Cheng, Y., Csernai, L. P., Magas, V. K., Schlei, B. R., & Strottman, D. (2010). Matching stages of heavy-ion collision models. Phys. Rev. C, 81(6), 064910–8pp.
Abstract: Heavy-ion reactions and other collective dynamical processes are frequently described by different theoretical approaches for the different stages of the process, like initial equilibration stage, intermediate locally equilibrated fluid dynamical stage, and final freeze-out stage. For the last stage, the best known is the Cooper-Frye description used to generate the phase space distribution of emitted, noninteracting particles from a fluid dynamical expansion or explosion, assuming a final ideal gas distribution, or (less frequently) an out-of-equilibrium distribution. In this work we do not want to replace the Cooper-Frye description, but rather clarify the ways of using it and how to choose the parameters of the distribution and, eventually, how to choose the form of the phase space distribution used in the Cooper-Frye formula. Moreover, the Cooper-Frye formula is used in connection with the freeze-out problem, while the discussion of transition between different stages of the collision is applicable to other transitions also. More recently, hadronization and molecular dynamics models have been matched to the end of a fluid dynamical stage to describe hadronization and freeze-out. The stages of the model description can be matched to each other on space-time hypersurfaces (just like through the frequently used freeze-out hypersurface). This work presents a generalized description of how to match the stages of the description of a reaction to each other, extending the methodology used at freeze-out, in simple covariant form which is easily applicable in its simplest version for most applications.
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IDS collaboration(Llanos-Exposito, M. et al), Algora, A., & Nacher, E. (2025). Structure of 128Sn selectively populated in the β decay of the 128In ground state. Phys. Rev. C, 111(6), 064310–13pp.
Abstract: High-resolution gamma-ray spectroscopy and fast-timing methods were employed to study the excited structure of 128Sn, populated via the beta-decay chain of 128Cd -> 128In -> 128Sn. The experiment was performed by online mass separation at the ISOLDE facility at CERN, profiting from intense and pure Cd beams obtained by a temperature-controlled quartz transfer line combined with resonant laser ionization. An extended 128Sn level scheme populated in the beta – decay of the low-spin 128In isomer was constructed, adding a total of 81 new gamma-ray transitions and 30 new levels. Lifetimes of excited states were measured using time-delayed beta gamma (t) and gamma gamma (t) coincidences. The lifetime of the (4+) state was measured for the first time, making it possible to deduce the B(E 2; 4+ -> 2+) transition strength. The previously measured (5-) state was reassessed with improved statistics. Additionally, an upper limit for the lifetime of the state at 2378 keV was established. The derived reduced transition probabilities support a tentative spin-parity assignment of (4-) for this level. The experimental level scheme and transition probabilities are compared with available shell-model calculations.
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AGATA Collaboration(Soderstrom, P. A. et al), & Gadea, A. (2012). High-spin structure in K-40. Phys. Rev. C, 86(5), 054320–9pp.
Abstract: High-spin states of K-40 have been populated in the fusion-evaporation reaction C-12(Si-30,np)K-40 and studied by means of gamma-ray spectroscopy techniques using one triple-cluster detector of the Advanced Gamma Tracking Array at the Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Legnaro. Several states with excitation energy up to 8 MeV and spin up to 10(-) have been discovered. These states are discussed in terms of J = 3 and T = 0 neutron-proton hole pairs. Shell-model calculations in a large model space have shown good agreement with the experimental data for most of the energy levels. The evolution of the structure of this nucleus is here studied as a function of excitation energy and angular momentum.
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Blank, B. et al, Agramunt, J., Algora, A., Guadilla, V., Montaner-Piza, A., Morales, A. I., et al. (2016). New neutron-deficient isotopes from Kr-78 fragmentation. Phys. Rev. C, 93(6), 061301–5pp.
Abstract: In an experiment with the RIKEN projectile fragment separator called BigRIPS at the RIKEN Nishina Center, the fragmentation of a Kr-78 beam allowed the observation of new neutron-deficient isotopes at the proton drip line. Clean identification spectra could be produced and Se-63, Kr-67, and Kr-68 were identified for the first time. In addition, Ge-59 was also observed. Three of these isotopes, Ge-59, Se-63, and Kr-67, are potential candidates for ground-state two-proton radioactivity. In addition, the isotopes Ge-58, Se-62, and Kr-66 were also sought but without success. The present experiment also allowed the determination of production cross sections for some of the most exotic isotopes. These measurements confirm the trend already observed that the empirical parametrization of fragmentation cross sections, EPAX, significantly overestimates experimental cross sections in this mass region.
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Guadilla, V. et al, Tain, J. L., Algora, A., Agramunt, J., Jordan, D., Monserrate, M., et al. (2020). Determination of beta-decay ground state feeding of nuclei of importance for reactor applications. Phys. Rev. C, 102(6), 064304–12pp.
Abstract: In beta-decay studies the determination of the decay probability to the ground state (g.s.) of the daughter nucleus often suffers from large systematic errors. The difficulty of the measurement is related to the absence of associated delayed gamma-ray emission. In this work we revisit the 4 pi gamma – beta method proposed by Greenwood and collaborators in the 1990s, which has the potential to overcome some of the experimental difficulties. Our interest is driven by the need to determine accurately the beta-intensity distributions of fission products that contribute significantly to the reactor decay heat and to the antineutrinos emitted by reactors. A number of such decays have large g.s. branches. The method is relevant for nuclear structure studies as well. Pertinent formulas are revised and extended to the special case of beta-delayed neutron emitters, and the robustness of the method is demonstrated with synthetic data. We apply it to a number of measured decays that serve as test cases and discuss the features of the method. Finally, we obtain g.s. feeding intensities with reduced uncertainty for four relevant decays that will allow future improvements in antineutrino spectrum and decay heat calculations using the summation method.
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