Measurement of polarization observables in gamma vector p vector to ppi+pi- using circular beam and longitudinal target polarization and the CLAS spectrometer at Jefferson Laboratory.

摘要

The study of baryon resonances offers a deeper understanding of the strong interaction, since the dynamics and relevant degrees of freedom hidden within them are reflected by the properties of the excited states of baryons. Higher-lying excited states at and above 1.7 GeV/c2 are generally predicted to have strong couplings to the pipiN final states via piDelta or rhoN states. Double-pion photo-production is, therefore, important for investigating properties of high-mass resonances. The excited states of the nucleon are usually found as broadly overlapping resonances, which may decay into a multitude of final states involving measons and baryons. Polarization observables make it possible to isolate single resonances from these other interference terms. The CLAS g9a (FROST) experiment, as part of the N* spectroscopy program at the Jefferson Laboratory, has accumulated photoproduction data using circularly-polarized photons incident on a longitudinally-polarized butanol target in the photon energy range 0.3 to 2.4 GeV. This document summarizes how the beam-helicity asymmetry, the target asymmetry, and the helicity difference for the reaction gammap → ppi+pi -- extract from the g9a dataset.