A Bayesian view of the Higgs sector with higher dimensional operators

Abstract

Abstract:We investigate the possibilities of New Physics affecting the Standard Model (SM) Higgs sector. An effective Lagrangian with dimension-six operators is used to capture the effect of New Physics. We carry out a global Bayesian inference analysis, considering the recent LHC data set including all available correlations, as well as results from Tevatron. Trilinear gauge boson couplings and electroweak precision observables are also taken into account. The case of weak bosons tensorial couplings is closely examined and NLO QCD corrections are taken into account in the deviations we predict. We consider two scenarios, one where the coefficients of all the dimension-six operators are essentially unconstrained, and one where a certain subset is loop suppressed. In both scenarios, we find that large deviations from some of the SM Higgs couplings can still be present, assuming New Physics arising at 3 TeV. In particular, we find that a significantly reduced coupling of the Higgs to the top quark is possible and slightly favored by searches on Higgs production in association with top quark pairs. The total width of the Higgs boson is only weakly constrained and can vary between 0.7 and 2.7 times the Standard Model value within 95% Bayesian credible interval (BCI). We also observe sizeable effects induced by New Physics contributions to tensorial couplings. In particular, the Higgs boson decay width into Zγ can be enhanced by up to a factor 12 within 95% BCI.

Anomalous gauge couplings from composite Higgs and warped extra dimensions

“…2 Here our dimension six basis is defined in such a way that (in renormalizable theories) the operators O F F , O W 3 are only generated pertubatively at the loop level while the other ones can potentially be generated at treelevel. This particularly convenient basis has been already used in [9], is discussed more formally in [10], and is consistent with the general basis presented in [11]. We display below only the operators which will feed into anomalous gauge couplings, or will be closely related to their study.…”

“…3 The four fermion operators O 4f and O 4f do not appear in the basis of ref. [9], as they can be eliminated in favor of the two operators (∂ρBµν ) 2 and (DρW a µν ) 2 , which played no role in the analysis of that paper.…”

“…generated by the running of the gauge coupling driven by composite states above the scale of conformal breaking, see e.g [19] and references therein. 9 The tree-level exchange of a dilaton would thus generate operators of the form…”

“…The expected deviations to the S and T parameters [25,26] and to Higgs anomalous couplings in terms of the effective operators of L (6) are [9] …”

“…S = 0.05 ± 0.09 , T = 0.08 ± 0.07 (7.10) with a correlation coefficient of +0.91. Constraints on a V (for a W = a Z ) and the ζ i are taken from the global fit of [9]. At 95% CL one has 0.96 < a V < 1.21 , −6.1 < ζ γ v × 10 3 < 0.9 , (7.11) the constraints on other ζ i being less stringent for our purpose.…”