Measurement of the Higgs boson production rate in association with top quarks in final states with electrons, muons, and hadronically decaying tau leptons at $\sqrt{s} =$ 13 TeV

TL;DR

This paper reports the most sensitive measurement to date of Higgs boson production in association with top quarks at 13 TeV, using CMS data, machine learning, and multiple decay channels to constrain the top-Higgs coupling.

Contribution

It presents a novel analysis combining multiple signatures and advanced techniques to measure tH and t-tbar-H production rates with high precision.

Findings

Measured t-tbar-H production rate at 0.92 ± 0.19 (stat) +0.17/-0.13 (syst) of SM expectation.

Observed significance of t-tbar-H signal is 4.7 standard deviations.

Constrains the top-Higgs coupling ratio κ_t within specific ranges at 95% CL.

Abstract

The rate for Higgs (H) bosons production in association with either one (tH) or two ($\mathrm{t\bar{t}}$H) top quarks is measured in final states containing multiple electrons, muons, or tau leptons decaying to hadrons and a neutrino, using proton-proton collisions recorded at a center-of-mass energy of 13 TeV by the CMS experiment. The analyzed data correspond to an integrated luminosity of 137 fb$^{-1}$. The analysis is aimed at events that contain H $\to$ WW, H $\to$ $\tau\tau$, or H $\to$ ZZ decays and each of the top quark(s) decays either to lepton+jets or all-jet channels. Sensitivity to signal is maximized by including ten signatures in the analysis, depending on the lepton multiplicity. The separation among the tH, the $\mathrm{t\bar{t}}$H, and the backgrounds is enhanced through machine-learning techniques and matrix-element methods. The measured production rates for the $\mathrm{t\bar{t}}$H and tH signals correspond to 0.92 $\pm$ 0.19 (stat) $^{+0.17}_{-0.13}$ (syst) and 5.7 $\pm$ 2.7 (stat) $\pm$ 3.0 (syst) of their respective standard model (SM) expectations. The corresponding observed (expected) significance amounts to 4.7 (5.2) standard deviations for $\mathrm{t\bar{t}}$H, and to 1.4 (0.3) for tH production. Assuming that the Higgs boson coupling to the tau lepton is equal in strength to its expectation in the SM, the coupling $y_{\mathrm{t}}$ of the Higgs boson to the top quark divided by its SM expectation, $\kappa_\mathrm{t}$ = $y_\mathrm{t} / y_\mathrm{t}^\mathrm{SM}$, is constrained to be within $-$0.9 $\lt$ $\kappa_\mathrm{t}$ $\lt$ $-$0.7 or 0.7 $\lt$ $\kappa_\mathrm{t}$ $\lt$ 1.1, at 95% confidence level. This result is the most sensitive measurement of the $\mathrm{t\bar{t}}$H production rate to date.