Abstract
A search for decays of the Higgs boson into a pair of new spin-zero particles, H→aa, where the a-bosons decay into a b-quark pair and a muon pair, is presented. The search uses 36.1 fb−1 of proton–proton collision data at s=13 TeV recorded by the ATLAS experiment at the LHC in 2015 and 2016. No significant deviation from the Standard Model prediction is observed. Upper limits at 95% confidence level are placed on the branching ratio (σH/σSM)×B(H→aa→bbμμ), ranging from 1.2×10−4 to 8.4×10−4 in the a-boson mass range of 20–60 GeV. Model-independent limits are set on the visible production cross-section times the branching ratio to the bbμμ final state for new physics, σvis(X)×B(X→bbμμ), ranging from 0.1 fb to 0.73 fb for mμμ between 18 and 62 GeV.
Highlights
The discovery of the Standard Model (SM) Higgs boson [1,2] has opened up new avenues to search for physics beyond the SM (BSM) with perspectives to search for non-SM or “exotic” decays of the Higgs boson
The analysis presented in this Letter performs the search in the bbμμ final state
Higgs boson production through the gluon– gluon fusion and vector-boson fusion (VBF) processes was modelled at next-to-leading order (NLO) using Powheg-Box v2 [31,32,33] interfaced with Pythia 8.186 [34] using the AZNLO set of tuned parameters [35] for the simulation of the bbμμ decay of the
Summary
The discovery of the Standard Model (SM) Higgs boson [1,2] has opened up new avenues to search for physics beyond the SM (BSM) with perspectives to search for non-SM or “exotic” decays of the Higgs boson Such searches could provide unique access to hidden-sector particles that are singlets under the SM gauge transformations [3]. Searches for the Higgs boson with a mass of 125 GeV decaying into two spin-zero particles, H → aa, have been performed in variou√s final states in ATLAS and CMS [23,24,25,26,27,28,29]. The CMS search with s = 8 TeV data in the bbμμ final state set 95% CL limits on (σH /σSM)×B(H → aa → bbμμ) between 2×10−4 and 8×10−4 in the a-boson mass range of 25–62.5 GeV [25]. The ATLAS Collaboration / Physics Letters B 790 (2019) 1–21 per limits on (σH /σSM) × B(H → aa) between 4% and 26% in the a-boson mass range of 15–60 GeV [28]
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