Botella, F. J., Branco, G. C., Rebelo, M. N., & Silva-Marcos, J. I. (2016). What if the masses of the first two quark families are not generated by the standard model Higgs boson? Phys. Rev. D, 94(11), 115031–6pp.
Abstract: We point out that in the standard model there is meaningful quark mixing even in the extreme chiral (EC) limit, where only the third generation of quarks acquires mass. This mixing is in general expected to be of order 1 and the fact that |V-13|(2) + |V-23|(2) approximate to 1.6 x 10(-3) implies a novel fine-tuning problem in the SM which we point out for the first time. We propose a possible way of avoiding this fine-tuning by introducing a symmetry S which leads to V-CKM = 1, with only the third generation of quarks acquiring mass. We consider two scenarios for generating the mass of the first two quark generations and full quark mixing based on the assumption that the masses of the first two quark families are not generated by the standard Higgs. One consists of the introduction of a second Higgs doublet which is neutral under S. The second scenario consists of assuming new physics at a high energy scale, contributing to the masses of light quark generations, in an effective field theory approach. This last scenario leads to couplings of the Higgs particle to s (s) over bar and c (c) over tilde which are significantly enhanced with respect to those of the SM. In both schemes, one has scalar-mediated flavor-changing neutral currents which are naturally suppressed. Flavor-violating top decays are predicted in the second scenario at the level Br(t -> hc) >= 5 x 10(-5).
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Villanueva-Domingo, P., Villaescusa-Navarro, F., Genel, S., Angles-Alcazar, D., Hernquist, L., Marinacci, F., et al. (2023). Weighing the Milky Way and Andromeda galaxies with artificial intelligence. Phys. Rev. D, 107(10), 103003–8pp.
Abstract: We present new constraints on the masses of the halos hosting the Milky Way and Andromeda galaxies derived using graph neural networks. Our models, trained on 2,000 state-of-the-art hydrodynamic simulations of the CAMELS project, only make use of the positions, velocities and stellar masses of the galaxies belonging to the halos, and are able to perform likelihood-free inference on halo masses while accounting for both cosmological and astrophysical uncertainties. Our constraints are in agreement with estimates from other traditional methods, within our derived posterior standard deviation.
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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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Rafi Alam, M., & Ruiz Simo, I. (2019). Weak production of strange Xi baryons off the nucleon. Phys. Rev. D, 100(3), 033001–10pp.
Abstract: The charged current Cabibbo-suppressed associated K Xi production off the nucleon induced by antineutrinos is studied at low and intermediate energies. The nonresonant terms are obtained using a microscopical model based on the SU( 3) chiral Lagrangian. The basic parameters of the model are f(pi), the pion decay constant, Cabibbo's angle, the proton and neutron magnetic moments, and the axial vector coupling constants for the baryons octet, D and F, that are obtained from the analysis of the semileptonic decays of neutron and hyperons. In addition, we also consider Sigma(*)(1385) resonance, which can decay in K Xi final state when this channel is open. The studied mechanism is the prime source of Xi production at antineutrino energies around 2 GeV and the calculated cross sections at these energies can be measured at the current and future neutrino experiments.
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Sobczyk, J. E., Rocco, N., Lovato, A., & Nieves, J. (2019). Weak production of strange and charmed ground-state baryons in nuclei. Phys. Rev. C, 99(6), 065503–16pp.
Abstract: We present results for the quasielastic weak production of Delta and Sigma hyperons induced by (nu) over bar. scattering off nuclei in the kinematical region of interest for accelerator neutrino experiments. We employ realistic hole spectral functions and we describe the propagation of the hyperons in the nuclear medium by means of a Monte Carlo cascade. The latter strongly modifies the kinematics and the relative production rates of the hyperons, leading to a nonvanishing Sigma(+) cross section, to a sizable enhancement of the Lambda production and to a drastic reduction of the Sigma(0) and Sigma(-) distributions. We also compute the quasielastic weak Lambda(c) production cross section, paying special attention to estimate the uncertainties induced by the model dependence of the vacuum n -> Lambda(c) weak matrix element. In this regard, the recent BESIII measurements of the branching ratios of Lambda(c) -> Lambda l(+)nu(l) (l = e, mu) are used to benchmark the available theoretical predictions.
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