Parity Doublets from a Relativistic Quark Model

Abstract

The Nucleon- and the Lambda-excitation spectrum exhibit parity doublets, i.e. states of the same spin but with opposite parity being almost degenerate in mass. It is shown that in a relativistic quark model with instantaneous interaction kernels, where confinement is implemented by a linearly rising potential and the major mass splittings are generated from an interaction based on instanton effects, this degeneracy occurs quite naturally: Once the parameters of the instanton induced interaction are fixed to reproduce the ground state octet-decuplet splittings, some states are selectively lowered to a position which is degenerate with states of opposite parity. Some observable consequences are briefly discussed.

Comments: 4 pages postscript including 3 figures, Proceedings of "Workshop on the Physics of Excited Nucleons" (NSTAR 2001), Mainz, Germany, 7-10 Mar 2001