Speaker
Description
WE perform an exploratory study of glueballs on a RBC/UKQCD gauge ensembles with a large
lattice size and with the $N_f = 2 + 1$ dynamical quark masses being tuned at the physical point. The
noises of glueball correlation functions are considerably reduced through the cluster-decomposition-
error-reduction scheme. The Bethe-Salpeter wave functions are obtained for the salar, the tensor
and the pseudoscalar glueballs by using the spatially extended glueball operators defined through
the gauge potential $A_\mu(x)$ in the Coulomb gauge. These wave functions show similar features of
non-relativistic two-gluon systems, which are used to optimize the signals of the related correlation
functions at the early time region, where the ground state masses in each channel can be extracted.
By the assumptions that the glueball operators defined in terms gauge potentials couple almost
exclusively to pure glueball states, the obtained masses are interpreted to be those of the ground
state pure gauge glueballs. For the most interesting scalar channel, the glueball mass is determined
to be 1.75(2) GeV, which is in good agreement with the QLQCD predictions and is close to the
mass of $f_0 (1710)$. Our result shows the existence of glueball states in the presence of dynamical
quarks, even though many systematic uncertainties have not yet be well tackled with.
