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Beam-helicity asymmetry arising from deeply virtual Compton scattering measured with kinematically complete event reconstruction

  • The Hermes Collaboration
  • A. Airapetian
  • N. Akopov
  • Z. Akopov
  • E. C. Aschenauer
  • W. Augustyniak
  • R. Avakian
  • A. Avetissian
  • E. Avetisyan
  • S. Belostotski
  • H. P. Blok
  • A. Borissov
  • J. Bowles
  • I. Brodski
  • V. Bryzgalov
  • J. Burns
  • M. Capiluppi
  • G. P. Capitani
  • E. Cisbani
  • G. Ciullo
  • M. Contalbrigo
  • P. F. Dalpiaz
  • W. Deconinck
  • R. De Leo
  • L. De Nardo
  • E. De Sanctis
  • M. Diefenthaler
  • P. Di Nezza
  • M. Düren
  • M. Ehrenfried
  • G. Elbakian
  • F. Ellinghaus
  • E. Etzelmüller
  • R. Fabbri
  • A. Fantoni
  • L. Felawka
  • S. Frullani
  • G. Gapienko
  • V. Gapienko
  • F. Garibaldi
  • G. Gavrilov
  • V. Gharibyan
  • F. Giordano
  • S. Gliske
  • M. Golembiovskaya
  • I. M. Gregor
  • H. Guler
  • M. Hartig
  • D. Hasch
  • A. Hillenbrand
  • M. Hoek
  • Y. Holler
  • I. Hristova
  • A. Ivanilov
  • H. E. Jackson
  • H. S. Jo
  • S. Joosten
  • R. Kaiser
  • G. Karyan
  • T. Keri
  • E. Kinney
  • A. Kisselev
  • V. Korotkov
  • V. Kozlov
  • B. Krauss
  • P. Kravchenko
  • V. G. Krivokhijine
  • L. Lagamba
  • L. Lapikás
  • I. Lehmann
  • P. Lenisa
  • A. López Ruiz
  • W. Lorenzon
  • S. Lu
  • X. Lu
  • B.-Q. Ma
  • D. Mahon
  • N. C. R. Makins
  • S. I. Manaenkov
  • L. Manfré
  • Y. Mao
  • B. Marianski
  • A. Martinez de la Ossa
  • H. Marukyan
  • C. A. Miller
  • Y. Miyachi
  • A. Movsisyan
  • M. Murray
  • A. Mussgiller
  • E. Nappi
  • Y. Naryshkin
  • A. Nass
  • M. Negodaev
  • W.-D. Nowak
  • A. Osborne
  • L. L. Pappalardo
  • R. Perez-Benito
  • A. Petrosyan
  • P. E. Reimer
  • A. R. Reolon
  • C. Riedl
  • K. Rith
  • G. Rosner
  • A. Rostomyan
  • L. Rubacek
  • J. Rubin
  • D. Ryckbosch
  • A. Schäfer
  • G. Schnell
  • K. P. Schüler
  • B. Seitz
  • C. Shearer
  • T.-A. Shibata
  • V. Shutov
  • M. Stancari
  • M. Statera
  • J. J. M. Steijger
  • J. Stewart
  • S. Taroian
  • A. Terkulov
  • R. Truty
  • A. Trzcinski
  • M. Tytgat
  • Y. Van Haarlem
  • C. Van Hulse
  • D. Veretennikov
  • V. Vikhrov
  • I. Vilardi
  • S. Wang
  • S. Yaschenko
  • Z. Ye
  • S. Yen
  • V. Zagrebelnyy
  • D. Zeiler
  • B. Zihlmann
  • P. Zupranski
Open Access
Article

Abstract

The beam-helicity asymmetry in exclusive electroproduction of real photons by the longitudinally polarized Hera positron beam scattering off an unpolarized hydrogen target is measured at Hermes. The asymmetry arises from deeply virtual Compton scattering and its interference with the Bethe-Heitler process. Azimuthal amplitudes of the beam-helicity asymmetry are extracted from a data sample consisting of epepγ events with detection of all particles in the final state including the recoiling proton. The installation of a recoil detector, while reducing the acceptance of the experiment, allows the elimination of background from epeN πγ events, which was estimated to contribute an average of about 12% to the signal in previous Hermes publications. The removal of this background from the present data sample is shown to increase the magnitude of the leading asymmetry amplitude by 0.054 ± 0.016 to −0.328 ± 0.027 (stat.) ± 0.045 (syst.).

Keywords

Lepton-Nucleon Scattering 

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Copyright information

© SISSA 2012

Authors and Affiliations

  • The Hermes Collaboration
  • A. Airapetian
    • 13
    • 16
  • N. Akopov
    • 27
  • Z. Akopov
    • 6
  • E. C. Aschenauer
    • 7
    • 28
  • W. Augustyniak
    • 26
  • R. Avakian
    • 27
  • A. Avetissian
    • 27
  • E. Avetisyan
    • 6
  • S. Belostotski
    • 19
  • H. P. Blok
    • 18
    • 25
  • A. Borissov
    • 6
  • J. Bowles
    • 14
  • I. Brodski
    • 13
  • V. Bryzgalov
    • 20
  • J. Burns
    • 14
  • M. Capiluppi
    • 10
  • G. P. Capitani
    • 11
  • E. Cisbani
    • 22
  • G. Ciullo
    • 10
  • M. Contalbrigo
    • 10
  • P. F. Dalpiaz
    • 10
  • W. Deconinck
    • 6
  • R. De Leo
    • 2
  • L. De Nardo
    • 12
    • 6
    • 23
  • E. De Sanctis
    • 11
  • M. Diefenthaler
    • 15
    • 9
  • P. Di Nezza
    • 11
  • M. Düren
    • 13
  • M. Ehrenfried
    • 13
  • G. Elbakian
    • 27
  • F. Ellinghaus
    • 5
  • E. Etzelmüller
    • 13
  • R. Fabbri
    • 7
  • A. Fantoni
    • 11
  • L. Felawka
    • 23
  • S. Frullani
    • 22
  • G. Gapienko
    • 20
  • V. Gapienko
    • 20
  • F. Garibaldi
    • 22
  • G. Gavrilov
    • 6
    • 19
    • 23
  • V. Gharibyan
    • 27
  • F. Giordano
    • 15
    • 10
  • S. Gliske
    • 16
  • M. Golembiovskaya
    • 7
  • I. M. Gregor
    • 7
  • H. Guler
    • 7
  • M. Hartig
    • 6
  • D. Hasch
    • 11
  • A. Hillenbrand
    • 7
  • M. Hoek
    • 14
  • Y. Holler
    • 6
  • I. Hristova
    • 7
  • A. Ivanilov
    • 20
  • H. E. Jackson
    • 1
  • H. S. Jo
    • 12
  • S. Joosten
    • 15
  • R. Kaiser
    • 14
    • 29
  • G. Karyan
    • 27
  • T. Keri
    • 14
    • 13
  • E. Kinney
    • 5
  • A. Kisselev
    • 19
  • V. Korotkov
    • 20
  • V. Kozlov
    • 17
  • B. Krauss
    • 9
  • P. Kravchenko
    • 9
    • 19
  • V. G. Krivokhijine
    • 8
  • L. Lagamba
    • 2
  • L. Lapikás
    • 18
  • I. Lehmann
    • 14
  • P. Lenisa
    • 10
  • A. López Ruiz
    • 12
  • W. Lorenzon
    • 16
  • S. Lu
    • 13
  • X. Lu
    • 7
  • B.-Q. Ma
    • 3
  • D. Mahon
    • 14
  • N. C. R. Makins
    • 15
  • S. I. Manaenkov
    • 19
  • L. Manfré
    • 22
  • Y. Mao
    • 3
  • B. Marianski
    • 26
  • A. Martinez de la Ossa
    • 6
    • 5
  • H. Marukyan
    • 27
  • C. A. Miller
    • 23
  • Y. Miyachi
    • 24
    • 30
  • A. Movsisyan
    • 27
  • M. Murray
    • 14
  • A. Mussgiller
    • 6
    • 9
  • E. Nappi
    • 2
  • Y. Naryshkin
    • 19
  • A. Nass
    • 9
  • M. Negodaev
    • 7
  • W.-D. Nowak
    • 7
  • A. Osborne
    • 14
  • L. L. Pappalardo
    • 10
  • R. Perez-Benito
    • 13
  • A. Petrosyan
    • 27
  • P. E. Reimer
    • 1
  • A. R. Reolon
    • 11
  • C. Riedl
    • 7
  • K. Rith
    • 9
  • G. Rosner
    • 14
  • A. Rostomyan
    • 6
  • L. Rubacek
    • 13
  • J. Rubin
    • 1
    • 15
  • D. Ryckbosch
    • 12
  • A. Schäfer
    • 21
  • G. Schnell
    • 4
    • 12
  • K. P. Schüler
    • 6
  • B. Seitz
    • 14
  • C. Shearer
    • 14
  • T.-A. Shibata
    • 24
  • V. Shutov
    • 8
  • M. Stancari
    • 10
  • M. Statera
    • 10
  • J. J. M. Steijger
    • 18
  • J. Stewart
    • 7
  • S. Taroian
    • 27
  • A. Terkulov
    • 17
  • R. Truty
    • 15
  • A. Trzcinski
    • 26
  • M. Tytgat
    • 12
  • Y. Van Haarlem
    • 12
  • C. Van Hulse
    • 4
    • 12
  • D. Veretennikov
    • 19
  • V. Vikhrov
    • 19
  • I. Vilardi
    • 2
  • S. Wang
    • 3
  • S. Yaschenko
    • 7
    • 9
  • Z. Ye
    • 6
  • S. Yen
    • 23
  • V. Zagrebelnyy
    • 6
    • 16
  • D. Zeiler
    • 9
  • B. Zihlmann
    • 6
  • P. Zupranski
    • 26
  1. 1.Physics Division, Argonne National LaboratoryArgonneUSA
  2. 2.Istituto Nazionale di Fisica Nucleare, Sezione di BariBariItaly
  3. 3.School of PhysicsPeking UniversityBeijingChina
  4. 4.Department of Theoretical PhysicsUniversity of the Basque Country UPV/EHU, 48080 Bilbao, Spain and IKERBASQUE, Basque Foundation for ScienceBilbaoSpain
  5. 5.Nuclear Physics LaboratoryUniversity of ColoradoBoulderUSA
  6. 6.DESYHamburgGermany
  7. 7.DESYZeuthenGermany
  8. 8.Joint Institute for Nuclear ResearchDubnaRussia
  9. 9.Physikalisches InstitutUniversität Erlangen-NürnbergErlangenGermany
  10. 10.Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara and Dipartimento di FisicaUniversità di FerraraFerraraItaly
  11. 11.Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di FrascatiFrascatiItaly
  12. 12.Department of Physics and AstronomyGhent UniversityGentBelgium
  13. 13.Physikalisches InstitutUniversität GießenGießenGermany
  14. 14.SUPA, School of Physics and AstronomyUniversity of GlasgowGlasgowUnited Kingdom
  15. 15.Department of PhysicsUniversity of IllinoisUrbanaUSA
  16. 16.Randall Laboratory of PhysicsUniversity of MichiganAnn ArborUSA
  17. 17.Lebedev Physical InstituteMoscowRussia
  18. 18.National Institute for Subatomic Physics (Nikhef)AmsterdamThe Netherlands
  19. 19.B.P. Konstantinov Petersburg Nuclear Physics InstituteGatchinaRussia
  20. 20.Institute for High Energy PhysicsProtvinoRussia
  21. 21.Institut für Theoretische PhysikUniversität RegensburgRegensburgGermany
  22. 22.Istituto Nazionale di Fisica Nucleare, Sezione di Roma, Gruppo Collegato Sanità and Istituto Superiore di SanitàRomaItaly
  23. 23.TRIUMFVancouverCanada
  24. 24.Department of PhysicsTokyo Institute of TechnologyTokyoJapan
  25. 25.Department of Physics and AstronomyVU UniversityAmsterdamThe Netherlands
  26. 26.National Centre for Nuclear ResearchWarsawPoland
  27. 27.Yerevan Physics InstituteYerevanArmenia
  28. 28.Brookhaven National LaboratoryUptonUSA
  29. 29.International Atomic Energy AgencyViennaAustria
  30. 30.Department of PhysicsYamagata UniversityYamagataJapan

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