Studying possible CP-violating Higgs couplings through top-quark pair productions at muon colliders

TL;DR

This paper investigates how CP-violating Higgs couplings can be detected through top-quark pair production at muon colliders, using model-independent analysis and asymmetry measurements under different muon polarizations.

Contribution

It introduces a comprehensive, model-independent framework for analyzing CP-violating Higgs couplings via top-quark pair production at muon colliders, including asymmetry and optimal-observable methods.

Findings

Longitudinal polarization asymmetry can signal CP violation.

Optimal-observable analysis is promising with fewer unknown parameters.

Measurement sensitivity depends on the size of the CP-violating parameters.

Abstract

We study possible anomalous CP-violating Higgs couplings to mu mu-bar and t t-bar fully model-independent way through top-quark pair productions at muon colliders. Assuming additional non-standard neutral Higgs bosons, whose couplings with top-quark and muon are expressed in the most general covariant form, we carry out analyses of effects which they are expected to produce via CP-violating asymmetries and also the optimal-observable (OO) procedure under longitudinal and transverse muon polarizations. We find the measurement of the asymmetry for longitudinal beam polarization could be useful to catch some signal of CP violation, and an OO analysis might also be useful if we could reduce the number of unknown parameters with a help of other experiments and if the size of the parameters is at least O(1) ~ O(10).