We prove that the { \em gauge dependent} gluon spin, gluon and quark orbital angular momenta operators have { \em gauge invariant} expectation values on hadron states with { \em definite} momentum and polarization, therefore the conventional decomposition of nucleon spin into contributions from the spin and orbital angular momentum of quark and gluon is { \em gauge independent}. Similar conclusions apply to the { \em gauge dependent} quark momentum and kinetic energy operators, and accordingly nucleon momentum and mass structures.
Categories: hep-ph