The Q2-dependence of the generalised Gerasimov–Drell–Hearn integral for the proton HERMES Collaboration

نویسندگان

  • A. Airapetian
  • N. Akopov
  • I. Akushevich
  • H. Avakian
  • C. Baumgarten
  • W. Brückner
  • L. De Nardo
  • E. De Sanctis
  • D. De Schepper
  • B. W. Filippone
  • E. Garutti
  • M. Hartig
  • R. Hertenberger
  • M. Iodice
  • A. Kisselev
  • V. Korotkov
  • E. Kotik
  • M. McAndrew
  • F. Menden
  • G. Rakness
  • D. Reggiani
  • D. Ryckbosch
چکیده

The dependence on Q2 (the negative square of the 4-momentum of the exchanged virtual photon) of the generalised Gerasimov–Drell–Hearn integral for the proton has been measured in the range 1.2 GeV2 < Q2 < 12 GeV2 by scattering longitudinally polarised positrons on a longitudinally polarised hydrogen gas target. The contributions of the nucleon-resonance and deep inelastic regions to this integral have been evaluated separately. The latter has been found to dominate for Q2 > 3 GeV2, while both contributions are important at low Q2. The total integral shows no significant deviation from a 1/Q2 behaviour in the measured Q2 range, and thus no sign of large effects due to either nucleon-resonance excitations or nonleading twist.  2000 Elsevier Science B.V. All rights reserved. * Corresponding author. E-mail address: [email protected] (M.G. Vincter). A. Airapetian / Physics Letters B 494 (2000) 1–8 3 PACS: 13.60.Hb; 13.88.+e; 25.20.Dc; 25.30.Fj

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تاریخ انتشار 2000