全国第十八届重味物理和CP破坏研讨会（HFCPV 2021）

New physics in inclusive $\bar{B}\to X_c \tau^-\bar{\nu}_\tau$ decay including $\mathcal{O}(\Lambda_{QCD}^2/m_b^2)$ and $\mathcal{O}(\alpha_s)$ corrections

Not scheduled

15m

暨南大学

Speaker

Ms 李 媛媛 (华中师范大学)

Description

Motivated by the $R(D^{(\ast)})$ anomalies observed in exclusive $\bar{B}\to D^{(\ast)}\tau^-\bar{\nu}_\tau$$ decays, which might hint at the violation of lepton flavor universality and could be interpreted as the tentative new-physics signals that couple non-universally to the three generations of leptons, we perform a detailed study of the new-physics effects in the inclusive $\bar{B}\to X_c\tau^-\bar{\nu}_\tau$$ decay, including both $\mathcal{O}(\Lambda_{QCD}^2/m_b^2)$ and $\mathcal{O}(\alpha_s)$ corrections. Our analysis is carried out both in a model-independent effective field theory framework and in the popular leptoquark models, focusing on the behaviors of the lepton energy spectrum $(1/\Gamma_0)d\Gamma/dE_\tau$, the $q^2$ distribution $(1/\Gamma_0)d\Gamma/dq^2$, the lepton-side forward-backward asymmetry $A_{FB}$, the $\tau$ polarization $P_\tau$, as well as the $q^2$-dependent ratio of the differential decay rates $B(q^2)=\frac{d\Gamma(\bar{B}\to X_c \tau^- \bar{\nu}_\tau)/dq^2}{d\Gamma(\bar{B}\to X_c \ell^- \bar{\nu}_\ell)/dq^2}$$, under different assumptions about the new-physics contributions. It is found that, under the combined constraints from the ratios $R(D^{(\ast)})$ and other relevant observables, the new-physics operators with different Dirac structures are insensitive to both the perturbative and non-perturbative corrections, in either the $\mathrm{1S}$ or the kinetic scheme. Some observables in inclusive $\bar{B}\to X_c\tau^-\bar{\nu}_\tau$ decay are also found to be helpful for discriminating the different new-physics scenarios proposed to account for the $R(D^{(\ast)})$ anomalies.