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Parton distributions for the pion in a chiral quark model
Parton distributions for the pion are studied in a chiral quark model
characterized by a quark propagator for which a spectral representation is
assumed. Electromagnetic and chiral symmetry constraints are imposed through
the relevant Ward-Takahashi identities for flavoured vertex functions.
Finiteness of the theory, requires the spectral function to be non-positive
definite. Straightforward calculation yields the result that the pion structure
function becomes one in the chiral limit, regardless of the details of the
spectral function. LO and NLO evolution provide a satisfactory description of
phenomenological parameterizations of the valence distribution functions but
fails to describe gluon and sea distributions.Comment: Latex, World Scientific, 8 pages, 1 figures. Talk given at the
Workshop on " Lepton Scattering, Hadrons and QCD " March 26 -- April 6, 2001.
Adelaide (Australia
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