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Xu, X. D. et al, & Cortina-Gil, D. (2025). Isospin Symmetry Breaking Disclosed in the Decay of Three-Proton Emitter 20Al. Phys. Rev. Lett., 135(2), 022502–9pp.
Abstract: The previously unknown nucleus 20Al has been observed for the first time by detecting its in-flight decays. Tracking trajectories of all decay products with silicon microstrip detectors allowed for a conclusion that 20Al is unbound with respect to three-proton (3p) emission. The 3p-decay energy of the 20Al ground state has been determined to be 1.93(+0.12-0.10) MeV through a detailed study of angular correlations of its decay products, 17Ne + p + p + p. This value is significantly smaller than the predictions inferred from the isospin symmetry by using the known neutron separation energy of its mirror nucleus 20N, which indicates a possible isospin symmetry breaking in the mirror nuclei 20Al and 20N. This observed isospin symmetry breaking is supported by the calculations of the continuum embedded theoretical frameworks, describing the observed 20Al ground state as a 1p s-wave state with a spin-parity of 1-, which differs from the spin-parity (2-) of the 20N ground state. The 20Al ground state decays by sequential 1p-2p emission via the intermediate ground state of 19Mg, which is the first observed case of “daughter” 2p radioactivity following 1p decay of the parent state.
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Karan, A., Leite, J., & Valle, J. W. F. (2025). Flavor-changing axions and Dirac neutrino masses. Phys. Rev. D, 111(11), 115023–18pp.
Abstract: Implementing the axion concept in the context of 3-3-1 extensions of the Standard Model leads to richer properties than in the simpler axion setups, and they are related to the Dirac neutrino seesaw mechanism. In this way, the smallness of neutrino masses, the strong CP problem, the nature of dark matter, and the number of families all have a common origin. Besides having an enhanced coupling to photons, our revamped axion can also be distinguished from both Dine-Fischler-Srednicki-Zhitnisky and Kim-Shifman-Vainshtein-Zakharov axions through its couplings to fermions. The latter lead to interesting phenomenological consequences, including flavor-changing axion-emitting two-body K, B, and D meson decays.
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Garcia-Cely, C., Marsili, L., Ringwald, A., & Spector, A. D. (2025). Polarimetric searches for axion dark matter and high-frequency gravitational waves using optical cavities. Phys. Rev. D, 112(2), 023031–20pp.
Abstract: We revisit birefringence effects associated with the evolution of the polarization of light as it propagates through axion dark matter or the background of a passing gravitational wave (GW). We demonstrate that this can be described by a unified formalism, highlighting a synergy between searches for axions and high-frequency GWs. We show that by exploiting this framework, the optical cavities used by the ALPS II experiment can potentially probe axion masses in the range ma similar to 10-9-10-6 eV, offering competitive sensitivity with existing laboratory and astrophysical searches. Also building on this approach, we propose using these optical cavities to search for high-frequency GWs by measuring changes in the polarization of their circulating laser fields. This makes it a promising method for exploring, in the near future, GWs with frequencies above 100 MHz and strain sensitivities on the order of 10-14 Hz-1/2. Such sensitivity allows the exploration of currently unconstrained parameter space, complementing other high-frequency GW experiments. This work contributes to the growing community investigating novel approaches for high-frequency GW detection.
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Grinstein, B., Lu, X. C., Miro, C., & Quílez, P. (2025). Most general EFTs from spurion analysis Hilbert series and minimal lepton flavor violation. J. High Energy Phys., 07(7), 259–41pp.
Abstract: We derive a saturation theorem for general Effective Field Theories (EFTs) constructed using spurion analysis. Let S be a set of spurion fields introduced to organize the breaking of a global symmetry Gf, and HS be the subgroup of Gf that remains unbroken under a generic vacuum expectation value < S >; we show that the EFT Lagrangian constructed from the spurion analysis saturates the EFT Lagrangian without the spurions but restricted to HS invariance, provided that arbitrary powers of the spurion fields are allowed. As examples, we study several implementations of the Minimal Lepton Flavor Violation (MLFV) principle, corresponding to various origins of the neutrino masses. In each scenario, we compute the Hilbert series to obtain the numbers of independent lepton flavor covariants that appear in the corresponding EFT at mass dimension 6. These numbers agree with the number of HS invariants in the EFT without the spurions, demonstrating the saturation theorem. Motivated by phenomenological connections, we provide linearly independent spurion polynomials for selected lepton flavor covariants. A supplementary material file supplies , a Mathematica notebook that provides functions for computing general Hilbert series of invariants and covariants of compact classical groups. It presents examples demonstrating the use of the code, including the Hilbert series for our MLFV scenarios.
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De Romeri, V., Donato, F., Maurin, D., Stefanuto, L., & Tolino, A. (2025). Antinuclei from primordial black holes. Phys. Rev. D, 112(2), 023003–16pp.
Abstract: Light primordial black holes (PBHs) may have originated in the early Universe, and could contribute to the dark matter in the Universe. Their Hawking evaporation into particles could eventually lead to the production of antinuclei, which propagate and arrive at Earth as cosmic rays with a flux peaked at GeV energies. We revisit here the antiproton and antideuteron signatures from PBH evaporation, relying on a lognormal PBH mass distribution, state-of-the-art propagation models, and an improved coalescence model for fusion into antideuterons. Our predictions are then compared with AntiMatter Spectrometer (AMS)-02 data on the antiproton flux. We find that the AMS-02 antiproton data severely constrain the Galactic PBH density, setting bounds that depend significantly on the parameters of the lognormal mass distribution, and that are comparable to or slightly stronger than bounds set from diverse messengers. We also discuss prospects for future detection of antideuterons. Given the bounds from AMS-02 antiproton data, we predict that if antideuterons were to be measured by AMS-02 or General Antiparticle Spectrometer, since the secondary contribution is subdominant, they would clearly be a signal of new physics, only part of which could, however, be explained by PBH evaporation.
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