The double spin asymmetry in the ep→e′π+n reaction has been measured for the first time in the resonance region for four-momentum transfer Q2=0.35–1.5GeV2. Data were taken at Jefferson Lab with the CLAS detector using a 2.6 GeV polarized electron beam incident on a polarized solid NH3 target. Comparison with predictions of phenomenological models shows strong sensitivity to resonance contributions. Helicity- 1/2 transitions are found to be dominant in the second and third resonance regions. The measured asymmetry is consistent with a faster rise with Q2 of the helicity asymmetry A1 for the F15(1680) resonance than expected from the analysis of the unpolarized data.
Physical Review Letters
DeVita, R.; Biselli, Angela; and CLAS Collaboration, "First Measurement of the Double Spin Asymmetry in e⃗ p⃗ →e′π+n in the Resonance Region" (2002). Physics Faculty Publications. 29.
R. De Vita et al. [CLAS Collaboration], "First Measurement of the Double Spin Asymmetry in e⃗ p⃗ →e′π+n in the Resonance Region", Phys. Rev. Lett. 88, 082001 (2002). DOI: 10.1103/PhysRevLett.88.082001