Speaker
Alexander Korzenev
(Mainz University)
Description
A first evaluation of the polarized valence quark
distribution\Delta u_v(x)+Delta d_v(x) from the COMPASS
experiment (CERN/SPS) is presented. The data were collected
by COMPASS in the years 2002--2004 using a 160 GeV polarized
muon beam scattered off a large polarized 6LiD target and
cover the range 1< Q2 < 100(GeV/c)2 and $0.006<x<0.7.
The analysis is based on the difference asymmetry, A^(h+ - h-),
for hadrons of opposite charges. This approach gives a direct
access to the valence quark helicity distributions because
fragmentation functions cancel out in LO QCD, so that the
expression for the difference asymmetry is given by the ratio
of polarized to unpolarized valence quark distributions.
Due to this very weak sensitivity to uncertainties coming
from the fragmentation, the results derived from A^(h+ - h-)
can be used as a crosscheck for those obtained from single hadron
asymmetries as in the SMC and HERMES analyzes.
Author
Alexander Korzenev
(Mainz University)
