Systematic analysis of charmonium photoproduction

• Published in: Journal of physics. G, Nuclear and particle physics Vol. 30; no. 10; pp. 1427 - 1444
• Main Authors: Sibirtsev, A, Krewald, S, Thomas, A W
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.10.2004; Institute of Physics
• Subjects: CHARMONIUM; CROSS SECTIONS; DISTRIBUTION FUNCTIONS; Exact sciences and technology; FORM FACTORS; GLUONS; Nuclear physics; PHOTOPRODUCTION; Physics; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; POMERANCHUK PARTICLES; SENSITIVITY; The physics of elementary particles and fields; VECTORS; Particle exchange; Charmonium; Quarks; Trajectories; Photoproduction; Form factors; Flavor; Pomerons; Gluons; Gluon model; Nucleons; Cross sections; Mathematical physics; Nuclear physics
• ISSN: 0954-3899; 1361-6471
• DOI: 10.1088/0954-3899/30/10/009

The available data on J/{Psi} photoproduction are analyzed in terms of pomeron exchange, two-gluon exchange and photon-gluon fusion models. Allowing the pomeron-quark interaction to be flavour-dependent and introducing both soft and hard pomerons it is possible to reproduce the data at {radical}s > 10 GeV and small |t|. The two-gluon exchange calculations indicate strong sensitivity to the gluon distribution function. The results obtained with the most modern MRST2001 and DL PDF reproduce the forward J/{Psi} photoproduction cross section at {radical}s > 10 GeV. The calculations with the photon-gluon fusion model and with MRST2001 and DL PDF are also in reasonable agreement with the data on the total J/{Psi} photoproduction cross section. However none of the models describe the data at {radical}s < 10 GeV or |t| {ge} 1 GeV{sup 2}. We attribute the J/{Psi} photoproduction at low energies and large |t| to a mechanism different from pomeron or two-gluon exchange. The authors consider that this might be the exchange of an axial vector trajectory that couples with the axial form factor of the nucleon.