Study of the Delta (1232) Using Double Polarization Asymmetries

Abstract

An extensive experimental program to measure the spin structure of the nucleus is underway in Hall B at Jefferson Lab using a polarized electron beam incident on a polarized target. Spin degrees of freedom offer the possibility to test, in an independent way, existing models of resonance electro-production. The present analysis selects the Delta+ (1232) in the exclusive channel $\vec{p}$($\vec{r}$ e, e'p)π0 from data of the EG1 run period, taken in the Fall of 1998, to extract single and double asymmetries in a Q2 range from 0.5 to 1.5 GeV2/c2. Results of the asymmetries are presented as a function of momentum transfer Q2. A comparison with the Effective Lagrangian Model by R. Davidson and N. Mukhopadhyay, the unitary isobar model MAID, and the dynamic model by Sato and Lee was performed. The data were found to be generally in good agreement with the models and a x2 comparison preferred the Sato-Lee model, which is tailored for the Delta (1232) photo- and electro-production. The present results are the first measurement of asymmetries for the exclusive reaction $\vec{p}$($\vec{e}$, e'p)π0 and will provide new constraints for the models.