Two-Photon Exchange Effect in the Elastic Electron-Nucleon Scattering

• Main Authors: Yu-Chun Chen, 陳佑駿
• Other Authors: Shin-Nan Yang
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/26172793068704348562

博士 === 國立臺灣大學 === 物理研究所 === 95 === When measuring the nucleon form factors, recent polarization experiments at the Thomas Jefferson Laboratory (JLab) have confirmed the earlier Rosenbluth measurements from SLAC at small Q2. However, at large Q2, a huge discrepancy appear between them. To solve this puzzle, the two-photon exchange contribution to elastic electron-proton scattering at large momentum transfer by using a quark-parton representation of virtual Compton scattering was estimated. And then we thus can relate the two-photon exchange amplitude to the generalized parton distributions which also enter in other wide angle scattering processes. We find that the interference of one- and two-photon exchange contribution is able to substantially resolve the difference between electric form factor measurements from Rosenbluth and polarization transfer experiments. Now we know higher-order QED effects can play an important role in precision measurements of nucleon elastic form factors in electron scattering.