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

TL;DR

This paper studies the decay modes of the light stop in supersymmetry, especially near the kinematic threshold, highlighting the importance of flavor-violating two-body decays alongside traditional three- and four-body channels.

Contribution

It provides an improved theoretical description of stop decays near the threshold, including FV effects, and implements this in the SUSY-HIT package for comprehensive analysis.

Findings

FV two-body decay can compete with three- and four-body decays

Proper treatment of the transition region improves decay predictions

FV decays are significant for experimental stop searches

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 $\tilde{t}_1\to W b \tilde{\chi}_1^0$ 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.