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

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 theta = 55 divided by 75 degrees and theta = 15 divided by 25 degrees) and 1 GeV (theta = 65 divided by 105 degrees). We briefly describe the experimental method, paying special attention to the radiative corrections. Some preliminary results are presented.