Search for direct top squark pair production in final states with two tau leptons in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector

TL;DR

This paper reports a search for direct top squark pair production in final states with tau leptons using 8 TeV proton-proton collision data from ATLAS, setting new exclusion limits on top squark masses.

Contribution

It introduces a novel search strategy for top squarks decaying via scalar taus in tau-rich final states at the LHC, extending previous mass exclusion limits.

Findings

No significant excess over Standard Model expectations.

Excluded top squark masses between 490 GeV and 650 GeV.

Set 95% confidence level exclusion limits based on scalar tau mass.

Abstract

A search for direct pair production of the supersymmetric partner of the top quark, decaying via a scalar tau to a nearly massless gravitino, has been performed using 20 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}=8$ TeV. The data were collected by the ATLAS experiment at the LHC in 2012. Top squark candidates are searched for in events with either two hadronically decaying tau leptons, one hadronically decaying tau and one light lepton, or two light leptons. No significant excess over the Standard Model expectation is found. Exclusion limits at 95% confidence level are set as a function of the top squark and scalar tau masses. Depending on the scalar tau mass, ranging from the 87 GeV LEP limit to the top squark mass, lower limits between 490 GeV and 650 GeV are placed on the top squark mass within the model considered.