Y(4260) on the lattice

We investigate the mass spectra of closed-charm mesons with $J^{PC} = 1^{--}$, for hybrid charmonium, molecules, and diquark-antidiquark operators, in quenched lattice QCD with exact chiral symmetry. For two lattice volumes $24^3 \times 48$ and $20^3 \times 40$, each of 100 gauge configurations generated with single-plaquette action at $\beta = 6.1$, we compute point-to-point quark propagators and measure the time-correlation functions of these exotic meson operators. For the molecular operator $\{(\qbar\gamma_5\gamma_i\c)(\cbar\gamma_5\q)- (\cbar\gamma_5\gamma_i\q)(\qbar\gamma_5\c) \}$, it detects a resonance with mass around $4238 \pm 31$ MeV, which is naturally identified with $Y(4260)$. Further, for any molecular and diquark-antidiquark operator, it detects heavier exotic charmed mesons, with quark content $(\c\s\cbar\sbar)$ around $4450 \pm 100$ MeV, and (\c\c\cbar\cbar) around $6400 \pm 50$ MeV.