# Towards Measuring the Stop Mixing Angle at the LHC

## TL;DR

This paper explores how to measure the stop mixing angle and CP-violating phase at the LHC using branching ratio ratios of the light stop decays, emphasizing the dependence on the stop sector parameters and the need for spectrum knowledge.

## Contribution

It proposes a method to determine the stop mixing angle and CP phase at the LHC through decay ratio observables, highlighting their sensitivity and the necessity of spectrum information.

## Key findings

- Ratios of branching ratios depend strongly on stop sector parameters.
- The method can potentially reveal the stop mass, mixing angle, and CP phase.
- Accurate spectrum knowledge is crucial, possibly requiring linear collider data.

## Abstract

We address the question of how to determine the stop mixing angle and its CP-violating phase at the LHC. As an observable we discuss ratios of branching ratios for different decay modes of the light stop ~t_1 to charginos and neutralinos. These observables can have a very strong dependence on the parameters of the stop sector. We discuss in detail the origin of these effects. Using various combinations of the ratios of branching ratios we argue that, depending on the scenario, the observable may be promising in exposing the light stop mass, the mixing angle and the CP phase. This will, however, require a good knowledge of the supersymmetric spectrum, which is likely to be achievable only in combination with results from a linear collider.