Elastic J/psi production at HERA
Collaboration
40 pages
Published in:
- Eur.Phys.J.C 46 (2006) 585-603
e-Print:
- hep-ex/0510016 [hep-ex]
Report number:
- DESY-05-161
Experiments:
Citations per year
Abstract:
Cross sections for elastic production of J/Psi mesons in photoproduction and electroproduction are measured in electron proton collisions at HERA using an integrated luminosity of 55 pb^{-1}. Results are presented for photon virtualities Q^2 up to 80 GeV^2. The dependence on the photon-proton centre of mass energy W_{gamma p} is analysed in the range 40 < \Wgp < 305 GeV in photoproduction and 40 < \Wgp < 160 GeV in electroproduction. The \Wgp dependences of the cross sections do not change significantly with Q^2 and can be described by models based on perturbative QCD. Within such models, the data show a high sensitivity to the gluon density of the proton in the domain of low Bjorken x and low Q^2. Differential cross sections d\sigma/dt, where t is the squared four-momentum transfer at the proton vertex, are measured in the range |t|<1.2 GeV^2 as functions of \Wgp and Q^2. Effective Pomeron trajectories are determined for photoproduction and electroproduction. The J/Psi production and decay angular distributions are consistent with s-channel helicity conservation. The ratio of the cross sections for longitudinally and transversely polarised photons is measured as a function of Q^2 and is found to be described by perturbative QCD based models.Note:
- 40 pages, 14 figures, 15 tables Report-no: DESY 05-161
- positron p: colliding beams
- positron p: exclusive reaction
- diffraction
- J/psi(3100): electroproduction
- J/psi(3100): photoproduction
- J/psi(3100): leptonic decay
- mass spectrum: dilepton
- channel cross section: energy dependence
- differential cross section: momentum transfer
- pomeron: exchange
References(50)
Figures(45)