Light Stop Searches at the LHC in Events with One Hard Photon or Jet and Missing Energy

TL;DR

This paper proposes a new search strategy for light stops in supersymmetry at the LHC, focusing on events with missing energy plus a hard photon or jet, effectively probing the parameter space relevant for baryogenesis.

Contribution

It introduces an alternative method for stop detection in the co-annihilation region using mono-photon or mono-jet signatures, enhancing search sensitivity.

Findings

Method can probe stop masses up to 160 GeV.

Complementary to Tevatron searches, fully covers baryogenesis-compatible parameter space.

Efficient in the challenging co-annihilation region.

Abstract

Low energy supersymmetric models provide a solution to the hierarchy problem and also have the necessary ingredients to solve two of the most outstanding issues in cosmology: the origin of the baryon asymmetry and the source of dark matter. In the MSSM, weak scale generation of the baryon asymmetry may be achieved in the presence of light stops, with masses lower than about 130 GeV. Moreover, the proper dark matter density may be obtained in the stop-neutralino co-annihilation region, where the stop-neutralino mass difference is smaller than a few tens of GeV. Searches for scalar top quarks (stops) in pair production processes at the Tevatron and at the Large Hadron Collider (LHC) become very challenging in this region of parameters. At the LHC, however, light stops proceeding from the decay of gluino pairs may be identified, provided the gluino mass is smaller than about 900 GeV. In this article we propose an alternative method for stop searches in the co-annihilation region, based on the search for these particles in events with missing energy plus one hard photon or jet. We show that this method is quite efficient and, when complemented with ongoing Tevatron searches, allows to probe stop masses up to about 160 GeV, fully probing the region of parameters consistent with electroweak baryogenesis in the MSSM.