Sneaky light stop
  A light supersymmetric top quark partner (stop) with a mass nearly degenerate with that of the Standard Model (SM) top quark can evade direct searches. The precise measurement of SM top properties such as the cross-section has been suggested to give a handle for this `stealth stop' scenario. We present an estimate of the potential impact a light stop may have on top quark mass measurements. The results indicate that certain light stop models may induce a bias of up to a few GeV, and that this effect can hide the shift in, and hence sensitivity from, cross-section measurements. The studies make some simplifying assumptions for the top quark measurement technique, and are based on truth-level samples. 
Till Eifert, Benjamin Nachman
hep-ph