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 √s=13 TeV

Abstract

A search for the standard model (SM) Higgs boson (H) produced with transverse momentum (pT) greater than 450 GeV and decaying to a charm quark-antiquark (c¯c) 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→c¯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→c¯c 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 SM expectation. The observed (expected) upper limit on σ(H)B(H→c¯c) is set at 47 (39) times the SM prediction at 95% confidence level.