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Helicity dependence of the γ 3He → πX reactions in the Δ(1232) resonance region

  • A2 Collaboration
  • S. Costanza
  • A. Mushkarenkov
  • F. Rigamonti
  • M. Romaniuk
  • P. Aguar Bartolomé
  • J. Ahrens
  • J. R. M. Annand
  • H. -J. Arends
  • R. Beck
  • A. Braghieri
  • V. Bekrenev
  • H. Berghäuser
  • W. J. Briscoe
  • S. N. Cherepnya
  • C. Collicott
  • E. J. Downie
  • P. Drexler
  • L. V. Fil’kov
  • A. Fix
  • D. I. Glazier
  • D. Hamilton
  • E. Heid
  • W. Heil
  • D. Hornidge
  • D. Howdle
  • I. Jaegle
  • G. M. Huber
  • O. Jahn
  • T. Jude
  • V. L. Kashevarov
  • I. Keshelashvili
  • R. Kondratiev
  • M. Korolija
  • J. Krimmer
  • B. Krusche
  • S. Kruglov
  • A. Kulbardis
  • V. Lisin
  • K. Livingston
  • I. J. D. MacGregor
  • J. Mancell
  • G. Mandaglio
  • D. M. Manley
  • J. C. McGeorge
  • D. G. Middleton
  • V. Metag
  • B. M. K. Nefkens
  • A. Nikolaev
  • M. Oberle
  • M. Ostrick
  • H. Ortega
  • P. B. Otte
  • B. Oussena
  • P. PedroniEmail author
  • F. Pheron
  • A. Polonski
  • S. Prakhov
  • G. Rosner
  • T. Rostomyan
  • A. J. Sarty
  • S. Schumann
  • A. Starostin
  • I. Supek
  • M. Thiel
  • A. Thomas
  • M. Unverzagt
  • D. P. Watts
  • D. Werthmüller
Regular Article - Experimental Physics

Abstract

The helicity dependences of the differential cross sections for the semi-inclusive γ 3He → π0 X and γ 3He → π± X reactions have been measured for the first time in the energy region 200 < E γ 450 MeV. The experiment was performed at the tagged photon beam facility of the MAMI accelerator in Mainz using a longitudinally polarised high-pressure 3He gas target. Hadronic products were measured with the large-acceptance Crystal Ball detector complemented with additional devices for charged-particle tracking and identification. Unpolarised differential cross sections and their helicity dependence are compared with theoretical calculations using the Fix-Arenhövel model. The effect of the intermediate excitation of the Δ(1232) resonance can be clearly seen from this comparison, especially for the polarised case, where nuclear effects are relatively small. The model provides a better theoretical description of the unpolarised charged pion photoproduction data than the neutral pion channel. It does significantly better in describing the helicity-dependent data in both channels. These comparisons provide new information on the mechanisms involved in pion photoproduction on 3He and suggest that a polarised 3He target can provide valuable information on the corresponding polarised quasi-free neutron reactions.

Keywords

Systematic Uncertainty Photon Beam Unpolarised Case Metastability Exchange Optical Pump Evaluate Cross Section 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© SIF, Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • A2 Collaboration
  • S. Costanza
    • 1
    • 2
  • A. Mushkarenkov
    • 1
  • F. Rigamonti
    • 1
    • 2
  • M. Romaniuk
    • 3
    • 4
  • P. Aguar Bartolomé
    • 5
  • J. Ahrens
    • 5
  • J. R. M. Annand
    • 6
  • H. -J. Arends
    • 5
  • R. Beck
    • 7
  • A. Braghieri
    • 1
  • V. Bekrenev
    • 8
  • H. Berghäuser
    • 9
  • W. J. Briscoe
    • 10
  • S. N. Cherepnya
    • 11
  • C. Collicott
    • 12
    • 13
  • E. J. Downie
    • 10
  • P. Drexler
    • 9
  • L. V. Fil’kov
    • 11
  • A. Fix
    • 14
  • D. I. Glazier
    • 6
    • 15
  • D. Hamilton
    • 6
  • E. Heid
    • 5
  • W. Heil
    • 16
  • D. Hornidge
    • 17
  • D. Howdle
    • 6
  • I. Jaegle
    • 18
  • G. M. Huber
    • 19
  • O. Jahn
    • 5
  • T. Jude
    • 15
  • V. L. Kashevarov
    • 5
  • I. Keshelashvili
    • 18
  • R. Kondratiev
    • 20
  • M. Korolija
    • 21
  • J. Krimmer
    • 16
  • B. Krusche
    • 18
  • S. Kruglov
    • 8
  • A. Kulbardis
    • 8
  • V. Lisin
    • 11
  • K. Livingston
    • 6
  • I. J. D. MacGregor
    • 6
  • J. Mancell
    • 6
  • G. Mandaglio
    • 3
    • 4
  • D. M. Manley
    • 22
  • J. C. McGeorge
    • 6
  • D. G. Middleton
    • 17
  • V. Metag
    • 9
  • B. M. K. Nefkens
    • 23
  • A. Nikolaev
    • 2
  • M. Oberle
    • 18
  • M. Ostrick
    • 5
  • H. Ortega
    • 5
  • P. B. Otte
    • 5
  • B. Oussena
    • 5
  • P. Pedroni
    • 1
    Email author
  • F. Pheron
    • 18
  • A. Polonski
    • 11
  • S. Prakhov
    • 5
    • 10
    • 23
  • G. Rosner
    • 6
  • T. Rostomyan
    • 18
  • A. J. Sarty
    • 13
  • S. Schumann
    • 5
  • A. Starostin
    • 23
  • I. Supek
    • 21
  • M. Thiel
    • 9
  • A. Thomas
    • 5
  • M. Unverzagt
    • 5
  • D. P. Watts
    • 15
  • D. Werthmüller
    • 18
  1. 1.Sezione di PaviaINFNPaviaItaly
  2. 2.Dipartimento di FisicaUniversità di PaviaPaviaItaly
  3. 3.Sezione di CataniaINFNCataniaItaly
  4. 4.Dipartimento di Fisica e Scienze della TerraUniversità di MessinaMessinaItaly
  5. 5.Institut für KernphysikUniversität MainzMainzGermany
  6. 6.SUPA School of Physics & AstronomyUniversity of GlasgowGlasgowUK
  7. 7.Helmholtz-Institut für Strahlen und KernphysikUniversity of BonnBonnGermany
  8. 8.Petersburg Nuclear Physics InstituteGatchinaRussia
  9. 9.II Physikalisches InstitutUniversity of GiessenGiessenGermany
  10. 10.The George Washington UniversityWashington, DCUSA
  11. 11.Institute for Nuclear ResearchMoscowRussia
  12. 12.Dalhousie UniversityHalifaxCanada
  13. 13.Saint Mary’s UniversityHalifaxCanada
  14. 14.Tomsk Polytechnic UniversityTomskRussia
  15. 15.SUPA School of Physics & AstronomyUniversity of EdinburghEdinburghUK
  16. 16.Institut für PhysikUniversität MainzMainzGermany
  17. 17.Mount Allison UniversitySackvilleCanada
  18. 18.Institut für PhysikUniversity of BaselBaselSwitzerland
  19. 19.University of ReginaReginaCanada
  20. 20.Lebedev Physical InstituteMoscowRussia
  21. 21.Rudjer Boskovic InstituteZagrebCroatia
  22. 22.Kent State UniversityKentUSA
  23. 23.University of CaliforniaLos AngelesUSA

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