T. Gehrmann et Wj. Stirling, SPIN-DEPENDENT PARTON DISTRIBUTIONS FROM POLARIZED STRUCTURE-FUNCTIONDATA, Zeitschrift fur Physik. C, Particles and fields, 65(3), 1995, pp. 461-470
In the past year, polarized deep inelastic scattering experiments at C
ERN and SLAC have obtained structure function measurements off proton,
neutron and deuteron targets at a level of precision never before ach
ieved. The measurements can be used to test the Bjorken and Ellis-Jaff
e sum rules, and also to obtain information on the parton distribution
s in polarized nucleons. We perform a global leading-order QCD fit to
the proton deep inelastic data in order to extract the spin-dependent
parton distributions. By using parametric forms which are consistent w
ith theoretical expectations at large and small x, we find that the qu
ark distributions are now rather well constrained. We assume that ther
e is no significant intrinsic polarization of the strange quark sea. T
he data are then consistent with a modest amount of the proton's spin
carried by the gluon, although the shape of the gluon distribution is
not well constrained, and several qualitatively different shapes are s
uggested. The spin-dependent distributions we obtain can be used as in
put to phenomenological studies for future polarized hadron-hadron and
lepton-hadron colliders.