Measurement of $\mathrm{t\overline{t}H}$ production in the $\mathrm{H\rightarrow b\overline{b}}$ decay channel in $41.5\,\mathrm{fb}^{-1}$ of proton-proton collision data at $\sqrt{s}=13\,\mathrm{TeV}$

A measurement of the associated production of a standard model Higgs boson with a top quark-antiquark pair ($\mathrm{t\overline{t}H}$) in proton-proton collisions at $\sqrt{s}=13\,\mathrm{TeV}$ is presented. The result is based on data recorded with the CMS detector at the CERN LHC in 2017 and corresponds to an integrated luminosity of $41.5\,\mathrm{fb}^{-1}$. Candidate $\mathrm{t\overline{t}H}$ events are selected based on the number of leptons in the event, targeting all $\mathrm{t\overline{t}}$ decay channels, and are categorised according to the number of jets. Multivariate analysis techniques are employed to further categorise the events and eventually discriminate between signal and background. A combined fit of multivariate discriminant distributions in all categories results in a best fit value of the $\mathrm{t\overline{t}H}$ signal strength relative to the standard model cross section, $\mu = \sigma/\sigma_{\mathrm{SM}}$, of $\hat{\mu} = 1.49\,{}^{+0.21}_{-0.20}\mathrm{(stat)}\,{}^{+0.39}_{-0.35}\mathrm{(syst)}$, corresponding to an observed (expected) significance of 3.7 (2.6) standard deviations. Combined with previous results obtained with $35.9\,\mathrm{fb}^{-1}$ of data recorded in 2016, a best-fit value of $\hat{\mu} = 1.15\,{}^{+0.15}_{-0.15}\mathrm{(stat)}\,{}^{+0.28}_{-0.25}\mathrm{(syst)}$ is found, corresponding to an observed (expected) significance of 3.9 (3.5) standard deviations above the background-only hypothesis. $$\textit{This document has been revised with respect to the version dated May 19, 2019.}$$