Zhang, G. et al, Algora, A., Nacher, E., Orrigo, S. E. A., Perez-Vidal, R. M., & Rubio, B. (2025). Approaching 100Sn: Structural evolution in 98,100Cd via lifetime measurements. Phys. Lett. B, 863, 139378–7pp.
Abstract: The lifetimes of low-lying excited states below the 8(+) seniority isomer were directly measured using fast timing detectors in the neutron-deficient isotopes Cd-98,Cd-100. This experiment was conducted with the DEcay SPECtroscopy (DESPEC) setup at GSI, where the ions of interest were produced via a fragmentation reaction and identified using the FRagment Separator (FRS) before being implanted in the AIDA active stopper system, and the gamma rays emitted during the de-excitation of isomeric states were detected by the LaBr3 FATIMA Array. The newly deduced values for the reduced transition probabilities were compared with shell-model calculations using different interactions and effective charges. The results indicate that, while Cd-98 aligns well with a seniority scheme description, in Cd-100 the transition strengths among low-lying states are not fully reproduced, and the nature of these states remains an open problem within the present theoretical description. Ultimately, a key element in the description of this region, crucial for nuclear physics and astrophysics, appears to be the proton-neutron term of the nuclear effective interaction.
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Alicki, R., Barenboim, G., & Jenkins, A. (2025). The irreversible relaxation of inflation. Phys. Lett. B, 866, 139519–6pp.
Abstract: Based on the results of a previous analysis of the Markovian master equation for the irreversible evolution of an open system embedded in de Sitter space [7], we include in the cosmological Friedmann equations a contribution from the presence of a physical bath at temperature T-dS = h//2 pi, where h is the Hubble parameter. We show that this provides a mechanism for the irreversible relaxation of the cosmological constant and a graceful exit to inflation, without need for subsequent reheating. Thermal particle production during inflation gives adiabatic, Gaussian, and approximately scale-invariant cosmological perturbations. We thus obtain the main features of inflation without any inflaton potential. To clarify the thermodynamic interpretation of these results, we consider the analogy of this irreversible relaxation to superfluorescence in quantum optics.
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IDS Collaboration(Olaizola, B. et al), Algora, A., & Nacher, E. (2025). The 76Cu conundrum remains unsolved. Phys. Lett. B, 866, 139551–8pp.
Abstract: Near the doubly-magic nucleus Ni-78 (Z = 28, N = 50), there has been a decades-long debate on the existence of a long-lived isomer in Cu-76. A recent mass measurement claimed to have settled the debate, by measuring the energy of the isomer and shedding light on the structure of the nucleus. In this work, we present new, more accurate, and precise values of the half-lives of the isomeric and ground states in Cu-76. Our findings suggest that both states have very similar half-lives, in the 600-700 ms range, in disagreement with the literature values, implying that they cannot be differentiated by their decay curves. These results raise more questions than they answer, reopening the debate and showing that the structures in Cu-76 are still not fully understood.
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Albaladejo, M., Canoa, A., Nieves, J., Pelaez, J. R., Ruiz Arriola, E., & Ruiz de Elvira, J. (2025). The role of chiral symmetry and the non-ordinary κ/K*0(700) nature in π±KS femtoscopic correlations. Phys. Lett. B, 866, 139552–5pp.
Abstract: We show that the use of realistic pi K interactions, obtained from a dispersive analysis of scattering data, as well as relativistic corrections, are essential to describe recently observed pi +/- KS femtoscopic correlations. We demonstrate that the spontaneous chiral symmetry breaking dynamics and the non-ordinary features of the kappa/K0*(700)resonance, together with large cancellations between isospin channels, produce a large suppression of pi +/- KS femtoscopic correlations compared to widely used models. Within an improved version of the standard on-shell factorization formalism, we illustrate that compensating for this interaction suppression leads to source radii smaller than 1 fm, contrary to usual expectations, as well as larger correlation strengths. The relation between these two parameters cannot be accommodated within naive models describing the nature of the resonances. This may raise concerns about the applicability of popular but too simple approaches for systems with light mesons. However, the correlation-suppression effects we demonstrate here will be relevant in any formalism, and substantial corrections may be expected for other femtoscopic systems involving light mesons.
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Zhang, X. Y., Shi, P. P., & Guo, F. K. (2025). Production of 1-+ exotic charmonium-like states in electron-positron collisions. Phys. Lett. B, 867, 139603–8pp.
Abstract: The absence of observed charmonium-like states with the exotic quantum numbers J=1+ has prompted us to investigate the production rates of the 1 DD, (2420) and D D, (2420) hadronic molecules, which we refer to as n and, respectively, in electron-positron collisions. Assuming a hadronic molecular nature for the vector charmonium-like states (4360) and yr(4415), we evaluate the radiative decay widths of (4360)-> 77 and (4415) yn. Using these decay widths, we estimate the cross sections for producing, and, in electron-positron annihilations, as well as the event numbers at the planned Super r-Charm Facility. Our results suggest that the ideal energy region for observing these states is around 4.44 and 4.50 GeV, just above the D D (2420) and D D (2460) thresholds, respectively.
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