Parity Doubling in the Meson Spectrum

Abstract

A simple argument for the restoration of parity symmetry high in the hadron spectrum is presented. The restoration scale is estimated to be 2.5 GeV. This in turn implies that typical quark model phenomenology such as scalar confinement or the $^3P_0$ decay model are only useful for low lying states. Minimal requirements for constructing more general phenomenologies are discussed. An additional mass degeneracy between $J^{++}$ and $ J^{--}$ states is shown to occur and an isovector $3^{++}$ state is predicted at roughly 1700 MeV, in contradiction with the naive quark model. Similarly, isovector and isoscalar $4^{--}$ states are predicted at 2000 MeV. Finally, these results imply that Regge trajectories must become nonlinear at high spin.