Measurement of CP Violation in Stop Cascade Decays at the LHC

TL;DR

This paper investigates the potential to observe CP violation in stop cascade decays at the LHC within the MSSM, highlighting the challenges due to dilution effects and emphasizing the need for high luminosity and precise measurements.

Contribution

It introduces a method to measure CP-violating effects in stop decays at the LHC and analyzes the impact of hadronic effects on observable asymmetries.

Findings

Large CP asymmetries at parton level can be significantly diluted at the hadronic level.

Measurable CP asymmetries are small but potentially detectable with high luminosity.

Precise measurements of masses and branching ratios are crucial for observing CP violation.

Abstract

We study the potential observation at the LHC of CP-violating effects in stop production and subsequent cascade decays, g g -> tilde{t}_i tilde{t}_i, tilde{t}_i -> t tilde{chi}^0_j, tilde{chi}^0_j -> tilde{\chi}^0_1 l^+ l^-, within the Minimal Supersymmetric Standard Model. We study T-odd asymmetries based on triple products between the different decay products. There may be a large CP asymmetry at the parton level, but there is a significant dilution at the hadronic level after integrating over the parton distribution functions. Consequently, even for scenarios where large CP intrinsic asymmetries are expected, the measurable asymmetry is rather small. High luminosity and precise measurements of masses, branching ratios and CP asymmetries may enable measurements of the CP-violating parameters in cascade decays at the LHC.