First Observation of the Rare Purely Baryonic Decay B⁰→pp¯

Abstract

The first observation of the decay of a B⁰ meson to a purely baryonic final state, B⁰→pp, is reported. The proton-proton collision data sample used was collected with the LHCb experiment at center-of-mass energies of 7 and 8 TeV and corresponds to an integrated luminosity of 3.0 fb⁻¹. The branching fraction is determined to be B(B⁰→pp)=(1.25±0.27±0.18)×10⁻⁸, where the first uncertainty is statistical and the second systematic. The decay mode B⁰→pp is the rarest decay of the B⁰ meson observed to date. The decay B[subscript s]⁰→pp is also investigated. No signal is seen and the upper limit B(B[subscript s]⁰→pp) < 1.5×10⁻⁸ at 90% confidence level is set on the branching fraction.