Measurement of the two-photon exchange contribution in elastic $ep$ scattering at VEPP-3
nucl-ex
/ Authors
A. V. Gramolin, J. Arrington, L. M. Barkov, V. F. Dmitriev, V. V. Gauzshtein, R. A. Golovin, R. J. Holt, V. V. Kaminsky, B. A. Lazarenko, S. I. Mishnev
and 11 more authors
N. Yu. Muchnoi, V. V. Neufeld, D. M. Nikolenko, I. A. Rachek, R. Sh. Sadykov, Yu. V. Shestakov, V. N. Stibunov, D. K. Toporkov, H. de Vries, S. A. Zevakov, V. N. Zhilich
/ Abstract
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 $θ= 55 ÷75^{\circ}$ and $θ= 15 ÷25^{\circ}$) and 1 GeV ($θ= 65 ÷105^{\circ}$). We briefly describe the experimental method, paying special attention to the radiative corrections. Some preliminary results are presented.