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Register a new userProbing Baryogenesis through the Higgs Self-Coupling
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The link between a modified Higgs self-coupling and the strong first-order phase transition necessary for baryogenesis is well explored for polynomial extensions of the Higgs potential. We broaden this argument beyond leading polynomial expansions of the Higgs potential to higher polynomial terms and to non-polynomial Higgs potentials. For our quantitative analysis we resort to the functional renormalization group, which allows us to evolve the full Higgs potential to higher scales and finite temperature. In all cases we find that a strong first-order phase transition manifests itself in an enhancement of the Higgs self-coupling by at least 50%, implying that such modified Higgs potentials should be accessible at the LHC.
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In this work we explore the sensitivity to the Higgs self-coupling $lambda$ in the production of two Higgs bosons via vector boson scattering at the LHC. Although these production channels, concretely $W^+W^- to HH$ and $ ZZ to HH$, have lower rates than gluon-gluon fusion, they benefit from being tree level processes, being independent of top physics and having very distinctive kinematics that allow to obtain very clean experimental signatures. This makes them competitive channels concerning the sensitivity to the Higgs self-coupling. In order to give predictions for the sensitivity to this coupling, we first study the role of $lambda$ at the subprocess level, both in and beyond the Standard Model, to move afterwards to the LHC scenario. We characterize the $ppto HHjj$ case first and then provide quantitative results for the values of $lambda$ that can be probed at the LHC in vector boson scattering processes after considering the Higgs boson decays. We focus mainly in $ppto bbar{b}bbar{b}jj$, since it has the largest signal rates, and also comment on the potential of other channels, such as $ppto bbar{b}gammagamma jj$, as they lead to cleaner, although smaller, signals. Our whole study is performed for a center of mass energy of $sqrt{s}=14$ TeV and for various future expected LHC luminosities.
The ATLAS and CMS collaborations of the LHC have observed that the Higgs boson decays into the bottom quark-antiquark pair, and have also established that the Higgs coupling with the top quark-antiquark pair is instrumental in one of the modes for Higgs production. This underlines the discovery of the Yukawa force at the LHC. We demonstrate the impact of this discovery on the Higgs properties that are related to the dynamics of electroweak symmetry breaking. We show that these measurements have considerably squeezed the allowed window for new physics contributing to the Higgs couplings with the weak gauge bosons and the third generation quarks. The expected constraints at the HL-LHC and future Higgs factories are also shown. We project these constraints on the parameter space of a few motivated scenarios beyond the Standard Model. We pick them under two broad categories, namely, the composite Higgs and its RS dual, as well as various types of multi-Higgs models. The latter category includes models with singlet scalars, Type I, II and BGL-type two-Higgs doublet models, and models with scalar triplets a la Georgi and Machacek.
We investigate Higgs boson pair production at hadron colliders for Higgs boson masses m_Hleq 140 GeV and rare decay of one of the two Higgs bosons. While in the Standard Model the number of events is quite low at the LHC, a first, albeit not very precise, measurement of the Higgs self-coupling is possible in the gg -> HH -> bbar{b}gammagamma channel. A luminosity-upgraded LHC could improve this measurement considerably. A 200 TeV VLHC could make a measurement of the Higgs self-coupling competitive with a next-generation linear collider. In the MSSM we find a significant region with observable Higgs pair production in the small tanbeta regime, where resonant production of two light Higgs bosons might be the only hint at the LHC of an MSSM Higgs sector.
We study the prospect of probing electroweak baryogenesis driven by an extra bottom Yukawa coupling $rho_{bb}$ in a general two Higgs doublet model via electric dipole moment (EDM) measurements and at the collider experiments. The parameter space receives meaningful constraints from 125 GeV Higgs $h$ boson signal strength measurements as well as several heavy Higgs boson searches at the Large Hadron Collider (LHC). In addition, we show that the asymmetry of the CP asymmetry of inclusive $Bto X_s gamma$ decay would provide complementary probe. A discovery is possible at the LHC via $bgto bA to b Z h$ process if $|rho_{bb}|sim 0.15$ and $250~mbox{GeV}lesssim m_A lesssim 350$ GeV, where $A$ is CP odd scalar. For $m_A> 2 m_t$ threshold, where $m_t$ is the top quark mass, one may also discover $bgto bA to b t bar t$ at the high luminosity LHC run if an extra top Yukawa coupling $|rho_{tt}|sim0.5$, though it may suffer from systematic uncertainties. For completeness we study $ggto t bar t A to t bar t b bar b $ but find it not promising.
We investigate potential quantum nonlinear corrections to Diracs equation through its sub-leading effect on neutrino oscillation probabilities. Working in the plane-wave approximation and in the $mu-tau$ sector, we explore various classes of nonlinearities, with or without an accompanying Lorentz violation. The parameters in our models are first delimited by current experimental data before they are used to estimate corrections to oscillation probabilities. We find that only a small subset of the considered nonlinearities have the potential to be relevant at higher energies and thus possibly detectable in future experiments. A falsifiable prediction of our models is an energy dependent effective mass-squared, generically involving fractional powers of the energy.
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