$\eta -{\eta }^{\prime }$ Mixture in Chiral Bag

Abstract

The $\eta -{\eta }^{\prime }$ mixture is discussed in the chiral bag model to calculate the pseudoscalar octet-singlet mixing angle consistent with the experimental data. The color anomaly is taken into account with the modified boundary conditions, which shows the relation between the ${\eta }^{\prime }$ mass and the gluon condensate inside the chiral bag. We show, however, that $\eta -{\eta }^{\prime }$ mixing angle can follow the Cheshire Cat Principle, i.e., insensitivity to the bag radius.

Comments: 11 pages, Latex