Structure Functions of Hadrons in the QCD Effective Theory

Abstract

We study the structure functions of hadrons with the low energy effective theory of QCD. We try to clarify a link between the low energy effective theory, where non-perturbative dynamics is essential, and the high energy deep inelastic scattering experiment. We calculate the leading twist matrix elements of the structure function at the low energy model scale within the effective theory. Calculated structure functions are taken to the high momentum scale with the help of the perturbative QCD, and compared with the experimental data. Through a comparison of the model calculations with the experiment, we discuss how the non-perturbative dynamics of the effective theory is reflected in the deep inelastic phenomena. We first evaluate the structure functions of the pseudoscalar mesons using the NJL model. The resulting structure functions show reasonable agreement with experiments. We then study the quark distribution functions of the nucleon using a covariant quark–diquark model. We calculate three leading twist distribution functions, the spin-independent f₁(x), the longitudinal spin distribution g₁(x), and the chiral-odd transversity spin distribution h₁(x). The results for f₁(x) and g₁(x) turn out to be consistent with available experiments because of the strong spin-0 diquark correlation.