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

TL;DR

This paper analyzes how new vector-like physics operators with different chiralities affect decay processes involving charged currents, revealing distinct impacts on observables like branching ratios and asymmetries.

Contribution

It provides a detailed helicity amplitude analysis of vector-like couplings in charged current decays, highlighting the differential effects of left and right-handed new physics interactions.

Findings

Left-handed vector-like interactions affect branching ratios but not asymmetries.

Right-handed vector-like interactions influence both branching ratios and angular observables.

The behavior of these couplings is consistent across different decay processes involving vector mesons.

Abstract

We investigate the cascade decay $B^{*0}_{s} \rightarrow D_s^-(\rightarrow \tau^-\,\bar\nu_{\tau})\,\ell^{+}\,{\nu}_\ell$ 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 $B^{*+}_c \rightarrow P(\rightarrow P'\,\mu^+\,\nu_{\mu})\,\ell^{+}\,{\nu}_\ell$ where $P$ is $B_s^0$ ($D^0$) and $P'$ is $D_s^{*-}$ ($K^-$).