Experimental comparison of Jψ production by π±, K±, p and p̄ beams at 39.5 GeV/c

Abstract Measurements have been made of relative production cross sections of the J ψ by π ± , K ± , p and p at 39.5 GeV/ c incident on copper. J ψ production rates from π − , K − and p are similar. The J ψ relative particle/anti-particle production cross sections for x >0 are σ(π + ) σ(π − )=(0.87±0.14) , σ (K + )/ σ (K − )=(0.85±0.5) and σ( p ) σ( p )=(0.15 ±0.08) . The small p/p cross section ratio disagrees with models of J/ψ production by gluon amalgamation.