Using the Covariant Spectator Theory to Extract N*
Franz Gross · 2012
Lessons from the history of the Δ Chew-Low theory (1955) • NO elementary Δ pole • Δ resonance generated by N exchange diagram (u channel pole) Bootstrap: resonance feedback (1960's) Discovery of quarks and recognition that the Δ is "elementary"• (i.e. it is REQUIRED for equivalence between hadronic and quark degrees of freedom) The Δ -N mass difference enters into many estimates.Is it the "bare" mass difference or the "dressed" mass difference? Conclusion: The existence of a bare delta pole is crucial to our understanding