Chiral symmetry restoration in excited hadrons

We consider the multiplet structures, appearing in hadronic physics. The basic types of the multiplets revealed are parity doublets, chiral multiplets, and multispin-parity clusters. We elucidate a new type of isospin supermultiplets in the baryon sector. The creation of parity doublets, chiral multiplets and their interrelation with multispin-parity clusters has been uncovered. The role of chiral symmetry breaking and restoration in the formation of the hadronic spectra has ...

The present status of low energy test of chiral invariance via chiral perturbation theory is reviewed, both in the meson and baryon sectors, and future prospects are discussed.

We study hadron correlators upon artificial restoration of the spontaneously broken chiral symmetry. In a dynamical lattice simulation we remove the lowest lying eigenmodes of the Dirac operator from the valence quark propagators and study evolution of the hadron masses obtained. All mesons and baryons in our study, except for a pion, survive unbreaking the chiral symmetry and their exponential decay signals become essentially better. From the analysis of the observed spectro...

It has recently been suggested that the parity doublet structure seen in the spectrum of highly excited baryons may be due to effective chiral symmetry restoration for these states. We review the recent developments in this field. We demonstrate with a simple quantum-mechanical example that it is a very natural property of quantum systems that a symmetry breaking effect which is important for the low-lying spectrum of the system, can become unimportant for the highly-lying st...

A review of chiral perturbation theory and that of recent developments on the comparison of its predictions with experiment is presented. Some interesting topics with scope for further elaboration are touched upon.

I will summarize the numerous contributions which were presented in the session, Hadronic and Spin Physics, largely dominated by new experimental results.

An approach to baryons in the framework of the microscopic Generalized Nambu-Jona-Lasinio chiral potential quark model is considered and quite general arguments are given in favor of effective restoration of chiral symmetry in excited baryons.

It is shown that the principal pattern in baryon spectroscopy, which is associated with the flavor-spin dependent hyperfine interaction, is due to the spontaneous breaking of chiral symmetry in QCD and thus cannot be addressed by chiral perturbation theory, which is based on the explicit chiral symmetry breaking.

This is a personal summary of the workshop. I overview the topics of the workshop and itemize what we learned at the workshop.

In this paper, we discuss the transition to the semiclassical regime in excited hadrons, and consequently, the restoration of chiral symmetry for these states. We use a generalised Nambu-Jona-Lasinio model with the interaction between quarks in the form of the instantaneous Lorentz-vector confining potential. This model is known to provide spontaneous breaking of chiral symmetry in the vacuum via the standard selfenergy loops for valence quarks. It has been shown recently tha...