1999/01/05 by B. L. Ioffe
Physics and Astronomy · #hep-ph
published as Heavy Ion Phys. 9 (1999) 29-48 · V. Gribov Memorial Volume, Heavy Physics, Academiai Kiado, Budapest, in press, 20 pages, LaTeX 2e, (file hip-atrc.sty is enclosed), 1 eps figure included using epsf.sty
arxiv created 1999/01/05 · arxiv updated 2009/11/30
Vacuum correlator of topological charge densities χ(q2) at low q2 in QCD is discussed: its value χ(0) and first derivative χ'(0) at q2=0 and the contributions of pseudoscalar quasi-Goldstone bosons to χ(q2) at low q2. The QCD sum rule \cite1, giving the connection of χ'(0) (for massless quarks) with the part of the proton spin Σ, carried by u,d,s quarks, is presented. From the requirement of selfconsistancy of the sum rule the values of χ'(0) and Σ were found. The same value of χ'(0) follows also from the experimental data on Σ. The contributions of π and η to χ(q2) are calculated basing on low energy theorems. In such calculation the π-η mixing, expressed in terms of quark mass ratios is of importance.