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

Abstract

We systematically revisit the baryonic four-body semileptonic decays of $B^{-}\to \mathbf{B}{\bar{\mathbf{B}}}^{\prime }{\ell }^{-}{\bar{\nu }}_{\ell }$ by the perturbative QCD counting rules with $\mathbf{B}$ representing octet baryons and $\ell =e,\mu$. We study the transition form factors of $B^{-}\to \mathbf{B}{\bar{\mathbf{B}}}^{\prime }$ in the limit of $(p_{\mathbf{B}}+p_{{\bar{\mathbf{B}}}^{\prime }}{)}^2\to \infty$ with the three-body $\bar{B}\to \mathbf{B}{\bar{\mathbf{B}}}^{\prime }M$ 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 $B^{-}\to p\bar{p}{\ell }^{-}{\bar{\nu }}_{\ell }$. In particular, we find that our new result of $\mathcal{B}(B^{-}\to p\bar{p}{\ell }^{-}{\bar{\nu }}_{\ell })=(5.21\pm 0.34)\times 10^{-6}$, which is about one order of magnitude lower than the previous theoretical prediction of $(10.4\pm 2.9)\times 10^{-5}$, agrees well with both experimental measurements of $(5.8_{-2.3}^{+2.6})\times 10^{-6}$ and $(5.3\pm 0.4)\times 10^{-6}$ by the Belle and LHCb Collaborations, respectively. We also evaluate the branching ratios and angular asymmetries in other channels of $B^{-}\to \mathbf{B}\bar{\mathbf{B}}{\ell }^{-}{\bar{\nu }}_{\ell }$, which can be tested by the ongoing experiments at LHCb and BelleII.

Comments: 15 pages, 5 figures