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

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

doi:10.1140/epja/i2008-10708-1

EPJ

Linearly polarised photon beams at ELSA and measurement of the beam asymmetry in $\pi^{0}_{}$ photoproduction off the proton

The CBELSA/TAPS Collaboration
D. Elsner¹^*, B. Bantes¹, O. Bartholomy², D. E. Bayadilov²^,3, R. Beck², Y. A. Beloglazov³, R. Castelijns⁵, V. Crede²^,6, A. Ehmanns², K. Essig², R. Ewald¹, I. Fabry², F. Frommberger¹, K. Fornet-Ponse¹, M. Fuchs², C. Funke², A. B. Gridnev³, E. Gutz², W. Hillert¹, S. Höffgen¹, P. Hoffmeister², I. Horn², I. Jaegle⁷, J. Junkersfeld², H. Kalinowsky², Frank Klein¹, Friedrich Klein¹, E. Klempt², M. Konrad¹, M. Kotulla⁷^,8, B. Krusche⁷, H. Löhner⁵, I. V. Lopatin³, J. Lotz², S. Lugert⁸, D. Menze¹, T. Mertens⁷, J. G. Messchendorp⁵, V. Metag⁸, C. Morales¹, M. Nanova⁸, D. V. Novinski²^,3, R. Novotny⁸, M. Ostrick¹, L. M. Pant⁸, H. van Pee², M. Pfeiffer⁸, A. V. Sarantsev²^,3, C. Schmidt², H. Schmieden¹, B. Schoch¹, S. Shende⁵, A. Süle¹, V. V. Sumachev³, T. Szczepanek², U. Thoma², D. Trnka⁸, D. Walther¹, C. Weinheimer² and C. Wendel²

¹ Physikalisches Institut der Universität Bonn, Bonn, Germany
² Helmholtz-Institut für Strahlen- und Kernphysik der Universität Bonn, Bonn, Germany
³ Petersburg Nuclear Physics Institute, Gatchina, Russia
⁴ Physikalisches Institut, Universität Erlangen, Erlangen, Germany
⁵ KVI, University of Groningen, Groningen, The Netherlands
⁶ Department of Physics, Florida State University, Tallahassee, USA
⁷ Physikalisches Institut, Universität Basel, Basel, Switzerland
⁸ II. Physikalisches Institut, Universität Giessen, Giessen, Germany

Received: 9 October 2008
Revised: 17 December 2008
Accepted: 17 December 2008
Published online: 13 February 2009

Abstract

At the electron accelerator ELSA a linearly polarised tagged photon beam is produced by coherent bremsstrahlung off 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 $\ensuremath P_{\gamma}=40$ % are typically achieved at half of the primary electron energy. The determination of $\ensuremath P_{\gamma}$ is confirmed by measuring the beam asymmetry, $\Sigma$ , in $\pi^{0}_{}$ photoproduction and by a comparison of the results to independent measurements using laser backscattering.

PACS: 13.60.-r Photon and charged-lepton interactions with hadrons – / 13.60.Le Meson production – / 13.88.+e Polarization in interactions and scattering –

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EPJ

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

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Linearly polarised photon beams at ELSA and measurement of the beam asymmetry in $\pi^{0}_{}$ photoproduction off the proton