Higgs couplings at the end of 2012

Abstract

Abstract Performing a fit to all publicly available data, we analyze the extent to which the latest results from the LHC and Tevatron constrain the couplings of the Higgs boson like state at ~ 125 GeV. To this end we assume that only Standard Model (SM) particles appear in the Higgs decays, but tree-level Higgs couplings to the up-quarks, down-quarks and vector bosons, relative to the SM are free parameters. We also assume that the leptonic couplings relative to the SM are the same as for the down-quark, and a custodial symmetry for the V = W, Z couplings. In the simplest approach, the effective Higgs couplings to gluons and photons are computed in terms of the previous parameters. This approach is also applied to Two-Higgs-Doublet Models of Type I and Type II. However, we also explore the possibility that the net Higgs to gg and γγ couplings have extra loop contributions coming from Beyond-the-Standard Model physics. We find that the SM p- value ~ 0.5 is more than 2σ away from fits in which: a) there is some non-SM contribution to the γγ coupling of the Higgs; or b) the sign of the top quark coupling to the Higgs is opposite that of the W coupling. In both these cases p-values ~ 0.9 can be achieved. Since option b) is difficult to realize in realistic models, it would seem that new physics contributions to the effective couplings of the Higgs are preferred.