Top squark mass: current limits revisited and new limits from Tevatron Run-I

Analyzing the ℓ+n-jets+E̸T (where n⩾2) data from Run-I of the Tevatron using the Bayesian technique, we obtain model independent limits on the product BR(t˜1→be+νeχ˜10)×BR(t˜1*→b¯qq¯′χ˜10) for different values of the lighter top squark (t˜1) mass and the lightest supersymmetric particle (χ˜10) mass. The signal events have been simulated by interfacing the 4-body decay of t˜1 at the parton level with the event generator PYTHIA. These limits have been translated into exclusion plots in the mt˜1–mχ˜10 plane, which also turn out to be fairly model independent for fixed values of the BR of the competing loop decay mode t˜1→cχ˜10. Assuming the loop decay BR to be negligible and using the leading order cross section for t˜1t˜1* pair production, we obtain conservatively mt˜1⩾77.0 (74.5) GeV for mχ˜10=5(15)GeV, while for BR(t˜1→cχ˜10)=20%, the corresponding limits are mt˜1⩾68.0 (65.0) GeV. Using the larger next to leading order cross section stronger limits are obtained. For example, if BR(t˜1→cχ˜10)=20%, mt˜1⩾73.0 (72.7) GeV for mχ˜10=5(15)GeV. Our limits nicely complement the ALEPH bounds which get weaker for low mχ˜10.