Search for bottom-squark pair production in $pp$ collision events at $\sqrt{s} = 13$ TeV with hadronically decaying $\tau$-leptons, $b$-jets and missing transverse momentum using the ATLAS detector

International audience ; A search for pair production of bottom squarks in events with hadronically decaying τ -leptons, b -tagged jets, and large missing transverse momentum is presented. The analyzed dataset is based on proton-proton collisions at s = 13 TeV delivered by the Large Hadron Collider and recorded by the ATLAS detector from 2015 to 2018, and corresponds to an integrated luminosity of 139 fb - 1 . The observed data are compatible with the expected Standard Model background. Results are interpreted in a simplified model where each bottom squark is assumed to decay into the second-lightest neutralino χ ˜ 2 0 and a bottom quark, with χ ˜ 2 0 decaying into a Higgs boson and the lightest neutralino χ ˜ 1 0 . The search focuses on final states where at least one Higgs boson decays into a pair of hadronically decaying τ -leptons. This allows the acceptance and thus the sensitivity to be significantly improved relative to the previous results at low masses of the χ ˜ 2 0 , where bottom-squark masses up to 850 GeV are excluded at the 95% confidence level, assuming a mass difference of 130 GeV between χ ˜ 2 0 and χ ˜ 1 0 . Model-independent upper limits are also set on the cross section of processes beyond the Standard Model.