Theoretical Summary of the HADRON99 conference

TL;DR

This paper summarizes the theoretical discussions and experimental findings from the HADRON99 conference, focusing on the Constituent Quark Model, QCD approaches, phenomenological analyses, and new experimental puzzles in hadron physics.

Contribution

It provides an overview of the latest theoretical efforts to justify the Constituent Quark Model within QCD and discusses recent experimental puzzles and phenomenological analyses.

Findings

QCD Sum Rules and lattice approaches offer potential justifications for the Constituent Quark Model.

Phenomenological analyses shed light on scalar and pseudoscalar mesons and the $ ho- ext{pi}$ puzzle.

New experimental observations include the $ar p p o ext{phi} ext{pi}$ process.

Abstract

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 outstanding problems like the nature of the scalar and pseudoscalar mesons and the low branching ratio for $\psi' \to \rho-\pi$ were presented. New experimental puzzles include the observation of $\bar p p \to \phi \pi$.