Measurement of the transverse–longitudinal cross sections in the π reaction in the Δ region

• DOI: 10.1016/s0370-2693(03)00675-0
• Publication Date: 2003-05-19T19:14:59Z
• Authors: C. Kunz; N.I. Kaloskamis; M.O. Distler; Z.-L. Zhou; R. Alarcon; D. Barkhuff; A.M. Bernstein; W. Bertozzi; J. Calarco; F. Casagrande; J. Chen; J. Comfort; G. Dodson; A. Dooley; K. Dow; M. Farkhondeh; S. Georgakopoulos; S. Gilad; R. Hicks; A. Hotta; X. Jiang; A. Karabarbounis; S. Kowalski; D.J. Margaziotis; C. Mertz; R. Miskimen; I. Nakagawa; C.N. Papanicolas; M.M. Pavan; G. Peterson; A. Ramirez; D. Rowntree; A.J. Sarty; J. Shaw; E. Six; N. Sparveris; S.-B. Soong; S. Stiliaris; T. Tamae; D. Tieger; C. Tschalaer; G. Tsentalovich; W. Turchinetz; C.E. Vellidis; G.A. Warren; S. Williamson; A. Young; J. Zhao; T. Zwart
• Keywords: Quadrupole magnet

Accurate measurements of the p(e,e?p)pi0 reaction were performed at Q^2=0.127(GeV/c)^2 in Delta resonance energy region. The experiments MIT-Bates Linear Accelerator used an 820 MeV polarized electron beam with out plane magnetic spectrometer system (OOPS). In this paper we report first simultaneous determination both TL and TL? (``fifth" or polarized) cross sections low Q^{2} where pion cloud contribution dominates quadrupole amplitudes (E2 C2). real imaginary parts transverse-longitudinal section provide a sensitive Coulomb amplitude test calculations. Comparisons model calculations are presented. empirical MAID calculation gives best overall agreement accurate data. parameters for values resonant multipoles |M_{1+}(I=3/2)|= (40.9 \pm 0.3)10^{-3}/m_pi, CMR= C2/M1= -6.5 0.3%, EMR=E2/M1=-2.2 0.9%, errors due to experimental uncertainties.