Measurement of the Proton and Deuteron Spin Structure Functions G1 and G2

The SLAC experiment E155 was a deep-inelastic scattering experiment that scattered polarized electrons off polarized proton and deuteron targets in the effort to measure precisely the proton and deuteron spin structure functions. The nucleon structure functions g1 and g2 are important quantities that help test our present models of nucleon structure. Such information can help quantify the constituent contributions to the nucleon spin. The structure functions g1p and G1d have been measured over the kinematic range 0.01 (le) x (le) 0.9 and 1 (le) Q2 (le) 40 GeV2 by scattering 48.4 GeV longitudinally polarized electrons off longitudinally polarized protons and deuterons. In addition, the structure functions g2p and g2d have been measured over the kinematic range 0.01 (le) x (le) 0.7 and 1 (le) Q2 (le) 17 GeV2 by scattering 38.8 GeV longitudinally polarized electrons off transversely polarized protons and deuterons. The measurements of g1 confirm the Bjorken sum rule and find the net quark polarization to be ΔΣ = 0.23 ± 0.04 ± 0.6 while g2 is found to be consistent with the g2WW model