Search for Higgs Boson Decay to a Charm Quark-Antiquark Pair in Proton-Proton Collisions at √<i>s</i>=13 TeV

A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, H ? cc-, produced in association with a leptonically decaying V (W or Z) boson is presented. The search is performed with proton-proton collisions at vs = 13 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb-1. Novel charm jet identification and analysis methods using machine learning techniques are employed. The analysis is validated by searching for Z ? cc- in VZ events, leading to its first observation at a hadron collider with a significance of 5.7 standard deviations. The observed (expected) upper limit on s(VH)B(H ? cc-) is 0.94 (0.50(-0.15)(+0.22) )pb at 95% confidence level (C.L.), corresponding to 14 (7.6(-2.3)(+3.4)) times the standard model prediction. For the Higgs-charm Yukawa coupling modifier, ?c, the observed (expected) 95% C.L. interval is 1.1 < |?(c)| < 5.5 (|?(c)| < 3.4), the most stringent constraint to date.