Observation of B+→p¯ΛK+K− and B+→¯pΛK+K+

Abstract

We report the study of B+→p¯ΛK+K− and B+→¯pΛK+K+ decays using a 772×106 B¯B pair data sample recorded on the Υ(4S) resonance with the Belle detector at KEKB. The following branching fractions are measured: B(B+→p¯ΛK+K−)=(4.10+0.45−0.43±0.50)×10−6, B(B+→¯pΛK+K+)=(3.70+0.39−0.37±0.44)×10−6, B(ηc→p¯ΛK−+c.c.)=(2.83+0.36−0.34±0.35)×10−3 and B(B+→p¯Λϕ)=( 7.95±2.09±0.77)×10−7, where c.c. denotes the corresponding charge-conjugation process. The intermediate resonance decays are excluded in the four-body decay measurements. We also find evidence for B(ηc→Λ(1520)¯Λ+c.c.)=(3.48±1.48±0.46)×10−3 and B(B+→Λ(1520)¯ΛK+)=( 2.23±0.63±0.25)×10−6. No significant signals are found for J/ψ→Λ(1520)¯Λ+c.c. and B+→¯Λ(1520)ΛK+; we set the 90% confidence level upper limits on their decay branching fractions as <1.80×10−3 and <2.08×10−6, respectively.