Measurement of the double polarisation observable E in single pseudoscalar meson production

Abstract: Polarisation observables are measured with the Crystal Barrel/TAPS experiment at ELSA for photoproduction reactions with various final states, using a circularly or linearly polarised photon beam and a longitudinally or transversely polarised frozen spin butanol target. The Crystal Barrel/TAPS setup provides a nearly 4$\pi$ angular coverage, a good energy resolution and a high detection efficiency for photons, and is therefore ideally suited to study final states comprising neutral mesons. Results for the measurement of the double polarisation observable E for pion and eta photoproduction off the proton are presented.