First evidence for the two-body charmless baryonic decay B-0 -> p(p)over-bar

The results of a search for the rare two-body charmless baryonic decays B-0 -> p (p) over bar and B-s(0) -> p (p) over bar are reported. The analysis uses a data sample, corresponding to an integrated luminosity of 0.9 fb(-1), of p p collision data collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. An excess of B-0 -> p (p) over bar 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 B-0 decay. No significant B-s(0) -> p (p) over bar 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(B-0 -> p (p) over bar) = (1.47(-0.51)(+0.62) (-0.14) (+0.35)) x 10(-8), B(B-s(0) -> p (p) over bar) = (2.84(-1.68)(+2.03) (+0.85)(-0.18)) x 10(-8), where the first uncertainty is statistical and the second is systematic.