Coupling spans of the Higgs-like boson

TL;DR

The paper addresses the challenge of constraining the total width Γ_h of a 125 GeV Higgs-like resonance using collider rate measurements, without assuming a fully SM-like width, by deriving a model-independent width span from data with minimal theoretical input.It introduces apparent squared-couplings a_P to relate production and decay rates, derives an upper bound Γ_h^max and a lower bound Γ_h^min from fits to ATLAS/CMS and Tevatron data, and uses these to bound exotic decay branching fractions as well as to bracket the couplings of the Higgs-like boson to SM particles.Numerical results place Γ_h^max around 0.52^{+0.82}_{-0.10} times the SM width and Γ_h^min around 1.05^{+1.26}_{-0.34} times the SM width (with wide 68.3%/95% CL ranges), yielding a width span near the SM value and an upper limit on non-SM decays of about 14% (68.3% CL) and 47% (95% CL) for the canonical doublet-case, thereby providing a data-driven route to probe Higgs couplings and possible new physics.

Abstract

Using the LHC and Tevatron data, we set upper and lower limits on the total width of the Higgs-like boson. The upper limit is based on the well-motivated assumption that the Higgs coupling to a W or Z pair is not much larger than in the Standard Model. These width limits allow us to convert the rate measurements into ranges for the Higgs couplings to various particles. A corollary of the upper limit on the total width is an upper limit on the branching fraction of exotic Higgs decays. Currently, this limit is 47% at the 95% CL if the electroweak symmetry is broken only by doublets.

Figures (2)

• Figure 1: $\Gamma_h^{\rm max}$ distribution obtained from Eq. (\ref{['upper-limit-doublet']}), and $\Gamma_h^{\rm min}$ distribution obtained from Eq. (\ref{['lower-limit']}). The span of $\Gamma_h/\Gamma_h^{\rm SM}$ lies between the dashed vertical lines, which mark the lower $1\sigma$ limit on $\Gamma_h^{\rm min}$ and the upper $1\sigma$ limit on $\Gamma_h^{\rm max}$.
• Figure 2: Spans of the Higgs couplings [see Eq. (\ref{['lower-upper']})] and total width, normalized to the SM values. The vertical lines at 0 and 1 correspond to no Higgs boson, and to the SM, respectively. The left-hand edge of each thick (thin) line represents the lower $1\sigma$ (95% CL) point on the distribution for the lower limit, while the right-hand edge represents the upper $1\sigma$ (95% CL) point on the distribution for the upper limit (as shown in Fig. 1 for $\Gamma_h$). If triplets or higher $SU(2)_W$ representations have VEVs, then the upper limits are pushed to higher values.