Lattice study of the magnetic moment and the spin structure of the nucleon

Using an approach free from momentum extrapolation, we calculate the nucleon magnetic moment and the fraction of the nucleon spin carried by the quark angular momentum in the quenched lattice QCD approximation. Quarks with three values of lattice mass, 210, 124, and 80 MeV, are formulated on the lattice using the standard Wilson approach. At every mass, 100 gluon configurations on a ${16}^3\times 32$ lattice with $\beta =6.0\mathrm{}$ are used for statistical averaging. The results are compared with previous calculations with momentum extrapolation. The contribution of the disconnected diagrams is studied at the largest quark mass using the noise theory technique.