First evidence for the two-body charmless baryonic decay B0→pp¯

The results of a search for the rare two-body charmless baryonic decays B0→ppˉ and B0s→ppˉ are reported. The analysis uses a data sample, corresponding to an integrated luminosity of 0.9 fb−1, of pp collision data collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. An excess of B0→ppˉ candidates with respect to background expectations is seen with a statistical significance of 3.3 standard deviations. This is the first evidence for a two-body charmless baryonic B0 decay. No significant B0s→ppˉ signal is observed, leading to an improvement of three orders of magnitude over previous bounds. If the excess events are interpreted as signal, the 68.3\% confidence level intervals on the branching fractions are B(B0→ppˉ)B(B0s→ppˉ)==(1.47+0.62−0.51+0.35−0.14)×10−8,(2.84+2.03−1.68+0.85−0.18)×10−8, where the first uncertainty is statistical and the second is systematic.