New physics and the tau polarization vector in b → cτ −ν¯τ decays

Abstract

For a general H_b→H_c τ ν_τ decay, we analyze the role of theτpolarization vector P^μ in the context of lepton flavor universality violation studies. We use a general phenomenological approach that includes several new physics terms and we make specific evaluations of P^μ fordifferent decays. We show that a P^μ component orthogonal to the plane determined by the final hadron and τ three-momenta is only possiblefor complex Wilson coefficients and it would be associated to a violation of the CP symmetry.