Measurement of the Spin Asymmetry in the Photoproduction of Pairs of High-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>p</mml:mi></mml:mrow><mml:mrow><mml:mi>T</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>Hadrons at HERMES
A. AirapetianYerevan Physics Institute, 375036, Yerevan, ArmeniaН. АкоповYerevan Physics Institute, 375036, Yerevan, ArmeniaM. AmarianIstituto Nazionale di Fisica Nucleare, Sezione Sanitá and Physics Laboratory, Istituto Superiore di Sanitá, 00161 Roma, ItalyE. C. AschenauerDESY, 15738 Zeuthen, GermanyHarut AvakianIstituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, ItalyR. AvakianYerevan Physics Institute, 375036, Yerevan, ArmeniaA. AvetissianYerevan Physics Institute, 375036, Yerevan, ArmeniaB. BainsDepartment of Physics, University of Illinois, Urbana, Illinois 61801C. BaumgartenSektion Physik, Universität München, 85748 Garching, GermanyM. BeckmannFakultät für Physik, Universität Freiburg, 79104 Freiburg, GermanyS. BelostotskiPetersburg Nuclear Physics Institute, St. Petersburg, 188350 RussiaAndrea BelzDepartment of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6T. BenischPhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyS. BernreutherPhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyN. BianchiIstituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, ItalyJ. BlouwNationaal Instituut voor Kernfysica en Hoge-Energiefysica (NIKHEF), 1009 DB Amsterdam, The NetherlandsH. BöttcherA. BorissovDESY, 15738 Zeuthen, GermanyJ. BrackNuclear Physics Laboratory, University of Colorado, Boulder, Colorado 80309-0446S. BrauksiepeFakultät für Physik, Universität Freiburg, 79104 Freiburg, GermanyB. BraunPhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyW. BrücknerMax-Planck-Institut für Kernphysik, 69029 Heidelberg, GermanyA. BrüllMax-Planck-Institut für Kernphysik, 69029 Heidelberg, 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. CarterW. K. Kellogg Radiation Lab, California Institute of Technology, Pasadena, California 91125P. ChumneyDepartment of Physics, New Mexico State University, Las Cruces, New Mexico 88003E. CisbaniIstituto Superiore di SanitàG.R. CourtPhysics Department, University of Liverpool, Liverpool L69 7ZE, United KingdomP. DalpiazDipartimento di Fisica, Università di Ferrara, 44100 Ferrara, ItalyE. De SanctisIstituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, ItalyD. De SchepperLaboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139E. 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, GermanyA. DvoredskyW. K. Kellogg Radiation Lab, California Institute of Technology, Pasadena, California 91125G. ElbakianYerevan Physics Institute, 375036, Yerevan, ArmeniaJ. ElyNuclear Physics Laboratory, University of Colorado, Boulder, Colorado 80309-0446A. FantoniIstituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, 00044 Frascati, ItalyM. FerstlPhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyK. FiedlerPhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyB. W. FilipponeW. K. Kellogg Radiation Lab, 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 Sanitá and Physics Laboratory, Istituto Superiore di Sanitá, 00161 Roma, ItalyM.-A. FunkDESY, Deutsches Elektronen Synchrotron 22603 Hamburg, GermanyY. GärberF. GaribaldiIstituto Nazionale di Fisica Nucleare, Sezione Sanitá and Physics Laboratory, Istituto Superiore di Sanitá, 00161 Roma, ItalyG. GavrilovPetersburg Nuclear Physics Institute, St. Petersburg, 188350 RussiaP. GeigerMax-Planck-Institut für Kernphysik, 69029 Heidelberg, GermanyV. GharibyanYerevan Physics Institute, 375036, Yerevan, ArmeniaA. GolendukhinPhysikalisches Institut, Philipps-Universität Marburg, 35037 Marburg, GermanyG. GrawSektion Physik, Universität München, 85748 Garching, GermanyO. GrebenioukPetersburg Nuclear Physics Institute, St. Petersburg, 188350 RussiaP. W. GreenDepartment of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2J1L. G. GreeniausDepartment of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2J1C. GroßhauserPhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyM. GuidalNationaal Instituut voor Kernfysica en Hoge-Energiefysica (NIKHEF), 1009 DB Amsterdam, The NetherlandsA. GutePhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyW. HaeberliDepartment of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706O. HansenPhysics Division, Argonne National Laboratory, Argonne, Illinois 60439D. HaschO. HäusserDepartment of Physics, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6F. H. HeinsiusFakultät für Physik, Universität Freiburg, 79104 Freiburg, GermanyR. HendersonTRIUMF, Vancouver, British Columbia, Canada V6T 2A3M. HenochPhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyR. HertenbergerSektion Physik, Universität München, 85748 Garching, GermanyY. HollerDESY, Deutsches Elektronen Synchrotron 22603 Hamburg, GermanyR. J. HoltDepartment of Physics, University of Illinois, Urbana, Illinois 61801W. HoprichMax-Planck-Institut für Kernphysik, 69029 Heidelberg, GermanyH. IhssenDESY, Deutsches Elektronen Synchrotron 22603 Hamburg, GermanyM. IodiceIstituto Nazionale di Fisica Nucleare, Sezione Sanitá and Physics Laboratory, Istituto Superiore di Sanitá, 00161 Roma, ItalyA. IzotovPetersburg Nuclear Physics Institute, St. Petersburg, 188350 RussiaH. E. JacksonPhysics Division, Argonne National Laboratory, Argonne, Illinois 60439A. JgounPetersburg Nuclear Physics Institute, St. Petersburg, 188350 RussiaR. KaiserDESY, 15738 Zeuthen, GermanyE. KinneyNuclear Physics Laboratory, University of Colorado, Boulder, Colorado 80309-0446A. KisselevPetersburg Nuclear Physics Institute, St. Petersburg, 188350 RussiaP. KitchingDepartment of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2J1Hisao KobayashiTokyo Institute of Technology, Tokyo 152, JapanN. KochPhysikalisches Institut, Philipps-Universität Marburg, 35037 Marburg, GermanyK. KönigsmannFakultät für Physik, Universität Freiburg, 79104 Freiburg, GermanyM. KolsteinNationaal Instituut voor Kernfysica en Hoge-Energiefysica (NIKHEF), 1009 DB Amsterdam, The NetherlandsH. KolsterSektion Physik, Universität München, 85748 Garching, GermanyВ. А. КоротковW. KorschDepartment of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506В. КозловLebedev Physical Institute, 117924 Moscow, RussiaL. KramerDepartment of Physics, Florida International University, Miami, Florida 33199M. KurisunoTokyo Institute of Technology, Tokyo 152, JapanG. S. KyleDepartment of Physics, New Mexico State University, Las Cruces, New Mexico 88003W. LachnitPhysikalisches Institut, Universität Erlangen-Nürnberg, 91058 Erlangen, GermanyW. LorenzonRandall Laboratory of Physics, University of Michigan, Ann Arbor, Michigan 48109-1120N. C. R. MakinsDepartment of Physics, University of Illinois, Urbana, Illinois 61801F. K. MartensDepartment of Physics, University of Alberta, Edmonton, Alberta, Canada T6G 2J1J. W. MartinLaboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139F. MasoliDipartimento di Fisica, Università di Ferrara, 44100 Ferrara, ItalyA.O. MateosLaboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139M. McAndrewPhysics Department, University of Liverpool, Liverpool L69 7ZE, United Kingdom
2000lv
ABI
Аннотация
We present a measurement of the longitudinal spin asymmetry ${A}_{||}$ in photoproduction of pairs of hadrons with high transverse momentum ${p}_{T}$. Data were accumulated by the HERMES experiment using a 27.5 GeV polarized positron beam and a polarized hydrogen target internal to the HERA storage ring. For ${h}^{+}{h}^{\ensuremath{-}}$ pairs with ${p}_{T}^{{h}_{1}}>1.5\mathrm{GeV}/c$ and ${p}_{T}^{{h}_{2}}>1.0\mathrm{GeV}/c$, the measured asymmetry is ${A}_{||}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}0.28\ifmmode\pm\else\textpm\fi{}0.12(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.02(\mathrm{syst})$. This negative value is in contrast to the positive asymmetries typically measured in deep inelastic scattering from protons, and is interpreted to arise from a positive gluon polarization.
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