COLOR ANOMALY AND FLAVOR-SINGLET AXIAL CHARGE OF THE PROTON IN THE CHIRAL BAG - THE CHESHIRE-CAT REVISITED

Quantum effects inside the chiral bag induce a color anomaly which req uires a compensating surface term to prevent breakdown of color gauge invariance, We show that the presence of this surface term first disco vered several years ago allows one to derive in a gauge-invariant way a chiral-bag version of the Shore-Veneziano two-component formula for the flavor-singlet axial charge of the proton. This has relevance to w hat is referred to as the ''proton spin problem'' on the one hand and to the Cheshire-Cat phenomenon in hadron structure on the other. We sh ow that when calculated to the leading order in the color gauge coupli ng and for a specific color electric monopole configuration in the bag , one can obtain a striking Cheshire-Cat phenomenon with a negligibly small singlet axial charge. (C) 1997 Published by Elsevier Science B.V .