Charmonium excited state spectrum in lattice QCD

TL;DR

This study uses a variational method with a large basis of interpolating fields in lattice QCD to reliably extract multiple excited charmonium states, providing insights into their spectrum and spin assignments.

Contribution

It demonstrates the feasibility of extracting multiple excited states in lattice QCD using a variational approach with covariant derivative-based interpolating fields and continuum limit insights.

Findings

Excited state masses are systematically higher than potential model predictions.

Knowledge of the continuum limit aids in spin assignment at a single lattice spacing.

Quenched approximation likely causes discrepancies in mass predictions.

Abstract

Working with a large basis of covariant derivative-based meson interpolating fields we demonstrate the feasibility of reliably extracting multiple excited states using a variational method. The study is performed on quenched anisotropic lattices with clover quarks at the charm mass. We demonstrate how a knowledge of the continuum limit of a lattice interpolating field can give additional spin-assignment information, even at a single lattice spacing, via the overlap factors of interpolating field and state. Excited state masses are systematically high with respect to quark potential model predictions and, where they exist, experimental states. We conclude that this is most likely a result of the quenched approximation.