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HK: Fachverband Hadronen und Kerne
HK 5: Hadron Structure and Spectroscopy II
HK 5.3: Talk
Monday, March 16, 2009, 15:00–15:15, H-ZO 30
kt-factorisation in the Drell-Yan process — •Fabian Eichstädt, Stefan Leupold, and Ulrich Mosel — Institut für Theoretische Physik, Universität Giessen, Germany
The transverse-momentum spectrum of Drell-Yan pairs still eludes a
complete, K-factor free description, as does to some extent also the
invariant-mass distribution. In this context we critically investigate
factorisation of unintegrated parton distributions in the Drell-Yan
process. We employ the full initial parton kinematics for the cross
section instead of the usual collinear approach simply folded by a
Gaussian for the transverse-momentum distribution. We find that the
standard, x-independent Gaussian kt-distribution for the initial
partons does not coincide with the parton-model result for the
double-differential Drell-Yan invariant mass distribution. It turns out
that one is very sensitive to the low-x behaviour of the sea-quark
parton distributions. We also suggest an alternative prescription which
weakens this sensitivity and brings the results back to the parton-model
results. We finally examine the consequences of the different
kt-distributions for the triple-differential Drell-Yan cross
section.
Work supported by DFG.