Resonances in QCD

TL;DR

This paper summarizes discussions from a 2015 workshop on the physics of resonances in QCD, focusing on understanding their nature, predicting exotic states, and guiding experimental efforts.

Contribution

It provides a comprehensive overview of current challenges and future directions in studying QCD resonances, emphasizing the need for coordinated theoretical and experimental work.

Findings

Identified key questions for understanding QCD resonances

Highlighted the importance of experimental efforts for exotic states

Summarized participant conclusions and future research directions

Abstract

We report on the EMMI Rapid Reaction Task Force meeting 'Resonances in QCD', which took place at GSI October 12-14, 2015. A group of 26 people met to discuss the physics of resonances in QCD. The aim of the meeting was defined by the following three key questions: What is needed to understand the physics of resonances in QCD? Where does QCD lead us to expect resonances with exotic quantum numbers? What experimental efforts are required to arrive at a coherent picture? For light mesons and baryons only those with ${\it up}$, ${\it down}$ and ${\it strange}$ quark content were considered. For heavy-light and heavy-heavy meson systems, those with ${\it charm}$ quarks were the focus. This document summarizes the discussions by the participants, which in turn led to the coherent conclusions we present here.