Theoretical summary of the conference Original Research Article

The Constituent Quark Model has provided a remarkable description of the experimentally observed hadron spectrum but still has no firm theoretical basis. Attempts to provide a QCD justification discussed at Hadron99 include QCD Sum Rules, instantons, relativistic potential models and the lattice. Phenomenological analyses to clarify out-standing problems like the nature of the scalar and pseudoscalar mesons and the low branching ratio for Ψ′ → ϱ - π were presented. New experimental puzzles include the observation of View the MathML source.