zur Nedden, M (reprint author), NIKHEF, NL-1009 DB Amsterdam, Netherlands.
Measurements of the kinematic distributions of J/psi mesons produced in p-C, p-Ti and p-W collisions at root s = 41.6 GeV in the Feynman-x region -0.34 < x(F) < 0.14 and for transverse momentum up to p(T) = 5.4 GeV/c are presented. The xF and pT dependencies of the nuclear suppression parameter, a, are also given. The results are based on 2.4 x 10(5) J/psi mesons reconstructed in both the e(+) e(-) and mu(+) mu(-) decay channels. The data have been collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The measurement explores the negative region of xF for the first time. The average value of a in the measured xF region is 0.981 +/- 0.015. The data suggest that the strong nuclear suppression of J/psi production previously observed at high xF turns into an enhancement at negative x(F)