Evidence for Some New Hyperon Resonances -- to be Checked by $K_L$ Beam Experiments

Abstract

Quenched and unquenched quark models predict very different patterns for the spectrum of the low excited hyperon states. Evidence is accumulating for the existence of some new hyperon resonances, such as a $\Sigma^*$ of spin-parity $J^P=1/2^-$ around 1400 MeV instead of 1620 MeV as listed in PDG, a new $\Sigma(1540)3/2^-$ resonance, a new narrow $\Lambda(1670)3/2^-$ resonance and a new $\Lambda(1680)3/2^+$ resonance. All these new hyperon resonances fit in the predicted pattern of the unquenched quark models very well. It is extremely important to check and establish the spectrum of these low excited hyperon states by the proposed $K_L$ beam experiments at JLAB.