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Photoproduction of \( \pi^{0}\)-pairs off protons and off neutrons

  • The A2 Collaboration
  • M. Dieterle
  • M. Oberle
  • J. Ahrens
  • J. R. M. Annand
  • H. J. Arends
  • K. Bantawa
  • P. A. Bartolome
  • R. Beck
  • V. Bekrenev
  • H. Berghäuser
  • A. Braghieri
  • D. Branford
  • W. J. Briscoe
  • J. Brudvik
  • S. Cherepnya
  • S. Costanza
  • B. Demissie
  • E. J. Downie
  • P. Drexler
  • L. V. Fil’kov
  • A. Fix
  • S. Garni
  • D. I. Glazier
  • D. Hamilton
  • E. Heid
  • D. Hornidge
  • D. Howdle
  • G. M. Huber
  • O. Jahn
  • T. C. Jude
  • A. Käser
  • V. L. Kashevarov
  • I. Keshelashvili
  • R. Kondratiev
  • M. Korolija
  • B. KruscheEmail author
  • V. Lisin
  • K. Livingston
  • I. J. D. MacGregor
  • Y. Maghrbi
  • J. Mancell
  • D. M. Manley
  • Z. Marinides
  • J. C. McGeorge
  • E. McNicoll
  • D. Mekterovic
  • V. Metag
  • S. Micanovic
  • D. G. Middleton
  • A. Mushkarenkov
  • A. Nikolaev
  • R. Novotny
  • M. Ostrick
  • P. Otte
  • B. Oussena
  • P. Pedroni
  • F. Pheron
  • A. Polonski
  • S. Prakhov
  • J. Robinson
  • T. Rostomyan
  • S. Schumann
  • M. H. Sikora
  • D. I. Sober
  • A. Starostin
  • Th. Strub
  • I. Supek
  • M. Thiel
  • A. Thomas
  • M. Unverzagt
  • N. K. Walford
  • D. P. Watts
  • D. Werthmüller
  • L. Witthauer
Open Access
Regular Article - Experimental Physics

Abstract.

Total cross sections, angular distributions, and invariant-mass distributions have been measured for the photoproduction of \( \pi^{0}\pi^{0}\) pairs off free protons and off nucleons bound in the deuteron. The experiments were performed at the MAMI accelerator facility in Mainz using the Glasgow photon tagging spectrometer and the Crystal Ball/TAPS detector. The accelerator delivered electron beams of 1508 and 1557MeV, which produced bremsstrahlung in thin radiator foils. The tagged photon beam covered energies up to 1400MeV. The data from the free proton target are in good agreement with previous measurements and were only used to test the analysis procedures. The results for differential cross sections (angular distributions and invariant-mass distributions) for free and quasi-free protons are almost identical in shape, but differ in absolute magnitude up to 15%. Thus, moderate final-state interaction effects are present. The data for quasi-free neutrons are similar to the proton data in the second resonance region (final-state invariant masses up to \( \approx 1550\) MeV), where both reactions are dominated by the \( N(1520)3/2^{-} \rightarrow \Delta(1232)3/2^{+}\pi\) decay. At higher energies, angular and invariant-mass distributions are different. A simple analysis of the shapes of the invariant-mass distributions in the third resonance region is consistent with strong contributions of an \( N^{\star}\rightarrow N\sigma\) decay for the proton, while the reaction is dominated by a sequential decay via a \( \Delta\pi\) intermediate state for the neutron. The data are compared to predictions from the Two-Pion-MAID model and the Bonn-Gatchina coupled-channel analysis.

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Copyright information

© The Author(s) 2015

Authors and Affiliations

  • The A2 Collaboration
  • M. Dieterle
    • 1
  • M. Oberle
    • 1
  • J. Ahrens
    • 2
  • J. R. M. Annand
    • 3
  • H. J. Arends
    • 2
  • K. Bantawa
    • 4
  • P. A. Bartolome
    • 2
  • R. Beck
    • 5
  • V. Bekrenev
    • 6
  • H. Berghäuser
    • 7
  • A. Braghieri
    • 8
  • D. Branford
    • 9
  • W. J. Briscoe
    • 10
  • J. Brudvik
    • 11
  • S. Cherepnya
    • 12
  • S. Costanza
    • 8
  • B. Demissie
    • 10
  • E. J. Downie
    • 2
    • 3
    • 10
  • P. Drexler
    • 7
  • L. V. Fil’kov
    • 12
  • A. Fix
    • 13
  • S. Garni
    • 1
  • D. I. Glazier
    • 3
  • D. Hamilton
    • 3
  • E. Heid
    • 2
  • D. Hornidge
    • 14
  • D. Howdle
    • 3
  • G. M. Huber
    • 15
  • O. Jahn
    • 2
  • T. C. Jude
    • 9
  • A. Käser
    • 1
  • V. L. Kashevarov
    • 12
    • 2
  • I. Keshelashvili
    • 1
  • R. Kondratiev
    • 16
  • M. Korolija
    • 17
  • B. Krusche
    • 1
    Email author
  • V. Lisin
    • 16
  • K. Livingston
    • 3
  • I. J. D. MacGregor
    • 3
  • Y. Maghrbi
    • 1
  • J. Mancell
    • 3
  • D. M. Manley
    • 4
  • Z. Marinides
    • 10
  • J. C. McGeorge
    • 3
  • E. McNicoll
    • 3
  • D. Mekterovic
    • 17
  • V. Metag
    • 7
  • S. Micanovic
    • 17
  • D. G. Middleton
    • 14
  • A. Mushkarenkov
    • 8
  • A. Nikolaev
    • 5
  • R. Novotny
    • 7
  • M. Ostrick
    • 2
  • P. Otte
    • 2
  • B. Oussena
    • 2
    • 10
  • P. Pedroni
    • 8
  • F. Pheron
    • 1
  • A. Polonski
    • 16
  • S. Prakhov
    • 2
    • 10
    • 11
  • J. Robinson
    • 3
  • T. Rostomyan
    • 1
  • S. Schumann
    • 2
  • M. H. Sikora
    • 9
  • D. I. Sober
    • 18
  • A. Starostin
    • 11
  • Th. Strub
    • 1
  • I. Supek
    • 17
  • M. Thiel
    • 7
  • A. Thomas
    • 2
  • M. Unverzagt
    • 2
    • 5
  • N. K. Walford
    • 1
  • D. P. Watts
    • 9
  • D. Werthmüller
    • 1
  • L. Witthauer
    • 1
  1. 1.Department of PhysicsUniversity of BaselBaselSwitzerland
  2. 2.Institut für KernphysikUniversity of MainzMainzGermany
  3. 3.SUPA School of Physics and AstronomyUniversity of GlasgowGlasgowUK
  4. 4.Kent State UniversityKentUSA
  5. 5.Helmholtz-Institut für Strahlen- und KernphysikUniversity of BonnBonnGermany
  6. 6.Petersburg Nuclear Physics InstituteGatchinaRussia
  7. 7.II. Physikalisches InstitutUniversity of GiessenGiessenGermany
  8. 8.INFN Sezione di PaviaPaviaItaly
  9. 9.SUPA School of PhysicsUniversity of EdinburghEdinburghUK
  10. 10.Center for Nuclear StudiesThe George Washington UniversityWashington, DCUSA
  11. 11.University of California Los AngelesLos AngelesUSA
  12. 12.Lebedev Physical InstituteMoscowRussia
  13. 13.Laboratory of Mathematical PhysicsTomsk Polytechnic UniversityTomskRussia
  14. 14.Mount Allison UniversityNew BrunswickCanada
  15. 15.University of ReginaReginaCanada
  16. 16.Institute for Nuclear ResearchMoscowRussia
  17. 17.Rudjer Boskovic InstituteZagrebCroatia
  18. 18.The Catholic University of AmericaWashington, DCUSA

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