Heidelberg 2015 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 31: Instrumentation 11

HK 31.3: Vortrag

Dienstag, 24. März 2015, 17:30–17:45, M/HS2

Symmetric Møller/Bhabha luminosity monitor for the OLYMPUS experiment — Luigi Capozza^2,3, Colton O’Connor⁴, Jürgen Diefenbach⁶, Boris Gläser⁶, •Dmitry Khaneft^1,2, Yue Ma^3,5, Frank Maas^2,3, Roberto Pérez Benito^2,3, and David Rodríguez Piñeiro^2,3 — ¹Johannes Gutenberg-Universität Mainz, Mainz, Germany — ²Helmholtz-Institut Mainz, Mainz, Germany — ³GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany — ⁴Massachusetts Institute of Technology, Cambridge, MA, USA — ⁵Currently at Advanced Meson Laboratory, Nishina Centre, RIKEN, Japan — ⁶Institut für Kernphysik, Mainz, Germany

The OLYMPUS experiment is motivated by the discrepancy between the proton electric to magnetic form factor ratio measured using unpolarized and polarized electron scattering. This discrepancy can be explained by a two-photon exchange (TPE) contribution in lepton-hadron scattering. Measuring the ratio of electron-proton and positron-proton elastic scattering cross sections the contribution of the TPE can be determined. For this purpose, very precise measurements of the relative luminosity have to be performed. The symmetric Møller/Bhabha luminosity monitor, made of calorimetric lead fluoride (PbF₂) Cherenkov detectors, provides precise data from counting coincidences Møller and Bhabha events. High sensitivity to the geometrical acceptance and alignment requires accurate study of systematic uncertainties.