Helicity asymmetry E measurement for single π0 photoproduction with a frozen spin target

The helicity asymmetry for single neutral pion photoproduction was measured using the CLAS detector in Hall B at the Thomas Jefferson National Accelerator Facility. This measurement used longitudinally polarized protons and circularly polarized photons with photon energies between 0.35 GeV to 2.4 GeV. The target was a frozen-spin butanol (C4H9OH) target, polarized at about 85%. The helicity asymmetry E for the γp → pπ0 was measured with missing-mass technique at the high statistics of about 12 x 106 events. The experimental results are compared to three available theoretical predictions, SAID, MAID, and EBAC. The preliminary results are in good agreement with the model calculations at low Eγ energy bins. However, a significant deviation is observed at high energy bins. Therefore, the new data will help to constrain the parameters of the theoretical models.