About a Possible Nonstrange Cousin of the Theta+ Pentaquark

Abstract

We discuss the implications of the suggested interpretation of the recently reported narrow pi N resonance (width \approx 25 MeV at 1680 MeV) as a pentaquark in the same multiplet as the Theta+. We consider a diquark-triquark pentaquark model involving a recoupling of the five quarks into a diquark-triquark system in non-standard color representations. We estimate the mass using a well-tested simple mass formula. Our rough numerical estimate puts the pi N pentaquark resonance at 1720 MeV, sufficiently close to the reported value of 1680 MeV to indicate that this approach deserves further more accurate investigation.

Comments: Invited talk at International Workshop "Narrow Nucleon Resonances: Predictions, Evidences, Perspectives", Edinburgh, Scotland, June 8--10, 2009. Added references and comments.