München 2006 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 22: Elektromagnetische und Hadronische Sonden
HK 22.3: Vortrag
Dienstag, 21. März 2006, 18:00–18:15, F
Drell-Yan process: quark kT and quark off–shellness vs. next–to–leading order of perturbative QCD — •Olena Linnyk, Stefan Leupold und Ulrich Mosel — Institut für Theoretische Physik, Universität Giessen, Germany
It has been shown1 that accounting for the off-shellness of quarks and gluons in proton greatly improved the agreement of theoretically calculated high energy cross sections with data. We study the relation between the aforesaid phenomenological corrections and the next-to-leading order (NLO) of the conventional perturbative QCD (pQCD). Drell-Yan lepton pair production p p → l+ l− X proves sensitive to the effects beyond leading order (LO) of pQCD. LO reaction mechanism with the assumption of on-shell collinear quarks fails to reproduce: (1) the magnitude of the double differential Drell-Yan cross section d2 σ/dQ2 d xF, the discrepancy being usually parametrized by a K-factor; (2) the average transverse momentum pT of the dileptons; (3) the triple differential cross section d3 σ/dQ2 d xF dpT,i.e. the pT-spectrum. Possible extensions of the LO pQCD are (a) addition of the NLO processes and (b) taking into account the quark transverse motion and off-shellness. We calculate the Drell-Yan process cross section in these two approaches. The results suggest that corrections due to quark off-shellness and intrinsic-kT contain NLO as well as higher twist contributions.
Work supported by BMBF.
1 J. Collins and H. Jung, hep-ph/0508280; O. Linnyk, S. Leupold and U. Mosel, hep-ph/0412138