Higgs couplings at the LHC

TL;DR

The paper assesses how the LHC can extract Higgs couplings to fermions and gauge bosons for a SM-like Higgs, focusing on the intermediate mass range where multiple decay channels exist. It maps production and decay rates to Higgs partial widths, using gluon fusion, weak-boson fusion, and associated production, and exploits ratios of observables to cancel major systematics. By combining LHC measurements across channels and leveraging assumptions such as $HWW$ and $HZZ$ universality and small unobserved widths, it forecasts 10–20% precision on several partial widths and 5–10% precision on ratios of couplings, with direct sensitivity to the top Yukawa via $ttH$ in the 110–130 GeV region. The results provide a framework for validating the Higgs mechanism and determining the dominant couplings of a SM-like Higgs at the LHC, with implications for testing electroweak symmetry breaking and mass generation for fermions and vector bosons.

Abstract

The observation of a SM-like Higgs boson in multiple channels at the LHC allows the extraction of Higgs couplings to gauge bosons and fermions. The precision achievable at the LHC, for an integrated luminosity of 200 fb^{-1}, is reviewed and updated.

Figures (2)

• Figure 1: Expected relative error on the determination of $B\sigma$ for various Higgs search channels at the LHC with 200 fb$^{-1}$ of data. Solid lines are for inclusive Higgs production channels which are dominated by gluon fusion. Expectations for weak boson fusion are given by the dashed lines. The black-dotted line is for $ttH,H\to b\bar{b}$ as analyzed in Ref. Drollinger:2001ym. The $ttH,H\to W^+W^-$Maltoni:2002jr (red dotted) and $WH,H\to b\bar{b}$Drollinger:2002uj (dash-dotted) curves assume 300 fb$^{-1}$ of data and high luminosity running.
• Figure 2: Relative accuracy expected at the LHC with 200 fb$^{-1}$ of data for (a) various ratios of Higgs boson partial widths and (b) the indirect determination of partial and total widths $\tilde{\Gamma}$ and $\tilde{\Gamma}_i=\Gamma_i(1-\epsilon)$. Width ratio extractions only assume $W,Z$ universality, which can be tested at the 15 to 30% level (solid line). Indirect width measurements assume $b,\tau$ universality in addition and require a small branching ratio $\epsilon$ for unobserved modes like $H\to c\bar{c}$. (See text).