Search for the Higgs boson produced in association with a $W$ boson and decaying to four $b$-quarks via two spin-zero particles in $pp$ collisions at 13 TeV with the ATLAS detector

TL;DR

This paper searches for exotic Higgs decays into four b-quarks via two new spin-zero particles in association with a W boson, using 13 TeV proton-proton collision data from ATLAS, setting upper limits on the process.

Contribution

It introduces a dedicated search for Higgs decays to new particles in the $H ightarrow aa ightarrow 4b$ channel with the ATLAS detector at 13 TeV, providing the first such limits in this mass range.

Findings

No significant excess observed above Standard Model predictions.

Upper limits on cross section times branching ratio range from 6.2 pb to 1.5 pb.

Constraints on exotic Higgs decay models are established.

Abstract

This paper presents a dedicated search for exotic decays of the Higgs boson to a pair of new spin-zero particles, $H \rightarrow aa$, where the particle $a$ decays to $b$-quarks and has a mass in the range of 20-60 GeV. The search is performed in events where the Higgs boson is produced in association with a $W$ boson, giving rise to a signature of a lepton (electron or muon), missing transverse momentum, and multiple jets from $b$-quark decays. The analysis is based on the full dataset of $pp$ collisions at $\sqrt{s} = 13$ TeV recorded in 2015 by the ATLAS detector at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 3.2 fb$^{-1}$. No significant excess of events above the Standard Model prediction is observed, and a $95\%$ confidence-level upper limit is derived for the product of the production cross section for $pp \rightarrow WH$ times the branching ratio for the decay $H \rightarrow aa \rightarrow 4b$. The upper limit ranges from 6.2 pb for an $a$-boson mass $m_a = 20$ GeV to 1.5 pb for $m_a = 60$ GeV.