Alternative Experimental Evidence for Chiral Restoration in Excited Baryons

It has been suggested that chiral symmetry is approximately restored in excited hadrons at zero temperature and density (effective symmetry restoration). Using very general chiral symmetry arguments, it is shown that those excited nucleons that are assumed from the spectroscopic patterns to be in approximate chiral multiplets must only weakly decay into the $N\pi$ channel, $(f_{N^{*}N\pi }/f_{NN\pi }{)}^2\ll 1$. However, those baryons that have no chiral partner must decay strongly with a decay constant comparable with $f_{NN\pi }$. It turns out that for all those well-established excited nucleons which can be classified into chiral doublets the ratio is $(f_{N^{*}N\pi }/f_{NN\pi }{)}^2\sim 0.1$ or much smaller for the high-spin states. In contrast, the only well-established excited nucleon for which the chiral partner cannot be identified from the spectroscopic data, $N(1520)$, has a decay constant into the $N\pi$ channel that is comparable with $f_{NN\pi }$.