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Double pion photoproduction off 40Ca

Bloch, F. ; Ahrens, J. ; Annand, J. ; Beck, R. ; Fog, L. ; Hornidge, D. ; Janssen, S. ; Kotulla, M. ; Krusche, B. ; McGeorge, J. ; MacGregor, I. ; Messchendorp, J. ; Metag, V. ; Novotny, R. ; Owens, R. ; Pfeiffer, M. ; Rost, M. ; Sanderson, R. ; Schadmand, S. ; Thomas, A. ; Watts, D.

In: The European Physical Journal A, 2007, vol. 32, no. 2, p. 219-228

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    Titre
    • Double pion photoproduction off 40Ca
    Auteur
    • Bloch, F.. Department of Physics and Astronomy, University of Basel, Ch-4056, Basel, Switzerland
    • Ahrens, J.. Institut für Kernphysik, Johannes-Gutenberg-Universität Mainz, D-55099, Mainz, Germany
    • Annand, J.. Department of Physics and Astronomy, University of Glasgow, G12 8QQ, Glasgow, UK
    • Beck, R.. Institut für Kernphysik, Johannes-Gutenberg-Universität Mainz, D-55099, Mainz, Germany
    • Fog, L.. Department of Physics and Astronomy, University of Glasgow, G12 8QQ, Glasgow, UK
    • Hornidge, D.. Institut für Kernphysik, Johannes-Gutenberg-Universität Mainz, D-55099, Mainz, Germany
    • Janssen, S.. II. Physikalisches Institut, Universität Giessen, D-35392, Giessen, Germany
    • Kotulla, M.. Department of Physics and Astronomy, University of Basel, Ch-4056, Basel, Switzerland
    • Krusche, B.. Department of Physics and Astronomy, University of Basel, Ch-4056, Basel, Switzerland
    • McGeorge, J.. Department of Physics and Astronomy, University of Glasgow, G12 8QQ, Glasgow, UK
    • MacGregor, I.. Department of Physics and Astronomy, University of Glasgow, G12 8QQ, Glasgow, UK
    • Messchendorp, J.. II. Physikalisches Institut, Universität Giessen, D-35392, Giessen, Germany
    • Metag, V.. II. Physikalisches Institut, Universität Giessen, D-35392, Giessen, Germany
    • Novotny, R.. II. Physikalisches Institut, Universität Giessen, D-35392, Giessen, Germany
    • Owens, R.. Department of Physics and Astronomy, University of Glasgow, G12 8QQ, Glasgow, UK
    • Pfeiffer, M.. II. Physikalisches Institut, Universität Giessen, D-35392, Giessen, Germany
    • Rost, M.. Institut für Kernphysik, Johannes-Gutenberg-Universität Mainz, D-55099, Mainz, Germany
    • Sanderson, R.. Department of Physics and Astronomy, University of Glasgow, G12 8QQ, Glasgow, UK
    • Schadmand, S.. II. Physikalisches Institut, Universität Giessen, D-35392, Giessen, Germany
    • Thomas, A.. Institut für Kernphysik, Johannes-Gutenberg-Universität Mainz, D-55099, Mainz, Germany
    • Watts, D.. Department of Physics and Astronomy, University of Glasgow, G12 8QQ, Glasgow, UK
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • The European Physical Journal A, 2007, vol. 32, no. 2, p. 219-228. Società Italiana di Fisica
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:318417
    Summary
    Abstract.: The photoproduction of π 0 π 0 and π 0 π ± pairs off 40Ca has been investigated with the TAPS detector using the Glasgow photon tagging spectrometer at the Mainz MAMI accelerator. Data have been taken for incident photon energies in the energy range from 200-820MeV. Total cross-sections have been extracted from threshold up to the maximum photon energy and invariant-mass distributions of the pion pairs have been obtained for incident photon energies between 400-500MeV and 500-550MeV. The double π 0 invariant-mass distributions show some relative enhancement with respect to the mixed charge channel at small invariant masses. The effects are smaller than previously observed for lead nuclei and the distributions do not significantly deviate from carbon data. The data are in good agreement with the results of recent calculations in the framework of the BUU model, with careful treatment of final-state interaction effects but without an explicit in-medium modification of scalar, iso-scalar pion pairs. This means that for Ca most of the experimentally observed effect can be explained by final-state interactions. Only at low incident photon energies there is still a small low mass enhancement of the double π 0 data over the BUU results