First measurement of the polarization observable E in the p→(γ→, π+) n reaction up to 2.25 GeV.
First results from the longitudinally polarized frozen-spin target (FROST) program are reported. The double-polarization observable E, for the reaction , has been measured using a circularly polarized tagged-photon beam, with energies from 0.35 to 2.37 GeV. The final-state pions were detected with the CEBAF Large Acceptance Spectrometer in Hall B at the Thomas Jefferson National Accelerator Facility. These polarization data agree fairly well with previous partial-wave analyses at low photon energies. Over much of the covered energy range, however, significant deviations are observed, particularly in the high-energy region where high-L multipoles contribute. The data have been included in new multipole analyses resulting in updated nucleon resonance parameters. We report updated fits from the Bonn–Gatchina, Jülich–Bonn, and SAID groups.
Physics Letters B
Strauch, Steffen; Briscoe, W. J.; Döring, M.; Klempt, E.; Nikonov, V. A.; Pasyuk, E.; Rönchen, D.; Biselli, Angela; and CLAS Collaboration, "First measurement of the polarization observable E in the p→(γ→, π+) n reaction up to 2.25 GeV." (2015). Physics Faculty Publications. 155.
Strauch, Steffen, W. J. Briscoe, M. Döring, E. Klempt, V. A. Nikonov, E. Pasyuk, D. Rönchen, Biselli A. et al [CLAS Collaboration]. "First measurement of the polarization observable E in the p→(γ→, π+) n reaction up to 2.25 GeV." Physics Letters B 750 (2015): 53-58. https://doi.org/10.1016/j.physletb.2015.08.053