Abstract:
A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, 𝐻β𝑐β’Β―𝑐, produced in association with a top quark-antiquark pair (𝑡β’Β―𝑡β’𝐻) is presented. The search is performed with data from proton-proton collisions at β𝑠 =13ββTeV, corresponding to an integrated luminosity of 138ββfbβ1. 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 𝑡β’Β―𝑡β’𝐻β’(𝐻β𝑏β’Β―𝑏) event rate relative to the standard model expectation is 0.91+0.26β0.22. The observed (expected) upper limit on the product of production cross section and branching fraction 𝜎β‘(𝑡β’Β―𝑡β’𝐻)β’β¬β‘(𝐻β𝑐β’Β―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 β𝑐β’Β―𝑐 via associated production with a 𝑊 or 𝑍 boson, the observed (expected) 95% confidence interval on the Higgs-charm Yukawa coupling modifier, 𝜅𝑐, is |𝜅𝑐| <3.5 (2.7), the most stringent constraint to date.