Observation of the semileptonic decay B+→ pp¯ μ+νμ

The Cabibbo-suppressed semileptonic decay B+→pp¯¯¯μ+νμ 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 pp¯¯¯ invariant mass using the decay mode B+ → J/ψK+ for normalisation. The total branching fraction is measured to be B(B+→pp¯¯¯μ+νμ)= (5.27+0.23−0.24±0.21±0.15)×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.