The dependence on Q(2) (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 < Q(2) < 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 Q(2) > 3 GeV2, while both contributions are important at low Q(2). The total integral shows no significant deviation from a 1/Q(2) behaviour in the measured Q(2) range, and thus no sign of large effects due to either nucleon-resonance excitations or nonleading twist. (C) 2000 Elsevier Science B.V. All rights reserved.
The Q(2)-dependence of the generalised Gerasimov-Drell-Hearn integral for the proton
DE LEO, Raffaele;
2000-01-01
Abstract
The dependence on Q(2) (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 < Q(2) < 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 Q(2) > 3 GeV2, while both contributions are important at low Q(2). The total integral shows no significant deviation from a 1/Q(2) behaviour in the measured Q(2) range, and thus no sign of large effects due to either nucleon-resonance excitations or nonleading twist. (C) 2000 Elsevier Science B.V. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
