Unintegrated gluon in the photon and heavy quark productionL. Motyka1, 2 and N. Tîmneanu1
1 High Energy Physics, Uppsala University, Box 535, 751 21 Uppsala, Sweden
2 Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Kraków, Poland
(Received: 4 September 2002 / Revised version: 6 November 2002 / Published online: 20 December 2002 )
The unintegrated gluon density in the photon is determined, using the Kimber-Martin-Ryskin prescription. In addition, a model of the unintegrated gluon is proposed, based on the saturation model extended to the large- x region. These gluon densities are applied to obtain cross sections for charm and bottom production in and collisions using the kt factorization approach. We investigate both direct and resolved photon contributions and make a comparison with the results from the collinear approach and the experimental data. An enhancement of the cross section due to inclusion of non-zero transverse momenta of the gluons is found. The charm production cross section is consistent with the data. The data exceed our conservative estimate for bottom production in collisions, but theoretical uncertainties are too large to claim a significant inconsistency. A substantial discrepancy between theory and the experiment is found for , which is not cured by the kt factorization approach.
© Società Italiana di Fisica, Springer-Verlag 2003