Revisiting semileptonic $B^{-}\to p\bar{p}{\mathrm{\ell }}^{-}{\bar{\nu }}_{\mathrm{\ell }}$ decays

We systematically revisit the baryonic four-body semileptonic decays of $B^- \to {\bf B}\bar{\bf B}'\ell^- \bar{\nu}{\ell}$ by the perturbative QCD counting rules with $\mathbf{B}$ representing octet baryons and $\mathrm{\ell }=e,\mu$. We study the transition form factors of $B^{-}\to \mathbf{B}{\bar{\mathbf{B}}}^{\mathrm{\prime }}$ in the limit of $(p_{\mathbf{B}}+p_{{\bar{\mathbf{B}}}^{\mathrm{\prime }}}{)}^2\to \mathrm{\infty }$ with the three-body $\bar{B}\to \mathbf{B}{\bar{\mathbf{B}}}^{\mathrm{\prime }}M$ and $B^{-}\to p\bar{p}{\mu }^{-}{\bar{\nu }}_{\mu }$ data along with $SU(3{)}_f$ flavor symmetry. We calculate the decay branching ratios and angular asymmetries as well as the differential decay branching fractions of $B^{-}\to p\bar{p}{\mathrm{\ell }}^{-}{\bar{\nu }}_{\mathrm{\ell }}$. In particular, we find that our new result of ${\cal B}( B^- \to p \bar{p} \ell^- \bar{\nu}{\ell})=(5.21\pm0.34)\times 10^{-6}$, which is about one order of magnitude lower than the previous theoretical prediction of $(10.4\pm2.9)\times 10^{-5}$,agreeswellwithbothexperimentalmeasurementsof$(5.8^{+2.6}{-2.3})\times 10^{-6}$and$(5.3\pm0.4)\times 10^{-6}$ by the Belle and LHCb Collaborations, respectively. We also evaluate the branching ratios and angular asymmetries in other channels of $B^- \to {\bf B}\bar{\bf B}\ell^- \bar{\nu}{\ell}$, which can be tested by the ongoing experiments at LHCb and BelleII.