Light stop decays into $W b \tilde{\chi}_1^0$ near the kinematic threshold

Understand

We investigate the decays of the light stop in scenarios with the lightest neutralino $\tilde{\chi}_1^0$ being the lightest supersymmetric particle, including flavour-violating (FV) effects.

• We analyse the region where the three-body decay $\tilde{t}_1\to W b \tilde{\chi}_1^0$ is kinematically allowed and provide a proper description of the transition region between the three-body decay and the four-body decay $\tilde{t}_1 \to\tilde{\chi}_1^0 b f \bar{f}'$.
• The improved treatment has been implemented in the Fortran package {\tt SUSY-HIT} and is used for the analysis of this region.
• A scan over the parameter range including all relevant experimental constraints reveals that the FV two-body decay into charm and $\tilde{\chi}_1^0$ can be as important as the three-, respectively, four-body decays if not dominant and therefore should be taken into account in order to complete the experimental searches for the light stop.