Search

The standard model (SM) one-loop contributions to the most general $H^*Z^*Z^*$ coupling are obtained via the background field method in terms of Passarino-Veltman scalar functions, from which the contributions to the $H^*ZZ$ and $HZZ^*$ couplings are obtained in terms of two $CP$-conserving $h_{1,2}^V$ and one $CP$-violating $h_3^V$ form factors ($V=H, Z$). The current CMS constraints on the $HZZ$ coupling ratios are then used to obtain bounds on the real and absorptive parts of the anomalous $HZZ$ couplings. The former are up to two orders of magnitude tighter than previous ones, whereas the latter are the first one of this kind. The effects of the absorptive parts of the $HZZ$ anomalous couplings, which have been overlooked in the past, are analyzed via the partial decay width $\Gamma_{H^\ast\rightarrow ZZ}$, and a significant deviation from the SM tree-level contribution is observed at low energies, though it becomes negligible at high energies. We also explore the possibility that polarized $Z$ gauge bosons are used for the study of non-SM $HZZ$ contributions via a new left-right asymmetry $\mathcal{A}_{LR}$, which is sensitive to $CP$-violating complex form factors and can be as large as the unity at most, though in a more conservative scenario it is four to five orders of magnitude larger than the SM prediction arising up to the three-loop level. The partial decay widths $\Gamma_{H^\ast\rightarrow Z_LZ_L}$ and $\Gamma_{H^\ast\rightarrow Z_RZ_R}$ are also studied in several scenarios and it is observed that the deviations from the SM can be large at high energies and increases as the energy increases. Thus, the use of polarized $Z$ gauge bosons could give hints of $CP$ violation. The Mathematica code for our analytical results and the numerical evaluation is available in our GitLab site., Comment: Similar to the PRD publication

We study the flavor-changing decay $h\to \tau \mu$ with $\tau=\tau^-+\tau^+$ and $\mu=\mu^-+\mu^+$ of a Higgs boson at future hadron colliders, namely: a) High Luminosity Large Hadron Collider, b) High Energy Large Hadron Collider and c) Future hadron-hadron Circular Collider. The theoretical framework adopted is the Two-Higgs-Doublet Model type III. The free model parameters involved in the calculation are constrained through Higgs boson data, Lepton Flavor Violating processes and the muon anomalous magnetic dipole moment; later they are used to analyze the branching ratio of the decay $h\to\tau\mu$ and to evaluate the $gg\to h$ production cross section. We find that at the Large Hadron Collider is not possible to claim for evidence of the decay $h\to\tau\mu$ achieving a signal significance about of $1.46\sigma$ by considering its final integrated luminosity, 300 fb$^{-1}$. More promising results arise at the High Luminosity Large Hadron Collider in which a prediction of 4.6$\sigma$ when an integrated luminosity of 3 ab$^{-1}$ and $\tan\beta=8$ are achieved. Meanwhile, at the High Energy Large Hadron Collider (Future hadron-hadron Circular Collider) a potential discovery could be claimed with a signal significance around $5.04\sigma$ ($5.43\sigma$) for an integrated luminosity of 3 ab$^{-1}$ and $\tan\beta=8$ (5 ab$^{-1}$ and $\tan\beta=4$)., Comment: Accepted version to be published in JHEP, typos corrected, added citations

We present a study of the flavor changing decays $\phi\to tc$ ($\phi=H_F,\,A_F$) of the $CP$-even and $CP$-odd scalar flavons at the large hadron collider and its next stage, the high-luminosity large hadron collider. The theoretical framework is an extension of the standard model that incorporates an extra complex singlet and invokes the Froggatt-Nielsen mechanism with an Abelian flavor symmetry. The projected exclusion and discovery regions in terms of the model parameters are reported. We find that $A_F$ could be detected at the LHC by considering a reasonable scenario of the model parameter space. As far as $H_F$ is concerned, we also found promising results that could be verified experimentally at the high-luminosity LHC., Comment: Substantial changes to the previous version

The study of the phenomenology of an extra neutral gauge boson, Z_H, can can help us to unravel the underlying theory. We study the decay of such a particle into two neutral gauge bosons, Z_H -> V_i Z (V_i=\gamma, Z), in two popular versions of the little Higgs model: the littlest Higgs model (LHM) and the simplest little Higgs model (SLHM). These decays are induced at the one-loop level by a fermion triangle and are interesting as they are strongly dependent on the mechanism of anomaly cancellation of the model. All the relevant tree-level two- and three-body decays of the Z_H gauge boson are also calculated. It is found that the branching ratios for the Z_H-> \gamma Z decays can be as large as that of a tree-level three-body decay but the Z_H-> ZZ decay is very suppressed. We also discuss the experimental prospects for detecting these decays at the LHC and a future linear collider. We conclude that the latter would offer more chances for the detection of such rare decays., Comment: Revised paper to match published version

The use of large underground high-energy physics experiments, for comic ray studies, have been used, in the past, at CERN, in order to measure, precisely, the inclusive cosmic ray flux in the energy range from 2x10^10 - 2x10^12 eV. ACORDE, ALICE Cosmic Rays DEtector, will act as Level 0 cosmic ray trigger and, together with other ALICE apparatus, will provide precise information on cosmic rays with primary energies around 10^15 - 10^17 eV. This paper reviews the main detector features, the present status, commissioning and integration with other apparatus. Finally, we discuss the ACORDE-ALICE cosmic ray physics program., Comment: Contribution to the 2007 Europhysics Conference on High Energy Physics - Manchester, England 19-25 July 2007; 3 pages, 3 figures