Köln 2004 – scientific programme

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HK: Physik der Hadronen und Kerne

HK 20: Theory III

HK 20.7: Talk

Tuesday, March 9, 2004, 17:30–17:45, E

The effect of quark off-shellness in high energy processes — •Olena Linnyk, Stefan Leupold, and Ulrich Mosel — Institut für Theoretische Physik, Universität Giessen, 35392 Giessen, Germany

We study the quark and gluon structure of hadrons going beyond the well-known picture of collinear non-interacting partons. Calculated are the effects of an initial quark off-shellness in several high energy processes. The interaction of the partons missed in the standard perturbative consideration is taken into account in the spectral functions of the quarks, and using a generalized factorization. The intrinsic motion of the partons is consistently treated as well. The quark off-shellness turns out to be important in the description of semi-exclusive observables such as the triple differential Drell-Yan cross section. Recent data of the Fermilab experiment E866 on continuum dimuon production are analyzed and the width of the quark spectral function in the proton is found to be approximately 150 MeV. The dependence of the width on the hard scale is investigated. The results of our calculations reveal the important role of the initial quark virtuality in high energy processes.
Work supported by the European graduate school Giessen–Copenhagen.