Parity doublets in the baryon spectrum

Abstract

Physics of the low-lying and high-lying hadrons in the light flavors sector is reviewed. While the low-lying hadrons are strongly affected by both $U(1{)}_A$ and spontaneous $SU(2{)}_L\times SU(2{)}_R$ breakings, in the high-lying hadrons these symmetries are restored. A manifestation is a persistence of the chiral multiplet structure in both baryon and meson spectra. A fundamental origin of this phenomenon is that effects of quantum fluctuations of both quark and gluon fields must vanish at large $n$ or $J$ and a semiclassical description becomes adequate. A relation between the chiral symmetry restoration and the string picture of excited hadrons is discussed.

Comments: 12 pages. Plenary talk given at 10th Int. Conf. on the Structure of Baryons (Baryons 04), October 25-29, 2004, Palaiseau, France; typos have been removed