Constituent Quark Model versus Nonperturbative QCD
Abstract
We discuss a few, apparently different (but actually, tightly related) problems: 1. The relation between QCD and valence quark model, 2. The asymptotic behavior of the nonperturbative pion wave function at and 3. The dimensional counting rules in the intermediate region of energy. The analysis is based on such general methods as dispersion relations, duality and PCAC. We calculate the asymptotic behavior of the wave function () at the end-point region ( and ) by analysing the corresponding large th moments in transverse and longitudinal directions. This information fixes the asymptotic behavior of at large ( which is turned out to be Gaussian commonly used in the phenomenological analyses). We discuss some applications of the obtained results. In particular, we calculate the nonleading ``soft" contribution to the pion form factor at intermediate momentum transfer. We argue, that due to the specific properties of , the corresponding contribution can temporarily {\bf simulate} the leading twist behavior in the extent region of . The same effect also takes place for the nucleon formfactor. Such a mechanism, if it is correct, would be an explanation of the phenomenological success of the dimensional counting rules at available, very modest energies for many different processes. We discuss some inclusive amplitudes also.
Cite
@article{arxiv.hep-ph/9605226,
title = {Constituent Quark Model versus Nonperturbative QCD},
author = {Ariel Zhitnitsky},
journal= {arXiv preprint arXiv:hep-ph/9605226},
year = {2007}
}
Comments
13 pages, latex, no figures. Talk given at the Workshop ``Continuous Advances in QCD,96''. Theoretical Physics Institute, University of Minnesota, Minneapolis, MN, March 28-31, 1996