Search for Higgs Boson and Observation of $Z$ Boson through Their Decay into a Charm Quark-Antiquark Pair in Boosted Topologies in Proton-Proton Collisions at $\sqrt{s}=13\text{}\text{}\mathrm{TeV}$

A search for the standard model (SM) Higgs boson ($H$) produced with transverse momentum (${p}_{T}$) greater than 450 GeV and decaying to a charm quark-antiquark ($c\overline{c}$) pair is presented. The search is performed using proton-proton collision data collected at $\sqrt{s}=13\text{}\text{}\mathrm{TeV}$ by the CMS experiment at the LHC, corresponding to an integrated luminosity of $138\text{}\text{}{\mathrm{fb}}^{-1}$. Boosted $H\to c\overline{c}$ decay products are reconstructed as a single large-radius jet and identified using a deep neural network charm tagging technique. The method is validated by measuring the $Z\to c\overline{c}$ decay process, which is observed in association with jets at high ${p}_{T}$ for the first time with a signal strength of ${1.00}_{-0.14}^{+0.17}\left(\mathrm{syst}\right)±\phantom{\rule{0ex}{0ex}}0.08\left(\mathrm{theo}\right)±0.06\left(\mathrm{stat}\right)$, defined as the ratio of the observed process rate to the SM expectation. The observed (expected) upper limit on $\sigma \left(H\right)B\left(H\to c\overline{c}\right)$ is set at 47 (39) times the SM prediction at 95% confidence level.