Charmonium resonances on the lattice

Gunnar Bali,Sara Collins,Sasa Prelovsek,Stefano Piemonte,M Padmanath,Daniel Mohler,Simon Weishäupl,M Della Morte,P Fritzsch,C Pena Ruano,E Gámiz Sánchez

doi:10.1051/epjconf/201817505020

Gunnar Bali, Sara Collins + Show 9 more

Open Access

https://doi.org/10.1051/epjconf/201817505020

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Abstract

The nature of resonances and excited states near decay thresholds is encoded in scattering amplitudes, which can be extracted from single-particle and multiparticle correlators in finite volumes. Lattice calculations have only recently reached the precision required for a reliable study of such correlators. The distillation method represents a significant improvement insofar as it simplifies quark contractions and allows one to easily extend the operator basis used to construct interpolators. We present preliminary results on charmonium bound states and resonances on the Nf = 2+1 CLS ensembles. The long term goal of our investigation is to understand the properties of the X resonances that do not fit into conventional models of quark-antiquark mesons. We tune various parameters of the distillation method and the charm quark mass. As a first result, we present the masses of the ground and excited states in the 0++ and 1−− channels

Highlights

The mysterious properties of exotic QCD resonances have motivated an increasing interest in nonperturbative lattice calculations during the last decade
Recently lattice QCD calculations have been able to reach sufficiently small lattice spacings and pion masses to allow for a reliable study of QCD resonances with heavy flavor content
It is clear that the systematic uncertainty of the tuning of the κc does not dramatically affect the physical picture that we aim to investigate, but that a clever choice of the charm quark mass can help to move the ψ(3770) toward a resonance state

Summary

Introduction

The mysterious properties of exotic QCD resonances have motivated an increasing interest in nonperturbative lattice calculations during the last decade. Monte-Carlo simulations of QCD regularized on the lattice can provide an alternative insight into the fundamental mechanisms of strong interactions, but the study of resonances is a challenge that requires a huge numerical and theoretical effort. Many simulations with either different volumes or in different moving frames are needed and a large number of configurations is required to measure the lattice energy levels with a sufficient precision to compute scattering observables. The aim of our project is the understanding of the nature of charmonium(-like) resonances and excited states near decay thresholds by means of non-perturbative lattice simulations. In this contribution we present our recent progress, regarding the calculation of the energy levels on the N f = 2 + 1

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