Abstract. The electric form factor of the neutron, GE,n, has been measured at the Mainz Microtron by recoil polarimetry in the quasielastic D( e, e ′ n)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. PACS. 13.40.Gp Electromagnetic form factors -14.20.Dh Protons and neutrons -13.88.+e Polarisation in interactions and scattering

The beam-helicity asymmetry has been measured simultaneously for the reactions → e p → e p γ and → e p → e p π 0 in the ∆(1232) resonance region at Q 2 = 0.35 (GeV/c) 2 . The experiment was performed at MAMI with a longitudinally polarized beam and an out-of-plane detection of the proton. The results are compared with calculations based on Dispersion Relations for virtual Compton scattering and with the MAID model for pion electroproduction. There is an overall good agreement between experiment and theoretical calculations. The remaining discrepancies may be ascribed to an imperfect parametrization of some γ ( * ) N → πN multipoles, mainly contributing to the non-resonant background. The beam-helicity asymmetry in both channels (γ and π 0 ) shows a good sensitivity to these multipoles and should allow future improvement in their parametrization. PACS. 13.40.-f Electromagnetic processes and properties -13.60.Fz Elastic and Compton scattering -13.60.Le Meson production -14.20.Gk Baryon resonances with S=0

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In two series of high-resolution coincidence experiments at the three-spectrometer facility at MAMI, the H(e,eЈ ϩ )X and 2 H(e,eЈp)X reactions were studied to search for narrow nucleon resonances below pion threshold. The missing-mass resolution was 0.6-1.6 MeV/c 2 full width at half maximum in the proton experiment and 0.9-1.3 MeV/c 2 in the deuteron experiment. The experiments covered the missing-mass region from the neutron mass up to about 1050 and 1100 MeV/c 2 , respectively. None of our measurements showed a signal for narrow resonances to a level of down to 10 Ϫ4 with respect to the neutron peak in the missing-mass spectra.