Transverse $τ$ polarization in $B_c \to τ\bar ν_τ γ$ decay

Abstract

The possible transverse polarization of the $τ$-lepton, which is $T$-odd and can be used to measure CP-violation, is estimated precisely in the radiative decay mode $B_c \to τ\bar ν_τγ$ with possible parameters for the multi Higgs doublet model and the R-parity violating supersymmetric model. We find that the up-bound of the transverse polarization with possible parameters in the models is at very different levels i.e. it can be $\leq 15\sim 23%$ for the former but $\leq 0.1 %$ for the latter, and it is accessible experimentally soon.