First measurement of target and double spin asymmetries for polarized e- polarized p --> e p pi0 in the nucleon resonance region above the Delta(1232)

TL;DR

This study presents the first measurements of target and double spin asymmetries in polarized electron-proton scattering producing pi0 in the nucleon resonance region, providing new insights into nucleon resonance structures.

Contribution

It provides the first experimental data on spin asymmetries in polarized e-p scattering for pi0 production in the nucleon resonance region, aiding in constraining nucleon resonance models.

Findings

Strong model sensitivity observed, especially for target asymmetry.

Data constrains electrocoupling amplitudes of nucleon resonances.

Results highlight the importance of including spin asymmetries in resonance analysis.

Abstract

The exclusive channel polarized proton(polarized e,e prime p)pi0 was studied in the first and second nucleon resonance regions in the Q2 range from 0.187 to 0.770 GeV2 at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). Longitudinal target and beam-target asymmetries were extracted over a large range of center-of-mass angles of the pi0 and compared to the unitary isobar model MAID, the dynamic model by Sato and Lee, and the dynamic model DMT. A strong sensitivity to individual models was observed, in particular for the target asymmetry and in the higher invariant mass region. This data set, once included in the global fits of the above models, is expected to place strong constraints on the electrocoupling amplitudes A_{1/2} and S_{1/2} for the Roper resonance N(1400)P11, and the N(1535)S11 and N(1520)D13 states.