Overview

Even though QCD is the underlying theory of nuclear interactions, its direct connection with various nuclear phenomena remains unclear. The fundamental questions about the role of the quark-gluon dynamics, confinement and the generation of mass remain qualitative at best. The vast majority of hadrons are unstable and in experimental measurements appear indirectly via complicated distributions of decay products. This poses substantial challenges in interpreting the experimental data and analyzing the spectrum of QCD experimentally as well as theoretically. In recent years new high-quality data from experimental facilities, together with rapid developments in ab-initio theoretical applications, have enabled us to address the most formidable questions regarding the formation of QCD bound states.

The aim of this program is to bring together theorists and experimentalists to review recent progress made in the determination and interpretation of the QCD spectrum, based on the results from experimental searches with the GlueX and CLAS12 detectors at Jefferson Lab (JLab) and other recent measurements including those at BES-III, Belle-II, COMPASS and LHCb, as well as theoretical investigations using novel QCD techniques that are being developed for lattice, amplitude-analysis and other ab-initio studies.

This program will be the first one completely dedicated to QCD spectroscopy at the INT. The physics motivation is to get insights about the governing patterns and rules of QCD from emergent phenomena. Specific topics include:

• Production and decay mechanisms;
• Exotic states: tetraquarks, pentaquarks, hybrids, glueballs;
• Source of masses of excited states;
• Structure of excited states;
• Controversial and missing states;
• Understanding the role of glue in the spectrum;
• Manifestation of confinement in the spectrum.

In the second week we will be organizing a workshop on "Unraveling QCD through hadron phenomenology". It will hope to answer the question "What can be rigorously understood of the low-lying spectrum of QCD?" and lay out the outstanding questions that will guide the future of the field. In the remaining weeks we plan to follow the standard INT-program format of one or two daily talks with plenty of time for discussions and collaborations. Each week will aim to focus on different topics relevant for the overall program:

• Week 1 (Aug 17 - 21): The exotic spectrum
• Week 2 (Aug 24 - 28): Workshop "Unraveling QCD through hadron phenomenology". A registration fee may apply, which includes participation in the workshop, lectures, and coffee breaks.
• Weeks 3-4 (Aug 31 - Sep 11): Accessing the spectrum
• Week 5 (Sep 14 - 18 ): The future of spectroscopy