Resonances in QCD

Abstract

We report on the EMMI Rapid Reaction Task Force meeting _s15Resonances in QCD_s15, which took place at GSI October 12-14, 2015 (Fig. 1). 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 eorts are required to arrive at a coherent picture? For light mesons and baryons only those with up, down and strange quark content were considered. For heavy-light and heavy-heavy meson systems, those with charm quarks were the focus. This document summarizes the discussions by the participants, which in turn led to the coherent conclusions we present here.