Performance of the Electromagnetic Calorimeter of the HERMES Experiment

The performance of the electromagnetic calorimeter of the HERMES experiment is described. The calorimeter consists of 840 radiation resistant F101 lead-glass counters. The response to positrons up to 27.5 GeV, the comparison between the measured energy and the momentum reconstructed from tracking, long-term stability, hadron rejection and neutral meson invariant mass reconstruction are shown.Comment: 22 pages, 13 figures, LaTeX, accepted by NI

Inclusive photoproton spectra from 12C at intermediate energies

Inclusive photoproton spectra have been measured at five laboratory angles and two photon energies: 159 and 198 MeV. A quasi-monochromatic photon beam, obtained by positron annihilation in-flight on a liquid hydrogen target, was used and the photon spectrum was measured on-line by a pair spectrometer. The experimental proton spectra are well described by assuming a dominant photon absorption mechanism by np quasi-deuteron pairs in the nucleus, provided that rescattering effects are taken into account