DOI 10.1007/s100520000251
Improved calculations of quark distributions in hadrons: the case of the pion
B.L. Ioffe - A.G. Oganesian
Institute of Theoretical and Experimental Physics,
B.Cheremushkinskaya 25, 117218, Moscow, Russia
Received: 14 July 1999 / Published online: 6 March 2000 - © Springer-Verlag 2000
Abstract
The earlier introduced method of calculation of quark distributions
in
hadrons, based on QCD sum rules, is improved. The imaginary part
of the
virtual photon forward scattering amplitude on some hadronic
current is
considered in the case, when initial and final virtualities of
the current
p21, and p22 are different,
.
The operator
product
expansion (OPE) in p21, p22 is performed. The sum rule
for quark
distribution is obtained using double dispersion representation
of the
amplitude on one side in terms of calculated in QCD OPE and on
the other
side in terms of physical states contributions. Double Borel
transformation
in p21, p22 is applied to the sum rule, killing background
non-diagonal transition terms which deteriorated the accuracy
in previous
calculations. The case of the valence quark distribution in the
pion
is considered,
which was impossible to treat by the previous method. OPE up
to dimension 6
operators is performed and leading order perturbative corrections
are
accounted. Valence u-quark distribution in
was found
at
intermediate x,
0.15 < x < 0.7, and normalization point
.
These results may be used as input for evolution equations.
Copyright Società Italiana di Fisica, Springer-Verlag 2000
