RATIO OF J PSI PRODUCTION CROSS-SECTIONS IN DEEP INELASTIC MUON SCATTERING FROM TIN AND CARBON/

UNIV NEUCHATEL CH-2000 NEUCHATEL SWITZERLAND UNIV FREIBURG W-7800 FREI BURG GERMANY UNIV CALIF SANTA CRUZ SANTA CRUZ CA 95064 UNIV MAINZ W-65 00 MAINZ GERMANY CERN CH-1211 GENEVA 23 SWITZERLAND INST NUCL STUDIES PL-00681 WARSAW POLAND UNIV HEIDELBERG W-6900 HEIDELBERG GERMANY UNIV ETAT MONS B-7000 MONS BELGIUM We present results on J/psi production i n muon interactions with tin and carbon targets at incident muon energ ies of 200 and 280 GeV. The ratio of cross sections per nucleon for J/ psi production on tin and carbon, R(Sn/C), is studied as a function of p(T)2, z and x. We find an enhancement for coherent J/psi production R(coh)(Sn/C) = 1.54 +/- 0.07, a suppression for quasielastic productio n R(qe)(Sn/C) = 0.79 +/- 0.06 and for inelastic production R(in)(Sn/C) = 1.13 +/- 0.08. The inelastic cross section ratio can be interpreted within the Colour Singlet model as an enhancement ot the gluon distri bution in tin with respect to that in carbon. The dependence of the ra tio on z and p(T)2 can explain the discrepancy between the results obt ained in previous experiments.