Correlator of topological charge densities at low $Q^2$ in QCD: connection with proton spin problem

B. L. Ioffe

Vacuum correlator of topological charge densities $\chi (q^2)$ at low $q^2$ in QCD is discussed: its value $\chi (0)$ and first derivative ${\chi }^{\prime }(0)$ at $q^2=0$ and the contributions of pseud…