Total Width of 125 GeV Higgs Boson

TL;DR

A way to estimate the branching fraction for the Higgs-boson decay to dark matter is described and a no-go theorem for the γγ signal of theHiggs boson at the LHC is discussed.

Abstract

By using the LHC and Tevatron measurements of the cross sections to various decay channels relative to the standard model Higgs boson, the total width of the putative 125 GeV Higgs boson is determined as 6.1 +7.7-2.9 MeV. We describe a way to estimate the branching fraction for Higgs decay to dark matter. We also discuss a No-Go theorem for the gammagamma signal of the Higgs boson at the LHC.

Figures (2)

• Figure 1: $\lambda_{f,S}$ dependence of the cross sections of various processes relative to the SM Higgs, for the case of a color-octet fermion (leptogluon:$F8$) with charge $Q_s=1$ and color-octet scalar ($S8$) with $Q_s=1$: $XA \equiv \sigma(X\bar{X}\rightarrow h^0\rightarrow A\bar{A}) /\sigma(X\bar{X}\rightarrow h^0_{\rm SM}\rightarrow A\bar{A})$. We consider three quantities $XA=g\gamma,gV,$ and $V\gamma$, corresponding to $gg\rightarrow \gamma\gamma$(solid blue), $gg\rightarrow VV(WW^*$ or $ZZ^*)$(short-dashed red), and $VV\rightarrow \gamma\gamma$(long-dashed green). $\lambda_{f,S}$ is the Higgs coupling normalized by the Yukawa couplings giving the masses by the Higgs mechanism. See Eq. (\ref{['eq6']}) for definition. The yellow vertical band in the top panel is preferred by the present data suggesting $\gamma\gamma$ enhancement.
• Figure 2: Regions of $\gamma\gamma$ enhancement in $\lambda_fN_cQ_f^2,\ \lambda_fC_f$ plane in $Q_f=1$ case. The $g\gamma>1$ region is divided into 4 colored regions: ($V\gamma<1$;$1<V\gamma<2$;$2<V\gamma$) are (yellow;brown;green), respectively. Red meshed region, which is preferred by the present experimental data, corresponds to $V\gamma>1$ and $gV<1$, where the latter is between the two horizontal lines, $\lambda_fC_f=0,-1.03$. Color-octet fermion(leptogluon), Color-triplet fermion, and Color-singlet fermion are shown by solid lines with the end points corresponding to $\lambda_f=-1$(square) and $\lambda_f=1$(circle). In $Q_f\neq 1$ case, the $x$-coordinates scale with $Q_f^2$. $\lambda_f=1$ corresponds to the case of its mass generated by Higgs mechanism. A color-octet fermion with $Q_f=1$ is consistent with the red meshed region at $\lambda_f\simeq -0.31$. For a new scalar, the lengths of the theory lines should be scaled by $1/4$; thus, a scalar octet has no overlap with the preferred red meshed region.