The OLYMPUS Experiment

Abstract

The OLYMPUS experiment was designed to measure the ratio between the positron-proton and electron-proton elastic scattering cross sections, with the goal of determining the contribution of two-photon exchange to the elastic cross section. Two-photon exchange might resolve the discrepancy between measurements of the proton form factor ratio, ${\mu }_p{G}_E^p/G_M^p$, made using polarization techniques and those made in unpolarized experiments. OLYMPUS operated on the DORIS storage ring at DESY, alternating between 2.01~GeV electron and positron beams incident on an internal hydrogen gas target. The experiment used a toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight detectors to measure rates for elastic scattering over the polar angular range of approximately $25^{\circ }$--$75^{\circ }$. Symmetric Møller/Bhabha calorimeters at $1.29^{\circ }$ and telescopes of GEM and MWPC detectors at $12^{\circ }$ served as luminosity monitors. A total luminosity of approximately 4.5~fb${}^{-1}$ was collected over two running periods in 2012. This paper provides details on the accelerator, target, detectors, and operation of the experiment.

40 pages, 26 figures

References in corpus (8)

• The electric and magnetic form factors of the proton
• Measurement of the proton electric to magnetic form factor ratio from \vec ^1H(\vec e, e'p)
• Polarization Transfer in the 4He(e,e'p)3H Reaction at Q^2 = 0.8 and 1.3 (GeV/c)^2
• Proton G_E/G_M from beam-target asymmetry
• Box diagram in the elastic electron-proton scattering
• The structure function method applied to polarized and unpolarized electron-proton scattering: a solution of the G_E(p)/G_M(p) discrepancy
• Is there model-independent evidence of the two-photon-exchange effect in the electron-proton elastic scattering cross section?
• Dispersive contributions to $e^{+}p/e^{-}p$ cross section ratio in forward regime

Cited by in corpus (21)

• Baryons as relativistic three-quark bound states
• The electric and magnetic form factors of the proton
• Measurement of the two-photon exchange contribution to the elastic $e^{\pm }p$ scattering cross sections at the VEPP-3 storage ring
• Two-photon exchange in elastic electron-proton scattering
• Towards a resolution of the proton form factor problem: new electron and positron scattering data
• Nucleon electromagnetic form factors from lattice QCD using a nearly physical pion mass
• Hard Two-Photon Contribution to Elastic Lepton-Proton Scattering: Determined by the OLYMPUS Experiment
• Subtracted dispersion relation formalism for the two-photon exchange correction to elastic electron-proton scattering: comparison with data
• PERLE: Powerful Energy Recovery Linac for Experiments - Conceptual Design Report
• Two-photon exchange correction in elastic unpolarized electron-proton scattering at small momentum transfer
• A new event generator for the elastic scattering of charged leptons on protons
• Nucleon form factors and final state radiative corrections to $e^{+}{e}^{-}\to \bar{p}p\gamma$
• The OLYMPUS Internal Hydrogen Target
• Timing Detectors with SiPM read-out for the MUSE Experiment at PSI
• Delta(1232) contribution to real photon radiative corrections for elastic electron-proton scattering
• Measurement and tricubic interpolation of the magnetic field for the OLYMPUS experiment
• A novel technique for determining luminosity in electron-scattering/positron-scattering experiments from multi-interaction events
• QED Radiative Corrections to Low-Energy Moller and Bhabha Scattering
• Design and Performance of a Lead Fluoride Detector as a Luminosity Monitor
• Measurement of the Charge-Averaged Elastic Lepton-Proton Scattering Cross Section by the OLYMPUS Experiment
• Development of large area focal plane detectors for MAGIX