Lattice searches for tetraquarks and mesonic molecules: light scalar mesons and XYZ states

Understand

Searches for tetraquarks and mesonic molecules in lattice QCD are briefly reviewed.

• In the light quark sector the most serious candidates are the lightest scalar resonances sigma, kappa, a0 and f0.
• In the hidden-charm sector I discuss lattice simulations of X(3872), Y(4260), Y(4140) and Z^+(4430).
• The most serious challenge in all these lattice studies is the presence of scattering states in addition to possible tetraquark/molecular states.