Probing quark-gluon interactions with transverse polarized scattering

Transverse polarized inelastic scattering extends the power of the electromagnetic interaction as a probe of nucleon dynamics beyond the leading order regime explored with longitudinally polarized DIS. The latter revealed the surprising result of the ``spin defect'' in the quark contribution to the nucleon spin, obtained from measurements of the leading twist $g_1$ spin structure function (SSF). In transverse polarized scattering, the twist-3 $g_2$ SSF contributes at the same order as $g_1$, so interactions between quarks and gluons can be studied, opening a window on the mechanisms of confinement. In this talk I will report the results of Jefferson Lab's Resonances Spin Structure (RSS) experiment measurement of the moments of $g_2$ and the $d_2$ twist-3 quark matrix element at a four-momentum transfer of 1.3 GeV$^2$. The extension of RSS physics by the related JLab Spin Asymmetries of the Nucleon Experiment - SANE, that covers the momentum transfer range from 2.5 to 6.5 GeV$^2$, will be reviewed.