TY - JOUR
T1 - Inelastic photoproduction of J/ψ mesons at HERA
AU - Adloff, C
AU - Coppens, Yves
AU - Dowell, John
AU - Faulkner, Peter
AU - Fleming, Yves
AU - Garvey, John
AU - Johnson, Carrie
AU - Kenyon, Ian
AU - Lamb, David
AU - Newman, Paul
AU - Rizvi, Syed
AU - Thompson, Paul
AU - Woehrling, Ethan-Etienne
PY - 2001/1/1
Y1 - 2001/1/1
N2 - An analysis of inelastic photoproduction of J/psi mesons is presented using data collected at the ep collider HERA corresponding to an integrated luminosity of above 80 pb(-1), Differential and double I <P-t/psi(2) <differential cross sections are measured in a wide kinematic region: 60 <W-gammap <260 GeV, 1 p(t,psi)(2) <60 GeV2 and 0.05 <z <0.9. where z is the fraction of the energy of the exchanged photon transferred to the J/psi meson in the rest frame of the target proton. Cross sections at z less than or similar to 0.3 are presented for the first time. Theoretical calculations within the Colour Singlet Model at NLO for direct photon processes are shown to give a good description of the data in the medium z region (0.3 <z <0.9) up to the highest p(t,psi)(2) values. A calculation using a k(t) factorisation approach in LO in the Colour Singlet Model is also able to describe these data. The data in the full z range are also compared to LO calculations within a non-relativistic QCD framework including colour octet and colour singlet contributions for direct and resolved photons. It seems possible to reconcile data and theory with modest contributions from colour octet processes. The polarisation of the J/psi meson is measured as a function of z and p(t,psi) and is reasonably described by the theoretical predictions.
AB - An analysis of inelastic photoproduction of J/psi mesons is presented using data collected at the ep collider HERA corresponding to an integrated luminosity of above 80 pb(-1), Differential and double I <P-t/psi(2) <differential cross sections are measured in a wide kinematic region: 60 <W-gammap <260 GeV, 1 p(t,psi)(2) <60 GeV2 and 0.05 <z <0.9. where z is the fraction of the energy of the exchanged photon transferred to the J/psi meson in the rest frame of the target proton. Cross sections at z less than or similar to 0.3 are presented for the first time. Theoretical calculations within the Colour Singlet Model at NLO for direct photon processes are shown to give a good description of the data in the medium z region (0.3 <z <0.9) up to the highest p(t,psi)(2) values. A calculation using a k(t) factorisation approach in LO in the Colour Singlet Model is also able to describe these data. The data in the full z range are also compared to LO calculations within a non-relativistic QCD framework including colour octet and colour singlet contributions for direct and resolved photons. It seems possible to reconcile data and theory with modest contributions from colour octet processes. The polarisation of the J/psi meson is measured as a function of z and p(t,psi) and is reasonably described by the theoretical predictions.
U2 - 10.1007/s10052-002-1009-8
DO - 10.1007/s10052-002-1009-8
M3 - Article
SN - 1434-6044
VL - 25
SP - 25
EP - 39
JO - European Physical Journal C
JF - European Physical Journal C
ER -