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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Batra, A., Câmara, H. B., Joaquim, F. R., Nath, N., Srivastava, R., & Valle, J. W. F. (2025). Axion framework with color-mediated Dirac neutrino masses. Phys. Lett. B, 868, 139629–11pp.
Abstract: We propose a KSVZ-type axion framework in which vector-like quarks (VLQ) and colored scalars generate Dirac neutrino masses radiatively. The global Peccei-Quinn symmetry (under which the exotic fermions are charged) addresses the strong CP problem and ensures the Dirac nature of neutrinos. The axion also accounts for the observed cosmological dark matter. We systematically explore all viable VLQ representations. Depending on the specific scenario, the framework predicts distinct axion-to-photon couplings, testable through haloscope and helioscope experiments, as well as potentially significant flavor-violating quark-axion interactions.
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Gao, F., Miramontes, A. S., Papavassiliou, J., & Pawlowski, J. M. (2025). Heavy-light mesons from a flavour-dependent interaction. Phys. Lett. B, 863, 139384–8pp.
Abstract: We introduce a new framework for the physics of heavy-light mesons, whose key element is the effective incorporation of flavour-dependent contributions into the corresponding bound-state and quark gap equations. These terms originate from the fully-dressed quark-gluon vertices appearing in the kernels of these equations, and provide a natural distinction between “light” and “heavy” quarks. In this approach, only the classical form factor of the quark-gluon vertex is retained, and is evaluated in the so-called “symmetric” configuration. The standard Slavnov-Taylor identity links this form factor to the quark wave-function, allowing for the continuous transition from light to heavy quarks through the mere variation of the current quark mass in the gap equation. The method is used to compute the masses and decay constants of specific pseudoscalars and vector heavy-light systems, showing good overall agreement with both experimental data and lattice simulations.
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