Left-right mixing on leptonic and semileptonic $b\to u$ decays

It has been known that there exists a disagreement emerged between the determination of $\mathrm{\mid }{V}_{ub}\mathrm{\mid }$ from inclusive $B\to X_u\mathrm{\ell }\nu$ decays and exclusive $B\to \pi \mathrm{\ell }\nu$ decays. In order to solve the mismatch, we investigate the left-right (LR) mixing effects, denoted by ${\xi }_u$, in leptonic and semileptonic $b\to u$ decays. We find that the new interactions $(V+A)\times (V-A)$ induced via the LR mixing can explain the mismatch between the values of $\mathrm{\mid }{V}_{ub}\mathrm{\mid }$ if Re$({\xi }_u)=-(0.14\pm 0.12)$. Furthermore, we also find that the LR mixing effects can enhance the branching fractions for $B \to \tau\nu$and$B \to \rho\ell\nu$ decays by 30% and 17%, respectively, while reducing the branching fraction for $B\to \gamma \mathrm{\ell }\nu$ decays by 18%.