Anomalous top-Higgs couplings and top polarisation in single top and Higgs associated production at the LHC

In this paper, we put constraints on anomalous CP -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 CP -violating phase ξ is currently limited in the range |ξ| <0.6π at 95% C.L. and may be further constrained to |ξ| <0.07π at TLEP. Under this consideration, we further investigate the observability of the scalar (ξ =0), pseudoscalar (ξ =0.5π) and mixed (ξ =0.25π) top-Higgs interactions through the channel pp→ t(→ ⁺νb)h(→ bb̄)j . We find that it is most promising to observe pure pseudoscalar interactions with y t = y 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.