The spin content of the proton in the chiral bag

Abstract We analyze the sum-rules of the nucleon spin structure functions using a two-phase chiral invariant quark model. Due to the axial anomaly, the flavor SU (3) singlet component outside the quark confinement cavity is suppressed. This singlet is also reduced inside the cavity due to (non-strange) intermediate qqqq q states gluon exchange current corrections. Chiral symmetry requires Goldstone pions outside which generate part of the proton spin.