Understand
We study the exclusive $b \to u \ell^- \bar{\nu}_{\ell} (\ell=\tau,\mu,e)$ decays in the MSSM with and without R-parity violation.
- From the experimental measurements of branching ratios $\mathcal{B}(B^-_u \to \tau^- \bar{\nu}_{\tau})$, $\mathcal{B}(B^-_u \to M'^0 \ell'^- \bar{\nu}_{\ell'})$ and $\mathcal{B}(\bar{B}^0_d \to M'^+ \ell'^- \bar{\nu}_{\ell'})$ $(\ell'=\mu,e, M'=\pi,\rho)$, we derive new upper bounds on the relevant new physics parameters within the decays.
- Using the constrained new physics parameter spaces, we predict the charged Higgs effects and the R-parity violating effects on the branching ratios, the normalized forward-backward asymmetries of charged leptons, and the ratios of longitudinal to transverse polarization of the vector mesons, which have not been measured or have not been well measured yet.
- We find that the charged Higgs effects and the R-parity violating effects could be large and measurable in some cases.