Observation of the semileptonic decay $B^{+}\to p\overline{p}\mu^{+}\nu_{\mu}$

The Cabibbo-suppressed semileptonic decay $ {B}^{+}\to p\overline{p}{\mu}^{+}{\nu}_{\mu } $ is observed for the first time using a sample of $pp$ collisions corresponding to an integrated luminosity of 1.0, 2.0 and 1.7 fb$^{−1}$ at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The differential branching fraction is measured as a function of the $ p\overline{p} $ invariant mass using the decay mode B$^{+}$→ J/ψK$^{+}$ for normalisation. The total branching fraction is measured to be $ \mathrm{\mathcal{B}}\left({B}^{+}\to p\overline{p}{\mu}^{+}{\nu}_{\mu}\right)=\left({5.27}_{-0.24}^{+0.23}\pm 0.21\pm 0.15\right)\times {10}^{-6}$, where the first uncertainty is statistical, the second systematic and the third is from the uncertainty on the branching fraction of the normalisation channel.