Search for top squarks at Tevatron inspired by dark matter and electroweak baryogenesis

The search for the top squark (t˜1) within the kinematic reach of Tevatron Run II is of great contemporary interest. Such a t˜1 can explain the baryon asymmetry of the universe provided 120 GeV⩽mt˜1⩽mt. Moreover if Δm≡mt˜1−mχ˜10 is small, where χ˜10 is the lightest supersymmetric particle (LSP), the dark matter relic density as obtained from the WMAP data may be explained via t˜1-LSP coannihilation. In this scenario the decay t˜1→cχ˜10 is likely to occur with 100% branching ratio but for small Δm the conventional di-jet+E̸T signal becomes unobservable. We propose a new search strategy based on the di-jet+E̸T signature accompanied by an isolated cluster of energy which arises from a decaying heavy particle with characteristic decay length. Our preliminary simulations with Pythia indicate that for 100 GeV⩽mt˜1⩽130 GeV this signal may be observable while somewhat lager mt˜1 may still provide hints of new physics.