Evidence for associated production of a Higgs boson with a top quark pair in final states with electrons, muons, and hadronically decaying $\tau$ leptons at $\sqrt{s} =$ 13 TeV

TL;DR

This paper reports evidence for the production of a Higgs boson with a top quark pair in proton-proton collisions at 13 TeV, using advanced analysis techniques to improve sensitivity and measure the signal rate.

Contribution

It presents the first evidence for t-tbar-H production in final states with electrons, muons, and hadronic tau decays at 13 TeV, utilizing matrix element and machine learning methods.

Findings

Measured signal rate is 1.23 times the SM expectation.

Observed significance is 3.2 sigma, indicating evidence for the process.

Set an upper limit of 2.1 times the SM rate at 95% CL.

Abstract

Results of a search for the standard model Higgs boson produced in association with a top quark pair ($\mathrm{t\overline{t}}$H) in final states with electrons, muons, and hadronically decaying $\tau$ leptons are presented. The analyzed data set corresponds to an integrated luminosity of 35.9 fb$^{-1}$ recorded in proton-proton collisions at $\sqrt{s} =$ 13 TeV by the CMS experiment in 2016. The sensitivity of the search is improved by using matrix element and machine learning methods to separate the signal from backgrounds. The measured signal rate amounts to 1.23 $^{+0.45}_{-0.43}$ times the production rate expected in the standard model, with an observed (expected) significance of 3.2$\sigma$ (2.8$\sigma$), which represents evidence for $\mathrm{t\overline{t}}$H production in those final states. An upper limit on the signal rate of 2.1 times the standard model production rate is set at 95% confidence level.