Revisiting the gluino mass limits in the pMSSM in the light of the latest LHC data and Dark Matter constraints

Abstract

The purpose of this paper is to examine the model dependence of the stringent constraints on the gluino mass obtained from the Large Hadron Collider (LHC) experiments by analyzing the Run II data using specific simplified models based on several ad hoc sparticle spectra which cannot be realized even in the fairly generic pMSSM models. We first revisit the bounds on the gluino mass placed by the ATLAS collaboration using the $1l + jets + \met$ data. We show that the exclusion region in the $M_{\widetilde{g}}-M_{\widetildeχ^0_1}$ plane in the pMSSM scenario sensitively depends on the mass hierarchy between the left and right squarks and composition of the lighter electroweakinos and, to a lesser extent, other parameters. Most importantly, for higgsino type lighter electroweakinos (except for the LSP), the bound on the gluino mass from this channel practically disappears. However, if such models are confronted by the ATLAS $jets + \met$ data, fairly strong limits are regained. Thus in the pMSSM an analysis involving a small number of channels may provide more reliable mass limits. We have also performed detailed analyses on neutralino dark matter (DM) constraints in the models we have studied and have found that for a significant range of LSP masses, the relic density constraints from the WMAP/PLANCK data are satisfied and LSP-gluino coannihilation plays an important role in relic density production. We have also checked the simultaneous compatibility of the models studied here with the direct DM detection, and the LHC constraints.