Frankfurt 2014 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 2: Hadronenstruktur und -spektroskopie

HK 2.1: Group Report

Monday, March 17, 2014, 14:00–14:30, HZ 3

Determining the Two-Photon Contribution to Elastic ep Scattering — •Jürgen Diefenbach for the OLYMPUS collaboration — Institut für Kernphysik, Universität Mainz

To determine the two-photon exchange contribution to the elastic electron-proton scattering cross section, the OLYMPUS experiment was carried out at the DORIS storage ring at DESY in Hamburg in 2012. Measuring the elastic scattering cross sections from hydrogen, alternating daily between electron and positron beams, along with a redundant determination of the luminosity, will yield a ratio between the positron and electron cross sections at the one percent level. This will help resolve the puzzle in the proton form factor ratio between Rosenbluth and polarization transfer measurements. The talk will give a review of the experiment as well as report on the current status of the data analysis.