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

Abstract

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

29 pages, 59 figures