Baryon resonances in the mean field approach and a simple explanation of the Theta+ pentaquark

TL;DR

This paper proposes a classification of baryon resonances using a mean field approach, providing a simple explanation for the Theta+ pentaquark as an exotic baryon resonance with specific mass and quantum numbers.

Contribution

It introduces a mean field classification scheme for baryon resonances and offers a novel interpretation of the Theta+ pentaquark as a Gamov–Teller-like excitation.

Findings

Identifies key baryon resonances as single-quark excitations.

Predicts the Theta+ pentaquark with a mass around 1570 MeV.

Provides a simple nuclear physics analogy for the Theta+.

Abstract

We suggest to classify baryon resonances as single-quark states in a mean field, and/or as its collective excitations. Identifying the Roper resonance N(1440), the nucleon resonance N(1535), and the singlet hyperon Lambda(1405) as single-quark excitations, we find that there must be an exotic S=+1 baryon resonance Theta+ (the "pentaquark") with a mass about 1440+1535-1405=1570 MeV and spin-parity one-half-plus. We argue that Theta+ is an analog of the Gamov--Teller excitation long known in nuclear physics.