Speaker
Description
We present the results of a lattice calculation of four-quark states with quark contents $q_1q_2\bar{Q}\bar{Q}, \, q_1,q_2 \subset u,d,s,c$ and $Q \equiv b,c$ in both spin one ($J=1$) and spin zero ($J=0$) sectors. For the spin one states we find that for both doubly heavy quarks and particularly for the doubly bottom quarks the ground state energy levels are below their respective thresholds. The ground state spectra of the spin zero four-quark states with various flavor combinations are seen to lie above their respective thresholds. We also present the results of heavy dibaryons where we find the ground state energy levels of a few six-quark combinations are below their respective thresholds. These calculations are performed on three dynamical $N_f=2+1+1$ highly improved staggered quark ensembles at lattice spacings of about 0.12, 0.09 and 0.06 fm. We use the overlap action for light to charm quarks while a non-relativistic action with non-perturbatively improved coefficients is employed for the bottom quark.
