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. 
TWQCD Collaboration: Ting-Wai Chiu, Tung-Han Hsieh