[Jlab-seminars] Physics Seminar

[Luci Collins]

*Physics Seminar
Fri. July 19, 2013
11:00AM
CEBAF Center AUD.**
Coffee & Cookies 10:45AM

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*Roberto Francisco
DESY

"The OLYMPUS Experiment"*

Recent determinations of the proton electric to magnetic form factor
ratio indicate an unexpected discrepancy between the obtained ratio using
polarization transfer measurements and the ratio from Rosenbluth
separation technique in unpolarized cross section measurements. This
discrepancy has been explained as the effect of two-photon exchange.
OLYMPUS experiment at DESY has been proposed to measure the ratio of
positron-proton and electron-proton elastic scattering cross sections.
The experiment will utilize intense beams of electrons and positrons in
the DORIS ring at 2.0 GeV incident an unpolarized internal hydrogen gas
target and the previous BLAST detector from the MIT-Bates Linear
Accelerator Center with modest upgrades.
In order to reduce the systematic error due to relative luminosity,
redundant measurements of the luminosity are necessary. The symmetric
Moller/Bhabha luminosity monitor build in Mainz consists of two symmetric
arrays of lead fluoride (PbF2) crystals. Results of the performance of
the symmetric Moller/Bhabha luminosity monitor will be presented in this
contribution together with the physics case for OLYMPUS and the current
status of the project.

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