Lattice calculation of the nucleon's spin-dependent structure function g2 reexamined

Our previous calculation of the spin-dependent structure function g₂ is reexamined. Interest in this structure function is to a great extent motivated by the fact that it receives contributions from twist-2 as well as from twist-3 operators already in leading order of 1/Q², thus offering the unique possibility of directly assessing higher-twist effects. In our former calculation the lattice operators were renormalized perturbatively and mixing with lower-dimensional operators was ignored. However, the twist-3 operator which gives rise to the matrix element d₂ mixes non-perturbatively with an operator of lower dimension. Taking this effect into account leads to a considerably smaller value of d₂, which is consistent with the experimental data.