The sum rule for the polarized structure function $g_2$ corresponding to the moment at $n=0$

Abstract

In the small $Q^2$ region, the sum rule for the polarized structure function $g_2$ corresponding to the moment at $n=0$ is derived. This sum rule shows that there is a tight connection among the resonances,the elastic and the continuum in the $g_2$. Further, the Born term contribution in this sum rule is proportional to $Q^2$ and very small compared with that in the corresponding sum rule for the polarized structure function $g_1$. However, the Born term contribution divided by $Q^2/2$ which also appears in the Schwinger sum rule for the $g_2$ corresponding to the moment at $n=1$ has a very similar behavior with that in the sum rule for the $g_1$ corresponding to the moment at $n=0$.

5pages,1figure, to appear in PRC typos corrected