Simultaneous Probe of the Charm and Bottom Quark Yukawa Couplings Using ttH 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 (ttH) 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 ttH⁢ (𝐻→𝑏⁢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 𝜎⁡ (ttH) ⁢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.