Chirality structure of vector like new physics operators in charged current transitions

Abstract

We investigate the cascade decay $B_s^{\ast 0}\to D_s^{-}(\to {\tau }^{-}{\bar{\nu }}_{\tau }){\ell }^{+}{\nu }_{\ell }$ induced by flavor changing charged currents in the context of the Standard Model and in vector-like couplings beyond the Standard Model. We employ the helicity amplitude formalism for analysis and highlight the role of new vector-like couplings in charged current interactions. We find, in particular, that while new left handed chiral-vector like interactions contribute to the branching ratio, they do not affect the forward-backward asymmetry, or the angular observables. On the other hand, the right handed chiral vector-like coupling in the case of this decay contributes to the branching ratio, forward-backward asymmetry and the angular observables. We confirm that this difference in behavior between the left and right handed NP couplings is a general feature of charged current processes with a vector meson going to a pseudoscalar at the tree level in effective weak theory by cross checking with the cascade decays $B_c^{\ast +}\to P(\to P^{\prime }{\mu }^{+}{\nu }_{\mu }){\ell }^{+}{\nu }_{\ell }$ where $P$ is $B_s^0$ ($D^0$) and $P^{\prime }$ is $D_s^{\ast -}$ ($K^{-}$).

Comments: 15 pages, 9 figures; accepted by The European Physical Journal Plus