Delving into new physics in semileptonic $b \to c \tau \bar \nu$ transitions

TL;DR

This paper investigates potential new physics in semileptonic $b o c au ar u$ decays by analyzing various decay processes and fitting experimental data to constrain new physics contributions.

Contribution

It provides a model-independent analysis of semileptonic $b o c$ transitions, exploring the effects of new physics on multiple decay channels and observables.

Findings

Constraints on new physics couplings from experimental data.

Predictions for branching ratios and asymmetries under new physics scenarios.

Insights into lepton non-universality in $B$ meson decays.

Abstract

Recently, several indications of lepton non-universality observables have been perceived in semileptonic $B$ meson decay processes, both in the neutral-current ($b \to s ll $) and charged-current ($b \to c l \bar \nu_l$) transitions. Influenced by these fascinating quotients, we examine the semileptonic decays involving the $b \to c l \bar \nu_l$ quark level transitions. We execute it through a model independent analysis in order to probe the nature of new physics. Taking into consideration the most general effective Hamiltonian, we scrutinize $\Lambda_b \to \Lambda_c \tau \bar \nu_\tau$, $ B_c^+ \to \eta_c \tau^+ \nu_\tau$, and $ B \to D^{**} \tau \bar \nu_\tau$ (where $D^{**} = \{D^*_0, D_1^*, D_1, D_2^*\}$ are the four lightest excited charm mesons) processes, in the presence of new physics. We perform a global fit to different sets of new coefficients, making use of the measurements on $R_{D}$, $R_{D^{*}}$, $R_{J/\psi}$, $P_{\tau}^{D^*}$ and the upper limit on Br($B_c^+ \to \tau^+ \nu_\tau$). We then inspect the effect of constrained new couplings on the branching ratios, forward-backward asymmetry parameters, lepton non-universality ratios (LNU), lepton and hadron polarization asymmetries of these decay modes.