Evidence for a spin-quartet of nucleon resonances at 2\,GeV

TL;DR

This paper presents evidence for a set of four nucleon resonances with different spins, all around 2 GeV, challenging traditional di-quark models and expanding understanding of nucleon structure.

Contribution

It provides the first multi-channel partial wave analysis demonstrating a spin-quartet of nucleon resonances at 2 GeV, which contradicts classical di-quark model expectations.

Findings

Identifies a spin-quartet of nucleon resonances with J^P=1/2^+ to 7/2^+

Resonances are within a 130 MeV mass gap centered at 1.97 GeV

Challenges the di-quark model assumptions for nucleon structure

Abstract

Results from a multi-channel partial wave analysis of elastic and inelastic $\pi N$ and $\gamma N$ induced reactions are presented. The analysis evidences the existence of a spin-quartet of nucleon resonances with total angular momenta $J^P=1/2^+,..., 7/2^+$. All states fall into a $\pm130$\,MeV mass gap centered at 1.97\,GeV. The spin quartet is at variance with S-wave diquark configurations required in classical di-quark models.