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Register a new userOn the determination of the structure of the scalar Higgs bosons couplings to vectorbosons
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In this paper we investigate the determination of the coupling structure of a Higgs boson at the LHC using angular correlations in the decay chain H -> ZZ -> 4l. We consider the most general couplings of a scalar to spin 1 particles and compare the angular correlations of the decay products using a maximum likelihood method. We use the full information from the LO matrix element including all posible correlations between the decay angles. In our analysis we include all possible mixings between the different coupling structures. We conclude that the coupling structure can in general be determined using this approach. But it has to be noted, that for Higgs boson masses below the ZZ-threshold the analysis is statistically limited. For higher Higgs boson masses reasonably strong limits on non standard couplings can be achieved at the LHC using the full integrated luminosity of 300 fb^-1.
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We study the indirect effects of new physics on the phenomenology of the recently discovered Higgs-like particle. In a model independent framework these effects can be parametrized in terms of an effective Lagrangian at the electroweak scale. In a theory in which the SU(2)_L x U(1)_Y gauge symmetry is linearly realized they appear at lowest order as dimension--six operators, containing all the SM fields including the light scalar doublet, with unknown coefficients. We discuss the choice of operator basis which allows us to make better use of all the available data on the new state, triple gauge boson vertex and electroweak precision tests, to determine the coefficients of the new operators. We illustrate our present knowledge of those by performing a global fit to the existing data which allows simultaneous determination of the eight relevant parameters quantifying the Higgs couplings to gluons, electroweak gauge bosons, bottom quarks, and tau leptons. We find that for all scenarios considered the standard model predictions for each individual Higgs coupling and observable are within the corresponding 68% CL allowed range. We finish by commenting on the implications of the results for unitarity of processes at higher energies. Note added: The analysis has been updated with all the public data available by October 2013. Updates of this analysis are provided at http://hep.if.usp.br/Higgs as well as n
We study the indirect effects of new physics on the phenomenology of the Higgs-like particle. Assuming that the recently observed state belongs to a light electroweak doublet scalar and that the SU(2)_L x U(1)_Y symmetry is linearly realized, we parametrize these effects in terms of an effective Lagrangian at the electroweak scale. We choose the dimension--six operator basis which allows us to make better use of all the available data to constrain the coefficients of the dimension-six operators. We perform a global 6--parameter fit which allows simultaneous determination of the standard model scalar couplings to gluons, electroweak gauge bosons, bottom quarks, and tau leptons. The results are based on the data released at Moriond 2013. Moreover, our formalism leads to strong constraints on the electroweak triple gauge boson couplings. Note added: The analysis has been updated with a NEW GLOBAL 6-PARAMETER FIT with all the public data available after Moriond 2013. Updates of this analysis are provided at the website http://hep.if.usp.br/Higgs, as well as n
We review the study of the charged Higgs and top quark associated production at the LHC with the presence of an additional scalar doublet. Top quark spin effects are related to the Higgs fermion couplings through this process. The angular distributions with respect to top quark spin turn out to be distinctive observables to study the $Htb$ interaction in different models.
A common lore has arisen that beyond the Standard Model (BSM) particles, which can be searched for at current and proposed experiments, should have flavorless or mostly third-generation interactions with Standard Model quarks. This theoretical bias severely limits the exploration of BSM phenomenology, and is especially constraining for extended Higgs sectors. Such limitations can be avoided in the context of Spontaneous Flavor Violation (SFV), a robust and UV complete framework that allows for significant couplings to any up or down-type quark, while suppressing flavor-changing neutral currents via flavor alignment. In this work we study the theory and phenomenology of extended SFV Higgs sectors with large couplings to any quark generation. We perform a comprehensive analysis of flavor and collider constraints of extended SFV Higgs sectors, and demonstrate that new Higgs bosons with large couplings to the light quarks may be found at the electroweak scale. In particular, we find that new Higgses as light as 100 GeV with order $sim$ 0.1 couplings to first or second generation quarks, which are copiously produced at LHC via quark fusion, are allowed by current constraints. Furthermore, the additional SFV Higgses can mix with the SM Higgs, providing strong theory motivation for an experimental program looking for deviations in the light quark-Higgs couplings. Our work demonstrates the importance of exploring BSM physics coupled preferentially to light quarks, and the need to further develop dedicated experimental techniques for the LHC and future colliders.
We study the possibility of discovering neutral scalar Higgs bosons in the $U(1)$-extended supersymmetric standard model (USSM) at the CERN Large Hadron Collider (LHC), by examining their productions via the exotic quark loop in the gluon fusion process at leading order. It is possible in some parameter region that the neutral scalar Higgs bosons may have stronger couplings with the exotic quarks than with top quark. In this case, the exotic quarks may contribute more significantly than top quark in productions of the neutral scalar Higgs bosons in the gluon fusion process. We find that there is indeed some parameter region in the USSM that supports our speculations.
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