in the 22Mg waiting point of x-ray burst nucleosynthesis flow to be significantly bypassed via the (α,p) reaction.

   @article{JayatissaPRL2023,
     title = {Study of the 22Mg Waiting Point Relevant for X-Ray Burst Nucleosynthesis via the 22Mg(α,p)25Al Reaction},
     author = {Jayatissa, H and Avila, M. L and Rehm, K. E and Mohr, P and Meisel, Z and Chen, J and Hoffman, C. R and Liang, J and M\"uller-Gatermann, C and Neto, D and Ong, W. J and Psaltis, A and Santiago-Gonzalez, D and Tang, T. L and Ugalde, C and Wilson, G},
     journal = {Physical Review Letters},
     volume = {131},
     issue = {11},
     pages = {112701},
     numpages = {6},
     year = {2023},
     month = sep,
     publisher = {American Physical Society},
     doi = {10.1103/PhysRevLett.131.112701}
   }

      
   
   
2. PRC

   Structure studies of 13Be from the 12Be(d,p) reaction in inverse kinematics on a solid deuteron target

   J. Kovoor, K. L. Jones, J. Hooker, M. Vostinar, R. Kanungo, S. D. Pain, M. Alcorta, J. Allen, C. Andreoiu, L.. Atar, and 35 more authors

   Physical Review C (2023)

   Abstract Bib

   The low-lying structure of 13Be has remained an enigma for decades. Despite numerous experimental and theoretical studies, large inconsistencies remain. Being both unbound and one neutron away from 14Be, the heaviest bound beryllium nucleus, 13Be is difficult to study through simple reactions with weak radioactive-ion beams or more complex reactions with stable-ion beams. Here, we present the results of a study using the 12Be(d,p)13Be reaction in inverse kinematics using a 9.5 MeV per nucleon 12Be beam from the ISAC-II facility. The solid deuteron target of IRIS was used to achieve an increased areal thickness compared to conventional deuterated polyethylene targets. The Q-value spectrum below −4.4 MeV was analyzed using a Bayesian method with geant4 simulations. A three-point angular distribution with the same Q-value gate was fit with a mixture of s- and p-wave, s- and d-wave, or pure p-wave transfer. The Q-value spectrum was also compared with geant simulations obtained using the energies and widths of states reported in four previous works. It was found that our results are incompatible with works that revealed a wide 5/2+ resonance but shows better agreement with ones that reported a narrower width.

   @article{KovoorPRC2023,
     title = {Structure studies of 13Be from the 12Be(d,p) reaction in inverse kinematics on a solid deuteron target},
     author = {Kovoor, J and Jones, K. L and Hooker, J and Vostinar, M and Kanungo, R and Pain, S. D and Alcorta, M and Allen, J and Andreoiu, C and Atar, L. and Bardayan, D. W and Bhattacharjee, S. S and Blankstein, D and Burbadge, C and Burcher, S and Catford, W. N and Cha, S and Chae, K and Connolly, D and Davids, B and Esker, N. E and Garcia, F. H and Gillespie, S and Ghimire, R and Gula, A and Hackman, G and Hallam, S and Hellmich, M and Henderson, J and Holl, M and Jassal, P and King, S and Knight, T and Kruecken, R and Lepailleur, A and Liang, J and Morrison, L and O'Malley, P. D and Pereira-Lopez, X and Psaltis, A and Radich, A and Refsgaard, J and Shotter, A. C and Williams, M and Workman, O},
     journal = {Physical Review C},
     volume = {108},
     issue = {3},
     pages = {034601},
     numpages = {8},
     year = {2023},
     month = sep,
     publisher = {American Physical Society},
     doi = {10.1103/PhysRevC.108.034601}
   }

      
   
   
3. A&A

   The gamma-process nucleosynthesis in core-collapse supernovae. I. A novel analysis of gamma-process yields in massive stars

   L. Roberti, M. Pignatari, A. Psaltis, A. Sieverding, P. Mohr, Zs. Fülöp, and M. Lugaro

   Astronomy & Astrophysics (2023)

   Abstract Bib

   Context. The γ-process nucleosynthesis in core-collapse supernovae is generally accepted as a feasible process for the synthesis of neutron-deficient isotopes beyond iron. However, crucial discrepancies between theory and observations still exist: the average yields of γ-process nucleosynthesis from massive stars are still insufficient to reproduce the solar distribution in galactic chemical evolution calculations, and the yields of the Mo and Ru isotopes are a factor of ten lower than the yields of the other γ-process nuclei. Aims. We investigate the γ-process in five sets of core-collapse supernova models published in the literature with initial masses of 15, 20, and 25 M at solar metallicity. Methods. We compared the γ-process overproduction factors from the different models. To highlight the possible effect of nuclear physics input, we also considered 23 ratios of two isotopes close to each other in mass relative to their solar values. Further, we investigated the contribution of C–O shell mergers in the supernova progenitors as an additional site of the γ-process. Results. Our analysis shows that a large scatter among the different models exists for both the γ-process integrated yields and the isotopic ratios. We find only ten ratios that agree with their solar values, all the others differ by at least a factor of three from the solar values in all the considered sets of models. The γ-process within C–O shell mergers mostly influences the isotopic ratios that involve intermediate and heavy proton-rich isotopes with A > 100. Conclusions. We conclude that there are large discrepancies both among the different data sets and between the model predictions and the solar abundance distribution. More calculations are needed; particularly updating the nuclear network, because the majority of the models considered in this work do not use the latest reaction rates for the γ-process nucleosynthesis. Moreover, the role of C–O shell mergers requires further investigation.

   @article{RobertiAA2023,
     doi = {10.1051/0004-6361/202346556},
     year = {2023},
     month = jul,
     publisher = {{EDP} Sciences},
     author = {Roberti, L and Pignatari, M and Psaltis, A and Sieverding, A and Mohr, P and F\"{u}l\"{o}p, Zs and Lugaro, M},
     title = {The gamma-process nucleosynthesis in core-collapse supernovae. I. A novel analysis of gamma-process yields in massive stars},
     journal = {Astronomy & Astrophysics}
   }

      
   
   
4. PRC

   Cross sections of the 83Rb(p,γ)84Sr and 84K(p,γ)85Rb reactions at energies characteristic of the astrophysical γ process

   M. Williams, B. Davids, G. Lotay, N. Nishimura, T. Rauscher, S. A. Gillespie, M. Alcorta, A. M. Amthor, G. C. Ball, S. S. Bhattacharjee, and 15 more authors

   Physical Review C (2023)

   Abstract Bib

   We have measured the cross section of the 83Rb(p,γ)84Sr radiative capture reaction in inverse kinematics using a radioactive beam of 83Rb at incident energies of 2.4 and 2.7A MeV. Prior to the radioactive beam measurement, the 84Kr(p,γ)85Rb radiative capture reaction was measured in inverse kinematics using a stable beam of 84Kr at an incident energy of 2.7A MeV. The effective relative kinetic energies of these measurements lie within the relevant energy window for the γ process in supernovae. The central values of the measured partial cross sections of both reactions were found to be 0.17–0.42 times the predictions of statistical model calculations. Assuming the predicted cross section at other energies is reduced by the same factor leads to a slightly higher calculated abundance of the p nucleus 84Sr, caused by the reduced rate of the 84Sr(γ,p)83Rb reaction derived from the present measurement.

   @article{WilliamsPRC2023,
     title = {Cross sections of the 83Rb(p,γ)84Sr and 84K(p,γ)85Rb reactions at energies characteristic of the astrophysical γ process},
     author = {Williams, M and Davids, B and Lotay, G and Nishimura, N and Rauscher, T and Gillespie, S. A and Alcorta, M and Amthor, A. M and Ball, G. C and Bhattacharjee, S. S and Bildstein, V and Catford, W. N and Doherty, D. T and Esker, N. E and Garnsworthy, A. B and Hackman, G and Hudson, K and Lennarz, A and Natzke, C and Olaizola, B and Psaltis, A and Svensson, C. E and Williams, J and Walter, D and Yates, D},
     journal = {Physical Review C},
     volume = {107},
     issue = {3},
     pages = {035803},
     numpages = {10},
     year = {2023},
     month = mar,
     publisher = {American Physical Society},
     doi = {10.1103/PhysRevC.107.035803}
   }

      
   
   

Conference Proceedings (2023)

1. INPC2022

   Using (α,xn) reaction rates and abundance ratios to constrain the weak r-process

   A. Psaltis, A. Arcones, M. L. Avila, C. J. Hansen, M. Jacobi, L. Lombardo, Z. Meisel, P. Mohr, F. Montes, W. J. Ong, and 1 more author

   Journal of Physics: Conference Series (2023)

   Abstract Bib

   he lighter heavy elements of the first r-process peak, between strontium and silver, can be synthesized in the moderately neutron-rich neutrino–driven ejecta of either core–collapse supernovae or neutron star mergers via the weak r–process. This nucleosynthesis scenario exhibits uncertainties from the absence of experimental data from (α, xn) reactions on neutron–rich nuclei, which are currently based on statistical model estimates. We have performed a new impact study to identify the most important (α, xn) reactions that can affect the production of the lighter heavy elements under different astrophysical conditions and using new, constrained (α, xn) reaction rates based on the Atomki-V2 αOMP. We have identified a list of relevant reactions that affect elemental abundance ratios that can be compared to abundances from metal-poor stars. Our results show how when reducing the nuclear physics uncertainties, we can use abundance ratios to constrain the astrophysical conditions/environment. This will be possible with the planned experiments to measure key (α, xn) reaction rates using the SECAR recoil separator at FRIB that will also be briefly discussed.

   @article{Psaltis-INPC-2023,
     doi = {10.1088/1742-6596/2586/1/012105},
     year = {2023},
     month = sep,
     publisher = {{IOP} Publishing},
     volume = {2586},
     number = {1},
     pages = {012105},
     author = {Psaltis, A and Arcones, A and Avila, M. L and Hansen, C. J and Jacobi, M and Lombardo, L and Meisel, Z and Mohr, P and Montes, F and Ong, W. J and Schatz, H},
     title = {Using (α,xn) reaction rates and abundance ratios to constrain the weak r-process},
     journal = {Journal of Physics: Conference Series}
   }

      
   
   
2. INPC2022

   Understanding globular cluster abundances through nuclear reactions

   P. Adsley, M. Williams, D S. Harrouz, D P. Carrasco-Rojas, N. Seréville, F. Hammache, R. Longland, B. Bastin, B. Davids, T. Faestermann, and 17 more authors

   Journal of Physics: Conference Series (2023)

   Abstract Bib

   Globular clusters contain multiple stellar populations, with some previous generation of stars polluting the current stars with heavier elements. Understanding the history of globular clusters is helpful in understanding how galaxies merged and evolved and therefore constraining the site or sites of this historic pollution is a priority. The acceptable temperature and density conditions of these polluting sites depend on critical reaction rates. In this paper, three experimental studies helping to constrain astrophysically important reaction rates are briefly discussed.

   @article{Adsley-INPC-2023,
     doi = {10.1088/1742-6596/2586/1/012100},
     year = {2023},
     month = sep,
     publisher = {{IOP} Publishing},
     volume = {2586},
     number = {1},
     pages = {012100},
     author = {Adsley, P and Williams, M and Harrouz, D S and Carrasco-Rojas, D P and de Ser{\'{e}}ville, N and Hammache, F and Longland, R and Bastin, B and Davids, B and Faestermann, T and Foug{\`{e}}res, C and Greife, U and Hertenberger, R and Hutcheon, D and Cognata, M La and Laird, AM and Lamia, L and Lennarz, A and Meyer, A and d'Oliveira Santos, F and Palmerini, S and Psaltis, A and Pizzone, R G and Romano, S and Ruiz, C and Tumino, A and Wirth, H-F},
     title = {Understanding globular cluster abundances through nuclear reactions},
     journal = {Journal of Physics: Conference Series}
   }

      
   
   
3. EMIS 2022

   Storage, accumulation and deceleration of secondary beams for nuclear astrophysics

   J. Glorius, Yu. A. Litvinov, M. Aliotta, F. Amjad, B. Brückner, C.G. Bruno, R. Chen, T. Davinson, S.F. Dellmann, T. Dickel, and 54 more authors

   Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms (2023)

   Abstract Bib

   Low-energy investigations on rare ion beams are often limited by the available intensity and purity of the ion species in focus. Here, we present the first application of a technique that combines in-flight production at relativistic energies with subsequent secondary beam storage, accumulation and finally deceleration to the energy of interest. Using the FRS and ESR facilities at GSI, this scheme was pioneered to provide a secondary beam of 118Te52+ for the measurement of nuclear proton-capture at energies of 6 and 7 MeV/u. The technique provided stored beam intensities of about 106 ions at high purity and brilliance, representing a major step towards low-energy nuclear physics studies using rare ion beams.

   @article{Glorius-NIMB-2023,
     title = {Storage, accumulation and deceleration of secondary beams for nuclear astrophysics},
     journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
     volume = {541},
     pages = {190-193},
     year = {2023},
     issn = {0168-583X},
     doi = {10.1016/j.nimb.2023.04.059},
     author = {Glorius, J and Litvinov, Yu. A and Aliotta, M and Amjad, F and Brückner, B and Bruno, C.G and Chen, R and Davinson, T and Dellmann, S.F and Dickel, T and Dillmann, I and Erbacher, P and Forstner, O and Geissel, H and Griffin, C.J and Grisenti, R and Gumberidze, A and Haettner, E. and Hess, R and Hillenbrand, P.-M and Hornung, C and Joseph, R and Jurado, B and Kazanseva, E and Knöbel, R and Kostyleva, D and Kozhuharov, C and Kuzminchuk, N and Langer, C and Leckenby, G and Lederer-Woods, C and Lestinsky, M and Litvinov, S and Löher, B and Lorenz, B and Lorenz, E and Marsh, J and Menz, E and Morgenroth, T and Mukha, I and Petridis, N and Popp, U and Psaltis, A and Purushothaman, S and Reifarth, R and Rocco, E and Roy, P and Sanjari, M.S and Scheidenberger, C and Sguazzin, M and Sidhu, R.S and Spillmann, U and Steck, M and Stöhlker, T and Swartz, J.A and Tanaka, Y.K and Törnqvist, H and Varga, L and Vescovi, D and Weick, H and Weigand, M and Woods, P.J and Yamaguchi, T and Zhao, J}
   }

      
   
   
4. ActaPhysPolB

   Helium Clustering in Neutron-rich Be Isotopes

   N. Vukman, N. Soić, M. Freer, M. Alcorta, D. Connolly, P. Čolović, T. Davinson, A Di. Pietro, A. Lennarz, A. Psaltis, and 4 more authors

   Acta Physica Polonica B Proceedings Supplement (2023)

   Abstract Bib

   The experimental study of the helium decays of the 10 Be and 12 Be excited states was performed at TRIUMF, Vancouver, using the transfer reactions of the 9 Li beam on the LiF target and resonant particle spectroscopy technique. P art of the results from the full dataset are presented here, for the 4 He+6 He (0+ ; 1.8 MeV, 2+ ), 6He+6He (0+ ; 1.8 MeV, 2+ ), and 4 He+8 He decays of the 10Be and 12Be excited states, respectively. The 6 He+6 He (1.8 MeV, 2+ ) decay channel was observed for the first time in the present experiment, while for the 4 He+6 He (1.8 MeV, 2+ ) decay channel, there was previously only one measurement available, which present results agree with. New highly excited states were observed in all decay channels studied. Although branching ratios and the spins of the states were not determined, important spectroscopic information is obtained and present results are in good agreement with the proposed α–Xn–α molecular structure of these isotopes, based on the comparison with previously published results.

   @article{Vukman-ActaPhysPolB-2023,
     year = {2023},
     publisher = {Jagiellonian University},
     volume = {16},
     number = {4},
     pages = {1},
     author = {Vukman, N and Soi{\'{c}}, N and Freer, M and Alcorta, M and Connolly, D and {\v{C}}olovi{\'{c}}, P and Davinson, T and Pietro, A Di and Lennarz, A and Psaltis, A and Ruiz, C and Shotter, A and Uroi{\'{c}}, M and Williams, M},
     title = {Helium Clustering in Neutron-rich Be Isotopes},
     journal = {Acta Physica Polonica B Proceedings Supplement}
   }

      
   
   
5. NPA-X

   Measurement of the 86Kr(α,n)89Sr cross section at energies relevant for the weak r-process

   C. Angus, M. Williams, A. Andreyev, S. Bhattacharjee, S. Buck, S. Chakraborty, B. Davids, C. Diget, A. Garnsworthy, C. Griffin, and 23 more authors

   EPJ Web Conference Series (2023)

   Abstract Bib

   The r-process has been shown to be robust in reproducing the abundance distributions of heavy elements, such as europium, seen in ultra-metal poor stars. In contrast, observations of elements 26 < Z < 47 display overabundances relative to r-process model predictions. A proposed additional source of early nucleosynthesis is the weak r-process in neutrino-driven winds of core-collapse supernovae. It has been shown that in this site (α,n) reactions are both crucial to nucleosynthesis and the main source of uncertainty in model-based abundance predictions. Aiming to improve the certainty of nucleosynthesis predictions, the cross section of the important reaction 86 Kr(α,n)89Sr has been measured at an energy relevant to the weak r-process. This experiment was conducted in inverse kinematics at TRIUMF with the EMMA recoil mass spectrometer and the TIGRESS gamma-ray spectrometer. A novel type of solid helium target was used.

   @article{Angus-NPAX-2023,
     author = {Angus, C and Williams, M and Andreyev, A and Bhattacharjee, S and Buck, S and Chakraborty, S and Davids, B and Diget, C and Garnsworthy, A and Griffin, C and Fernandez, A and Hackman, G and Hudson, K and Hufschmidt, D and Karayonchev, V and Kim, Y and Laird, A and Lennarz, A and Mashtakov, K and Machule, P and Natzke, C and Pak, K and Psaltis, A and Radich, A and Rauscher, T and Rhodes, D and Sauvage, T and Simon, A and Svensson, C and Upadhyayula, S and Williams, J and Yates, D and Zidar, T},
     title = {Measurement of the 86Kr(α,n)89Sr cross section at energies relevant for the weak r-process},
     doi = {10.1051/epjconf/202327911003},
     journal = {EPJ Web Conference Series},
     year = {2023},
     volume = {279},
     pages = {11003}
   }

      
   
   
6. NPA-X

   Proton capture on stored radioactive 118Te ions

   S. F. Dellmann, J. Glorius, Y. A. Litvinov, R. Reifarth, K. Al-Khasawneh, M. Aliotta, L. Bott, B. Brückner, C. Bruno, R. J. Chen, and 53 more authors

   EPJ Web Conference Series (2023)

   Abstract Bib

   Experimental determination of the cross sections of proton capture on radioactive nuclei is extremely difficult. Therefore, it is of substantial interest for the understanding of the production of the p-nuclei. For the first time, a direct measurement of proton-capture cross sections on stored, radioactive ions became possible in an energy range of interest for nuclear astrophysics. The experiment was performed at the Experimental Storage Ring (ESR) at GSI by making use of a sensitive method to measure (p,γ) and (p,n) reactions in inverse kinematics. These reaction channels are of high relevance for the nucleosyn- thesis processes in supernovae, which are among the most violent explosions in the universe and are not yet well understood. The cross section of the 118 Te(p,γ) reaction has been measured at energies of 6 MeV/u and 7 MeV/u. The heavy ions interacted with a hydrogen gas jet target. The radiative recombination pro- cess of the fully stripped 118 Te ions and electrons from the hydrogen target was used as a luminosity monitor. An overview of the experimental method and preliminary results from the ongoing analysis will be presented.

   @article{Dellmann-NPAX-2023,
     author = {Dellmann, S. F and Glorius, J and Litvinov, Y. A and Reifarth, R and Al-Khasawneh, K and Aliotta, M and Bott, L and Br\"uckner, B and Bruno, C and Chen, R. J and Davinson, T and Dickel, T and Dillmann, I and Dmytriev, D and Erbacher, P and Freire-Fern\'andez, D and Forstner, O and Geissel, H and G\"obel, K and Griffin, C. J and Grisenti, R and Gumberidze, A and Haettner, E and Hagmann, S and Heil, M and He\ss, R and Hillenbrand, P.-M and Joseph, R and Jurado, B and Kozhuharov, C. and Kulikov, I and L\"oher, B and Langer, C and Leckenby, G and Lederer-Woods, C and Lestinsky, M and Litvinov, S and Lorenz, B. A and Lorenz, E and Marsh, J and Menz, E and Morgenroth, T and Petridis, N and Pibernat, J and Popp, U and Psaltis, A and Sanjari, S and Scheidenberger, C and Sguazzin, M and Sidhu, R. S and Spillmann, U and Steck, M and St\"ohlker, T and Surzhykov, A and Swartz, J. A and T\"ornqvist, H and Varga, L and Vescovi, D and Weick, H and Weigand, M and Woods, P and Xing, Y and Yamaguchi, T},
     title = {Proton capture on stored radioactive 118Te ions},
     doi = {10.1051/epjconf/202327911018},
     journal = {EPJ Web Conference Series},
     year = {2023},
     volume = {279},
     pages = {11018}
   }

      
   
   
7. NPA-X

   Constraining nucleosythesis in neutrino-driven winds using the impact of (α,xn) reaction rates

   A. Psaltis, A. Arcones, M. L. Avila, M. Jacobi, C. J. Hansen, L. Lombardo, Z. Meisel, P. Mohr, F. Montes, W. J. Ong, and 1 more author

   EPJ Web Conference Series (2023)

   Abstract Bib

   The lighter heavy elements of the first r-process peak, between strontium and silver, can be synthesized in the moderately neutron-rich neutrino–driven ejecta of either core–collapse supernovae or neutron star mergers via the weak r–process. This nucleosynthesis scenario exhibits uncertainties from the absence of experimental data from (α, xn) reactions on neutron–rich nuclei, which are currently based on statistical model estimates. We have per- formed a new impact study to identify the most important (α, xn) reactions that can affect the production of the lighter heavy elements under different astrophysical conditions using new, constrained (α, xn) reaction rates based on the Atomki-V2 αOMP. Our results show how when reducing the nuclear physics uncertainties, we can use abundance ratios to constrain the astrophysical conditions/environment. This can be achieved in the near future, when the key (α, xn) reaction rates will be measured experimentally in radioactive beam facilities.

   @article{Psaltis-NPAX-2023,
     author = {Psaltis, A and Arcones, A and Avila, M. L and Jacobi, M and Hansen, C. J and Lombardo, L and Meisel, Z and Mohr, P and Montes, F and Ong, W. J and Schatz, H},
     title = {Constraining nucleosythesis in neutrino-driven winds using the impact of (α,xn) reaction rates},
     doi = {10.1051/epjconf/202327908002},
     journal = {EPJ Web Conference Series},
     year = {2023},
     volume = {279},
     pages = {08002}
   }

      
   
   
8. SantaTecla

   RIB induced reactions: Studying astrophysical reactions with low-energy RI beam at CRIB

   H. Yamaguchi, S. Hayakawa, N.R. Ma, H. Shimizu, K. Okawa, Q. Zhang, L. Yang, D. Kahl, M. La Cognata, L. Lamia, and 53 more authors

   EPJ Web Conference Series (2023)

   Abstract Bib

   Astrophysical reactions involving radioactive isotopes (RI) often play an important role in high-temperature stellar environments. The experi- mental studies on the reaction rates for those are still limited mainly due to the technical difficulties in producing high-quality RI beams. A direct measure- ment of those reactions would be still challenging in many cases, however, we can make a reliable evaluation of the reaction rates by an indirect method or by studying the resonance prorerties. Here we introduce recent examples of exper- imental studies on such RI-involving astrophysical reactions, performed at Cen- ter for Nuclear Study, the University of Tokyo, using the low-energy RI beam separator CRIB. One is for the neutron-induced destruction reactions of 7 Be in the Big-Bang nucleosynthesis, and the other is the study on the 22Mg(α, p) reac- tion relevant in X-ray bursts, which was performed with the resonant scattering method from the inverse reaction channel.

   @article{Yamaguci-EPJ-2023,
     author = {Yamaguchi, H and Hayakawa, S and Ma, N.R and Shimizu, H and Okawa, K and Zhang, Q and Yang, L and Kahl, D and La Cognata, M and Lamia, L and Abe, K and Beliuskina, O and Cha, S.M and Chae, K.Y and Cherubini, S and Figuera, P and Ge, Z and Gulino, M and Hu, J and Inoue, A and Iwasa, N and Kim, A and Kim, D and Kiss, G and Kubono, S and La Commara, M and Lattuada, M and Lee, E.J and Moon, J.Y and Palmerini, S and Parascandolo, C and Park, S.Y and Phong, V.H and Pierroutsakou, D and Pizzone, R.G and Rapisarda, G.G and Romano, S and Spitaleri, C and Tang, X.D and Trippella, O and Tumino, A and Zhang, N.T and Lam, Y.H and Heger, A and Jacobs, A.M and Xu, S.W and Ma, S.B and Ru, L.H and Liu, E.Q and Liu, T and Hamill, C.B and Murphy, A. St J and Su, J and Fang, X and Kwag, M.S and Duy, N.N and Uyen, N.K and Kim, D.H and Liang, J and Psaltis, A and Sferrazza, M and Johnston, Z and Li, Y.Y},
     title = {RIB induced reactions: Studying astrophysical reactions with low-energy RI beam at CRIB},
     doi = {10.1051/epjconf/202327501015},
     journal = {EPJ Web Conference Series},
     year = {2023},
     volume = {275},
     pages = {01015}
   }

      
   
   

Journal Articles (2022)

1. JPhysG

   Horizons: nuclear astrophysics in the 2020s and beyond

   H. Schatz, A. D. Becerril-Reyes, A. Best, E. F. Brown, K. Chatziioannou, K. A. Chipps, C. M. Deibel, R. Ezzeddine, D. K. Galloway, C. J. Hansen, and 155 more authors

   Journal of Physics G: Nuclear and Particle Physics (2022)

   Abstract Bib

   Nuclear astrophysics is a field at the intersection of nuclear physics and astrophysics, which seeks to understand the nuclear engines of astronomical objects and the origin of the chemical elements. This white paper summarizes progress and status of the field, the new open questions that have emerged, and the tremendous scientific opportunities that have opened up with major advances in capabilities across an ever growing number of disciplines and subfields that need to be integrated. We take a holistic view of the field discussing the unique challenges and opportunities in nuclear astrophysics in regards to science, diversity, education, and the interdisciplinarity and breadth of the field. Clearly nuclear astrophysics is a dynamic field with a bright future that is entering a new era of discovery opportunities.

   @article{SchatzJPhysG2022,
     doi = {10.1088/1361-6471/ac8890},
     year = {2022},
     publisher = {{IOP} Publishing},
     volume = {49},
     number = {11},
     pages = {110502},
     author = {Schatz, H and Becerril-Reyes, A. D and Best, A and Brown, E. F and Chatziioannou, K and Chipps, K. A and Deibel, C. M and Ezzeddine, R and Galloway, D. K and Hansen, C. J and Herwig, F and Ji, A. P and Lugaro, M and Meisel, Z and Norman, D and Read, J. S and Roberts, L. F and Spyrou, A and Tews, I and Timmes, F. X and Travaglio, C and Vassh, N and Abia, C and Adsley, P and Agarwal, S and Aliotta, M and Aoki, W and Arcones, A and Aryan, A and Bandyopadhyay, A and Banu, A and Bardayan, D. W and Barnes, J and Bauswein, A and Beers, T. C and Bishop, J and Boztepe, T and C{\^{o}}t{\'{e}}, B and Caplan, M. E and Champagne, A. E and Clark, J. A and Couder, M and Couture, A and de Mink, S. E and Debnath, S and deBoer, R. J and den Hartogh, J and Denissenkov, P and Dexheimer, V and Dillmann, I and Escher, J. E and Famiano, M. A and Farmer, R and Fisher, R and Fr\"{o}hlich, C and Frebel, A and Fryer, C and Fuller, G and Ganguly, A. K and Ghosh, S and Gibson, B. K and Gorda, T and Gourgouliatos, K. N and Graber, V and Gupta, M and Haxton, W. C and Heger, A and Hix, W. R and Ho, W. C. G and Holmbeck, E. M and Hood, A. A and Huth, S and Imbriani, G and Izzard, R. G and Jain, R and Jayatissa, H and Johnston, Z and Kajino, T and Kankainen, A and Kiss, G. G and Kwiatkowski, A and Cognata, M. La and Laird, A. M and Lamia, L and Landry, P and Laplace, E and Launey, K. D and Leahy, D and Leckenby, G and Lennarz, A and Longfellow, B and Lovell, A. E and Lynch, W. G and Lyons, S. M and Maeda, K and Masha, E and Matei, C and Merc, J and Messer, B and Montes, F and Mukherjee, A and Mumpower, M. R and Neto, D and Nevins, B and Newton, W. G and Nguyen, L. Q and Nishikawa, K and Nishimura, N and Nunes, F. M and O'Connor, E. and O'Shea, B. W and Ong, W-J and Pain, S. D and Pajkos, M. A and Pignatari, M and Pizzone, R. G and Placco, V. M and Plewa, T and Pritychenko, B and Psaltis, A and Puentes, D and Qian, Y-Z and Radice, D and Rapagnani, D and Rebeiro, B. M and Reifarth, R and Richard, A. L and Rijal, N and Roederer, I. U and Rojo, J. S and K, J. S. and Saito, Y and Schwenk, A and Sergi, M. L and Sidhu, R. S and Simon, A and Sivarani, T and Sk{\'{u}}lad{\'{o}}ttir, {\'{A}} and Smith, M. S and Spiridon, A and Sprouse, T. M and Starrfield, S and Steiner, A. W and Strieder, F and Sultana, I and Surman, R and Sz\"{u}cs, T and Tawfik, A and Thielemann, F and Trache, L and Trappitsch, R and Tsang, M. B and Tumino, A and Upadhyayula, S and Mart{\'{\i}}nez, J. O Valle and der Swaelmen, M Van and V{\'{a}}zquez, C Viscasillas and Watts, A and Wehmeyer, B and Wiescher, M and Wrede, C and Yoon, J and Zegers, R. G. T and Zermane, M. A and Zingale, M},
     title = {Horizons: nuclear astrophysics in the 2020s and beyond},
     journal = {Journal of Physics G: Nuclear and Particle Physics}
   }

      
   
   
2. FrontPhys

   Cluster decays of 12Be excited states

   N. Vukman, N. Soić, M. Freer, M. Alcorta, D. Connolly, P. Čolović, T. Davinson, A. Di Pietro, A. Lennarz, A. Psaltis, and 3 more authors

   (2022)

   Abstract Bib

   An experimental study of the helium-cluster decays of the ¹²Be excited states has been performed using the ⁹Li + ⁷Li → α + α + ⁸He and ⁹Li + ⁷Li → α + ⁶He + ⁶He reactions at the ⁹Li beam energy of 74.8 MeV. At excitation energies between 10 and 25 MeV, the ¹²Be excited states decaying into the ⁴He + ⁸He, ⁶He + ⁶He, and ⁶He + ⁶He*(1.8 MeV, J^π = 2⁺) have been observed. Most of the observed states decaying into the ⁴He + ⁸He and ⁶He + ⁶He correspond to previously reported states. The decay to the ⁶He + ⁶He*(1.8 MeV, J^π = 2⁺) channel has been observed for the first time. Two of the five states observed in this new decay channel are also observed in the ground state channel ⁶He + ⁶He, while two may correspond to the ⁴He + ⁸He decaying states. The states around 13.5 and 20.0 MeV decay to the ⁶He + ⁶He and ⁴He + ⁸He channels, while the state around 22.3 MeV decays into all three decay channels examined. This experiment is complementary to all previous studies of the ¹²Be cluster states because of the different reaction mechanisms used for the population of the ¹²Be cluster states. The observation of the states at high excitations with these exotic decay properties strongly supports the molecular structure of the ¹²Be excited states.

   @aricle{Vukman2022,
     title = {Cluster decays of 12Be excited states},
     author = {Vukman, N and Soić, N and Freer, M and Alcorta, M and Connolly, D and Čolović, P and Davinson, T and Di Pietro, A and Lennarz, A and Psaltis, A and Ruiz, C and Uroić, M and Williams, M},
     volume = {10},
     year = {2022},
     doi = {10.3389/fphy.2022.1009421},
     journal = {Frontiers in Physics}
   }

      
   
   
3. PRC

   First inverse kinematics measurement of resonances in 7Be(α,γ)11C relevant to neutrino-driven wind nucleosynthesis using DRAGON

   A. Psaltis, A.A. Chen, R. Longland, D.S. Connolly, C.R. Brune, B. Davids, J. Fallis, R. Giri, U. Greife, D.A. Hutcheon, and 11 more authors

   Physical Review C (2022)

   Abstract Bib

   A possible mechanism to explain the origin of the light p nuclei in the Galaxy is the nucleosynthesis in the proton-rich neutrino-driven wind ejecta of core-collapse supernovas via the νp process. However, this production scenario is very sensitive to the underlying supernova dynamics and the nuclear physics input. As far as the nuclear uncertainties are concerned, the breakout from the pp chains via the 7Be(α,γ)11 C reaction has been identified as an important link which can influence the nuclear flow and, therefore, the efficiency of the ν p process. However, its reaction rate is poorly known over the relevant temperature range, T = 1.5–3 GK. We report on the first direct measurement of two resonances of the 7Be(α,γ)11C reaction with previously unknown strengths using an intense radioactive 7Be beam from the Isotope Separator and Accelerator (ISAC-I) Center facility and the DRAGON recoil separator in inverse kinematics. We have decreased the 7Be(α, γ)11C reaction rate uncertainty to ≈ 9.4–10.7% over the relevant temperature region.

   @article{PsaltisPRC2022,
     title = {First inverse kinematics measurement of resonances in 7Be(α,γ)11C relevant to neutrino-driven wind nucleosynthesis using DRAGON},
     author = {Psaltis, A and Chen, A.A and Longland, R and Connolly, D.S and Brune, C.R and Davids, B and Fallis, J and Giri, R and Greife, U and Hutcheon, D.A and Kroll, L and Lennarz, A and Liang, J and Lovely, M and Luo, M and Marshall, C and Paneru, S.N and Parikh, A and Ruiz, C and Shotter, A.C and Williams, M},
     journal = {Physical Review C},
     volume = {106},
     issue = {4},
     pages = {045805},
     numpages = {14},
     year = {2022},
     month = oct,
     publisher = {American Physical Society},
     doi = {10.1103/PhysRevC.106.045805}
   }

      
   
   
4. PRL

   Direct Measurement of Resonances in 7Be(α,γ)11C Relevant to νp-Process Nucleosynthesis

   A. Psaltis, A.A. Chen, R. Longland, D.S. Connolly, C.R. Brune, B. Davids, J. Fallis, R. Giri, U. Greife, D.A. Hutcheon, and 11 more authors

   Physical Review Letters (2022)

   Abstract Bib

   We have performed the first direct measurement of two resonances of the 7Be(α,γ)11C reaction with unknown strengths using an intense radioactive Be beam and the DRAGON recoil separator. We report on the first measurement of the 1155 and 1110 keV resonance strengths of 1.73 +/- 0.25(stat) +/- 0.40(syst) eV and 125 −25+27(stat) +/- 15(syst) meV, respectively. The present results have reduced the uncertainty in the 7Be(α,γ)11C reaction rate to ∼9.4%–10.7% over T   1.5–3 GK, which is relevant for nucleosynthesis in the neutrino-driven outflows of core-collapse supernovae (νp process). We find no effect of the new, constrained reaction rate on νp-process nucleosynthesis.

   @article{PsaltisPRL2022,
     title = {Direct Measurement of Resonances in 7Be(α,γ)11C Relevant to νp-Process Nucleosynthesis},
     author = {Psaltis, A and Chen, A.A and Longland, R and Connolly, D.S and Brune, C.R and Davids, B and Fallis, J and Giri, R and Greife, U and Hutcheon, D.A and Kroll, L and Lennarz, A and Liang, J and Lovely, M and Luo, M and Marshall, C and Paneru, S.N and Parikh, A and Ruiz, C and Shotter, A.C and Williams, M},
     journal = {Physical Review Letters},
     volume = {129},
     issue = {16},
     pages = {162701},
     numpages = {6},
     year = {2022},
     month = oct,
     publisher = {American Physical Society},
     doi = {10.1103/PhysRevLett.129.162701}
   }

      
   
   
5. A&A

   Chemical Evolution of R-process Elements in Stars (CERES). I. Stellar parameters and chemical abundances from Na to Zr

   L. Lombardo, P. Bonifacio, P. François, C J. Hansen, E. Caffau, M. Hanke, A. Skúladóttir, A. Arcones, M. Eichler, M. Reichert, and 3 more authors

   Astronomy & Astrophysics (2022)

   Abstract Bib

   Aims. The Chemical Evolution of R-process Elements in Stars (CERES) project aims to provide a homogeneous analysis of a sample of metal-poor stars ([Fe/H]<–1.5). We present the stellar parameters and the chemical abundances of elements up to Zr for a sample of 52 giant stars. Methods. We relied on a sample of high signal-to-noise UVES spectra. We determined stellar parameters from Gaia photometry and parallaxes. Chemical abundances were derived using spectrum synthesis and model atmospheres. Results. We determined chemical abundances of 26 species of 18 elements: Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, and Zr. For several stars, we were able to measure both neutral and ionised species, including Si, Sc, Mn, and Zr. We have roughly doubled the number of measurements of Cu for stars at [Fe/H] ≤ −2.5. The homogeneity of the sample made it possible to highlight the presence of two Zn-rich stars ([Zn/Fe]∼+0.7), one r-rich and the other r-poor. We report the existence of two branches in the [Zn/Fe] versus [Ni/Fe] plane and suggest that the high [Zn/Fe] branch is the result of hypernova nucleosynthesis. We discovered two stars with peculiar light neutron-capture abundance patterns: CES1237+1922 (also known as BS 16085-0050), which is ∼1 dex underabundant in Sr, Y, and Zr with respect to the other stars in the sample, and CES2250-4057 (also known as HE 2247-4113), which shows a ∼1 dex overabundance of Sr with respect to Y and Zr. Conclusions. The high quality of our dataset allowed us to measure hardly detectable ions. This can provide guidance in the development of line formation computations that take deviations from local thermodynamic equilibrium and hydrodynamical effects into account.

   @article{LombardoA&A2022,
     title = {Chemical Evolution of R-process Elements in Stars ({CERES)}. I.
                    Stellar parameters and chemical abundances from Na to Zr},
     author = {Lombardo, L and Bonifacio, P and Fran{\c c}ois, P and Hansen, C J and Caffau, E and Hanke, M and Sk{\'u}lad{\'o}ttir, A and Arcones, A and Eichler, M and Reichert, M and Psaltis, A and Koch Hansen, A. J and Sbordone, L},
     journal = {Astronomy & Astrophysics},
     publisher = {EDP Sciences},
     month = aug,
     volume = {665},
     pages = {A10},
     year = {2022},
     doi = {10.1051/0004-6361/202243932}
   }

      
   
   
6. ApJ

   Constraining nucleosynthesis in neutrino-driven winds: Observations, simulations, and nuclear physics

   A. Psaltis, A. Arcones, F. Montes, P. Mohr, C J. Hansen, M. Jacobi, and H. Schatz

   The Astrophysical Journal (2022)

   Abstract Bib

   A promising astrophysical site to produce the lighter heavy elements of the first r-process peak (Z = 38 − 47) is the moderately neutron-rich (0.4<Ye<0.5) neutrino-driven ejecta of explosive environments, such as core-collapse supernovae and neutron star mergers, where the weak r-process operates. This nucleosynthesis exhibits uncertainties from the absence of experimental data from (α, xn) reactions on neutron-rich nuclei, which are currently based on statistical model estimates. In this work, we report on a new study of the nuclear reaction impact using a Monte Carlo approach and improved (α, xn) rates based on the Atomki-V2 α optical model potential. We compare our results with observations from an up-to-date list of metal-poor stars with [Fe/H] < -1.5 to find conditions of the neutrino-driven wind where the lighter heavy elements can be synthesized. We identified a list of (α, xn) reaction rates that affect key elemental ratios in different astrophysical conditions. Our study aims to motivate more nuclear physics experiments on (α, xn) reactions using the current and new generation of radioactive beam facilities and also more observational studies of metal-poor stars.

   @article{PsaltisApJ2022,
     title = {Constraining nucleosynthesis in neutrino-driven winds:
                    Observations, simulations, and nuclear physics},
     author = {Psaltis, A and Arcones, A and Montes, F and Mohr, P and Hansen, C J and Jacobi, M and Schatz, H},
     journal = {The Astrophysical Journal},
     volume = {935},
     number = {1},
     pages = {27},
     month = aug,
     year = {2022},
     doi = {10.3847/1538-4357/ac7da7}
   }

      
   
   
7. PRL

   Constraining the 30P(p,γ)31S Reaction Rate in ONe Novae via the Weak, Low-Energy, β-Delayed Proton Decay of 31Cl

   T. Budner, M. Friedman, C. Wrede, B. A. Brown, J. José, D. Pérez-Loureiro, L. J. Sun, J. Surbrook, Y. Ayyad, D. W. Bardayan, and 13 more authors

   Physical Review Letters (2022)

   Abstract Bib

   The 30P(p,γ)31S reaction plays an important role in understanding the nucleosynthesis of A≥30 nuclides in oxygen-neon novae. The Gaseous Detector with Germanium Tagging was used to measure 31Cl β-delayed proton decay through the key Jπ=3/2+, 260-keV resonance. The intensity I260βp=8.3+1.2−0.9×10−6 represents the weakest β-delayed, charged-particle emission ever measured below 400 keV, resulting in a proton branching ratio of Γp/Γ=2.5+0.4−0.3×10−4. By combining this measurement with shell-model calculations for Γγ and past work on other resonances, the total 30P(p,γ)31S rate has been determined with reduced uncertainty. The new rate has been used in hydrodynamic simulations to model the composition of nova ejecta, leading to a concrete prediction of 30Si:28Si excesses in presolar nova grains and the calibration of nuclear thermometers.

   @article{BudnerPRL2022,
     title = {Constraining the 30P(p,γ)31S Reaction Rate in ONe Novae via the Weak, Low-Energy, β-Delayed Proton Decay of 31Cl},
     author = {Budner, T and Friedman, M and Wrede, C and Brown, B. A and Jos\'e, J and P\'erez-Loureiro, D and Sun, L. J and Surbrook, J and Ayyad, Y and Bardayan, D. W and Chae, K and Chen, A. A and Chipps, K. A and Cortesi, M and Glassman, B and Hall, M. R and Janasik, M and Liang, J and O'Malley, P and Pollacco, E and Psaltis, A and Stomps, J and Wheeler, T},
     journal = {Physical Review Letters},
     volume = {128},
     issue = {18},
     pages = {182701},
     numpages = {7},
     year = {2022},
     month = may,
     publisher = {American Physical Society},
     doi = {10.1103/PhysRevLett.128.182701}
   }

      
   
   
8. NIM B

   Use of Bayesian Optimization to understand the structure of nuclei

   J. Hooker, J. Kovoor, K. L. Jones, R. Kanungo, M. Alcorta, J. Allen, C. Andreoiu, L. Atar, D. W. Bardayan, S. S. Bhattacharjee, and 34 more authors

   Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms (2022)

   Abstract Bib

   Monte Carlo simulations are widely used in nuclear physics to model experimental systems. In cases where there are significant unknown quantities, such as energies of states, an iterative process of simulating and fitting is often required to describe experimental data. We describe a Bayesian approach to fitting experimental data, designed for data from a 12Be(d,p) reaction measurement, using simulations made with GEANT4. Q-values from the 12C(d,p) reaction to well-known states in 13C are compared with simulations using BayesOpt. The energies of the states were not included in the simulation to reproduce the situation for 13Be where the states are poorly known. Both cases had low statistics and significant resolution broadening owing to large proton energy losses in the solid deuterium target. Excitation energies of the lowest three excited states in 13C were extracted to better than 90 keV, paving a way for extracting information on 13Be.

   @article{HookerNIMB2022,
     title = {Use of Bayesian Optimization to understand the structure of nuclei},
     journal = {Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms},
     iso = {Nucl. Instrum. Methods Phys. Res. B},
     volume = {512},
     pages = {6},
     year = {2022},
     issn = {0168-583X},
     author = {Hooker, J and Kovoor, J and Jones, K. L and Kanungo, R and Alcorta, M and Allen, J and Andreoiu, C and Atar, L and Bardayan, D. W and Bhattacharjee, S. S and Blankstein, D and Burbadge, C and Burcher, S and Catford, W. N and Cha, S and Chae, K and Connolly, D and Davids, B and Esker, N and Garcia, F. H and Gillespie, S and Ghimire, R and Gula, A and Hackman, G and Hallam, S and Hellmich, M and Henderson, J and Holl, M and Jassal, P and King, S and Knight, T and Kruecken, R and Lepailleur, A and Liang, J and Morrison, L and O’Malley, P. D and Pain, S. D and Pereira-Lopez, X and Psaltis, A and Radich, A and Shotter, A. C and Vostinar, M and Williams, M and Workman, O},
     keywords = {Bayesian optimization, Geant4 simulation, Low-energy reactions, Stable ion beam, Radioactive ion beam, Transfer reaction, Direct reaction},
     doi = {10.1016/j.nimb.2021.11.014}
   }

      
   
   

Conference Proceedings (2022)

1. NIC-XVI

   Measuring the 15O(α,γ)19Ne reaction in Type I X-ray bursts using the GADGET II TPC: Hardware

   T. Wheeler, A. Adams, J. Allmond, H. Alvarez Pol, E. Argo, Y. Ayyad, D.. Bardayan, D. Bazin, T. Budner, A. Chen, and 20 more authors

   In EPJ Web Conference Series (2022)

   Abstract Bib

   Sensitivity studies have shown that the 15O(α,γ)19Ne reaction is the most important reaction rate uncertainty affecting the shape of light curves from Type I X-ray bursts. This reaction is dominated by the 4.03 MeV resonance in 19Ne. Previous measurements by our group have shown that this state is populated in the decay sequence of 20Mg. A single 20Mg(βp α)15O event through the key 15O(α,γ)19Ne resonance yields a characteristic signature: the emission of a proton and alpha particle. To achieve the granularity necessary for the identification of this signature, we have upgraded the Proton Detector of the Gaseous Detector with Germanium Tagging (GADGET) into a time projection chamber to form the GADGET II detection system. GADGET II has been fully constructed, and is entering the testing phase.

   @inproceedings{Wheeler-NIC-XVI,
     author = {Wheeler, T and Adams, A and Allmond, J and Alvarez Pol, H and Argo, E and Ayyad, Y and Bardayan, D. and Bazin, D and Budner, T and Chen, A and Chipps, K and Davids, B and Dopfer, J and Friedman, M and Fynbo, H and Grzywacz, R and Jose, J and Liang, J. and Mahajan, R and Pain, S and P\'erez-Loureiro, D. and Pollacco, E. and Psaltis, A and Ravishankar, S. and Rogers, A. and Schaedig, L and Sun, L. J and Surbrook, J and Weghorn, L and Wrede, C},
     title = {Measuring the 15O(α,γ)19Ne reaction in Type I X-ray bursts using the GADGET II TPC: Hardware},
     booktitle = {EPJ Web Conference Series},
     year = {2022},
     volume = {260},
     pages = {11046},
     doi = {10.1051/epjconf/202226011046}
   }

      
   
   
2. NIC-XVI

   Measuring the 15O(α,γ)19Ne Reaction in Type I X-ray Bursts using the GADGET II TPC: Software

   R. Mahajan, A. Adams, J. Allmond, H. Alvarez Pol, E. Argo, Y.. Ayyad, D. Bardayan, D. Bazin, T. Budner, A. Chen, and 20 more authors

   In EPJ Web Conference Series (2022)

   Abstract Bib

   15O(α,γ)19Ne is regarded as one of the most important thermonuclear reactions in type I X-ray bursts. For studying the properties of the key resonance in this reaction using β decay, the existing Proton Detector component of the Gaseous Detector with Germanium Tagging (GADGET) assembly is being upgraded to operate as a time projection chamber (TPC) at FRIB. This upgrade includes the associated hardware as well as software and this paper mainly focusses on the software upgrade. The full detector set up is simulated using the ATTPCROOTv 2 data analysis framework for 20Mg and 241Am.

   @inproceedings{Mahajan-NIC-XVI,
     author = {Mahajan, R and Adams, A and Allmond, J and Alvarez Pol, H and Argo, E and Ayyad, Y. and Bardayan, D and Bazin, D and Budner, T and Chen, A and Chipps, K and Davids, B and Dopfer, J and Friedman, M and Fynbo, H and Grzywacz, R and Jose, J and Liang, J and Pain, S and Perez-Loureiro, D and Pollacco, E and Psaltis, A and Ravishankar, S and Rogers, A and Schaedig, L and Sun, L. J and Surbrook, J and Wheeler, T and Weghorn, L and Wrede, C},
     title = {Measuring the 15O(α,γ)19Ne Reaction in Type I X-ray Bursts using the GADGET II TPC: Software},
     booktitle = {EPJ Web Conference Series},
     year = {2022},
     volume = {260},
     pages = {11034},
     doi = {10.1051/epjconf/202226011034}
   }

      
   
   
3. NIC-XVI

   Exploring the uncertainties of (α, n) reactions for the weak r-process

   A. Psaltis, A. Arcones, M. L. Avila, M. Jacobi, Z. Meisel, P. Mohr, F. Montes, and W. J. Ong

   In EPJ Web Conference Series (2022)

   Abstract Bib

   “Light” heavy elements (Z = 38 − 47) can be synthesized in the neutrino–driven ejecta of core–collapse supernovae via the weak r–process. This nucleosynthesis scenario exhibits uncertainties from the absence of experimental data from (α, n) reactions on neutron–rich nuclei, and are mostly based on statistical model calculations. We present preliminary results from a recent sensitivity study, using the Atomki–V2 α-nucleus potential to identify the most important (α, n) reactions that can affect the production of “light” heavy elements between strontium and silver under different astrophysical conditions. We also discuss the planning of studies to experimentally determine (α, xn) reaction rates using the MUSIC detector at Argonne National Laboratory and the SECAR recoil separator at FRIB.

   @inproceedings{Psaltis-NIC-XVI,
     author = {Psaltis, A and Arcones, A and Avila, M. L and Jacobi, M and Meisel, Z and Mohr, P and Montes, F and Ong, W. J},
     title = {Exploring the uncertainties of (α, n) reactions for the weak r-process},
     booktitle = {EPJ Web Conference Series},
     year = {2022},
     volume = {260},
     pages = {07003},
     doi = {10.1051/epjconf/202226007003}
   }

      
   
   
4. NIC-XVI

   First measurement of 25Al+p resonant scattering relevant to the astrophysical reaction 22Mg(α,p)25Al

   J. Hu, H. Yamaguchi, Y.H. Lam, A. Heger, D. Kahl, A.M. Jacobs, Z. Johnston, S.W. Xu, N.T. Zhang, S.B. Ma, and 27 more authors

   In EPJ Web Conference Series (2022)

   Abstract Bib

   Type I X-ray bursts (XRBs) are the most frequently observed thermonuclear explosions in nature. The 22Mg(α,p)25Al reaction plays a critical role in XRB models. However, experimental information is insufficient to deduce a precise 22Mg(α,p)25Al reaction rate for the respective XRB temperature range. A new measurement of 25Al+p resonant scattring was performed up to the astrophysically interested energy region of 22Mg(α,p)25Al. Several resonances were observed in the excitation functions, and their level properties have been determined based on an R-matrix analysis. In particular, proton widths and spin-parities of four natural-parity resonances above the α threshold of 26Si, which can contribute the reaction rate of 22Mg(α,p)25Al, were first experimentally determined.

   @inproceedings{Hu-NIC-XVI,
     author = {Hu, J and Yamaguchi, H and Lam, Y.H and Heger, A and Kahl, D and Jacobs, A.M and Johnston, Z and Xu, S.W and Zhang, N.T and Ma, S.B and Ru, L.H and Liu, E.Q and Liu, T and Hayakawa, S and Yang, L and Shimizu, H and Hamill, C.B and Murphy, A. StJ and Su, J and Fang, X and Chae, K.Y and Kwag, M.S and Cha, S.M and Duy, N.N and Uyen, N.K and Kim, D.H and Pizzone, R.G and La Cognata, M and Cherubini, S and Romano, S and Tumino, A and Liang, J and Psaltis, A and Sferrazza, M and Kim, D and Li, Y.Y and Kubono, S},
     title = {First measurement of 25Al+p resonant scattering relevant to the astrophysical reaction 22Mg(α,p)25Al},
     booktitle = {EPJ Web Conference Series},
     year = {2022},
     volume = {260},
     pages = {05001},
     doi = {10.1051/epjconf/202226005001}
   }

      
   
   
5. NIC-XVI

   Experimental studies on astrophysical reactions at the low-energy RI beam separator CRIB

   H. Yamaguchi, S. Hayakawa, N.R. Ma, H. Shimizu, K. Okawa, L. Yang, D. Kahl, M. La Cognata, L. Lamia, K. Abe, and 52 more authors

   In EPJ Web Conference Series (2022)

   Abstract Bib

   Experimental studies on astrophysical reactions involving radioactive isotopes (RI) often accompany technical challenges. Studies on such nuclear reactions have been conducted at the low-energy RI beam separator CRIB, operated by Center for Nuclear Study, the University of Tokyo. We discuss two cases of astrophysical reaction studies at CRIB; one is for the 7Be+n reactions which may affect the primordial 7Li abundance in the Big-Bang nucleosynthesis, and the other is for the 22Mg(α, p) reaction relevantin X-ray bursts.

   @inproceedings{Yamaguchi-NIC-XVI,
     author = {Yamaguchi, H and Hayakawa, S and Ma, N.R and Shimizu, H and Okawa, K and Yang, L and Kahl, D and La Cognata, M and Lamia, L and Abe, K and Beliuskina, O and Cha, S.M and Chae, K.Y and Cherubini, S and Figuera, P and Ge, Z and Gulino, M and Hu, J and Inoue, A and Iwasa, N and Kim, A and Kim, D and Kiss, G and Kubono, S and La Commara, M and Lattuada, M and Lee, E.J and Moon, J.Y and Palmerini, S and Parascandolo, C and Park, S.Y and Phong, V. H and Pierroutsakou, D and Pizzone, R.G and Rapisarda, G.G and Romano, S and Spitaleri, C and Tang, X.D and Trippella, O and Tumino, A and Zhang, N.T and Lam, Y.H and Heger, A and Jacobs, A.M and Xu, S.W and Ma, S.B and Ru, L.H and Liu, E.Q and Liu, T and Hamill, C.B and St J. Murphy, A and Su, J and Fang, X and Kwag, M.S and Duy, N.N and Uyen, N.K and Kim, D.H and Liang, J and Psaltis, A and Sferrazza, M and Johnston, Z and Li, Y.Y},
     title = {Experimental studies on astrophysical reactions at the low-energy RI beam separator CRIB},
     booktitle = {EPJ Web Conference Series},
     year = {2022},
     volume = {260},
     pages = {03003},
     doi = {10.1051/epjconf/202226003003}
   }

      
   
   

Journal Articles (2021)

1. PRC

   First direct measurement of 59Cu(p,α)56Ni: A step towards constraining the Ni-Cu cycle in the cosmos

   J. S. Randhawa, R. Kanungo, J. Refsgaard, P. Mohr, T. Ahn, M. Alcorta, C. Andreoiu, S. S. Bhattacharjee, B. Davids, G. Christian, and 28 more authors

   Physical Review C (2021)

   Abstract Bib

   Reactions on proton-rich nuclides drive the nucleosynthesis in core collapse supernovae (CCSNe) and in x-ray bursts (XRBs). CCSNe eject the nucleosynthesis products to the interstellar medium and hence are a potential inventory of p nuclei, whereas in XRBs nucleosynthesis powers the light curves. In both astrophysical sites the Ni-Cu cycle, which features a competition between 59Cu(p,α)56Ni and 59Cu(p,γ)60Zn, could potentially halt the production of heavier elements. Here, we report the first direct measurement of 59Cu(p,α)56Ni using a reaccelerated 59Cu beam and a cryogenic solid hydrogen target. Our results show that the reaction proceeds predominantly to the ground state of 56Ni, and the experimental rate has been found to be lower than Hauser-Feshbach based statistical model predictions. New results hints that the νp process could operate at higher temperatures than previously inferred and therefore remains a viable site for synthesizing the heavier elements.

   @article{RandhawaPRC2022,
     title = {First direct measurement of 59Cu(p,α)56Ni: A step towards constraining the Ni-Cu cycle in the cosmos},
     author = {Randhawa, J. S and Kanungo, R and Refsgaard, J and Mohr, P and Ahn, T and Alcorta, M and Andreoiu, C and Bhattacharjee, S. S and Davids, B and Christian, G and Chen, A. A and Coleman, R and Garrett, P. E and Grinyer, G. F and Gyabeng Fuakye, E and Hackman, G and Hollett, J and Jain, R and Kapoor, K and Kr\"ucken, R and Laffoley, A and Lennarz, A and Liang, J and Meisel, Z and Nikhil, B and Psaltis, A and Radich, A and Rocchini, M and Saei, N and Saxena, M and Singh, M and Svensson, C and Subramaniam, P and Talebitaher, A and Upadhyayula, S and Waterfield, C and Williams, J and Williams, M},
     journal = {Physical Review C},
     iso = {Phys. Rev. C},
     volume = {104},
     issue = {4},
     pages = {L042801},
     numpages = {6},
     year = {2021},
     month = oct,
     publisher = {American Physical Society},
     doi = {10.1103/PhysRevC.104.L042801}
   }

      
   
   
2. ApJ

   Post-explosion Evolution of Core-collapse Supernovae

   M. Witt, A. Psaltis, H. Yasin, C. Horn, M. Reichert, T. Kuroda, M. Obergaulinger, S. M. Couch, and A. Arcones

   The Astrophysical Journal (2021)

   Abstract Bib

   We investigate the post-explosion phase in core-collapse supernovae with 2D hydrodynamical simulations and a simple neutrino treatment. The latter allows us to perform 46 simulations and follow the evolution of the 32 explosion models during several seconds. We present a broad study based on three progenitors (11.2, 15, and 27 M⊙), different neutrino heating efficiencies, and various rotation rates. We show that the first seconds after shock revival determine the final explosion energy, remnant mass, and properties of ejected matter. Our results suggest that a continued mass accretion increases the explosion energy even at late times. We link the late-time mass accretion to initial conditions such as rotation strength and shock deformation at explosion time. Only some of our simulations develop a neutrino-driven wind (NDW) that survives for several seconds. This indicates that NDWs are not a standard feature expected after every successful explosion. Even if our neutrino treatment is simple, we estimate the nucleosynthesis of the exploding models for the 15 M⊙ progenitor after correcting the neutrino energies and luminosities to get a more realistic electron fraction.

   @article{WittApJ2021,
     iso = {ApJ},
     journal = {The Astrophysical Journal},
     year = {2021},
     month = oct,
     publisher = {American Astronomical Society},
     volume = {921},
     number = {1},
     pages = {19},
     author = {Witt, M and Psaltis, A and Yasin, H and Horn, C and Reichert, M and Kuroda, T and Obergaulinger, M and Couch, S. M and Arcones, A},
     first = {M. Witt},
     title = {Post-explosion Evolution of Core-collapse Supernovae},
     doi = {10.3847/1538-4357/ac1a6d}
   }

      
   
   
3. PRL

   Advancement of Photospheric Radius Expansion and Clocked Type-I X-Ray Burst Models with the New 22Mg(α,p)25Al Reaction Rate Determined at the Gamow Energy

   J. Hu, H. Yamaguchi, Y. H. Lam, A. Heger, D. Kahl, A. M. Jacobs, Z. Johnston, S. W. Xu, N. T. Zhang, S. B. Ma, and 27 more authors

   Physical Review Letters (2021)

   Abstract Bib

   We report the first (in)elastic scattering measurement of 25Al+p with the capability to select and measure in a broad energy range the proton resonances in 26Si contributing to the 22Mg(α,p) reaction at type I x-ray burst energies. We measured spin-parities of four resonances above the α threshold of 26Si that are found to strongly impact the 22Mg(α,p) rate. The new rate advances a state-of-the-art model to remarkably reproduce light curves of the GS 1826–24 clocked burster with mean deviation <9% and permits us to discover a strong correlation between the He abundance in the accreting envelope of the photospheric radius expansion burster and the dominance of 22Mg(α,p) branch.

   @article{HuPRL2022,
     title = {Advancement of Photospheric Radius Expansion and Clocked Type-I X-Ray Burst Models with the New 22Mg(α,p)25Al Reaction Rate Determined at the Gamow Energy},
     author = {Hu, J and Yamaguchi, H and Lam, Y. H and Heger, A and Kahl, D and Jacobs, A. M and Johnston, Z and Xu, S. W and Zhang, N. T and Ma, S. B and Ru, L. H and Liu, E. Q and Liu, T and Hayakawa, S and Yang, L and Shimizu, H and Hamill, C. B and Murphy, A. St J and Su, J and Fang, X and Chae, K. Y and Kwag, M. S and Cha, S. M and Duy, N. N and Uyen, N. K and Kim, D. H and Pizzone, R. G and La Cognata, M and Cherubini, S and Romano, S and Tumino, A and Liang, J and Psaltis, A and Sferrazza, M and Kim, D and Li, Y. Y and Kubono, S},
     journal = {Physical Review Letters},
     volume = {127},
     issue = {17},
     pages = {172701},
     numpages = {7},
     year = {2021},
     month = oct,
     publisher = {American Physical Society},
     doi = {10.1103/PhysRevLett.127.172701}
   }

      
   
   
4. PLB

   Proton inelastic scattering reveals deformation in 8He

   M. Holl, R. Kanungo, Z. H. Sun, G. Hagen, J. A. Lay, A. M. Moro, P. Navrátil, T. Papenbrock, M. Alcorta, D. Connolly, and 20 more authors

   Physics Letters B (2021)

   Abstract Bib

   A measurement of proton inelastic scattering of 8He at 8.25A MeV at TRIUMF shows a resonance at 3.54(6) MeV with a width of 0.89(11) MeV. The energy of the state is in good agreement with coupled cluster and no-core shell model with continuum calculations, with the latter successfully describing the measured resonance width as well. Its differential cross section analyzed with phenomenological collective excitation form factor and microscopic coupled reaction channels framework consistently reveals a large deformation parameter = 0.40(3), consistent with no-core shell model predictions of a large neutron deformation. This deformed double-closed shell at the neutron drip-line opens a new paradigm.

   @article{HollPLB2021,
     title = {Proton inelastic scattering reveals deformation in 8He},
     author = {Holl, M and Kanungo, R and Sun, Z. H and Hagen, G and Lay, J. A and Moro, A. M and Navr{\'a}til, P and Papenbrock, T and Alcorta, M and Connolly, D and Davids, B and Diaz Varela, A and Gennari, M and Hackman, G and Henderson, J and Ishimoto, S and Kilic, A. I and Krucken, R and Lennarz, A and Liang, J and Measures, J and Mitting, W and Paetkau, O and Psaltis, A and Quaglioni, S and Randhawa, J. S and Smallcombe, J and Thompson, I. J and Vorabbi, M and Williams, M},
     journal = {Physics Letters B},
     pages = {136710},
     year = {2021},
     publisher = {Elsevier},
     doi = {10.1016/j.physletb.2021.136710}
   }

      
   
   
5. ADNDT

   Astrophysical reaction rates of α-induced reactions for nuclei with 26≤ Z≤ 83 from the new Atomki-V2 α-nucleus potential

   P. Mohr, Zs. Fülöp, Gy. Gyürky, GG. Kiss, T. Szücs, A. Arcones, M. Jacobi, and A. Psaltis

   Atomic Data and Nuclear Data Tables (2021)

   Abstract Bib

   The new Atomki-V2 -nucleus potential is applied to calculate astrophysical reaction rates of intermediate mass and heavy target nuclei from iron (Z=26) up to bismuth (Z=83). Overall, reaction rates of α-induced reactions are provided for 4359 target nuclei, covering as well neutron-deficient as extremely neutron-rich target nuclei from the proton to the neutron dripline. Contrary to previous rate compilations, these new calculations include all relevant exit channels with the dominating (α, xn) reactions for neutron-rich target nuclei.

   @article{MohrADNDT2021,
     title = {Astrophysical reaction rates of $\alpha$-induced reactions for nuclei with 26≤ Z≤ 83 from the new Atomki-V2 $\alpha$-nucleus potential},
     author = {Mohr, P and F{\"u}l{\"o}p, Zs and Gy{\"u}rky, Gy and Kiss, GG and Sz{\"u}cs, T and Arcones, A and Jacobi, M and Psaltis, A},
     journal = {Atomic Data and Nuclear Data Tables},
     pages = {101453},
     volume = {142},
     year = {2021},
     issn = {0092-640X},
     publisher = {Elsevier},
     doi = {10.1016/j.adt.2021.101453}
   }

      
   
   
6. PRC

   Activation thick target yield measurement of 100Mo(α,n)103Ru for studying the weak r-process nucleosynthesis

   T. N. Szegedi, G. G. Kiss, P. Mohr, A. Psaltis, M. Jacobi, G. G. Barnaföldi, T. Szücs, Gy. Gyürky, and A. Arcones

   Physical Review C (2021)

   Abstract Bib

   Background: Light (30≤Z≤45) neutron-rich isotopes are thought to be synthesized in the neutrino-driven ejecta of core-collapse supernovae explosions via the weak r process. Recent nucleosynthesis studies have demonstrated that (α,xn) reactions play a particularly important role in the production of these isotopes. α-nucleus optical model potentials (α-OMPs) are used to model this nucleosynthesis scenario. Purpose: The different α-OMP model parameters can affect the calculated cross sections by more than an order of magnitude in the relevant energy regions, which affects the production of light neutron-rich isotopes. Consequently, to constrain the astrophysical conditions characterizing the supernovae ejecta, the uncertainty of the nuclear physics input has to be reduced. Methods: The cross section of the 100Mo(α,n)103Ru reaction was measured by means of the activation method. 0.5 mm thick molybdenum disks were irradiated with Eα = 7.0 to Eα = 13.0 MeV α beams. Thick target yields and reaction cross sections were determined via γ-ray spectroscopy. Results: Cross sections at several energies below the Coulomb barrier were measured, reaching the astrophysically relevant energy region. Large discrepancies between the experimental values and statistical model predictions calculated using the well-known α-OMPs were found. The measured cross section data could be excellently described by the Atomki-V2 potential. Therefore, this α-OMP was used to derive the astrophysical reaction rates as a function of temperature. Conclusions: The successful reproduction of the measured cross sections in a wide energy region confirm the reliability of the Atomki-V2 potential. The usage of the new 100Mo(α,n)103Ru experimental data along with the Atomki-V2 potential reduces the nuclear uncertainties of the weak r-process production yields of nuclei with 36≤Z≤50 to a marginal level.

   @article{SzegediPRC2021,
     title = {Activation thick target yield measurement of 100Mo(α,n)103Ru for studying the weak r-process nucleosynthesis},
     author = {Szegedi, T. N and Kiss, G. G and Mohr, P and Psaltis, A and Jacobi, M and Barnaf\"oldi, G. G and Sz\"ucs, T and Gy\"urky, Gy and Arcones, A},
     journal = {Physical Review C},
     volume = {104},
     issue = {3},
     pages = {035804},
     numpages = {7},
     year = {2021},
     month = sep,
     publisher = {American Physical Society},
     doi = {10.1103/PhysRevC.104.035804}
   }

      
   
   
7. PRL

   First Direct Measurement of an Astrophysical p-Process Reaction Cross Section Using a Radioactive Ion Beam

   G. Lotay, S. A. Gillespie, M. Williams, T. Rauscher, M. Alcorta, A. M. Amthor, C. A. Andreoiu, D. Baal, G. C. Ball, S. S. Bhattacharjee, and 28 more authors

   Physical Review Letters (2021)

   Abstract Bib

   We have performed the first direct measurement of the 83Rb(p,γ) radiative capture reaction cross section in inverse kinematics using a radioactive beam of 83Rb at incident energies of 2.4 and 2.7A  MeV. The measured cross section at an effective relative kinetic energy of Ecm=2.393  MeV, which lies within the relevant energy window for core collapse supernovae, is smaller than the prediction of statistical model calculations. This leads to the abundance of 84Sr produced in the astrophysical p process being higher than previously calculated. Moreover, the discrepancy of the present data with theoretical predictions indicates that further experimental investigation of p-process reactions involving unstable projectiles is clearly warranted.

   @article{LotayPRL2022,
     title = {First Direct Measurement of an Astrophysical $p$-Process Reaction Cross Section Using a Radioactive Ion Beam},
     author = {Lotay, G and Gillespie, S. A and Williams, M and Rauscher, T and Alcorta, M and Amthor, A. M and Andreoiu, C. A and Baal, D and Ball, G. C and Bhattacharjee, S. S and Behnamian, H and Bildstein, V and Burbadge, C and Catford, W. N and Doherty, D. T and Esker, N. E and Garcia, F. H and Garnsworthy, A. B and Hackman, G and Hallam, S and Hudson, K. A and Jazrawi, S and Kasanda, E and Kennington, A. R. L and Kim, Y. H and Lennarz, A and Lubna, R. S and Natzke, C. R and Nishimura, N and Olaizola, B and Paxman, C and Psaltis, A and Svensson, C. E and Williams, J and Wallis, B and Yates, D and Walter, D and Davids, B},
     journal = {Physical Review Letters},
     volume = {127},
     issue = {11},
     pages = {112701},
     numpages = {6},
     year = {2021},
     month = sep,
     publisher = {American Physical Society},
     doi = {10.1103/PhysRevLett.127.112701}
   }

      
   
   
8. PRC

   Proton capture on 34S in the astrophysical energy regime of O-Ne novae

   M. Lovely, A. Lennarz, D. Connolly, M. Williams, M. Alcorta, A. A. Chen, B. Davids, N. E. Esker, C. Fry, S. A. Gillespie, and 12 more authors

   Physical Review C (2021)

   Abstract Bib

   Nuclear reaction sensitivity studies have shown that the final isotopic abundance of O-Ne nova nucleosynthesis is dependent on the 34S(p,γ)35Cl reaction at astrophysical energies corresponding to peak nova burning temperatures of 0.1–0.4 GK. Isotopic ratios of the S, Cl, and Ar products are all used in various methods of cosmochemical analysis of presolar meteoritic grains. Due to the lack of direct experimental data, the 34S+p reaction rate has been estimated using statistical modeling or information from indirect nucleon transfer experiments. In order to provide direct reaction information, the resonance strengths of several low energy resonances, Ec.m.=272–495 keV, in the 34S(p,γ)35Cl reaction were measured for the first time in inverse kinematics using the DRAGON recoil separator located at TRIUMF, Canada’s Particle Accelerator Centre in Vancouver.

   @article{LovelyPRC2021,
     title = {Proton capture on 34S in the astrophysical energy regime of O-Ne novae},
     author = {Lovely, M and Lennarz, A and Connolly, D and Williams, M and Alcorta, M and Chen, A. A and Davids, B and Esker, N. E and Fry, C and Gillespie, S. A and Giri, R and Greife, U and Hussein, A and Hutcheon, D and Karpesky, J and Kroll, L and Liang, J and O'Malley, P. D and Paneru, S and Psaltis, A and Ruiz, C and Shotter, A. C},
     collaboration = {DRAGON Collaboration},
     journal = {Physical Review C},
     volume = {103},
     issue = {5},
     pages = {055801},
     numpages = {10},
     year = {2021},
     month = may,
     publisher = {American Physical Society},
     doi = {10.1103/PhysRevC.103.055801}
   }

      
   
   
9. NIM A

   Beyond the acceptance limit of DRAGON: The case of the 6Li(α, γ)10B reaction

   A. Psaltis, A.A. Chen, D.S. Connolly, B. Davids, G. Gilardy, R. Giri, U. Greife, W. Huang, D.A. Hutcheon, J. Karpesky, and 7 more authors

   Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (2021)

   Abstract Bib

   Radiative capture reactions play a pivotal role for our understanding of the origin of the elements in the cosmos. Recoil separators provide an effective way to study these reactions, in inverse kinematics, and take advantage of the use of radioactive ion beams. However, a limiting factor in the study of radiative capture reactions in inverse kinematics is the momentum spread of the product nuclei, which can result in an angular spread larger than the geometric acceptance of the separator. The DRAGON facility at TRIUMF is a versatile recoil separator, designed to study radiative capture reactions relevant to astrophysics in the A∼10−30 region. In this work we present the first attempt to study with DRAGON a reaction, 6Li(α,γ)10B, for which the recoil angular spread exceeds DRAGON’s acceptance. Our result is in good agreement with the literature value, showing that DRAGON can measure resonance strengths of astrophysically important reactions even when not all the recoils enter the separator.

   @article{PsaltisNIMA2020,
     title = {Beyond the acceptance limit of DRAGON: The case of the 6Li($\alpha$, $\gamma$)10B reaction},
     author = {Psaltis, A and Chen, A.A and Connolly, D.S and Davids, B and Gilardy, G and Giri, R and Greife, U and Huang, W and Hutcheon, D.A and Karpesky, J and Lennarz, A and Liang, J and Lovely, M and Paneru, S.N and Ruiz, C and Tenkila, G and Williams, M},
     journal = {Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment},
     pages = {164828},
     volume = {987},
     year = {2021},
     publisher = {Elsevier},
     doi = {10.1016/j.nima.2020.164828}
   }

      
   
   

Conference Proceedings (2021)

Journal Articles (2020)

1. PRC

   First inverse kinematics study of the 22Ne(p, γ)23Na reaction and its role in AGB star and classical nova nucleosynthesis

   M. Williams, A. Lennarz, A.M. Laird, U. Battino, J. José, D. Connolly, C. Ruiz, A. Chen, B. Davids, N. Esker, and 11 more authors

   Physical Review C (2020)

   Abstract Bib

   Background: Globular clusters are known to exhibit anomalous abundance trends such as the sodium-oxygen anticorrelation. This trend is thought to arise via pollution of the cluster interstellar medium from a previous generation of stars. Intermediate-mass asymptotic giant branch stars undergoing hot bottom burning (HBB) are a prime candidate for producing sodium-rich oxygen-poor material, and then expelling this material via strong stellar winds. The amount of 23Na produced in this environment has been shown to be sensitive to uncertainties in the 22Ne(p,γ)23Na reaction rate. The 22Ne(p,γ)23Na reaction is also activated in classical nova nucleosynthesis, strongly influencing predicted isotopic abundance ratios in the Na-Al region. Therefore, improved nuclear physics uncertainties for this reaction rate are of critical importance for the identification and classification of pre-solar grains produced by classical novae. Purpose: At temperatures relevant for both HBB in AGB stars and classical nova nucleosynthesis, the 22Ne(p,γ)23Na reaction rate is dominated by narrow resonances, with additional contribution from direct capture. This study presents new strength values for seven resonances, as well as a study of direct capture. Method: The experiment was performed in inverse kinematics by impinging an intense isotopically pure beam of 22Ne onto a windowless H2 gas target. The 23Na recoils and prompt γ rays were detected in coincidence using a recoil mass separator coupled to a 4π bismuth-germanate scintillator array surrounding the target. Results: For the low-energy resonances, located at center of mass energies of 149, 181, and 248 keV, we recover stength values of ωγ149=0.17+0.05−0.04, ωγ181=2.2±0.4, and ωγ248=8.2±0.7 μeV, respectively. These results are in broad agreement with recent studies performed by the LUNA and TUNL groups. However, for the important reference resonance at 458 keV we obtain a strength value of ωγ458=0.44±0.02 eV, which is significantly lower than recently reported values. This is the first time that this resonance has been studied completely independently from other resonance strengths. For the 632-keV resonance we recover a strength value of ωγ632=0.48±0.02 eV, which is an order of magnitude higher than a recent study. For reference resonances at 610- and 1222-keV, our strength values are in agreement with the literature. In the case of direct capture, we recover an S factor of 60 keV b, consistent with prior forward kinematics experiments. Conclusions: In summary, we have performed the first direct measurement of 22Ne(p,γ)23Na in inverse kinematics. Our results are in broad agreement with the literature, with the notable exception of the 458-keV resonance, for which we obtain a lower strength value. We assessed the impact of the present reaction rate in reference to a variety of astrophysical environments, including AGB stars and classical novae. Production of 23Na in AGB stars is minimally influenced by the factor of 4 increase in the present rate compared to the STARLIB-2013 compilation. The present rate does however impact upon the production of nuclei in the Ne-Al region for classical novae, with dramatically improved uncertainties in the predicted isotopic abundances present in the novae ejecta.

   @article{WilliamsPRC2020,
     year = {2020},
     publisher = {American Physical Society ({APS})},
     volume = {102},
     number = {3},
     author = {Williams, M and Lennarz, A and Laird, A.M and Battino, U and Jos{\'{e}}, J and Connolly, D and Ruiz, C and Chen, A and Davids, B and Esker, N and Fulton, B.R and Garg, R and Gay, M and Greife, U and Hager, U and Hutcheon, D and Lovely, M and Lyons, S and Psaltis, A and Riley, J.E and Tattersall, A},
     title = {First inverse kinematics study of the
     		22Ne(p, γ)23Na
     		 reaction and its role in {AGB} star and classical nova nucleosynthesis},
     journal = {Physical Review C},
     doi = {10.1103/physrevc.102.035801}
   }

      
   
   
2. PLB

   First inverse kinematics measurement of key resonances in the 22Ne(p, γ)23Na reaction at stellar temperatures

   A. Lennarz, M. Williams, A.M. Laird, U. Battino, A.A. Chen, D. Connolly, B. Davids, N. Esker, R. Garg, M. Gay, and 10 more authors

   Physics Letters B (2020)

   Abstract Bib

   In this Letter we report on the first inverse kinematics measurement of key resonances in the reaction which forms part of the NeNa cycle, and is relevant for 23Na synthesis in asymptotic giant branch (AGB) stars. An anti-correlation in O and Na abundances is seen across all well-studied globular clusters (GC), however, reaction-rate uncertainties limit the precision as to which stellar evolution models can reproduce the observed isotopic abundance patterns. Given the importance of GC observations in testing stellar evolution models and their dependence on NeNa reaction rates, it is critical that the nuclear physics uncertainties on the origin of 23Na be addressed. We present results of direct strengths measurements of four key resonances in at E = 149 keV, 181 keV, 248 keV and 458 keV. The strength of the important E = 458 keV reference resonance has been determined independently of other resonance strengths for the first time with an associated strength of ωγ = 0.439(22) eV and with higher precision than previously reported. Our result deviates from the two most recently published results obtained from normal kinematics measurements performed by the LENA and LUNA collaborations but is in agreement with earlier measurements. The impact of our rate on the Na-pocket formation in AGB stars and its relation to the O-Na anti-correlation was assessed via network calculations. Further, the effect on isotopic abundances in CO and ONe novae ejecta with respect to pre-solar grains was investigated.

   @article{LennarzPRB2020,
     title = {First inverse kinematics measurement of key resonances in the 22Ne(p, $\gamma$)23Na reaction at stellar temperatures},
     author = {Lennarz, A and Williams, M and Laird, A.M and Battino, U and Chen, A.A and Connolly, D and Davids, B and Esker, N and Garg, R and Gay, M and Greife, U and Hager, U and Hutcheon, D and Jose, J and Lovely, M and Lyons, L and Psaltis, A and Riley, J.E and Tattersall, A and Ruiz, C},
     journal = {Physics Letters B},
     pages = {135539},
     volume = {807},
     year = {2020},
     publisher = {Elsevier},
     doi = {10.1016/j.physletb.2020.135539}
   }

      
   
   

Conference Proceedings (2020)

1. NPA-IX

   Study of the 7Be(α, γ)11C reaction with DRAGON for vp–process nucleosynthesis

   A. Psaltis, A.A. Chen, L. Kroll, J. Liang, D.S. Connolly, B. Davids, D.A. Hutcheon, A. Lennarz, C. Ruiz, M. Williams, and 11 more authors

   In Journal of Physics: Conference Series (2020)

   Abstract Bib

   The production of the p–nuclei is one of the unsolved puzzles in nuclear astrophysics. A possible mechanism is the nucleosynthesis in the neutrino–driven winds of core–collapse supernovae (νp–process), but it carries uncertainties, mostly in the supernova dynamics and the nuclear physics input. The pp-chain breakout reaction 7Be(α,γ)11C, which occurs prior to the supernova explosion, was identified as an important link which can influence the nuclear flow of the z/p-process and the final abundances of the p-nuclei. Nevertheless, its reaction rate is poorly known over the relevant energy range (T=1.5-3 GK). To improve the 7Be(α,γ)11C rate for vp-process nucleosynthesis temperatures, the first measurement of the strengths of two important resonances with unknown strength was recently performed at TRIUMF. A radioactive 7Be beam (t1/2 = 53.24 d) beam and the DRAGON recoil separator were used. The experimental details and preliminary results for the resonance strengths will be discussed.

   @inproceedings{Psaltis-NPA-IX,
     title = {Study of the 7Be($\alpha$, $\gamma$)11C reaction with DRAGON for vp--process nucleosynthesis},
     author = {Psaltis, A and Chen, A.A and Kroll, L and Liang, J and Connolly, D.S and Davids, B and Hutcheon, D.A and Lennarz, A and Ruiz, C and Williams, M and Greife, U and Karpesky, J and Lovely, M and Brune, C and Paneru, S. N and Giri, R and Luo, M and Tenkila, G and Fallis, J and Marshall, C and Shotter, A.C},
     booktitle = {Journal of Physics: Conference Series},
     volume = {1668},
     number = {1},
     pages = {012035},
     year = {2020},
     organization = {IOP Publishing},
     doi = {10.1088/1742-6596/1668/1/012035}
   }

      
   
   
2. NPA-IX

   Spectroscopic Study of 39Ca for Endpoint Nucleosynthesis in Classical Novae

   J. Liang, A.A. Chen, M. Anger, S. Bishop, T. Faestermann, C. Fry, R. Hertenberger, A. Psaltis, D. Seiler, P. Tiwari, and 2 more authors

   In Journal of Physics: Conference Series (2020)

   Abstract Bib

   Classical novae are environments which can produce heavier elements up to mass A   40. These nuclides at the endpoint of nova nucleosynthesis consist of elements such as Ar, K, and Ca. There is an order of magnitude discrepancy with the predicted and theoretical abundances of these endpoint nuclides produced in a classical nova. The uncertainty in the theoretical 38K(p,γ)39Ca reaction rate has been shown to affect the abundances by an order of magnitude or more. The only direct measurement of this reaction rate was performed with the DRAGON facility at TRIUMF; however additional spectroscopic data could aid the interpretation of this data as well as motivate further study of this reaction rate. In this study, we present the preliminary results of a spectroscopic study of 39Ca using the 40Ca(d,t)39Ca reaction carried out at the Maier-Leibnitz Laboratory in Garching, Germany.

   @inproceedings{Liang-NPA-IX,
     title = {Spectroscopic Study of 39Ca for Endpoint Nucleosynthesis in Classical Novae},
     author = {Liang, J and Chen, A.A and Anger, M and Bishop, S and Faestermann, T and Fry, C and Hertenberger, R and Psaltis, A and Seiler, D and Tiwari, P and Wirth, H.-F and Wrede, C},
     booktitle = {Journal of Physics: Conference Series},
     volume = {1668},
     number = {1},
     pages = {012025},
     year = {2020},
     organization = {IOP Publishing},
     doi = {10.1088/1742-6596/1668/1/012025}
   }

      
   
   
3. OMEG15

   Study on 26mAl(p, γ) Reaction at the SNe Temperature

   H. Shimizu, D. Kahl, H. Yamaguchi, K. Abe, O. Beliuskina, S.M. Cha, K.Y. Chae, A.A. Chen, Z. Ge, S. Hayakawa, and 16 more authors

   In Proceedings of the 15th International Symposium on Origin of Matter and Evolution of Galaxies (OMEG15) (2020)

   Abstract Bib

   The γ-ray observatory has been detecting β-delayed γ-rays from 26Al for more than two decades. The half life of 26Al is 7.75 × 105 years and is sufficiently short on the scale of the galactic evolution but long enough to disperse in the interstellar medium. Hence, the abundance of this nuclide is one of the candidates to understand nucleosynthesys in massive environments such as Wolf–Rayet stars, AGB stars and supernovae. However, the abundance of 26Al in the interstellar medium from the observed flux has been inconsistent with nuclear reaction network calculations. One of the clues to solve this discrepancy is its isomer, 26mAl. Because its spin-parity is 0+, it directly decays to the ground state of 26Mg without emitting γ-rays. Despite the difference of the spin-parity between the ground state and the isomeric state, they could be under thermal equilibrium in high temperature environments, so that there is a possibility that the calculated flux sinks below the network calculations. To complement one of the destructive reactions of 26mAl, the experiment of the resonant elastic scattering of the 26mAl(p, γ) reaction with the cocktail 26g,mAl RI beam was conducted.

   @inproceedings{Hhimizu-OMEG15,
     title = {Study on 26mAl(p, $\gamma$) Reaction at the SNe Temperature},
     author = {Shimizu, H and Kahl, D and Yamaguchi, H and Abe, K and Beliuskina, O and Cha, S.M and Chae, K.Y and Chen, A.A and Ge, Z and Hayakawa, S and and Imai, N and Iwasa, N and Kim, A and Kim, D.H and Kim, M.J and Kubono, S and Kwag, M.S and Liang, J and Moon, J.Y and Nishimura, S and Oka, S and Park, S.Y and Psaltis, A and Teranishi, T and Ueno, Y and Yang, L},
     booktitle = {Proceedings of the 15th International Symposium on Origin of Matter and Evolution of Galaxies (OMEG15)},
     pages = {011073},
     year = {2020},
     doi = {10.7566/JPSCP.31.011073}
   }

      
   
   

Journal Articles (2019)

1. PRC

   Cross-section measurements of radiative proton-capture reactions in 112Cd at energies of astrophysical interest

   A. Psaltis, A. Khaliel, E.-M. Assimakopoulou, A. Kanellakopoulos, V. Lagaki, M. Lykiardopoulou, E. Malami, P. Tsavalas, A. Zyriliou, and T.J. Mertzimekis

   Physical Review C (2019)

   Abstract Bib

   Reactions involving the group of nuclei commonly known as p nuclei are part of the nucleosynthetic mechanisms at astrophysical sites. The 113In nucleus is such a case with several open questions regarding its origin at extreme stellar environments. In this work, the experimental study of the cross sections of the radiative proton-capture reaction 112Cd(p,γ)113In is attempted for the first time at energies lying inside the Gamow window with an isotopically enriched 112Cd target. Two different techniques, the in-beam γ-ray spectroscopy and the activation method, have been applied. The latter method is required to account for the presence of a low-lying 113In isomer at 392 keV having a halflife of \approx100 min. From the cross sections, the astrophysical S factors and the isomeric ratios have been additionally deduced. The experimental results are compared to detailed Hauser-Feshbach theoretical calculations using TALYS, and discussed in terms of their significance to the optical model potential involved.

   @article{PsaltisPRC2019,
     title = {Cross-section measurements of radiative proton-capture reactions in 112Cd at energies of astrophysical interest},
     author = {Psaltis, A and Khaliel, A and Assimakopoulou, E.-M and Kanellakopoulos, A and Lagaki, V and Lykiardopoulou, M and Malami, E and Tsavalas, P and Zyriliou, A and Mertzimekis, T.J},
     journal = {Physical Review C},
     volume = {99},
     number = {6},
     pages = {065807},
     year = {2019},
     doi = {10.1103/PhysRevC.99.065807},
   }

      
   
   

Conference Proceedings (2019)

1. NIC XV

   Radiative Alpha Capture on 7Be with DRAGON at Energies Relevant to the νp-Process

   A. Psaltis, A.A. Chen, D.S. Connolly, B. Davids, N. Esker, G. Gilardy, U. Greife, W. Huang, D.A. Hutcheon, J. Karpesky, and 9 more authors

   In Nuclei in the Cosmos XV (2019)

   Abstract Bib

   The origin of the p-nuclei, has been a long-standing puzzle in nuclear astrophysics. The νp-process is a candidate for the production of the light p-nuclei, but it presents high sensitivity to both supernova dynamics and nuclear physics. It has been recently shown that the breakout from pp-chains through the 7Be(α,γ)11C reaction, which occurs prior to νp-process, can significantly influence the reaction flow, and subsequently the production of p-nuclei in the 90<A<110 region. Nevertheless, this reaction has not been studied well yet in the relevant temperature range - T = 1.5–3 GK. To that end, the first direct study of important resonances of the 7Be(α,γ)11C reaction with unknown strengths using DRAGON was recently performed at TRIUMF. The reaction was studied in inverse kinematics using a radioactive 7Be (t1/2 = 53.24 d) beam provided by ISAC-I and two resonances above the 11C α-separation energy - Qα=7543.62 keV - were measured. The experimental details, in particular how the recoil transmission and BGO efficiencies were accounted for considering the large cone angle for this reaction, will be presented and discussed alongside some preliminary results.

   @inproceedings{Psaltis-NPA-XV,
     title = {Radiative Alpha Capture on 7Be with DRAGON at Energies Relevant to the νp-Process},
     author = {Psaltis, A and Chen, A.A and Connolly, D.S and Davids, B and Esker, N and Gilardy, G and Greife, U and Huang, W and Hutcheon, D.A and Karpesky, J and Lennarz, A and Liang, J and Lovely, M and Paneru, S.N and Giri, R and Ruiz, C and Tenkila, G and Wen, W and Williams, M},
     booktitle = {Nuclei in the Cosmos XV},
     pages = {425--428},
     year = {2019},
     publisher = {Springer},
     doi = {10.1007/978-3-030-13876-9_81}
   }

      
   
   
2. NIC XV

   First Radiative Proton-Capture Cross-Section Measurements in Mid-Weight Nuclei Relevant to the p-Process

   A. Psaltis, A. Khaliel, E-M. Assimakopoulou, A. Babounis, A. Kanellakopoulos, V. Lagaki, M. Lykiardopoulou, E. Malami, I. Psyrra, K. Zyriliou, and 1 more author

   In Nuclei in the Cosmos XV (2019)

   Abstract Bib

   One of the important, but still unsettled topics in Nuclear Astrophysicsis the production of thep-nuclei. Thep-process relies on an extended reactionnetwork, which can be described theoretically by the Hauser–Feshbach statisticalmodel, which in turn relies strongly on experimental data. To provide reliable dataforp-nuclei, an experimental campaign at the Tandem Accelerator Laboratory ofNCSR “Demokritos”, focusing on107,109Ag(p,γ)108,110Cd and112Cd(p,γ)113Inreaction cross-sections measurements was carried out. Both reactions were studiedusing a set of four HPGe detectors via the in-beamγ-ray spectroscopy, while for thelatter the activation method was additionally employed to account for the populationof a low-lying isomeric state. Total cross sections for proton beam energies lyinginside the Gamow window for energies relevant top-process nucleosynthesis wereobtained for the first time. Experimental results are compared to Hauser–Feshbachcalculations performed with the latest version of the TALYScode (v1.9). An overallgood agreement has been achieved. These results provide important new input forthe theoretical description of thep-process, but additionally for the origin of thecross-pointp-nucleus113In.

   @inproceedings{Psaltis-NIC-XV,
     title = {First Radiative Proton-Capture Cross-Section Measurements in Mid-Weight Nuclei Relevant to the p-Process},
     author = {Psaltis, A and Khaliel, A and Assimakopoulou, E-M and Babounis, A and Kanellakopoulos, A and Lagaki, V and Lykiardopoulou, M and Malami, E and Psyrra, I and Zyriliou, K and Mertzimekis, T.J},
     booktitle = {Nuclei in the Cosmos XV},
     pages = {421--424},
     year = {2019},
     publisher = {Springer},
     doi = {10.1007/978-3-030-13876-9_80}
   }

      
   
   
3. NIC XV

   Spectroscopic Study on 39Ca Using the 40Ca(d,t)39Ca Reaction for Classical Nova Endpoint Nucleosynthesis

   J. Liang, A.A. Chen, M. Anger, S. Bishop, T. Faestermann, C. Fry, R. Hertenberger, A. Psaltis, D. Seiler, P. Tiwari, and 2 more authors

   In Nuclei in the Cosmos XV (2019)

   Abstract Bib

   In classical novae simulations, the uncertainty in the reaction rate of 38K(p,γ) has been shown to affect the abundances of endpoint nuclides significantly. To better understand the reaction rate, we have done a spectroscopic study on 39Ca. The reaction 40Ca(d,t)39Ca at a beam energy of 22 MeV was used to populate excited states of 39Ca. Tritons were momentum analyzed using a high resolution quadrupole-dipole-dipole-dipole (Q3D) magnetic spectrograph at 4 angles. Preliminary resonance energies for 39Ca within the energetic region of interest for classical novae - 6.0–6.4 MeV - were determined.

   @inproceedings{Liang-NIC-XV,
     title = {Spectroscopic Study on 39Ca Using the 40Ca(d,t)39Ca Reaction for Classical Nova Endpoint Nucleosynthesis},
     author = {Liang, J and Chen, A.A and Anger, M and Bishop, S and Faestermann, T and Fry, C and Hertenberger, R and Psaltis, A and Seiler, D and Tiwari, P and Wirth, H.-F and Wrede, C},
     booktitle = {Nuclei in the Cosmos XV},
     pages = {397--400},
     year = {2019},
     publisher = {Springer},
     doi = {10.1007/978-3-030-13876-9_74}
   }

      
   
   
4. La Rábida 18

   Examining the Helium Cluster Decays of the 12Be Excited States by Triton Transfer to the 9Li Beam

   N. Vukman, N. Soić, P. Čolović, M. Uroić, M. Freer, T. Davinson, A. Di Pietro, M. Alcorta, D. Connolly, A. Lennarz, and 4 more authors

   In International Scientific Meeting on Nuclear Physics-Basic concepts in Nuclear Physics: theory, experiments, and applications (2019)

   Abstract Bib

   We present the first results of the experiment: “Examining the helium cluster decays of the 12Be excited states by triton transfer to the 9Li beam” (spokespersons: N. Soić, M. Freer), done at TRIUMF, Vancouver, CA, with the main goal of providing precise experimental data on the internal structure of the 12Be excited states.

   @inproceedings{Vukman-Rabida,
     title = {Examining the Helium Cluster Decays of the 12Be Excited States by Triton Transfer to the 9Li Beam},
     author = {Vukman, N and Soi{\'c}, N and {\v{C}}olovi{\'c}, P and Uroi{\'c}, M and Freer, M and Davinson, T and Di Pietro, A and Alcorta, M and Connolly, D and Lennarz, A and Ruiz, C and Shotter, A and Williams, W and Psaltis, A},
     booktitle = {International Scientific Meeting on Nuclear Physics-Basic concepts in Nuclear Physics: theory, experiments, and applications},
     pages = {257--258},
     year = {2019},
     organization = {Springer},
     doi = {10.1007%2F978-3-030-22204-8\_43}
   }

      
   
   

Journal Articles (2018)

Conference Proceedings (2018)

1. Santa Tecla

   Isomeric 26Al beam production with CRIB

   H. Shimizu, D. Kahl, H. Yamaguchi, K. Abe, O. Beliuskina, S.M. Cha, K.Y. Chae, A.A. Chen, Z. Ge, S. Hayakawa, and 16 more authors

   In EPJ Web of Conferences (2018)

   Abstract Bib

   We performed an experiment to measure proton resonant elastic scattering of a mixed 26m,gAl beam with a thick target in inverse kinematics by using CNS RI beam separator, located at RIKEN Nishina Center. It aimed to search for strong proton resonances and determine level properties of low spin-parity states in 27Si. Diagnosis of the 26mAl purity of the beam by annihilation radiation are discussed.

   @inproceedings{Shimizu-Santa-Tecla,
     title = {Isomeric 26Al beam production with CRIB},
     author = {Shimizu, H and Kahl, D and Yamaguchi, H and Abe, K and Beliuskina, O and Cha, S.M and Chae, K.Y and Chen, A.A and Ge, Z and Hayakawa, S and Imai, N and Iwasa, N and Kim, A and Kim, D.H and Kim, M.J and Kubono, S and Kwag, M.S and Liang, J and Moon, J.Y and Nishimura, S and Oka, S and Park, S.Y and Psaltis, A and Teranishi, T and Ueno, Y and Yang, L},
     booktitle = {EPJ Web of Conferences},
     volume = {184},
     pages = {02013},
     year = {2018},
     organization = {EDP Sciences},
     doi = {10.1051/epjconf/201818402013}
   }

      
   
   
2. OMEG 2017

   Impact of the 26mAl(p, γ) reaction to galactic 26Al yield

   D. Kahl, H. Shimizu, H. Yamaguchi, K. Abe, O. Beliuskina, S.M. Cha, K.Y. Chae, A.A. Chen, Z. Ge, S. Hayakawa, and 16 more authors

   In AIP Conference Proceedings (2018)

   Abstract Bib

   Astrophysical observables that are directly linked to nuclear physics inputs provide critical and stringent constraints on nucleosynthetic models. As 26Al was the first specific radioactivity observed in the Galaxy, its origin has fascinated the nuclear astrophysics community for nearly forty years. Despite extensive research, the precise origins of 26Al remain elusive. At present, the sum of all putative stellar contributions generally overestimates the 26Al mass in the interstellar medium. Among the many reactions that influence the yield of 26Al, radiative proton capture on its isomer 26mAl is one of the least constrained reactions by experimental data. To this end, we developed a 26Al isomeric beam and performed proton elastic scattering to search for low-spin states in 27Si. The experimental method and the preliminary results of this on-going study will be presented.

   @inproceedings{Kahl-OMEG,
     title = {Impact of the 26mAl(p, $\gamma$) reaction to galactic 26Al yield},
     author = {Kahl, D and Shimizu, H and Yamaguchi, H and Abe, K and Beliuskina, O and Cha, S.M and Chae, K.Y and Chen, A.A and Ge, Z and Hayakawa, S and and Imai, N and Iwasa, N and Kim, A and Kim, D.H and Kim, M.J and Kubono, S and Kwag, M.S and Liang, J and Moon, J.Y and Nishimura, S and Oka, S and Park, S.Y and Psaltis, A and Teranishi, T and Ueno, Y and Yang, L},
     booktitle = {AIP Conference Proceedings},
     volume = {1947},
     number = {1},
     pages = {020003},
     year = {2018},
     organization = {AIP Publishing LLC},
     doi = {10.1063/1.5030807}
   }

      
   
   

Journal Articles (2017)

1. PRC

   First cross-section measurements of the reactions 107,109Ag(p, γ)108,110Cd at energies relevant to the p process

   A. Khaliel, T.J. Mertzimekis, E.-M. Asimakopoulou, A. Kanellakopoulos, V. Lagaki, A. Psaltis, I. Psyrra, and E. Mavrommatis

   Physical Review C (2017)

   Abstract Bib

   Background: One of the primary objectives of the field of Nuclear Astrophysics is the study of the elemental and isotopic abundances in the universe. Although significant progress has been made in understanding the mechanisms behind the production of a large number of nuclides in the isotopic chart, there are still many open questions regarding a number of neutron-deficient nuclei, the p nuclei. To that end, experimentally deduced nuclear reaction cross sections can provide invaluable input to astrophysical models. Purpose: The reactions 107,109Ag(p,γ)108,110Cd have been studied at energies inside the astrophysically relevant energy window in an attempt to provide experimental data required for the testing of reaction-rate predictions in terms of the statistical model of Hauser-Feshbach around the p nucleus 108Cd. Methods: The experiments were performed with in-beam γ-ray spectroscopy with proton beams accelerated by the Tandem Van de Graaff Accelerator at NCSR “Demokritos” impinging a target of natural silver. A set of high-purity germanium detectors was employed to record the emitted radiation. Results: A first set of total cross-section measurements in radiative proton-capture reactions involving 107,109Ag, producing the p-nucleus 108Cd, inside the astrophysically relevant energy window is reported. The experimental results are compared to theoretical calculations, using talys. An overall good agreement between the data and the theoretical calculations has been found. Conclusions: The results reported in this work add new information to the relatively unexplored p process. The present measurements can serve as a reference point in understanding the nuclear parameters in the related astrophysical environments and for future theoretical modeling and experimental works.

   @article{KhalielPRC2017,
     title = {First cross-section measurements of the reactions 107,109Ag(p, $\gamma$)108,110Cd at energies relevant to the p process},
     author = {Khaliel, A and Mertzimekis, T.J and Asimakopoulou, E.-M and Kanellakopoulos, A and Lagaki, V and Psaltis, A and Psyrra, I and Mavrommatis, E},
     journal = {Physical Review C},
     volume = {96},
     number = {3},
     pages = {035806},
     year = {2017},
     publisher = {APS},
     doi = {10.1103/PhysRevC.96.035806}
   }

      
   
   

Conference Proceedings (2017)

1. NPA8

   Isomer beam elastic scattering: 26mAl(p, p) for astrophysics

   D. Kahl, H. Shimizu, H. Yamaguchi, K. Abe, O. Beliuskina, S.M. Cha, K.Y. Chae, A.A. Chen, Z. Ge, S. Hayakawa, and 16 more authors

   In EPJ Web of Conferences (2017)

   Abstract Bib

   The advent of radioactive ground-state beams some three decades ago ultimately sparked a revolution in our understanding of nuclear physics. However, studies with radioactive isomer beams are sparse and have often required sophisticated apparatuses coupled with the technologies of ground-state beams due to typical mass differences on the order of hundreds of keV and vastly different lifetimes for isomers. We present an application of a isomeric beam of 26mAl to one of the most famous observables in nuclear astrophysics: galactic 26Al. The characteristic decay of 26Al in the Galaxy was the first such specific radioactivity to be observed originating from outside the Earth some four decades ago. We present a newly-developed, novel technique to probe the structure of low-spin states in 27Si. Using the Center for Nuclear Study low-energy radioisotope beam separator (CRIB), we report on the measurement of 26mAl proton resonant elastic scattering conducted with a thick target in inverse kinematics. The preliminary results of this on-going study are presented.

   @inproceedings{Kahl-NPA8,
     title = {Isomer beam elastic scattering: 26mAl(p, p) for astrophysics},
     author = {Kahl, D and Shimizu, H and Yamaguchi, H and Abe, K and Beliuskina, O and Cha, S.M and Chae, K.Y and Chen, A.A and Ge, Z and Hayakawa, S and Imai, N and Iwasa, N and Kim, A and Kim, D.H and Kim, M.J and Kubono, S and Kwag, M.S and Liang, J and Moon, J.Y and Nishimura, S and Oka, S and Park, S.Y and Psaltis, A and Teranishi, T and Ueno, Y and Yang, L},
     booktitle = {EPJ Web of Conferences},
     volume = {165},
     pages = {01030},
     year = {2017},
     organization = {EDP Sciences},
     doi = {10.1051/epjconf/201716501030}
   }

      
   
   

Journal Articles (2016)

1. NIM A

   An online database of nuclear electromagnetic moments

   T.J. Mertzimekis, K. Stamou, and A. Psaltis

   Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (2016)

   Abstract Bib

   Measurements of nuclear magnetic dipole and electric quadrupole moments are considered quite important for the understanding of nuclear structure both near and far from the valley of stability. The recent advent of radioactive beams has resulted in a plethora of new, continuously flowing, experimental data on nuclear structure – including nuclear moments – which hinders the information management. A new, dedicated, public and user friendly online database (http://magneticmoments.info) has been created comprising experimental data of nuclear electromagnetic moments. The present database supersedes existing printed compilations, including also non-evaluated series of data and relevant meta-data, while putting strong emphasis on bimonthly updates. The scope, features and extensions of the database are reported.

   @article{MertzimekisNIMA2016,
     title = {An online database of nuclear electromagnetic moments},
     author = {Mertzimekis, T.J and Stamou, K and Psaltis, A},
     journal = {Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment},
     volume = {807},
     pages = {56--60},
     year = {2016},
     publisher = {Elsevier},
     doi = {10.1016/j.nima.2015.10.096}
   }

      
   
   

Conference Proceedings (2016)