Measurement of the Beam-Spin Azimuthal Asymmetry Associated with Deeply-Virtual Compton Scattering
A. AirapetianYerevan Physics Institute, 375036 Yerevan, ArmeniaН. АкоповYerevan Physics Institute, 375036 Yerevan, ArmeniaZ. AkopovYerevan Physics Institute, 375036 Yerevan, ArmeniaM. AmarianIstituto Nazionale di Fisica Nucleare, Sezione Roma 1, Gruppo Sanità and Physics Laboratory, Istituto Superiore di Sanità, 00161 Roma, ItalyE. C. AschenauerH. AvakianIstituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, ItalyR. AvakianYerevan Physics Institute, 375036 Yerevan, ArmeniaA. AvetissianYerevan Physics Institute, 375036 Yerevan, ArmeniaE. AvetissianYerevan Physics Institute, 375036 Yerevan, ArmeniaP. BaileyDepartment of Physics, University of Illinois, Urbana, Illinois 61801B. BainsDepartment of Physics, University of Illinois, Urbana, Illinois 61801V. BaturinPetersburg Nuclear Physics Institute, St. Petersburg, Gatchina, 188350 RussiaC. BaumgartenSektion Physik, Universität München, 85748 Garching, GermanyM. BeckmannFakultät für Physik, Universität Freiburg, 79104 Freiburg, GermanyS. BelostotskiPetersburg Nuclear Physics Institute, St. Petersburg, Gatchina, 188350 RussiaS. BernreutherDepartment of Physics, Tokyo Institute of Technology, Tokyo 152, JapanN. BianchiIstituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, ItalyH. BöttcherA. BorissovDESY, Deutsches Elektronen Synchrotron, 22603 Hamburg, GermanyO. BouhaliNationaal Instituut voor Kernfysica en Hoge-Energiefysica (NIKHEF), 1009 DB Amsterdam, The NetherlandsM. BouwhuisDepartment of Physics, University of Illinois, Urbana, Illinois 61801J. BrackNuclear Physics Laboratory, University of Colorado, Boulder, Colorado 80309-0446S. BrauksiepeFakultät für Physik, Universität Freiburg, 79104 Freiburg, GermanyW. BrücknerMax-Planck-Institut für Kernphysik, 69029 Heidelberg, GermanyA. BrüllLaboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139I. BrunnPhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyH. J. BultenDepartment of Physics and Astronomy, Vrije Universiteit, 1081 HV Amsterdam, The NetherlandsG. P. CapitaniIstituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, ItalyP. ChumneyDepartment of Physics, New Mexico State University, Las Cruces, New Mexico 88003E. CisbaniIstituto Nazionale di Fisica Nucleare, Sezione Roma 1, Gruppo Sanità and Physics Laboratory, Istituto Superiore di Sanità, 00161 Roma, ItalyG. CiulloIstituto Nazionale di Fisica Nucleare, Sezione di Ferrara and Dipartimento di Fisica, Università di Ferrara, 44100 Ferrara, ItalyG.R. CourtPhysics Department, University of Liverpool, Liverpool L69 7ZE, United KingdomP.F. DalpiazIstituto Nazionale di Fisica Nucleare, Sezione di Ferrara and Dipartimento di Fisica, Università di Ferrara, 44100 Ferrara, ItalyR. De LeoIstituto Nazionale di Fisica Nucleare, Sezione di Bari, 70124 Bari, ItalyL. De NardoDepartment of Physics, University of Alberta, Edmonton, Alberta T6G 2J1, CanadaE. De SanctisIstituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, ItalyD. De SchepperPhysics Division, Argonne National Laboratory, Argonne, Illinois 60439-4843E. DevitsinLebedev Physical Institute, 117924 Moscow, RussiaP. K. A. de Witt HubertsNationaal Instituut voor Kernfysica en Hoge-Energiefysica (NIKHEF), 1009 DB Amsterdam, The NetherlandsP. Di NezzaIstituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, ItalyM. DürenPhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyM. EhrenfriedG. ElbakianYerevan Physics Institute, 375036 Yerevan, ArmeniaF. EllinghausJ. ElyNuclear Physics Laboratory, University of Colorado, Boulder, Colorado 80309-0446R. FabbriIstituto Nazionale di Fisica Nucleare, Sezione di Ferrara and Dipartimento di Fisica, Università di Ferrara, 44100 Ferrara, ItalyA. FantoniIstituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, ItalyA. FechtchenkoJoint Institute for Nuclear Research, 141980 Dubna, RussiaL. FelawkaTRIUMF, Vancouver, British Columbia V6T 2A3, CanadaB. W. FilipponeW. K. Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125H. FischerFakultät für Physik, Universität Freiburg, 79104 Freiburg, GermanyB. FoxNuclear Physics Laboratory, University of Colorado, Boulder, Colorado 80309-0446J. FranzFakultät für Physik, Universität Freiburg, 79104 Freiburg, GermanyS. FrullaniIstituto Nazionale di Fisica Nucleare, Sezione Roma 1, Gruppo Sanità and Physics Laboratory, Istituto Superiore di Sanità, 00161 Roma, ItalyY. GärberDESY Zeuthen, 15738 Zeuthen, GermanyF. GaribaldiIstituto Nazionale di Fisica Nucleare, Sezione Roma 1, Gruppo Sanità and Physics Laboratory, Istituto Superiore di Sanità, 00161 Roma, ItalyE. GaruttiNationaal Instituut voor Kernfysica en Hoge-Energiefysica (NIKHEF), 1009 DB Amsterdam, The NetherlandsG. GavrilovPetersburg Nuclear Physics Institute, St. Petersburg, Gatchina, 188350 RussiaV. GharibyanYerevan Physics Institute, 375036 Yerevan, ArmeniaA. GolendukhinSektion Physik, Universität München, 85748 Garching, GermanyG. GrawSektion Physik, Universität München, 85748 Garching, GermanyO. GrebenioukPetersburg Nuclear Physics Institute, St. Petersburg, Gatchina, 188350 RussiaP. W. GreenDepartment of Physics, University of Alberta, Edmonton, Alberta T6G 2J1, CanadaL. G. GreeniausDepartment of Physics, University of Alberta, Edmonton, Alberta T6G 2J1, CanadaA. GutePhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyW. HaeberliDepartment of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706K. HafidiPhysics Division, Argonne National Laboratory, Argonne, Illinois 60439-4843M. HartigTRIUMF, Vancouver, British Columbia V6T 2A3, CanadaD. HaschIstituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, ItalyD. HeesbeenNationaal Instituut voor Kernfysica en Hoge-Energiefysica (NIKHEF), 1009 DB Amsterdam, The NetherlandsF. H. HeinsiusFakultät für Physik, Universität Freiburg, 79104 Freiburg, GermanyM. HenochPhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyR. HertenbergerSektion Physik, Universität München, 85748 Garching, GermanyW.H.A. HesselinkDepartment of Physics and Astronomy, Vrije Universiteit, 1081 HV Amsterdam, The NetherlandsG. HofmanNuclear Physics Laboratory, University of Colorado, Boulder, Colorado 80309-0446Y. HollerDESY, Deutsches Elektronen Synchrotron, 22603 Hamburg, GermanyR. J. HoltDepartment of Physics, University of Illinois, Urbana, Illinois 61801B. HommezDepartment of Subatomic and Radiation Physics, University of Gent, 9000 Gent, BelgiumG. IaryginJoint Institute for Nuclear Research, 141980 Dubna, RussiaA. IzotovPetersburg Nuclear Physics Institute, St. Petersburg, Gatchina, 188350 RussiaH. E. JacksonPhysics Division, Argonne National Laboratory, Argonne, Illinois 60439-4843A. JgounPetersburg Nuclear Physics Institute, St. Petersburg, Gatchina, 188350 RussiaPeter JungR. KaiserJ. KanesakaDepartment of Physics, Tokyo Institute of Technology, Tokyo 152, JapanE. KinneyNuclear Physics Laboratory, University of Colorado, Boulder, Colorado 80309-0446A. KisselevPetersburg Nuclear Physics Institute, St. Petersburg, Gatchina, 188350 RussiaP. KitchingDepartment of Physics, University of Alberta, Edmonton, Alberta T6G 2J1, CanadaHideaki KobayashiDepartment of Physics, Tokyo Institute of Technology, Tokyo 152, JapanN. KochPhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyK. KönigsmannFakultät für Physik, Universität Freiburg, 79104 Freiburg, GermanyH. KolsterLaboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139В. А. КоротковE. KotikDepartment of Physics, University of Alberta, Edmonton, Alberta T6G 2J1, CanadaВ. КозловLebedev Physical Institute, 117924 Moscow, RussiaBernhard KraußPhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyV. G. KrivokhijineJoint Institute for Nuclear Research, 141980 Dubna, RussiaG. S. KyleDepartment of Physics, New Mexico State University, Las Cruces, New Mexico 88003L. LagambaIstituto Nazionale di Fisica Nucleare, Sezione di Bari, 70124 Bari, ItalyA. LazievDepartment of Physics and Astronomy, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
2001en
ABI
Abstract
The beam-spin asymmetry in hard electroproduction of photons has been measured. The data have been accumulated by the HERMES experiment at DESY using the HERA 27.6 GeV longitudinally polarized positron beam and an unpolarized hydrogen-gas target. The asymmetry in the azimuthal distribution of the produced photons in the angle $\ensuremath{\varphi}$ relative to the lepton scattering plane was determined with respect to the helicity state of the incoming positron beam. The beam-spin analyzing power in the $\mathrm{sin}\ensuremath{\varphi}$ moment was measured to be $\ensuremath{-}0.23\ifmmode\pm\else\textpm\fi{}0.04(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.03(\mathrm{syst})$ in the missing-mass range below 1.7 GeV. The observed asymmetry is attributed to the interference of the Bethe-Heitler and deeply virtual Compton scattering processes.
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Cited by 20 references