First measurement of the polarization observable E in the p→(γ→,π+)n reaction up to 2.25 GeV

CLAS Collaboration

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19 Scopus citations


First results from the longitudinally polarized frozen-spin target (FROST) program are reported. The double-polarization observable E, for the reaction γ→p→→π+n, 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.

Original languageEnglish (US)
Pages (from-to)53-58
Number of pages6
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
StatePublished - Nov 12 2015


  • Baryon spectroscopy
  • FROST experiment
  • Pion photoproduction
  • Polarization observables

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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