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Fujita, Y., Rubio, B., Adachi, T., Blank, B., Fujita, H., Gelletly, W., et al. (2015). Gamow-Teller excitations studied by weak and strong interactions. Acta Phys. Pol. B, 46(3), 657–668.
Abstract: Studying weak nuclear responses, especially the Gamow-Teller (GT) transitions starting from stable as well as unstable nuclei, provide crucial and critical information on nuclear structure. Therefore, the study of GT transitions is a key issue in nuclear physics and also nuclear-astrophysics. Under the assumption of isospin symmetry, it is expected that the structure of mirror nuclei and the GT transitions starting from their ground states are identical. We have studied the corresponding GT transitions starting from T-z = +/- 1 and +/- 2 p f -shell nuclei, respectively, by means of hadronic (He-3,t) charge-exchange reactions and mirror beta decays. The results on GT strength distributions measured in beta decays and (He-3,t) reactions performed at an intermediate incident energy of 140 MeV/nucleon and 0 degrees are compared. The combined results help provide an understanding of nuclear structure of nuclei far-from-stability.
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Orrigo, S. E. A. et al, Rubio, B., Agramunt, J., Algora, A., & Molina, F. (2015). β-delayed γ-proton decay in 56Zn: analysis of the charged-particle spectrum. Acta Phys. Pol. B, 46(3), 709–712.
Abstract: A study of the beta decay of the proton-rich T-z = 2 nucleus Zn-56 has been reported in a recent publication. A rare and exotic decay mode, beta-delayed gamma-proton decay, has been observed there for the first time in the fp shell. Here, we expand on some of the details of the data analysis, focussing on the charged particle spectrum.
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IGISOL Collaboration(Briz, J. A. et al), Algora, A., Tain, J. L., Guadilla, V., Agramunt, J., Estevez, E., et al. (2016). Total absorption spectroscopy of fission fragments relevant for reactor antineutrino spectra determination. Acta Phys. Pol. B, 47(3), 755–762.
Abstract: The contribution of each fission fragment to the reactor antineutrino spectra was determined using the summation method based on the existing information on fission yields and decay data contained in nuclear databases and the reactor evolution code MURE. The beta decay of some of the main contributors has been studied using the Total Absorption Spectroscopy (TAS) technique during two experimental campaigns at the IGISOL facility, in Jyvaskyla (Finland). Results on the decay of Rb-92, the most important contributor in the 4-8 MeV energy region are reported. The status of the analysis of the second experiment is presented as well.
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Fujita, Y., Rubio, B., Molina, F., Adachi, T., Fujita, H., Blank, B., et al. (2016). The Tz = ±1 → 0 and ±2 →±1 Mirror Gamow–Teller transitions in pf-shell nuclei. Acta Phys. Pol. B, 47(3), 867–881.
Abstract: Gamow-Teller (GT) transitions are the most common weak-interaction processes in the Universe. They play important roles in various processes of nucleosynthesis, for example, in the rapid proton-capture process (rp-process). In the pf-shell region, the rp-process runs through neutron-deficient nuclei with T-z = -2, -1, and 0 mainly by means of GT and Fermi transitions, where T-z is the z component of isospin T defined by T-z = (N = Z)/2. Under the assumption of isospin symmetry, mirror nuclei with reversed Z and N numbers, and thus with opposite signs of T-z, have the same structure. Therefore, symmetry is also expected for the GT transitions starting from and ending up in mirror nuclei. We have been studying the T-z = -2 -> -1 and -1 -> 0 GT transitions in beta decays, while those from stable T-z = +2 and +1 nuclei by means of hadronic (He-3; t) charge-exchange (CE) reactions. The results from these studies are compared in order to examine the mirror-symmetry structure in nuclei. In addition, these results are combined for the better understanding of GT transitions in the pf-shell region.
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Kiss, G. G. et al, Tarifeño-Saldivia, A., Tain, J. L., Agramunt, J., Algora, A., Domingo-Pardo, C., et al. (2022). Measuring the beta-decay Properties of Neutron-rich Exotic Pm, Sm, Eu, and Gd Isotopes to Constrain the Nucleosynthesis Yields in the Rare-earth Region. Astrophys. J., 936(2), 107–18pp.
Abstract: The beta-delayed neutron-emission probabilities of 28 exotic neutron-rich isotopes of Pm, Sm, Eu, and Gd were measured for the first time at RIKEN Nishina Center using the Advanced Implantation Detector Array (AIDA) and the BRIKEN neutron detector array. The existing beta-decay half-life (T (1/2)) database was significantly increased toward more neutron-rich isotopes, and uncertainties for previously measured values were decreased. The new data not only constrain the theoretical predictions of half-lives and beta-delayed neutron-emission probabilities, but also allow for probing the mechanisms of formation of the high-mass wing of the rare-earth peak located at A approximate to 160 in the r-process abundance distribution through astrophysical reaction network calculations. An uncertainty quantification of the calculated abundance patterns with the new data shows a reduction of the uncertainty in the rare-earth peak region. The newly introduced variance-based sensitivity analysis method offers valuable insight into the influence of important nuclear physics inputs on the calculated abundance patterns. The analysis has identified the half-lives of Sm-168 and of several gadolinium isotopes as some of the key variables among the current experimental data to understand the remaining abundance uncertainty at A = 167-172.
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