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

Abstract

In this letter we explore beyond the Standard Model top-Higgs Yukawa couplings as a function of a CP-mixing parameter $\hat{I}{¾}_t$ 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 $\hat{I}{¾}_t$. 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 $\hat{I}{¾}_t$ even when including the realistic effects of detector smearing and a conservative estimate of systematic error.

5 pages, 4 figures, 1 table