Ifup-th 3/95
نویسندگان
چکیده
where e, e label the helicity states and k is the momentum transfer. In a naive wave function picture G1(0) can be interpreted as the fraction of the nucleon spin carried by the quarks. Experimental determinations lead to an unexpectedly small value of G1(0), calling for a theoretical explanation in the context of a nonperturbative study in QCD. G1(0) can be extracted from the nucleon matrix element of the topological charge density q(x) by using the fact that in the chiral limit the anomalous divergence of j μ is proportional to the topological charge density. In the presence of dynamical fermions, one has
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