Charmonium Spectrum from Quenched QCD with Overlap Fermions

TL;DR

This study uses overlap fermions in quenched QCD to compute the charmonium spectrum, achieving controlled discretization errors and providing insights into hyperfine splitting discrepancies.

Contribution

First application of overlap fermions to charmonium spectrum in quenched QCD, demonstrating controlled discretization errors and potential resolution of hyperfine splitting discrepancies.

Findings

Discretization errors are about 5%.

Hyperfine splitting is 88(4) MeV (r_0 scale).

Results suggest overlap fermions may resolve hyperfine splitting discrepancies.

Abstract

We present the first study of the charmonium spectrum using overlap fermions, on quenched configurations. Simulations are performed on $16^3 \times 72$ lattices, with Wilson gauge action at $\beta$ = 6.3345. We demonstrate that we have discretization errors under control at about 5%. We obtain 88(4) MeV for hyperfine splitting using the $r_0$ scale, and 121(6) MeV using the ($1\bar{P}-1\bar{S}$) scale. This paper raises the possibility that the discrepancy between the lattice results and the experimental value for charmonium hyperfine splitting can be resolved using overlap fermions to simulate the charm quark on lattice.