J/<font face="Symbol">y</font> production in photon-photon collisions

by Matthias STEINHAUSER (University of Hamburg)

Friday 15 Feb 2002, 14:00 → 15:00 Europe/Zurich

TH Auditorium (CERN)

The production of a J/y meson in association with one or two jets in gg collisions is discussed. For the process gg -> J/y + X theoretical predictions for the transverse-momentum distribution of J/y mesons promptly produced within the factorization formalism of nonrelativistic quantum chromodynamics including the contributions from both direct and resolved photons are presented. The results are compared with data taken by the DELPHI Collaboration at LEP2. They nicely confirm these predictions, while they disfavour those obtained within the traditional colour-singlet model. In the case of two jets in the final state we concentrate on the direct-photon contribution, which is expected to be dominant for large J/y-meson transverse momentum and/or large dijet invariant mass. We work at leading order in the factorization formalism of non-relativistic QCD and include all relevant colour-octet processes. Distributions in J/y-meson transverse momentum and rapidity appropriate for CERN LEP2, a future e+e- linear collider, and a possible gg collider mode of the latter are presented.