Evidence for a positive longitudinal double-spin asymmetry <A(l)(rho)> = 0.24 +/- 0.11(stat) +/- 0.02(syst) in the cross section for exclusive diffractive rho (0)(770) vector-meson production in polarised lepton-proton scattering was observed by the HERMES experiment. The longitudinally polarised 27.56 GeV HERA positron beam was scattered off a longitudinally polarised pure hydrogen gas target. The average invariant mass of the photon-proton system has a value of <W > = 4.9 GeV, while the average negative squared four-momentum of the virtual photon is <Q(2)> = 1.7 GeV2. The ratio of the present result to the corresponding spin asymmetry in inclusive deep-inelastic scattering is in agreement with an early theoretical prediction based on the generalised vector-meson dominance model. (C) 2001 Published by Elsevier Science B.V.
Double-spin asymmetry in the cross section for exclusive rho(0) production in lepton-proton scattering
DE LEO, Raffaele;
2001-01-01
Abstract
Evidence for a positive longitudinal double-spin asymmetry <A(l)(rho)> = 0.24 +/- 0.11(stat) +/- 0.02(syst) in the cross section for exclusive diffractive rho (0)(770) vector-meson production in polarised lepton-proton scattering was observed by the HERMES experiment. The longitudinally polarised 27.56 GeV HERA positron beam was scattered off a longitudinally polarised pure hydrogen gas target. The average invariant mass of the photon-proton system has a value of <W > = 4.9 GeV, while the average negative squared four-momentum of the virtual photon is <Q(2)> = 1.7 GeV2. The ratio of the present result to the corresponding spin asymmetry in inclusive deep-inelastic scattering is in agreement with an early theoretical prediction based on the generalised vector-meson dominance model. (C) 2001 Published by Elsevier Science B.V.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
