A Search for an Exotic Meson in the Gamma P to Delta-plus-plus Pi-minus Eta Reaction Dissertation

(2012). A Search for an Exotic Meson in the Gamma P to Delta-plus-plus Pi-minus Eta Reaction . 10.25148/etd.FI12071114

thesis or dissertation chair


  • Schott, Diane M


  • A Partial Waves Analysis (PWA) of gamma p to Delta++ X to p pi+ pi- (eta) data taken with the CLAS detector at Jefferson Lab is presented in this work. This reaction is of interest because the Delta++ restricts the isospin of the possible X states, leaving the PWA with a smaller combination of partial waves, making it ideal to look for exotic mesons. It was proposed by Isgur and Paton that photoproduction is a plausible source for the Jpc=1-+ state through flux tube excitation. The pi1(1400) is such a state that has been produced with the use of hadron production but it has yet to be seen in photoproduction. A mass independent amplitude analysis of this channel was performed, followed by a mass dependent fit to extract the resonance parameters. The procedure used an event-based maximum likelihood method to maintain all correlations in the kinematics. The intensity and phase motion is mapped out for the contributing signals without requiring assumptions about the underlying processes. The strength of the PWA is in the analysis of the phase motion, which for resonance behavior is well defined. In the data presented, the eta pi- invariant mass spectrum shows contributions from the a0(980) and a2(1320) partial waves. No pi1 was observed under a clear a2 signal after the angular distributions of the decay products were analyzed using an amplitude analysis. In addition, this dissertation discusses trends in the data, along with the implemented techniques.

publication date

  • June 22, 2012


  • high energy nuclear physics
  • meson spectroscopy
  • partial wave analysis
  • photoproduction

Digital Object Identifier (DOI)