# Charmonium resonances from 2+1 flavor CLS lattices

## TL;DR

This paper advances lattice QCD methods to study charmonium resonances, focusing on coupled-channel scattering and spectrum analysis using CLS ensembles, addressing the complexities of open decay channels.

## Contribution

It introduces new techniques for calculating single-channel and coupled-channel scattering matrices for charmonium states on lattice ensembles.

## Key findings

- Progress in determining scattering matrices in scalar and vector channels.
- Updated results on charmonium spectrum in moving frames.
- Enhanced understanding of open decay channels in lattice calculations.

## Abstract

Many exotic charmonium resonances have been identified recently in experiment, however their nature and properties are mostly unknown. Algorithmic and theoretical progress in lattice calculations has enabled reliable numerical investigation of the spectrum below the strong decay threshold, while the study of charmonium resonances remains an open challenge. The main difficulty to overcome is the presence of many open decay channels which are coupled together, resulting in a complex finite volume quantization condition. We report on our recent progress towards the determination of single-channel and coupled-channel scattering matrices in the scalar and vector channels on CLS ensembles. We also present an update concerning the study of the charmonium spectrum in moving frames.