Born-Oppenheimer EFT (BOEFT) for XYZ exotics

Two decades ago the χc1 (3872) was discovered in the hadron spectrum with two heavy quarks. The discovery fueled a surge in experimental research, uncovering dozens of so called XYZ exotics states lying outside the conventional quark model, as well as theoretical investigations into new forms of matter, such as quark-gluon hybrids, mesonic molecules, and tetraquarks, with the potential of disclosing new information about the fundamental strong force. In this talk we show how the Born–Oppenheimer effective field theory, derived from Quantum Chromodynamics on the basis of scale separation and symmetries, can address quarkonium XYZ exotics of any composition. We derive the Schrödinger coupled equations that describe hybrids, tetraquarks, pentaquarks, doubly heavy baryons, and quarkonia at leading order, incorporating nonadiabatic terms, and present the predicted multiplets. We provide the precise form of the few nonperturbative low-energy universal correlators and we calculate their short-distance behavior. Furthermore, we outline how spin-dependent corrections and mixing terms can be incorporated using matching computations and the direct phenomenological impact of the avoided level crossing phenomenon in the QCD static energies. We use the BOEFT to settle the issue of the nature and composition of the exotics χc1 (3872) and T+ (3875), that stand out for their striking characteristics, and present several phenomenological predictions on the XYZ properties, including pentaquarks. Finally we recollect how this changes our perspective on the strong force.