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Diffractive Photoproduction of J/psi Mesons with Large Momentum Transfer at HERA |
| Reference |
Final results expected for DIS03, Spring 2003 |
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| Contact |
Duncan Brown |
| Abstract |
The diffractive photoproduction of J/psi mesons has been measured with the H1 detector at the ep collider HERA using an integrated luminosity of 79 pb-1. The differential cross section d sigma (gamma p -> J/psi Y) / dt is studied in the range 2 < |t| < 30 GeV^2, 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 W in three t intervals, spanning the range 50 < W < 200 GeV. A fast rise of the cross section is observed for each t range and yields a slope for the effective Pomeron trajectory of alpha^\prime = -0.017 \pm 0.008 (stat.) \pm 0.005 (syst.) GeV-2. Perturbative QCD models based on BFKL evolution are able to describe the data. The data are found to be compatible with s-channel helicity conservation, in contrast to light vector meson production at high t. |
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