A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, $H\to c\overline{c}$, produced in association with a leptonically decaying $V$ ($W$ or $Z$) boson is presented. The search is performed with proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ collected by the CMS experiment, corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$. Novel charm jet identification and analysis methods using machine learning techniques are employed. The analysis is validated by searching for $Z\to c\overline{c}$ 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 $\sigma (VH)\mathcal{B}(H\to c\overline{c})$ 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, ${\kappa }_c$, the observed (expected) 95% C.L. interval is $1.1<|{\kappa }_c|<5.5$ ($|{\kappa }_c|<3.4$), the most stringent constraint to date.

• Received 11 May 2022
• Accepted 7 July 2022

DOI:https://doi.org/10.1103/PhysRevLett.131.061801

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