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Register a new userHiggs boson decay to lepton pair and photon and possible non-Hermiticity of the Yukawa interaction
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The production of lepton pairs in the Higgs boson decay $h to ell^+ ell^- gamma$ is studied. The emphasis is put on the structure of the Higgs boson interaction with the fermions. This interaction is chosen as a mixture of the scalar and pseudo-scalar couplings, and, in addition, it is supposed to be non-Hermitian. We study prediction of this model for the observables in the $h to ell^+ ell^- gamma$ decay for the $e^+ e^-$, $mu^+ mu^-$ and $tau^+ tau^-$ pairs. The differential decay width and lepton forward-backward asymmetry are calculated as functions of the dilepton invariant mass for several sets of $h f bar{f}$ coupling constants. The influence of non-Hermitian $h f bar{f}$ interaction on the forward-backward asymmetry is studied, and large influence of a possible non-Hermiticity of the Higgs interaction with the top quarks on forward-backward asymmetry for $e^+ e^-$ and $mu^+ mu^-$ pairs is stressed.
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The issue of Hermiticity of the Higgs boson interaction with fermions is addressed. A model for non-Hermitian Yukawa interaction is proposed and approximation of one fermion generation is considered. Symmetry properties of the corresponding $h f bar{f}$ Lagrangian with respect to the discrete P, C and T transformations are analyzed, and the modified Dirac equation for the free fermion is studied. Longitudinal polarization of the fermions in the decay $h to f bar{f}$, which arises due to non-Hermiticity of the $h f bar{f}$ interaction, is discussed. It is suggested to study effects of this non-Hermiticity in the decay $h to tau^- tau^+ to mu^- {bar u}_mu u_tau , mu^+ u_mu {bar u}_tau$, for which observables (asymmetries) are constructed which take nonzero values for a non-Hermitian $h tau^- tau^+$ interaction. These asymmetries are analyzed for various configurations of the muon energies.
The Higgs-boson decay h -> gamma l+ l- for various lepton states l = (e, mu, tau) is analyzed. The differential decay width and forward-backward asymmetry are calculated as functions of the dilepton invariant mass in a model where the Higgs boson interacts with leptons and quarks via a mixture of scalar and pseudoscalar couplings. These couplings are partly constrained from data on the decays to leptons, h -> l+ l-, and quarks h -> q bar{q} (where q = (c, b)), while the Higgs couplings to the top quark are chosen from the two-photon and two-gluon decay rates. Nonzero values of the forward-backward asymmetry will manifest effects of new physics in the Higgs sector. The decay width and asymmetry integrated over the dilepton invariant mass are also presented.
We present new calculations of the differential decay rates for $Hto ell^+ell^- gamma$ with $ell=e$ or $mu$ in the Standard Model. The branching fractions and forward-backward asymmetries, defined in terms of the flight direction of the photon relative to the lepton momenta, depend on the cuts on energies and invariant masses of the final state particles. For typical choices of these cuts we find the branching ratios $B(Hto e bar e gamma)=5.8cdot 10^{-5}$ and $B(Hto mu bar mu gamma)=6.4cdot 10^{-5}$ and the forward-backward asymmetries $mathcal{A}^{(e)}_{text{FB}}=0.343$ and $mathcal{A}^{(mu)}_{text{FB}}=0.255$. We provide compact analytic expressions for the differential decay rates for the use in experimental analyses.
The discovery of the Standard Model (SM) Higgs boson at the LHC completed the theory of electroweak and strong interactions. To determine the Higgs bosons intrinsic properties, more measurements on its various decay channels are still necessary. In this paper, we investigate $Hto ellbar{ell}Z$ and $Hto u_ellbar{ u}_ell Z$ (with $ell=e$, $mu$, $tau$) processes at the next-to-leading order electroweak accuracy. The total decay widths, and the differential decay rates with respect to various kinematic variables are obtained. For a typical choice of cut on the invariant mass of lepton pair, we find the branching ratios $mathcal{B}(Hto ellbar{ell}Z)=7.5times 10^{-4}$ (with $ell=e, mu$), $mathcal{B}(Hto tau^-tau^+ Z)=7.3times 10^{-4}$, and $mathcal{B}(Hto u_ellbar{ u}_ell Z)=1.5times 10^{-3}$ (with $ell=e, mu, tau$), which are attainable in the LHC experiments.
We study Higgs boson pair production processes at future hadron and lepton colliders including the photon collision option in several new physics models; i.e., the two-Higgs-doublet model, the scalar leptoquark model, the sequential fourth generation fermion model and the vector-like quark model. Cross sections for these processes can deviate significantly from the standard model predictions due to the one-loop correction to the triple Higgs boson coupling constant. For the one-loop induced processes such as $gg to hh$ and $gammagammato hh$, where $h$ is the (lightest) Higgs boson and $g$ and $gamma$ respectively represent a gluon and a photon, the cross sections can also be affected by new physics particles via additional one-loop diagrams. In the two-Higgs-doublet model and scalar leptoquark models, cross sections of $e^+e^-to hhZ$ and $gammagammato hh$ can be enhanced due to the non-decoupling effect in the one-loop corrections to the triple Higgs boson coupling constant. In the sequential fourth generation fermion model, the cross section for $ggto hh$ becomes very large because of the loop effect of the fermions. In the vector-like quark model, effects are small because the theory has decoupling property. Measurements of the Higgs boson pair production processes can be useful to explore new physics through the determination of the Higgs potential.
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