Polarized structure function $g_2$ in the CM bag model

Abstract

The spin-dependent structure functions $g_1(x)$, $g_2(x)$, $g_2^{WW}(x)$ and ${\bar{g}}_2(x)$ and their moments are studied in the CM bag model. The results show that (i) ${\int }_0^1{g}_2(x)dx=0$, i.e. the Burkhardt-Cottingham sum rule holds, hence $g_2(x)$ must have at least one non-trivial zero besides $x=0$ and $x=1$. (ii) ${\int }_0^1{x}^2{g}_2(x)dx$ is negative for the proton, neutron and deuteron. (iii) ${\int }_0^1{x}^2{g}_2(x)dx$ is about one order of magnitude smaller than ${\int }_0^1{x}^2{g}_1(x)dx$, hence the twist-3 matrix element is approximately equal to the twist-2 matrix element. The results are compared with most recent data and predictions from the MIT bag model, lattice QCD and QCD sum rules.

Comments: 29 pages, revtex, uses epsfig.sty, 12 ps figures included