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Davesne, D., Navarro, J., Pastore, A., & Lallouet, Y. (2025). Isovector properties of effective finite-range nuclear interactions. Eur. Phys. J. A, 61(2), 28–23pp.
Abstract: We discuss several properties of two families of finite-range interactions in infinite nuclear matter, aiming in particular to their isovector properties. We find that the recent parameterisations of both Gogny and Nakada provide a reasonable description of the properties of the infinite medium as well as an equation of state capable of sustaining a two solar mass neutron star. We also discuss the pairing properties in the spin-singlet channel for both families of interactions.
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LHCb Collaboration(Aaij, R. et al), Fernandez Casani, A., Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., et al. (2025). Long-lived particle reconstruction downstream of the LHCb magnet. Eur. Phys. J. C, 85(1), 7–30pp.
Abstract: Charged-particle trajectories are usually reconstructed with the LHCb detector using combined information from the tracking devices placed upstream and downstream of the 4 T m dipole magnet. Trajectories reconstructed using only information from the tracker downstream of the dipole magnet, which are referred to as T tracks, have not been used for physics analysis to date. The challenges of the reconstruction of long-lived particles with T tracks for physics use are discussed and solutions are proposed. The feasibility and the tracking performance are studied using samples of long-lived Lambda and K-S(0) hadrons decaying between 6.0 and 7.6 m downstream of the proton-proton collision point, thereby traversing most of the magnetic field region and providing maximal sensitivity to magnetic and electric dipole moments. The reconstruction can be expanded upstream to about 2.5 m for use in direct searches of exotic long-lived particles. The data used in this analysis have been recorded between 2015 and 2018 and correspond to an integrated luminosity of 6 fb(-1). The results obtained demonstrate the possibility to further extend the decay volume and the physics reach of the LHCb experiment.
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Calderon Bustillo, J., del Rio, A., Sanchis-Gual, N., Chandra, K., & Leong, S. H. W. (2025). Testing Mirror Symmetry in the Universe with LIGO-Virgo Black-Hole Mergers. Phys. Rev. Lett., 134(3), 031402–10pp.
Abstract: Certain precessing black-hole mergers produce gravitational waves with net circular polarization, understood as an imbalance between right- and left-handed amplitudes. According to the cosmological principle, such emission must average to zero across all binary mergers in our Universe to preserve mirrorreflection symmetry at very large scales. We present a new independent gravitational-wave test of this hypothesis. Using a novel observable based on the Chern-Pontryagin pseudoscalar, we measure the emission of net circular polarization across 47 black-hole mergers recently analyzed by [T. Islam et al., arXiv:2309.14473.] with a state-of-the art model for precessing black-hole mergers in general relativity. The average value obtained is consistent with zero. Remarkably, however, we find that at least 82% of the analyzed sources must have produced net circular polarization. Of these, GW200129 shows strong evidence for mirror asymmetry, with a Bayes factor of 12.6 or, equivalently, 93.1% probability. We obtain consistent (although stronger) results of 97.5% and 94.3%, respectively, using public results on this event from [M. Hannam et al., Nature (London) 610, 652 (2022).] and performing our own parameter inference. This finding further implies evidence of astrophysical sources that can spontaneously emit circularly polarized photons by quantum effects. Forthcoming black-hole merger detections will enable stronger constraints on large-scale mirror asymmetry and the cosmological principle.
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Ding, G. J., & Valle, J. W. F. (2025). The symmetry approach to quark and lepton masses and mixing. Phys. Rep., 1109, 1–105.
Abstract: The Standard Model lacks an organizing principle to describe quark and lepton “flavours”. Neutrino oscillation experiments show that leptons mix very differently from quarks, adding a major challenge to the flavour puzzle. We briefly sketch the seesaw and the dark-matter-mediated “scotogenic” neutrino mass generation approaches. We discuss the limitations of popular neutrino mixing patterns and examine the possibility that they arise from symmetry, giving a bottom-up approach to residual flavour and CP symmetries. We show how such family and/or CP symmetries can yield novel, viable and predictive mixing patterns. Model-independent ways to predict lepton mixing and neutrino mass sum rules are reviewed. We also discuss UV-complete flavour theories in four and more space-time dimensions. As benchmark examples we present an A4 scotogenic construction with trimaximal mixing pattern TM2 and another with S4 flavour symmetry and generalized CP symmetry. Higher-dimensional flavour completions are also briefly discussed, such as 5-D warped flavordynamics with a T ' symmetry yielding a TM1 mixing pattern, detectable neutrinoless double beta decay rates and a very good global fit of flavour observables. We also mention 6-D orbifolds as a way to fix the structure of the 4-D family symmetry. We give a scotogenic benchmark orbifold model predicting the "golden'' quark-lepton mass relation, stringent neutrino oscillation parameter regions, and an excellent global flavour fit, including quark observables. Finally, we discuss promising recent progress in tackling the flavour issue through the use of modular symmetries.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Libralon, S., Martinez-Vidal, F., Oyanguren, A., et al. (2024). Search for the Bs0 → μ+ μ-γ decay. J. High Energy Phys., 07(7), 101–27pp.
Abstract: A search for the fully reconstructed B-s(0)-> mu(+)mu(-)gamma decay is performed at the LHCb experiment using proton-proton collisions at root s = 13 TeV corresponding to an integrated luminosity of 5.4 fb(-1). No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set B(B-s(0)-> mu(+)mu(-)gamma) < 4.2 x 10(-8), m(mu(+)mu(-)) is an element of[2m(mu),1.70] GeV/c(2), B(B-s(0) -> mu(+)mu(-)gamma) < 7.7 x 10(-8), m(mu(+)mu(-)) is an element of [1.70, 2.88] GeV/c(2), B(B-s(0) -> mu(+)mu(-)gamma) < 4.2 x 10(-8), m(mu(+)mu(-) ) is an element of[3.92, m(Bs0)]GeV/c(2), at 95% confidence level. Additionally, upper limits are set on the branching fraction in the [2m(mu), 1.70] GeV/c(2) dimuon mass region excluding the contribution from the intermediate phi(1020) meson, and in the region combining all dimuon-mass intervals.
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