Münster 2011 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 17: Hadronenstruktur und -spektroskopie V

HK 17.2: Talk

Tuesday, March 22, 2011, 14:30–14:45, C-2

Symmetric Moeller/Bhabha Luminosity Monitor — •Roberto Perez Benito — Helmholtz-Institut Mainz, Johannes Gutenberg-Universitaet Johann-Joachim-Becher-Weg 45, 55128 Mainz, Germany

Recent determinations of the proton electric to magnetic elastic form factor ratio from polarization transfer measurements at Jefferson Lab indicate an discrepancy with the elastic form factor ratio obtained using the Rosenbluth separation technique in unpolarized cross section measurements. This discrepancy has been explained as the effect of two-photon exchange in the calculation of the elastic electron-proton scattering cross section.

The OLYMPUS experiment at DESY has been proposed to measure the ratio of positron-proton and electron-proton elastic scattering cross sections to quantify the effect of two-photon exchange to a percent level. In order to control the systematic uncertainties to the percent level the Symmetric Moeller/Bhabha Luminosity Monitor was proposed. The design and aspected performance will be presented.