PROTON SPIN CONTENT AND QCD TOPOLOGICAL SUSCEPTIBILITY

The part of the proton spin Sigma carried by u,d,s quarks is calculate d in the framework of the QCD sum rules in the external fields. The op erators up to dimension 9 an accounted for. An important contribution comes from the operator of dimension 3, which in the limit of massless lc,d,s quarks is equal to the derivative of the QCD topological susce ptibility chi'(0) The comparison with the experimental data on Sigma g ives chi'(0)=(2.3 +/- 0.6)x 10(-3) GeV2. The limits on Sigma and chi'( 0) are found from self-consistency of the sum rule, Sigma greater than or equal to 0.05, chi'(0)greater than or equal to 1.6x10(-3) GeV2. Th e values of g(A)=1.37+/-0.10 and g(A)(8)=0.65+/-0.15 are also determin ed.