eta-glueball mixing from N-f=2 lattice QCD

We perform the first lattice study on the mixing of the isoscalar pseudoscalar meson eta and the pseudoscalar glueball Gin the Nf 1/4 2 QCD at the pion mass m pi approximate to 350 MeV. The eta mass is determined to be m eta 1/4 714o6 thorn o16 thorn MeV. Through the Witten-Veneziano relation, this value can be matched to a mass value of similar to 981 MeV for the SU(3) counterpart of eta. Based on a large gauge ensemble, the eta - G mixing energy and the mixing angle are determined to be jxj 1/4 107o15 thorn o2 thorn MeV and j theta j 1/4 3.46o46 thorn degrees from the eta - G correlators that are calculated using the distillation method. We conclude that the eta - G mixing is tiny and the topology induced interaction contributes most of eta mass owing to the QCD UAo1 thorn anomaly.