Perturbative QCD Core of Hadrons and Color Transparency Phenomena

TL;DR

This paper argues that hadrons have a significant perturbative QCD core of about 0.4-0.5 fm, which explains color transparency phenomena and dominates certain high-momentum transfer processes.

Contribution

It introduces a model of hadrons with a perturbative QCD core surrounded by a condensate layer, explaining color transparency and quasi-elastic scattering at high Q^2.

Findings

The pQCD core radius is about 0.4-0.5 fm.

Color transparency can be derived from QCD factorization.

Quasi-elastic processes are dominated by the pQCD core at high Q^2.

Abstract

In the current paper, we argue that the ground state of a hadron contains a significant perturbative quantum chromodynamics (pQCD) core as the result of color gauge invariance and of the values of chiral and gluon vacuum condensates. The evaluation within the method of dispersion sum rules (DSR) of the vacuum matrix elements of the correlator of local currents with the proper quantum numbers leads to the value of the radius of the pQCD core of a nucleon of about 0.4--0.5 fm. The selection of the initial and final states allows to select processes in which the pQCD core of the projectile gives the dominant contribution to the process. It is explained that the transparency of nuclear matter for the propagation of a spatially small and color-neutral wave packet of quarks and gluons -- a color transparency (CT) phenomenon -- for a group of hard processes off nuclear targets can be derived in the form of the QCD factorization theorem accounting for the color screening phenomenon Based on the success of the method of DSR, we argue that a pQCD core in a hadron wave function is surrounded by the layer consisting of quarks interacting with quark and gluon condensates. As a result, in the quasi-elastic processes $e+A\to e'+N +(A-1)^{*}$, the quasi-Feynman mechanism could be dominating in a wide range of the momentum transfer squared, $Q^2$. In this scenario, a virtual photon is absorbed by a single quark, which carries a large fraction of the momentum of the nucleon and dominates in a wide range of $Q^2$. CT should reveal itself in these processes at an extremely large $Q^2$ as the consequence of the presence of the Sudakov form factors, which squeeze a nucleon.