Search for the decay of the Higgs boson to a pair of light pseudoscalar bosons in the final state with four bottom quarks in proton-proton collisions at √s=13TeV

Abstract

A search is presented for the decay of the 125GeV Higgs boson (H) to a pair of new light pseudoscalar bosons (a), followed by the prompt decay of each a boson to a bottom quark-antiquark pair, H → aa → bbbb. The analysis is performed using a data sample of proton-proton collisions collected with the CMS detector at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 138fb−1. To reduce the background from standard model processes, the search requires the Higgs boson to be produced in association with a leptonically decaying W or Z boson. The analysis probes the production of new light bosons in a 15 < ma < 60GeV mass range. Assuming the standard model predictions for the Higgs boson production cross sections for pp → WH and ZH, model independent upper limits at 95% confidence level are derived for the branching fraction B(H → aa → bbbb). The combined WH and ZH observed upper limit on the branching fraction ranges from 1.10 for ma = 20GeV to 0.36 for ma = 60GeV, complementing other measurements in the µµττ, ττττ and bbℓℓ (ℓ = µ,τ) channels.