Measurement of inelastic J/PSI production in deep inelastic scattering at HERA

The inelastic production of J/psi mesonsin ep collisions has been studied with the ZEUS detector at HERAusing an integrated luminosity of 109 pb(-1). The J/psi mesonswere identified using the decay channel J/psi -> mu(+)mu(-). The measurements were performed in the kinematic range 2 < Q(2) < 80 GeV2, 50 < W < 250 GeV, 0.2 < z < 0.9 and -1.6 < Y-lab < 1.3, where Q(2) is the virtuality of the exchanged photon, W is the photon-proton centre-of-mass energy, z is the fraction of the photon energy carried by the J/psi mesonin the proton rest frameand Ylab is the rapidity of the J/psi in the laboratory frame. The measured cross sections are compared to theoretical predictions within the non-relativistic QCD framework including colour-singlet and colour- octetcontributions, as well as to predictions based on the k(T)-factorisation approach. Calculations of the colour-singlet process generally agree with the data, whereas inclusion of colour- octetterms spoils this agreement.