Pion Production Model - Connection between Dynamics and Quark Models

We discuss the difficulties in testing the hadron models by using the N^* parameters extracted from the empirical amplitude analyses of the pi-N and gamma-N reaction data. As an alternative or perhaps a more advantageous approach, we present a Hamiltonian formulation that can relate the pion production dynamics and the constituent quark models of N^* structure. The application of the approach in investigating the Delta and N^*(S_{11}) excitations is reviewed. It is found that while the Delta excitation can be described satisfactory, the pi-N scattering in S_{11} channel can not be described by the constituent quark models based on either the one-gluon-exchange or one-meson-exchange mechanisms. A phenomenological quark-quark potential has been constructed to reproduce the S_{11} amplitude.Comment: 11 pages, 4 figures, to be published in Proceedings of NSTAR2000 workshop held at Jefferson Laboratory, Feb., 200

Status of Dynamical Coupled-Channel Analysis by Collaboration@EBAC

The development and results of the Dynamical Coupled-Channels analysis by a collaboration at the Excited Baryon Analysis Center (EBAC) are reported.Comment: 5 pages, 4 figures. Contribution to Eleventh Conference on the Intersections of Particle and Nuclear Physics --- CIPANP 2012, May 28, 2012 - June 3, 2012, St. Petersburg, FL, US

EBAC-DCC Analysis of World Data of pi N, gamma N, and N(e,e') Reactions

The development, results, and prospect of the Dynamical Coupled-Channels analysis at Excited Baryon Analysis Center (EBAC-DCC) are reported.Comment: 6 pages, 7 figures. Contribution to the proceedings of the 8th International Workshop on the Physics of Excited Nucleons (NSTAR2011), Newport News, VA, USA, May 17-20, 201

UA(1)U_A(1) symmetry restoration in QCD with NfN_f flavors

Recently, there have been reports that the chirally restored phase of QCD is effectively symmetric under $U(N_f) \times U(N_f)$ rather than $SU(N_f)\times SU(N_f)$. We supplement their argument by including the contributions from topologically nontrivial gauge field configurations and discuss how the conclusions are modified. General statements are made concerning the particle spectrum of QCD with light $N_f$ flavors in the high temperature chirally restored phase.Comment: 6 pages, no figures, revte