Measurements of J/ψ→pp̄

Abstract The process J/ψ→p p is studied using 57.7×10 6 J / ψ events collected with the BESII detector at the Beijing Electron Positron Collider. The branching ratio is determined to be Br (J/ψ→p p )=(2.26±0.01±0.14)×10 −3 , and the angular distribution is well described by dN d cos θ p =1+α cos 2 θ p with α =0.676±0.036±0.042, where θ p is the angle between the proton and beam directions. The value of α obtained is in good agreement with the predictions of first-order QCD.