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R3B Collaboration(Boillos, J. M. et al), & Nacher, E. (2022). Isotopic cross sections of fragmentation residues produced by light projectiles on carbon near 400A MeV. Phys. Rev. C, 105(1), 014611–13pp.
Abstract: We measured 135 cross sections of residual nuclei produced in fragmentation reactions of C-12, N-14, and O-13-16,O-20,O-22 projectiles impinging on a carbon target at kinetic energies of near 400A MeV, most of them for the first time, with the R B-3/LAND setup at the GSI facility in Darmstadt (Germany). The use of this state-of-the-art experimental setup in combination with the inverse kinematics technique gave the full identification in atomic and mass numbers of fragmentation residues with a high precision. The cross sections of these residues were determined with uncertainties below 20% for most of the cases. These data are compared to other previous measurements with stable isotopes and are also used to benchmark different model calculations.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Analysis of Neutral B-Meson Decays into Two Muons. Phys. Rev. Lett., 128(4), 041801–13pp.
Abstract: The branching fraction B(B-s(0)->mu(+)mu(-)) = (3.09(-0.43-0.11)(+0.46+0.15)) x 10(-9) and the effective lifetime to tau(B-s(0) -> mu(+)mu(-)) = 2.07 +/- 0.29 +/- 0.03 ps are measured, where the first uncertainty is statistical and the second systematic. No significant signal for B-0 ->mu(+)mu(-)gamma) and B-s(0)->mu(+)mu(-)gamma decays is found and upper limits B(B(B-0 ->mu(+)mu(-)) < 2.6 x 10(-10) and B(B-s(0) -> mu(+)mu(-)gamma) < 2.0 x 10(-9) at the 95% C.L. are determined, where the latter is limited to the range m(mu mu) > 4.9 GeV/c(2). The results are in agreement with the standard model expectations.Branching fraction and effective lifetime measurements of the rare decay B-s(0) -> mu(+)mu(-) and searches for the decays B-0 -> mu(+)mu(-) and B-s(0) -> mu(+)mu(-)gamma are reported using proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a luminosity of 9 fb(-1).
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Rosa, J. L., Lobo, F. S. N., & Olmo, G. J. (2021). Weak-field regime of the generalized hybrid metric-Palatini gravity. Phys. Rev. D, 104(12), 124030–11pp.
Abstract: In this work we explore the dynamics of the generalized hybrid metric-Palatini theory of gravity in the weak-field, slow-motion regime. We start by introducing the equivalent scalar-tensor representation of the theory, which contains two scalar degrees of freedom, and perform a conformal transformation to the Einstein frame. Linear perturbations of the metric in a Minkowskian background are then studied for the metric and both scalar fields. The effective Newton constant and the PPN parameter. of the theory are extracted after transforming back to the (original) Jordan frame. Two particular cases where the general method ceases to be applicable are approached separately. A comparison of these results with observational constraints is then used to impose bounds on the masses and coupling constants of the scalar fields.
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Alvarez, A., Cepedello, R., Hirsch, M., & Porod, W. (2022). Temperature effects on the Z(2) symmetry breaking in the scotogenic model. Phys. Rev. D, 105(3), 035013–8pp.
Abstract: It is well known that the scotogenic model for neutrino mass generation can explain correctly the relic abundance of cold dark matter. There have been claims in the literature that an important part of the parameter space of the simplest scotogentic model can be constrained by the requirement that no Z(2)-breaking must occur in the early universe. Here we show that this requirement does not give any constraints on the underlying parameter space at least in those parts, where we can trust perturbation theory. To demonstrate this, we have taken into account the proper decoupling of heavy degrees of freedom in both the thermal potential and in the RGE evolution.
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Coogan, A., Bertone, G., Gaggero, D., Kavanagh, B. J., & Nichols, D. A. (2022). Measuring the dark matter environments of black hole binaries with gravitational waves. Phys. Rev. D, 105(4), 043009–22pp.
Abstract: Large dark matter overdensities can form around black holes of astrophysical and primordial origin as they form and grow. This “dark dress” inevitably affects the dynamical evolution of binary systems and induces a dephasing in the gravitational waveform that can be probed with future interferometers. In this paper, we introduce a new analytical model to rapidly compute gravitational waveforms in the presence of an evolving dark matter distribution. We then present a Bayesian analysis determining when dressed black hole binaries can be distinguished from GR-in-vacuum ones and how well their parameters can be measured, along with how close they must be to be detectable by the planned Laser Interferometer Space Antenna (LISA). We show that LISA can definitively distinguish dark dresses from standard binaries and characterize the dark matter environments around astrophysical and primordial black holes for a wide range of model parameters. Our approach can be generalized to assess the prospects for detecting, classifying, and characterizing other environmental effects in gravitational wave physics.
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Balbinot, R., & Fabbri, A. (2022). Quantum correlations across the horizon in acoustic and gravitational black holes. Phys. Rev. D, 105(4), 045010–20pp.
Abstract: We investigate, within the framework of quantum field theory in curved space, the correlations across the horizon of a black hole in order to highlight the particle-partner pair creation mechanism at the origin of Hawking radiation. The analysis concerns both acoustic black holes, formed by Bose-Einstein condensates, and gravitational black holes. More precisely, we have considered a typical acoustic black hole metric with two asymptotic homogeneous regions and the Schwarzschild metric as describing a gravitational black hole. By considering equal-time correlation functions, we find a striking disagreement between the two cases: the expected characteristic peak centered along the trajectories of the Hawking particles and their partners seems to appear only for the acoustic black hole and not for the gravitational Schwarzschild one. The reason for that is the existence of a quantum atmosphere displaced from the horizon as the locus of origin of Hawking radiation together, and this is the crucial aspect, with the presence of a central singularity in the gravitational case swallowing everything is trapped inside the horizon. Correlations, however, are not absent in the gravitational case; to see them, one simply has to consider correlation functions at unequal times, which indeed display the expected peak.
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LHCb Collaboration(Aaij, R. et al), Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., & Ruiz Vidal, J. (2022). Evidence for a New Structure in the J/psi p and J/psi(p)over-bar Systems in B-s(0) -> J/psi p(p)over-bar Decays. Phys. Rev. Lett., 128(6), 062001–11pp.
Abstract: An amplitude analysis of flavor-untagged B-s(0) -> J=psi p (p) over bar decays is performed using a sample of 797 +/- 31 decays reconstructed with the LHCb detector. The data, collected in proton-proton collisions between 2011 and 2018, correspond to an integrated luminosity of 9 fb(-1). Evidence for a new structure in the J=psi p and J=psi(p) over bar systems with a mass of 4337(-4-2)(+7+2) MeV and a width of 29(-12-14)(+26+14) MeV is found, where the first uncertainty is statistical and the second systematic, with a significance in the range of 3.1 to 3.7 sigma, depending on the assigned J(P) hypothesis.
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n_TOF Collaboration(Tagliente, G. et al), Domingo-Pardo, C., Giubrone, G., Tain, J. L., & Tarifeño-Saldivia, A. (2022). Zr-92(n, gamma) and (n,tot) measurements at the GELINA and n_TOF facilities. Phys. Rev. C, 105(2), 025805–14pp.
Abstract: Background: Stellar nucleosynthesis of elements heavier than iron is driven by neutron capture processes. Zr-92 is positioned at a strategic point along the slow nucleosynthesis path, given its proximity to the neutron magic number N = 50 and its position at the matching region between the weak and main slow processes. Purpose: In parallel with recent improved astronomical data, the extraction of accurate Maxwellian averaged cross sections (MACSs) derived from a more complete and accurate set of resonance parameters should allow for a better understanding of the stellar conditions at which nucleosynthesis takes place. Methods: Transmission and capture cross section measurements using enriched Zr-92 metallic samples were performed at the time-of flight facilities GELINA of JRC-Geel (BE) and nTOF of CERN (CH). The neutron beam passing through the samples was investigated in transmission measurements at GELINA using a Li-glass scintillator. The gamma rays emitted during the neutron capture reactions were detected by C6D6 detectors at both GELINA and nTOF. Results: Resonance parameters of individual resonances up to 81 keV were extracted from a combined resonance shape analysis of experimental transmissions and capture yields. For the majority of the resonances the parity was determined from an analysis of the transmission data obtained with different sample thicknesses. Average resonance parameters were calculated. Conclusions: Maxwellian averaged cross sections were extracted from resonances observed up to 81 keV. The MACS for kT = 30 keV is fully consistent with experimental data reported in the literature. The MACSs for kT less than or similar to 15 keV are in good agreement with those derived from the ENDF/B-VIII.0 library and recommended in the KADoNTS database. For kT higher than 30 keV differences are observed. A comparison with MACSs obtained with the cross sections recommended in the JEFF-3.3 and JENDL-4.0 libraries shows discrepancies even for kT less than or similar to 15 keV.
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BABAR Collaboration(Lees, J. P. et al), Martinez-Vidal, F., & Oyanguren, A. (2022). Search for Lepton Flavor Violation in Upsilon(3S) -> e(+/-)mu(-/+). Phys. Rev. Lett., 128(9), 091804–7pp.
Abstract: We report on the first search for electron-muon lepton flavor violation (LFV) in the decay of a b quark and b antiquark bound state. We look for the LFV decay Upsilon(3S) -> e(+/-) mu(-/+) in a sample of 118 million gamma(3S) mesons from 27 fb(-1) of data collected with the BABAR detector at the SLAC PEP-II e(+) e(-) collider operating with a 10.36 GeV center-of-mass energy. No evidence for a signal is found, and we set a limit on the branching fraction B[Upsilon(3S) -> e(+/-) mu(-/+)] < 3.6 x 10(-7) at 90% C. L. This result can be interpreted as a limit Lambda(NP)/g(NP)(2) > 80 TeV on the energy scale Lambda(NT) divided by the coupling-squared g(NP)(2) of relevant new physics (NP).
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Lopez-Ibañez, M. L., Melis, A., Jay Perez, M., Rahat, M. H., & Vives, O. (2022). Constraining low-scale flavor models with (g-2)(mu) and lepton flavor violation. Phys. Rev. D, 105(3), 035021–21pp.
Abstract: We present here two concrete examples of models where a sub-TeV scale breaking of their respective T-13 and A(5) flavor symmetries is able to account for the recently observed discrepancy in the muon anomalous magnetic moment, (g – 2)(mu). Similarities in the flavor structures of the charged-lepton Yukawa matrix and dipole matrix yielding (g – 2)(mu) give rise to strong constraints on low-scale flavor models when bounds from lepton flavor violation (LFV) are imposed. These constraints place stringent limits on the off- diagonal Yukawa structure, suggesting a mostly (quasi)diagonal texture for models with a low flavor breaking scale A(f). We argue that many of the popular flavor models in the literature designed to explain the fermion masses and mixings are not suitable for reproducing the observed discrepancy in (g – 2)(mu), which requires a delicate balance of maintaining a low flavor scale while simultaneously satisfying strong LFV constraints.
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