Many faces of low mass neutralino dark matter in the unconstrained MSSM, LHC data and new signals

TL;DR

This paper explores the diverse dark matter mechanisms in an unconstrained MSSM where strongly interacting sparticles are heavy, analyzing LHC data and simulating signals in various electroweak scenarios to identify potential new physics signals.

Contribution

It demonstrates that relaxing mass constraints in the MSSM allows for varied electroweak sectors and novel dark matter production mechanisms, with only minor changes to existing LHC mass limits.

Findings

Mass limits are relaxed by up to 12-20% in some scenarios.

Electroweak signals can be detectable if strongly interacting sparticles are within LHC reach.

New dark matter production mechanisms are possible in unconstrained MSSM models.

Abstract

If all strongly interacting sparticles (the squarks and the gluinos) in an unconstrained minimal supersymmetric standard model (MSSM) are heavier than the corresponding mass lower limits in the minimal supergravity (mSUGRA) model, obtained by the current LHC experiments, then the existing data allow a variety of electroweak (EW) sectors with light sparticles yielding dark matter (DM) relic density allowed by the WMAP data. Some of the sparticles may lie just above the existing lower bounds from LEP and lead to many novel DM producing mechanisms not common in mSUGRA. This is illustrated by revisiting the above squark-gluino mass limits obtained by the ATLAS Collaboration, with an unconstrained EW sector with masses not correlated with the strong sector. Using their selection criteria and the corresponding cross section limits, we find at the generator level using Pythia, that the changes in the mass limits, if any, are by at most 10-12% in most scenarios. In some cases, however, the relaxation of the gluino mass limits are larger ($\approx 20%$). If a subset of the strongly interacting sparticles in an unconstrained MSSM are within the reach of the LHC, then signals sensitive to the EW sector may be obtained. This is illustrated by simulating the $blj$$\etslash$, $l= e and \mu $, and $b\tau j$$\etslash$ signals in i) the light stop scenario and ii) the light stop-gluino scenario with various light EW sectors allowed by the WMAP data. Some of the more general models may be realized with non-universal scalar and gaugino masses.