N: Accomplishments of first funding period

  • Elastic charge form factor of the Deuteron
    Data has been taken in March 2014. In addition to the proposed elastic kinematics the deuteron breakup was studied at very low momentum transfer. The elastic cross section data will be used to extract the charge radius of the deuteron whereas the breakup data contains information of the polarizibility. Both data sets experiments may shed some light on the proton radius puzzle. The analysis is ongoing.
  • High precision pion spectroscopy of \(\mathbf{\Lambda}\)-hypernuclei
    In 2012 the first high-resolution spectroscopy of pionic decays of strange systems was performed in electron scattering of a \(^9{Be}\) target in order to study ground-states masses of \(\Lambda\)-hypernuclei. Kaons were detected in a short-orbit spectrometer with a broad momentum acceptance at zero degree with respect to the beam. Positrons were suppressed by a lead wall. With this dedicated setup reactions of strangeness production were efficiently tagged. In coincidence, pions were detected with two high-resolution spectrometers. About 103 pionic weak decays were collected, the majority from a wide momentum distribution. A monochromatic peak at \(p_\pi\) ≈ 133MeV/c was observed that is a unique signature for the two-body decay \(^4_\Lambda\mathrm{H}\to\mathrm{^4He}~+~\pi^-\) of hyperhydrogen stopped inside the target. Its binding energy is \(B_\Lambda\) = 2.14 ± 0.02 (stat.) ± 0.09 (syst.) MeV with respect to the \(^3{H} + \Lambda\) mass. A publication is in preparation.
    In June 2014 a second run was performed yielding a significant improvement of statistics. At the same time we expect better a mass resolution and less background from free hyperon decays in flight. The analysis has started. First results are expected end 2014.
  • Inclusive electron scattering on \(\mathbf{^{3,4}}\)He at low momentum transfer
    The 2009 data set is being analysed, currently. First results, including a comparison with ab-initio calculations, can be expected by the end of 2014.
  • Technical development of a \(\mathbf{^{6,7}}\)Li target for use in electron scattering experiments
    To achieve high luminosities without melting the target the lithum was mounted on a water cooled frame. A 2mm target (106mg/cm\(^2\)) has been tested successfully with beam currents up to 30\(\mu\)A. The Li-target is ready for production.
  • Neutron detector development and construction
    This is a common Project with S1. The commissioning of the first two layers of the neutron detector is planned for october 2014.