New physics in inclusive $B \to X_c\ell \bar{\nu}$ decay in light of $R(D^{(*)})$ measurements

TL;DR

This paper investigates how new physics operators with various Lorentz structures could influence inclusive B to Xc tau nu decays, providing predictions for decay ratios, differential rates, and asymmetries, and exploring leptoquark models as explicit NP scenarios.

Contribution

It introduces a comprehensive analysis of NP effects on inclusive B decays, including predictions for decay ratios and the impact of specific leptoquark models, extending beyond Standard Model expectations.

Findings

Predicted ratios of decay rates with NP effects

Identified signatures of leptoquark models in decay observables

Quantified radiative and nonperturbative corrections to SM decay rates

Abstract

In this work we study the effects of new-physics (NP) operators with different Lorentz structures on the inclusive $B \to X_c\tau \bar{\nu}$ decay and make predictions for the ratio of total decay rates $R(X_c)=\frac{\Gamma(B \to X_c\tau \bar{\nu}_\tau)}{\Gamma(B \to X_c \ell \bar{\nu}_\ell)}$ with $\ell=e, \mu$, the differential decay rates, $\frac{d\Gamma}{dq^2}$ and $\frac{d\Gamma}{dE_\tau}$, forward-backward asymmetry $A_{FB}$ and the ratio of the differential decay rates $B(q^2)=\frac{d\Gamma(B \to X_c\tau \bar{\nu}_\tau)/dq^2}{d\Gamma(B \to X_c \ell \bar{\nu}_\ell)/dq^2}$. In addition, we introduce some leptoquark models as explicit models of the NP operators and study their effects on the inclusive decay. We consider $\mathcal{O}(\alpha_s)$ radiative and $1/m_b$ nonperturbative corrections to the Standard Model (SM) decay rate and ignore their small effects in the NP contributions.