CP Violating Asymmetry in Stop Decay into Bottom and Chargino

TL;DR

This paper calculates the CP violating decay rate asymmetry in stop decays within the MSSM at full one-loop level, analyzing parameter dependencies and potential observability at the LHC.

Contribution

It provides the first full one-loop calculation of CP asymmetry in stop decays, including a simplified formula and detailed numerical analysis considering experimental constraints.

Findings

Asymmetries up to 25% are possible.

Vertex corrections are suppressed compared to self-energy contributions.

Feasibility of measuring the asymmetry at the LHC is discussed.

Abstract

In the MSSM with complex parameters, loop corrections to the decay of a stop into a bottom quark and a chargino can lead to a CP violating decay rate asymmetry. We calculate this asymmetry at full one-loop level and perform a detailed numerical study, analyzing the dependence on the parameters and complex phases involved. If the stop can decay into a gluino, the self-energy and the vertex correction dominate due to the strong coupling. It is shown that the vertex contribution is always suppressed. We therefore give a simple approximate formula for the asymmetry. We account for the constraints on the parameters coming from several experimental limits. Asymmetries up to 25 percent are obtained. We also comment on the feasibility of measuring this asymmetry at the LHC.