Impact of LHC Searches on NLSP Top Squark and Gluino Mass

TL;DR

This paper analyzes how 7 TeV LHC searches constrain the masses of the NLSP top squark and gluino in supersymmetric models, excluding certain mass ranges and setting lower bounds based on various search channels.

Contribution

It provides the first detailed analysis of LHC search sensitivities specifically for NLSP top squark scenarios with decay into neutralino and charm quark, including gluino decay contributions.

Findings

Stop masses up to 160 GeV are constrained by monojet searches.

NLSP stop mass below 130-140 GeV is excluded depending on mass difference.

Gluino masses below approximately 600-700 GeV are excluded by b-jet and same-sign dilepton searches.

Abstract

We explore the implications of 7 TeV LHC searches for a scenario in which one of the stops is the next-to lightest supersymmetric particle (NLSP). The NLSP stop (\tilde{t}_1) is assumed to decay exclusively into neutralino and charm quark. We consider processes where the stops are pair produced together with a hard QCD jet. We also consider stop quarks from gluino decays, \tilde{g}\to t\tilde{t}_1^\ast+\bar{t}\tilde{t}_1. We show that the monojet ATLAS and CMS searches corresponding to 1 fb^{-1} of integrated luminosity are sensitive to stop masses of up to 160 GeV, with the 20% neutralino-stop coannihilation region essentially ruled out for M_{\tilde{t}_1}\lesssim 140 GeV. The region M_{\tilde{t}_1}\lesssim 130 GeV is excluded with even relatively larger mass difference, M_{\tilde{t}_1}-M_{\tilde{\chi}_1^0}\sim 40 GeV, by the multi-jets search. The b-jet and same-sign dilepton searches are sensitive to a heavier gluino because they only pick up gluino pair production events followed by top quarks decaying into b-jets and same-sign dileptons, respectively. We find that the LHC data places a lower limit on the gluino mass in this scenario of about 600 GeV (700 GeV) from b-jets (same-sign dileptons) searches.