Simultaneous Probe of the Charm and Bottom Quark Yukawa Couplings Using $t\bar{t}H$ Events

A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, H → c c ¯ , produced in association with a top quark-antiquark pair ( t t ¯ H ) is presented. The search is performed with data from proton-proton collisions at 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 t t ¯ H ( H → b b ¯ ) event rate relative to the standard model expectation is 0.91 − 0.22 + 0.26 . The observed (expected) upper limit on the product of production cross section and branching fraction σ ( t t ¯ H ) B ( H → c 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 → c c ¯ via associated production with a W or Z boson, the observed (expected) 95% confidence interval on the Higgs-charm Yukawa coupling modifier, κ c , is | κ c | < 3.5 (2.7), the most stringent constraint to date.