F E Maas,
K Aulenbacher,
S Baunack,
L Capozza,
J Diefenbach,
B Gläser,
Y Imai,
T Hammel,
D von Harrach,
E-M Kabuss, [......],
J Arvieux, M Elyakoubi,
R Frascaria,
R Kunne,
M Morlet,
S Ong,
J Vandewiele,
S Kowalski,
R Suleiman,
S Taylor
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ABSTRACT: We report on a measurement of the asymmetry in the scattering of transversely polarized electrons off unpolarized protons, A( perpendicular), at two Q2 values of 0.106 and 0.230 (GeV/c)(2) and a scattering angle of 30 degrees <theta(e)<40 degrees . The measured transverse asymmetries are A( perpendicular)(Q(2)=0.106 (GeV/c)(2))=(-8.59+/-0.89(stat)+/-0.75(syst))x10(-6) and A( perpendicular)(Q(2)=0.230 (GeV/c)(2))=(-8.52+/-2.31(stat)+/-0.87(syst))x10(-6). The first errors denote the statistical error and the second the systematic uncertainties. From comparison with theoretical estimates of A( perpendicular) we conclude that piN-intermediate states give a substantial contribution to the imaginary part of the two-photon amplitude. There is no obvious reason why this should be different for the real part of the two-photon amplitude, which enters into the radiative corrections for the Rosenbluth separation measurements of the electric form factor of the proton.
Physical Review Letters 03/2005; 94(8):082001. · 7.37 Impact Factor
