10:30 AM–12:18 PM, Sunday, October 26, 2008
- Simmons Ballroom 2-3
Chair: Lawrence Cardman, Jefferson Lab
Abstract ID: BAPS.2008.DNP.MA.2
11:06 AM–11:42 AM
Richard Lebed
(Arizona State University)
Why do baryon resonance multiplets exist, and what controls their formation and decays? It is natural to consider them as merely excited states of some three-quark or meson-nucleon potential. But these are just simplistic quantum-mechanical pictures that recognize neither the full field-theoretical complexities of QCD nor the extremely brief lifetimes of resonances due to quark pair production. Both of these issues are addressed by the $1/N_c$ expansion of QCD, where $N_c$ is the number of color charges. Constraints arising at large $N_c$ on meson-baryon scattering amplitudes not only create linear relationships between them, thus linking distinct partial waves and their embedded resonances, but also restrict the possible resonant decay channels. I present strong experimental evidence in favor of this approach, describe the multiplet structure that it predicts, and show how to perform the analysis beyond the strict large $N_c$ limit by incorporating $1/N_c$-suppressed effects.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2008.DNP.MA.2