Quarks, diquarks and QCD mixing in the $N^{\ast }$ resonance spectrum

Abstract

We identify a "$\Lambda$ selection rule" for $N^{\ast }$ resonances in the presence of QCD mixing effects. We quantify these mixing effects from existing data and predict amplitudes for exciting {\bf 20} representations in SU(6), which are forbidden in strict diquark models. By classifying Particle-Data-Group (PDG) states at N=2, we show that $\gamma N\to K\Lambda$, $K^{\ast }\Lambda$, $K\Sigma$, $K^{\ast }\Sigma$, and $J/\psi \to \bar{p}{N}^{\ast }$ are ideal probes of baryon dynamics and for establishing whether strongly correlated diquarks survive for $L>0$.

Comments: Extended version accepted by PRD