Speaker
Description
A novel search for exotic decays of the Higgs boson to pairs of long-lived
neutral particles, each decaying to a bottom quark pair, is performed
using 139 fb$^{-1}$ of $\sqrt{s} = 13$ TeV proton-proton collision data
collected with the ATLAS detector at the LHC. Events consistent with the
production of a Higgs boson in association with a $Z$ boson are analyzed,
with the leptonic decay of the $Z$ mitigating the trigger challenges associated
with displaced objects. Long-lived particle (LLP) decays are reconstructed from
inner detector tracks as displaced vertices with high mass and track multiplicity
relative to Standard Model processes. The analysis selection requires the
presence of at least two displaced vertices, effectively suppressing Standard Model
backgrounds. The residual background contribution is estimated using a fully data
driven technique. No excess over the Standard Model prediction is observed, and
upper limits are set on the branching ratio of the Higgs boson to pairs of LLPs.
Branching ratios of >=10% are excluded at the 95% confidence level for
LLP mean proper lifetimes $c\tau$ as small as 4 mm and as large as 110 mm.
For LLP masses below 40 GeV, these results represent the most stringent
constraints to date for this range of proper lifetimes.
