New backgrounds in Trilepton, Dilepton and Dilepton plus Tau Jet SUSY Signals at the Tevatron

We determine the Tevatron's reach in supersymmetric parameter space in trilepton, like-sign dilepton, and dilepton plus tau-jet channels, taking all relevant backgrounds into account. We show results for the minimal supergravity model. With a standard set of cuts we find that the previously unaccounted for $W\gamma^\ast$ background is larger than all other backgrounds combined. We include cuts on the dilepton invariant mass and the $W$-boson transverse mass to reduce the $W\gamma^\ast$ background to a reasonable level. We optimize cuts at each point in supersymmetry parameter space in order to maximize signal-to-noise.