ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2023). Search for nonresonant pair production of Higgs bosons in the b b-bar b b-bar final state in pp collisions at √s=13 TeV with the ATLAS detector. Phys. Rev. D, 108(5), 052003–38pp.
Abstract: A search for nonresonant Higgs boson pair production in the b (b) over barb (b) over bar final state is presented. The analysis uses 126 fb(-1) of pp collision data at root s = 13 TeV collected with the ATLAS detector at the Large Hadron Collider, and targets both the gluon-gluon fusion and vector-boson fusion production modes. No evidence of the signal is found and the observed (expected) upper limit on the cross section for nonresonant Higgs boson pair production is determined to be 5.4 (8.1) times the Standard Model predicted cross section at 95% confidence level. Constraints are placed on modifiers to the HHH and HHVV couplings. The observed (expected) 2 sigma constraints on the HHH coupling modifier, kappa(lambda), are determined to be [-3.5, 11.3] ([-5.4, 11.4]), while the corresponding constraints for the HHVV coupling modifier, kappa(2V), are [-0.0, 2.1] ([-0.1, 2.1]). In addition, constraints on relevant coefficients are derived in the context of the Standard Model effective field theory and Higgs effective field theory, and upper limits on the HH production cross section are placed in seven Higgs effective field theory benchmark scenarios.
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Di Valentino, E., Gariazzo, S., Giare, W., Melchiorri, A., Mena, O., & Renzi, F. (2023). Novel model-marginalized cosmological bound on the QCD axion mass. Phys. Rev. D, 107(10), 103528–16pp.
Abstract: We present model-marginalized limits on mixed hot dark matter scenarios, which consider both thermal neutrinos and thermal QCD axions. A novel aspect of our analyses is the inclusion of small-scale cosmic microwave background (CMB) observations from the Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT), together with those from the Planck satellite and baryon acoustic oscillation (BAO) data. After marginalizing over a number of well-motivated nonminimal background cosmologies, the tightest 95% Confidential Level (CL) upper bound we obtain is 0.21 eV, both for P m nu and ma, from the combination of ACT, Planck and BAO measurements. Restricting the analyses to the standard ?CDM picture, we find P m nu < 0.16 eV and ma < 0.18 eV, both at 95% CL Interestingly, the best background cosmology is never found within the minimal ?CDM plus hot relics, regardless of the datasets exploited in the analyses. The combination of Planck with either BAO, SPT or ACT prefers a universe with a nonzero value of the running in the primordial power spectrum with strong evidence. Small-scale CMB probes, both alone and combined with BAO, either prefer, with substantial evidence, nonflat universes (as in the case of SPT) or a model with a time varying dark energy component (as in the case of ACT).
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de Anda, F. J., Medina, O., Valle, J. W. F., & Vaquera-Araujo, C. A. (2023). Revamping Kaluza-Klein dark matter in an orbifold theory of flavor. Phys. Rev. D, 108(3), 035046–11pp.
Abstract: We suggest a common origin for dark matter, neutrino mass and family symmetry within the orbifold theory proposed in [Phys. Lett. B 801, 135195 (2020); Phys. Rev. D 101, 116012 (2020)]. Flavor physics is described by an A(4) family symmetry that results naturally from compactification. Weakly interacting massive particle dark matter emerges from the first Kaluza-Klein excitation of the same scalar that drives family symmetry breaking and neutrino masses through the inverse seesaw mechanism. In addition to the “golden” quark-lepton mass relation and predictions for 0 nu beta beta decay, the model provides a good global description of all flavor observables.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Measurement of lepton universality parameters in B+ -> K+ l+ l- and B0 -> K0 l+ l- decays. Phys. Rev. D, 108(3), 032002–46pp.
Abstract: A simultaneous analysis of the B thorn & RARR; K thorn e thorn e- and B0 & RARR; K & DBLBOND;0e thorn e- decays is performed to test muonelectron universality in two ranges of the square of the dilepton invariant mass, q2. The measurement uses a sample of beauty meson decays produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb-1. A sequence of multivariate selections and strict particle identification requirements produce a higher signal purity and a better statistical sensitivity per unit luminosity than previous LHCb lepton universality tests using the same decay modes. Residual backgrounds due to misidentified hadronic decays are studied using data and included in the fit model. Each of the four lepton universality measurements reported is either the first in the given q2 interval or supersedes previous LHCb measurements. The results are compatible with the predictions of the Standard Model.
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Beltran-Palau, P., del Rio, A., & Navarro-Salas, J. (2023). Quantum corrections to the Schwarzschild metric from vacuum polarization. Phys. Rev. D, 107(8), 085023–15pp.
Abstract: We explore static and spherically symmetric solutions of the 4-dimensional semiclassical Einstein's equations using the quantum vacuum polarization of a conformal field as a source. These solutions may be of interest for the study of exotic compact objects (ECOs). The full backreaction problem is addressed by solving the semiclassical Tolman-Oppenheimer-Volkoff (TOV) equations making use of effective equations of state inspired by the trace anomaly and an extra simplifying and reasonable assumption. We combine analytical and numerical techniques to solve the resulting differential equations, both perturbatively and nonperturbatively in h. In all cases the solution is similar to the Schwarzschild metric up p ffiffito the vicinity of the classical horizon r = 2M. However, at r = 2M + epsilon, with epsilon similar to O(root h), we find a coordinate singularity. In the case of matching with a static star, this leads to an upper bound in the compactness, and sets a constraint on the family of stable ECOs. We also study the corrections that the quantum-vacuum polarization induces on the propagation of waves, and discuss the implications. For the pure vacuum case, we can further extend the solution by using appropriate coordinates until we reach another singular point, where this time a null curvature singularity arises and prevents extending beyond. This picture qualitatively agrees with the results obtained in the effective two-dimensional approach, and reinforces the latter as a reasonable method.
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