Experimental study of isovector spin sum rules
Abstract
We present the Bjorken integral extracted from Jefferson Lab experiment EG1b for 0.05<Q2<2.92 GeV2. The integral is fit to extract the twist-4 element f2p-n which appears to be relatively large and negative. Systematic studies of this higher twist analysis establish its legitimacy at Q2 around 1 GeV2. We also performed an isospin decomposition of the generalized forward spin polarizability γ0. Although its isovector part provides a reliable test of the calculation techniques of Chiral Perturbation Theory, our data disagree with the calculations.
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