  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.
