Helium nuclei, deuteron, and dineutron in 2+1 flavor lattice QCD

We calculate the binding energies for multinucleon bound states with the nuclear mass number less than or equal to 4 in 2 + 1 flavor QCD at the lattice spacing of a = 0.09 fm employing a relatively heavy quark mass corresponding to m(pi) = 0.51 GeV. To distinguish a bound state from attractive scattering states, we investigate the volume dependence of the energy shift between the ground state and the state of free nucleons by changing the spatial extent of the lattice from 2.9 to 5.8 fm. We conclude that He-4, He-3, deuteron and dineutron are bound at m(pi) = 0.51 GeV. We compare their binding energies with those in our quenched studies and also with several previous investigations.