Anomalous Top-Higgs Couplings and Top Polarisation in Single Top and Higgs Associated Production at the LHC

Abstract

In this paper, we put constraints on anomalous $\mathcal{C}\mathcal{P}$-violating top-Higgs couplings using the currently available Higgs data and explore the prospect of measuring these couplings at 240 GeV TLEP. We find that the $\mathcal{C}\mathcal{P}$-violating phase $\xi$ is currently limited in the range $|\xi |<0.6\pi$ at 95\% C.L. and may be further constrained to $|\xi |<0.07\pi$ at TLEP. Under this consideration, we further investigate the observability of the scalar ($\xi =0$), pseudoscalar ($\xi =0.5\pi$) and mixed ($\xi =0.25\pi$) top-Higgs interactions through the channel $pp\to t(\to {\ell }^{+}{\nu }_{\ell }b)h(\to b\overline{b})j$. We find that it is most promising to observe pure pseudoscalar interactions with $y_t=y_t^{SM}$, although this will be challenging due to a low signal to background ratio. We also find that the anomalous top-Higgs couplings can lead to sizeable differences in lepton forward-backward asymmetries and can be distinguished by measuring the lepton angular distributions from polarised top quarks at 14 TeV LHC.

Comments: 16pp, 8 figures and 2 tables; v2; updated to match published version