Investigation of the Second Moment of the Nucleon's g1 and g2 Structure   Functions in Two-Flavor Lattice QCD
  The reduced matrix elements a_2 and d_2 are computed in lattice QCD with N_f=2 flavors of light dynamical (sea) quarks. For proton and neutron targets we obtain as our best estimates d_2^(p)=0.004(5) and d_2^(n)=-0.001(3), respectively, in the MSbar scheme at Q^2=5 GeV^2, while for a_2 we find a_2^(p)=0.077(12) and a_2^(n)=-0.005(5), where the errors are purely statistical. 
M. G\"ockeler, R. Horsley, D. Pleiter, P.E.L. Rakow, A. Sch\"afer, G.   Schierholz, H. St\"uben, J.M. Zanotti