Top polarisation as a probe of CP-mixing top-Higgs coupling in $tjh$ signals

TL;DR

This study investigates how top polarization observables in $pp o thj$ at 14 TeV HL-LHC can reveal CP-mixing in top-Higgs couplings, using machine learning to enhance sensitivity and improve exclusion limits.

Contribution

It introduces a novel approach using angular variables and machine learning to probe CP-mixing in top-Higgs interactions at the HL-LHC.

Findings

Angular variables are sensitive to CP-mixing parameter $\xi_t$

Machine learning enhances signal sensitivity

Projected exclusion limits on $\xi_t$ are improved

Abstract

In this letter we explore beyond the Standard Model top-Higgs Yukawa couplings as a function of a CP-mixing parameter $\xi_t$ at the 14 TeV HL-LHC in the process $pp\to thj$. We observe that angular variables of the decay products of the top are non-trivially sensitive to $\xi_t$. This fact is exploited in a full detector level analysis that employs machine learning techniques to optimize signal sensitivity on a suite of variables, including lepton azimuthal angle. The key result of this study is an improved projected exclusion limit on $\xi_t$ even when including the realistic effects of detector smearing and a conservative estimate of systematic error.