Glueballs on the Lattice

In SU(3) lattice Yang-Mills theory, we show that the extracted lowest scalar glueball mass using open and periodic boundary conditions at the same lattice volume and lattice spacing agree for the range of lattice scales explored. By relating the functional averages of a generic scalar operator in simulations with open and periodic boundary conditions respectively for SU(3) lattice gauge theory, we also show that the scalar glueball mass and the glueball to vacuum matrix element can be extracted very efficiently from the former. We have also extracted the pseudoscalar glueball mass from topological charge density correlator, which appears to be insensitive to the range of lattice spacings explored. To reduce the cut off artifacts, recently proposed gradient flow is used.