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Linearly polarised photon beams at ELSA and measurement of the beam asymmetry in pi0 photoproduction omikron the proton

: Elsner, D.; Bantes, B.; Bartholomy, O.; Bayadilov, D.E.; Beck, R.; Beloglazov, A.; Castelijns, R.; Crede, V.; Ehmanns, A.; Essig, K.; Ewald, R.; Fabry, I.; Frommberger, F.; Fornet-Ponse, K.; Fuchs, M.; Funke, C.; Gridnev, A.B.; Gutz, E.; Hillert, W.; Höffgen, Stefan; Hoffmeister, P.; Horn, I.; Jaegle, I.; Junkersfeld, J.; Kalinowsky, H.; Klein, F.; Klein, F.; Klempt, E.; Konrad, M.; Kotulla, M.; Krusche, B.; Löhner, H.; Lopatin, V.; Lotz, J.; Lugert, S.; Menze, D.; Mertens, T.; Messchendorp, J.G.; Metag, V.; Morales, C.; Nanova, M.; Novinski, D.V.; Novotny, R.; Ostrick, M.; Pant, L.M.; Pee, H. van; Pfeiffer, M.; Sarantsev, A.V.; Schmidt, C.; Schmieden, H.; Schoch, B.; Shende, S.V.; Süle, A.; Sumachev, V.V.; Szczepanek, T.; Thoma, U.; Trnka, D.; Walther, D.; Weinheimer, C.; Wendel, C.

Fulltext ()

The European physical journal. A, Hadrons and nuclei 39 (2009), No.3, pp.373-381
ISSN: 1434-6001
ISSN: 1434-601X
ISSN: 1431-5831
Journal Article, Electronic Publication
Fraunhofer INT ()

At the electron accelerator ELSA a Iinearly polarised tagged photon beam is produced by coherent bremsstrahlung omikron a diamond crystal. Orientation and energy range of the linear polarisation can be deliberately chosen by accurate positioning of the crystal with a goniometer. The degree of polarisation is determined by the form of the scattered electron spectrum. Good agreement between experiment and expectations on the basis of the experimental conditions is obtained. Polarisation degrees of Rhogamma = 40% are typically achieved at half of the primary electron energy. The determination of Rhogamma is confirmed by measuring the beam asymmetry, Sigma, in pi0 photoproduction and by a comparison of the results to independent measurements using laser backscattering.