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

Abstract

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 ${\tilde{t}}_1\to Wb{\tilde{\chi }}_1^0$ is kinematically allowed and provide a proper description of the transition region between the three-body decay and the four-body decay ${\tilde{t}}_1\to {\tilde{\chi }}_1^{0}bf{\bar{f}}^{\prime }$. 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.

Comments: 7 pages, 5 figures; matches journal version; appendix with analytic formula for three-body decay width added