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 √<i>s</i> = 13 TeV

Abstract

A search for the standard model (SM) Higgs boson (H) produced with transverse momentum greater than 450 GeV and decaying to a charm quark-antiquark (cc¯) pair is presented. The search is performed using proton-proton collision data collected at √s = 13 TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 138 fb^{−1}. Boosted H → cc¯ 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 → cc¯ decay process, which is observed in association with jets at high pT for the first time with a signal strength of 1.00 +0.17−0.14 (syst) ± 0.08 (theo) ± 0.06 (stat), defined as the ratio of the observed process rate to the standard model expectation. The observed (expected) upper limit on σ(H) B(H → cc¯) is set at 47 (39) times the SM prediction at 95% confidence level.