Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)




Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, GE/GM, obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange (TPEX) contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, this thesis reports measurements, of the GEp2gamma experiment, of polarization transfer observables in the elastic H ( e&ar;,e' p&ar; ) reaction for three different beam energies at a fixed squared momentum transfer Q² = 2.5 GeV², spanning a wide range of the virtual photon polarization parameter, epsilon. The scattered electrons were detected in coincidence with the protons by the new electromagnetic lead-glass calorimeter BigCal and the High Momentum Spectrometer (HMS), respectively. We extract the polarization of the recoil proton by measuring the azymuthal asymmetry in the angular distribution after a secondary scattering in the CH2 analyzer blocks of the new, double focal plane polarimeter (FPP) installed in the detector hut of the HMS.



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