We perform a global analysis of all available spin-dependent proton structure function data, covering a large range of Q^2, 1 < Q^2 < 30 GeV^2, and calculate the lowest moment of the g_1 structure function as a function of Q^2. From the Q^2 dependence of the lowest moment we extract matrix elements of twist-4 operators, and determine the color electric and magnetic polarizabilities of the proton to be \chi_E = 0.026 +- 0.015 (stat) + 0.021/-0.024 (sys) and \chi_B = -0.013 -+ 0.007 (stat) - 0.010/+0.012 (sys), respectively.
@article{arxiv.hep-ph/0404195,
title = {Higher twist analysis of the proton g_1 structure function},
author = {M. Osipenko and W. Melnitchouk and S. Simula and P. Bosted and V. Burkert and M. E. Christy and K. Griffioen and C. Keppel and S. E. Kuhn},
journal= {arXiv preprint arXiv:hep-ph/0404195},
year = {2008}
}