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Nuclear instruments & methods in physics research / A 826, 6 - 14(2015). doi:10.1016/j.nima.2016.04.071, Precise luminosity measurements for the OLYMPUS two-photon exchange experiment at DESY were performed by counting scattering events with alternating beams of electrons and positrons incident on atomic electrons in a gaseous hydrogen target. Final products of M$\phi$ller, Bhabha, and pair annihilation interactions were observed using a pair of lead fluoride ($PbF_{2}$) Cherenkov calorimeters with custom housings and electronics, adapted from a system used by the A4 parity violation experiment at MAMI. This paper describes the design, calibration, and operation of these detectors. An explanation of the Monte Carlo methods used to simulate the physical processes involved both at the scattering vertices and in the detector apparatus is also included., Published by North-Holland Publ. Co., Amsterdam

Nuclear instruments & methods in physics research / A 741, 1 - 17 (2014). doi:10.1016/j.nima.2013.12.035, 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, $\mu_p G^p_E/G^p_M$, 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 M{\o}ller/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., Published by North-Holland Publ. Co., Amsterdam

This paper reports on measurements of the 3He(e, epp) reaction measured at AmPS and the 3He(e, epn) reaction measured at MAMI. The measurements were performed in similar kinematics to allow a comparison to be made between the cross sections of the two reactions. Results are shown for both reactions together with a comparison for the 3He(e, e epp) data with continuum Faddeev calculations.

The electron-target-asymmetries A_parallel and A_perpendicular with target spin parallel and perpendicular to the momentum transfer q were measured for both the two-- and three-body breakup of 3He in the 3He(e,e'p)-reaction. Polarized electrons were scattered off polarized 3He in the quasielastic regime in parallel kinematics with the scattered electron and the knocked-out proton detected using the Three-Spectrometer-Facility at MAMI. The results are compared to Faddeev calculations which take into account Final State Interactions as well as Meson Exchange Currents. The experiment confirms the prediction of a large effect of Final State Interactions in the asymmetry of the three-body breakup and of an almost negligible one for the two-body breakup.

The electric form factor of the neutron, G_En, has been measured at the Mainz Microtron by recoil polarimetry in the quasielastic D(e_pol,e'n_pol)p reaction. Three data points have been extracted at squared four-momentum transfers Q^2 = 0.3, 0.6 and 0.8 (GeV/c)^2. Corrections for nuclear binding effects have been applied., 9 pages, 7 figures, 2 tables. Accepted for publication in EPJA

In two series of high-resolution coincidence experiments at the three-spectrometer facility at MAMI, the $\mathrm{H}{(e,e}^{\ensuremath{'}}{\ensuremath{\pi}}^{+})X$ and ${}^{2}\mathrm{H}{(e,e}^{\ensuremath{'}}p)X$ reactions were studied to search for narrow nucleon resonances below pion threshold. The missing-mass resolution was $0.6--1.6\mathrm{MeV}{/c}^{2}$ full width at half maximum in the proton experiment and $0.9--1.3\mathrm{MeV}{/c}^{2}$ in the deuteron experiment. The experiments covered the missing-mass region from the neutron mass up to about 1050 and $1100\mathrm{MeV}{/c}^{2},$ respectively. None of our measurements showed a signal for narrow resonances to a level of down to ${10}^{\ensuremath{-}4}$ with respect to the neutron peak in the missing-mass spectra.