par Aktas, Adil;Collard, Caroline ;Favart, Laurent ;Janssen, Xavier ;Marage, Pierre ; [et al.]
Référence Physics letters. Section B, 568, 3-4, page (205-218)
Publication Publié, 2003
Article révisé par les pairs
Résumé : The diffractive photoproduction of J/ψ mesons is measured with the H1 detector at the ep collider HERA using an integrated luminosity of 78 pb -1. The differential cross section dσ(γp → J/ψY)/dt is studied in the range 2 < t < 30 GeV2, where t is the square of the four-momentum transferred at the proton vertex. The cross section is also presented as a function of the photon-proton centre-of-mass energy Wγp in three t intervals, spanning the range 50 < Wγp < 200 GeV. A fast rise of the cross section with Wγp is observed for each t range and the slope for the effective linear Pomeron trajectory is measured to be α′ = -0.0135 ± 0.0074(stat.) ± 0.0051(syst.) GeV-2. The measurements are compared with perturbative QCD models based on BFKL and DGLAP evolution. The data are found to be compatible with s-channel helicity conservation. © 2003 Published by Elsevier B.V.