Search for the Higgs boson produced in association with a vector boson and decaying into two spin-zero particles in the H → aa → 4b channel in pp collisions at s√=13TeV with the ATLAS detector

Agni Bethani, Brian Cox, Jonathan Crane, Cinzia Da Via, Nicholas Dann, Sam Dysch, Alessandra Forti, David Lack, Jiri Masik, Stephen Menary, Francisca Munoz Sanchez, Alexander Oh, Emily Orgill, Joleen Pater, Yvonne Peters, Andrew Pilkington, Darren Price, Yang Qin, Jacob Rawling, Nicolas ScharmbergSavanna Shaw, Stephen Watts, Terence Wyatt, The ATLAS Collaboration

    Research output: Contribution to journalArticlepeer-review

    Abstract

    A search for exotic decays of the Higgs boson into a pair of spin-zero particles, H → aa, where the a-boson decay sin to b-quarks promptly or with a mean proper lifetime cτa up to 6 mm and has a mass in the range of 20–60 GeV, is presented. The search is performed in events where the Higgs boson is produced in association with a W or Z boson, giving rise to a signature of one or two charged leptons (electrons or muons) and multiple jets from b-quark decays. The analysis is based on the dataset of proton-proton collisions at s√=13 TeV recorded in 2015 and 2016 by the ATLAS detector at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 36.1 fb−1. No significant excess of events above the Standard Model background prediction is observed, and 95% confidence-level upper limits are derived for the production cross-sections for pp → WH, ZH and their combination, times the branching ratio of the decay chain H → aa → 4b. For a-bosons which decay promptly, the upper limit on the combination of cross-sections for WH and ZH times the branching ratio of H → aa → 4b ranges from 3.0 pb for ma = 20 GeV to 1.3 pb for ma = 60 GeV, assuming that the ratio of WH to ZH cross-sections follows the Standard Model prediction. For a-bosons with longer proper lifetimes, the most stringent limits are 1.8 pb and 0.68 pb, respectively, at cτa ∼ 0.4 mm.
    Original languageEnglish
    JournalThe Journal of High Energy Physics
    Volume2018
    Issue number31
    Early online date4 Oct 2018
    DOIs
    Publication statusPublished - Oct 2018

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