Search for decays of the Higgs boson into a pair of pseudoscalar particles decaying into $b\bar{b}\tau^+\tau^-$ using $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

TL;DR

This paper searches for exotic Higgs decays into pseudoscalar pairs that decay into $b\bar{b}$ and $\tau^+\tau^-$, setting upper limits on the branching ratio in the mass range 12-60 GeV using 13 TeV ATLAS data.

Contribution

It provides the first constraints on Higgs decays into pseudoscalars decaying into $b\bar{b}$ and $\tau^+\tau^-$ in the specified mass range with 13 TeV data.

Findings

No significant excess observed above SM predictions.

Upper limits on branching ratio range from 2.2% to 3.9%.

Analysis uses 140 fb$^{-1}$ of data from ATLAS at 13 TeV.

Abstract

This paper presents a search for exotic decays of the Higgs boson into a pair of new pseudoscalar particles, $H\rightarrow aa$, where one pseudoscalar decays into a $b$-quark pair and the other decays into a $\tau$-lepton pair, in the mass range $12\leq m_{a}\leq 60$ GeV. The analysis uses $pp$ collision data at $\sqrt{s} = 13$ TeV collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 140 ${fb}^{-1}$. No significant excess above the Standard Model (SM) prediction is observed. Assuming the SM Higgs boson production cross-section, the search sets upper limits at 95% confidence level on the branching ratio of Higgs bosons decaying into $b\bar{b}\tau^+\tau^-$, $\mathcal{B}(H \rightarrow aa \rightarrow b\bar{b}\tau^+\tau^-)$, between 2.2% and 3.9% depending on the pseudoscalar mass.