Measurement of the two-photon exchange contribution in elastic ep scattering at VEPP–3

• Published in: Nuclear physics. Section B, Proceedings supplement Vol. 225-227; pp. 216 - 220
• Main Authors: Gramolin, A.V., Arrington, J., Barkov, L.M., Dmitriev, V.F., Gauzshtein, V.V., Golovin, R.A., Holt, R.J., Kaminsky, V.V., Lazarenko, B.A., Mishnev, S.I., Muchnoi, N.Yu, Neufeld, V.V., Nikolenko, D.M., Rachek, I.A., Sadykov, R.Sh, Shestakov, Yu.V., Stibunov, V.N., Toporkov, D.K., de Vries, H., Zevakov, S.A., Zhilich, V.N.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2012
• Subjects: elastic electron-proton scattering; electromagnetic form factors of the proton; two-photon exchange; two-photon exchange; elastic electron-proton scattering; electromagnetic form factors of the proton
• ISSN: 0920-5632; 1873-3832
• DOI: 10.1016/j.nuclphysbps.2012.02.045

We report on the status of the Novosibirsk experiment on a precision measurement of the ratio R of the elastic e+p and e−p scattering cross sections. Such measurements determine the two-photon exchange effect in elastic electron-proton scattering. The experiment is conducted at the VEPP–3 storage ring using a hydrogen internal gas target. The ratio R is measured with a beam energy of 1.6 GeV (electron/positron scattering angles are θ=55÷75° and θ=15÷25°) and 1 GeV (θ=65÷105°). We briefly describe the experimental method, paying special attention to the radiative corrections. Some preliminary results are presented.