Search for a Higgs boson produced in association with a charm quark and decaying to a W boson pair in proton-proton collisions at $$ \sqrt{s}=13 $$ TeV

A bstract This paper presents a search for a Higgs boson produced in association with a charm quark (cH) which allows to probe the Higgs-charm Yukawa coupling strength modifier κ c . Higgs boson decays to a pair of W bosons are considered, where one W boson decays to an electron and a neutrino, and the other W boson decays to a muon and a neutrino. The data, corresponding to an integrated luminosity of 138 fb − 1 , were collected between 2016 and 2018 with the CMS detector at the LHC at a center-of-mass energy of $$ \sqrt{s}=13 $$ s = 13 TeV. Upper limits at the 95% confidence level (CL) are set on the ratio of the measured yield to the standard model expectation for cH production. The observed (expected) upper limit is 1065 (506), corresponding to an observed (expected) constraint of |κ c | < 211 (95). When combined with the previous search for cH in the diphoton decay channel of the Higgs boson, the limits are interpreted as observed (expected) constraints at 95% CL on the value of κ c , |κ c | < 47 (51).