Experimental study of isovector spin sum rules

Understand

We present the Bjorken integral extracted from Jefferson Lab experiment EG1b for $0.05<Q^{2}<2.92$ GeV$^2$.

• The integral is fit to extract the twist-4 element $f_{2}^{p-n}$ which appears to be relatively large and negative.
• Systematic studies of this higher twist analysis establish its legitimacy at $Q^{2}$ around 1 GeV$^{2}$.
• We also performed an isospin decomposition of the generalized forward spin polarizability $\gamma_{0}$.