Measurement of the π⁺-meson polarizabilities via the γp→γπ⁺n reaction

Ahrens, J. and Alexeev, V. M. and Annand, J. R. M. and Arends, H. J. and Beck, R. and Caselotti, G. and Cherepnya, S. N. and Drechsel, D. and Fil`kov, L. V. and Fohl, K. and Giller, I. and Gralmayr, P. and Hehl, T. and Hornidge, D. and Kashevarov, V. L. and Kotulla, N. and Krambrich, D. and Krusche, B. and Lang, M. and McGeorge, J. C. and MacGregor, I. J. D. and Metag, V. and Moinester, M. and Novotny, R. and Pfeiffer, M. and Rost, M. and Schadmand, S. and Scherer, S. and Thomas, A. and Unkmeir, C. and Walcher, T.. (2005) Measurement of the π⁺-meson polarizabilities via the γp→γπ⁺n reaction. The European physical journal. A, Hadrons and nuclei, Vol. 23, H. 1. pp. 113-127.

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Official URL: http://edoc.unibas.ch/dok/A5261941

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An experiment on the radiative pi(+)-meson photoproduction from the proton (gammap -< gammapi(+)n) was carried out at the Mainz Microtron MAMI in the kinematic region 537 MeV > E-gamma > 817 MeV, 140degrees less than or equal to theta(gammagamma`)(cm) less than or equal to 180degrees. The pi(+)-meson polarizabilities have been determined from a comparison of the data with the predictions of two different theoretical models, the first one being based on an effective pole model with pseudoscalar coupling while the second one is based on diagrams describing both resonant and nonresonant contributions. The validity of the models has been verified by comparing the predictions with the present experimental data in the kinematic region where the pion polarizability contribution is negligible (s(1) > 5m(pi)(2)) and where the difference between the predictions of the two models does not exceed 3%. In the region, where the pion polarizability contribution is substantial (5 > s(1)/m(pi)(2) > 15, -12 > t/m(pi)(2) > -2), the difference (alpha - beta)(pi+) of the electric (alpha) and the magnetic (beta) polarizabilities has been determined. As a result we find (alpha - beta)(pi+) = (11.6 +/- 1.5(stat) +/- 3.0(syst) +/- 0.5(mod)) x 10(-4) fm(3). This result is at variance with recent calculations in the framework of chiral perturbation theory.
Faculties and Departments:05 Faculty of Science > Departement Physik > Former Organization Units Physics > Hadronenphysik (Krusche)
UniBasel Contributors:Krusche, Bernd
Item Type:Article, refereed
Article Subtype:Research Article
Note:Variant title: Measurement of the pi(+)-meson polarizabilities via the gamma P →gamma pi(+)n reaction -- Publication type according to Uni Basel Research Database: Journal article
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Last Modified:22 Mar 2012 14:26
Deposited On:22 Mar 2012 13:55

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