Charmonium spectrum from quenched QCD with overlap fermions

We present the first study of the charmonium spectrum using overlap fermions, on quenched configurations. Simulations are performed on 163×72 lattices, with Wilson gauge action at β=6.3345. We demonstrate that we have discretization errors, as indicated by the dispersion relation, at about 5%. We obtain 88(4) MeV for the 1S hyperfine splitting using the r0 scale, and 121(6) MeV using the (1P¯−1S¯) scale. This Letter should encourage the pursuit of using the same chiral fermions for both heavy and light quarks on the same lattice.