Eur. Phys. J. C (2011) 71: 1631
https://doi.org/10.1140/epjc/s10052-011-1631-4

Regular Article - Theoretical Physics

Inclusive J/ψ photoproduction and polarization at HERA in the k _T -factorization approach

¹ P.N. Lebedev Physics Institute, 119991, Moscow, Russia
² D.V. Skobeltsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University, 119991, Moscow, Russia

^* e-mail: lipatov@theory.sinp.msu.ru

Received: 1 February 2011
Revised: 25 March 2011
Published online: 27 April 2011

Abstract

We investigate the inclusive photoproduction of J/ψ mesons at HERA within the framework of the k _T -factorization QCD approach. Our study is based on the color singlet model supplemented with the relevant off-shell matrix elements and the CCFM and KMR unintegrated gluon densities in a proton and in a photon. Both the direct and resolved photon contributions are taken into account. Our predictions are compared with the recent experimental data taken by the H1 and ZEUS collaborations. Special attention is put on the J/ψ polarization parameters λ and ν, which are sensitive to the production dynamics.