Squeezed condensate of gluons and $\eta -{\eta }^{\prime }$ mass difference

D. Blaschke, H. -P. Pavel, V. N. Pervushin +2

We consider a mechanism to create the $\eta -{\eta }^{\prime }$ mass difference by the gluon anomaly in a squeezed vacuum. We find that the mass shift of the ${\eta }_0$ governing this mass difference is…