Simultaneous probe of the charm and bottom quark Yukawa couplings using $\mathrm{t\bar{t}}$H events

Abstract

A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, H $\to$ $\mathrm{c\bar{c}}$, produced in association with a top quark-antiquark pair ($\mathrm{t\bar{t}}$H) is presented. The search is performed with data from proton-proton collisions at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. Advanced machine learning techniques are employed for jet flavor identification and event classification. The Higgs boson decay to a bottom quark-antiquark pair is measured simultaneously and the observed $\mathrm{t\bar{t}}$H (H $\to$ $\mathrm{b\bar{b}}$) event rate relative to the standard model expectation is 0.91 $^{+0.26}_{-0.22}$. The observed (expected) upper limit on the product of production cross section and branching fraction $\sigma$($\mathrm{t\bar{t}}$H) $\mathcal{B}$(H $\to$ $\mathrm{c\bar{c}}$) is 0.11 (0.13) pb at 95% confidence level, corresponding to 7.8 (8.7) times the standard model prediction. When combined with the previous search for H $\to$ $\mathrm{c\bar{c}}$ via associated production with a W or Z boson, the observed (expected) 95% confidence interval on the Higgs-charm Yukawa coupling modifier, $\kappa_\mathrm{c}$, is $\lvert{\kappa_\mathrm{c}}\rvert$ $\lt$ 3.5 (2.7), the most stringent constraint to date.