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Measurement of the beam-helicity asymmetry I-circle dot in the photoproduction of pi(0)-pairs off the proton and off the neutron

Oberle, M. and Krusche, B. and Ahrens, J. and Annand, J. R. M. and Arends, H. J. and Bantawa, K. and Bartolome, P. A. and Beck, R. and Bekrenev, V. and Berghaeuser, H. and Braghieri, A. and Branford, D. and Briscoe, W. J. and Brudvik, J. and Cherepnya, S. and Demissie, B. and Dieterle, M. and Downie, E. J. and Drexler, P. and Fil`kov, L. V. and Fix, A. and Glazier, D. I. and Heid, E. and Hornidge, D. and Howdle, D. and Huber, G. M. and Jahn, O. and Jaegle, I. and Jude, T. C. and Kaeser, A. and Kashevarov, V. L. and Keshelashvili, I. and Kondratiev, R. and Korolija, M. and Kruglov, S. P. and Kulbardis, A. and Lisin, V. and Livingston, K. and MacGregor, I. J. D. and Maghrbi, Y. and Mancell, J. and Manley, D. M. and Marinides, Z. and Martinez, M. and McGeorge, J. C. and McNicoll, E. and Mekterovic, D. and Metag, V. and Micanovic, S. and Middleton, D. G. and Mushkarenkov, A. and Nefkens, B. M. K. and Nikolaev, A. and Novotny, R. and Ostrick, M. and Oussena, B. and Pedroni, P. and Pheron, F. and Polonski, A. and Prakhov, S. N. and Robinson, J. and Rosner, G. and Rostomyan, T. and Schumann, S. and Sikora, M. H. and Sober, D. I. and Starostin, A. and Supek, I. and Thiel, M. and Thomas, A. and Unverzagt, M. and Watts, D. P. and Werthmueller, D. and Witthauer, L. and Zehr, F.. (2013) Measurement of the beam-helicity asymmetry I-circle dot in the photoproduction of pi(0)-pairs off the proton and off the neutron. Physics letters. B, Vol. 721, H. 4-5. pp. 237-243.

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Official URL: http://edoc.unibas.ch/dok/A6223422

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Abstract

Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of neutral pion pairs in the reactions (gamma) over right arrowp -< p pi(0)pi(0) and (gamma) over right arrowd -< (n)p pi(0)pi(0), (gamma) over right arrowd -< (p)n pi(0)pi(0) off free protons and off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow magnetic spectrometer. Decay photons from the pi(0) mesons, recoil protons, and recoil neutrons were detected in the 4 pi covering electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. After kinematic reconstruction of the final state, excellent agreement was found between the results for free and quasi-free protons. This demonstrates that the free-nucleon behavior of such observables can be extracted from measurements with quasi-free nucleons, which is the only possibility for the neutron. Contrary to expectations, the measured asymmetries are very similar for reactions off protons and neutrons. The results are compared to the predictions from the Two-Pion MAID reaction model and (for the proton) also to the Bonn-Gatchina coupled channel analysis. (C) 2013 Elsevier B.V. All rights reserved.
Faculties and Departments:05 Faculty of Science > Departement Physik > Physik > Hadronenphysik (Krusche)
UniBasel Contributors:Krusche, Bernd
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:North-Holland
ISSN:0370-2693
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:27 Mar 2014 13:12
Deposited On:27 Mar 2014 13:12

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