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

Abstract

A search for pair production of bottom squarks in events with hadronically decaying $\tau$-leptons, $b$-tagged jets and large missing transverse momentum is presented. The analyzed dataset is based on proton-proton collisions at $\sqrt{s}$ = 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 ${\tilde{\chi }}_2^0$ and a bottom quark, with ${\tilde{\chi }}_2^0$ decaying into a Higgs boson and the lightest neutralino ${\tilde{\chi }}_1^0$. The search focuses on final states where at least one Higgs boson decays into a pair of hadronically decaying $\tau$-leptons. This allows the acceptance and thus the sensitivity to be significantly improved relative to the previous results at low masses of the ${\tilde{\chi }}_2^0$, where bottom-squark masses up to 850 GeV are excluded at the 95% confidence level, assuming a mass difference of 130 GeV between ${\tilde{\chi }}_2^0$ and ${\tilde{\chi }}_1^0$. Model-independent upper limits are also set on the cross section of processes beyond the Standard Model.

45 pages in total, author list starting page 29, 8 figures, 8 tables, published in Phys. Rev. D. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/SUSY-2018-40

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