Measurements of the Proton and Deuteron Spin Structure Functiong2and AsymmetryA2

We have measured proton and deuteron virtual photon-nucleon asymmetries $A_2^p$ and $A_2^d$ and structure functions $g_2^p$ and $g_2^d$ over the range $0.03<x<\mathrm{}0.8\mathrm{}$ and $1.3<\mathrm{}{Q}^2<10\mathrm{}(\mathrm{GeV}/c{)}^2$ by inelastically scattering polarized electrons off polarized ammonia targets. Results for $A_2$ are significantly smaller than the positivity limit $\sqrt{R}$ for both targets. Within experimental precision the $g_2$ data are well described by the twist-2 contribution, $g_2^{\mathrm{WW}}$. Twist-3 matrix elements have been extracted and are compared to theoretical predictions.