Internal structure of newly discovered exotic heavy-quark hadrons

Determine whether the recently observed exotic hadrons containing charm quarks are predominantly compact multi-quark configurations (tetraquarks or pentaquarks), hadronic molecular bound states of conventional hadrons, or superpositions of both. This requires comprehensive amplitude analyses and complementary measurements capable of establishing their internal dynamics and isospin partners with high precision.

Background

LHCb, Belle II, and BESIII have reported a surge of exotic hadrons—states not fitting simple qq̄ or qqq classifications—particularly in amplitude analyses of B-hadron decays.

Their nature remains unsettled: competing interpretations include compact multiquark states and loosely bound hadronic molecules, with the possibility that different states or even a single state may exhibit mixed characteristics.

A high-luminosity Z-pole run would enable precision amplitude analyses (including modes with neutral final states) to search for isospin partners and refine the spectroscopy required to resolve these scenarios.