Measurement of angular distributions and R = σL/σT in diffractive electroproduction of ρ0 mesons


Journal Article

Production and decay angular distributions were extracted from measurements of exclusive electroproduction of the ρ0(770) meson over a range in the virtual photon negative four-momentum squared 0.5 < Q2 < 4 GeV2 and the photon-nucleon invariant mass range 3.8 < W < 6.5 GeV. The experiment was performed with the HERMES spectrometer, using a longitudinally polarized positron beam and a 3He gas target internal to the HERA e± storage ring. The event sample combines ρ0 mesons produced incoherently off individual nucleons and coherently off the nucleus as a whole. The distributions in one production angle and two angles describing the ρ0 → π+π- decay yielded measurements of eight elements of the spin-density matrix, including one that had not been measured before. The results are consistent with the dominance of helicity conserving amplitudes and natural parity exchange. The improved precision achieved at 4 < W < 7 GeV, in combination with other data at W > 7 GeV, reveals evidence for an energy dependence in the ratio R of the longitudinal to transverse cross sections at constant Q2.

Full Text

Duke Authors

Cited Authors

  • Ackerstaff, K; Airapetian, A; Akopov, N; Amarian, M; Aschenauer, EC; Avakian, H; Avakian, R; Avetissian, A; Bains, B; Beckmann, M; Belostotski, S; Belz, JE; Benisch, T; Bernreuther, S; Bianchi, N; Blanchard, S; Blouw, J; Böttcher, H; Borissov, A; Brack, J; Braun, B; Bray, B; Brückner, W; Brüll, A; Bruins, EEW; Bulten, HJ; Capitani, GP; Carter, P; Cisbani, E; Court, GR; Delheij, PPJ; De Sanctis, E; De Schepper, D; Devitsin, E; de Witt Huberts, PKA; Düren, M; Dvoredsky, A; Elbakian, G; Emerson, J; Fantoni, A; Fechtchenko, A; Ferstl, M; Fiedler, K; Filippone, BW; Fischer, H; Fox, B; Franz, J; Frullani, S; Funk, MA; Gärber, Y; Gagunashvili, ND; Galumian, P; Gao, H; Garibaldi, F; Gavrilov, G; Geiger, P; Gharibyan, V; Golendukhin, A; Graw, G; Grebeniouk, O; Green, PW; Greeniaus, LG; Grosshauser, C; Gute, A; Gyurjyan, V; Haas, JP; Haeberli, W; Häusser, O; Hansen, JO; Hasch, D; Henderson, R; Henkes, T; Hertenberger, R; Holler, Y; Holt, RJ; Ihssen, H; Iodice, M; Izotov, A; Jackson, HE; Jgoun, A; Jones, C; Kaiser, R; Kinney, E; Kirsch, M; Kisselev, A; Kitching, P; Königsmann, K; Kolstein, M; Kolster, H; Korsch, W; Kozlov, V; Kramer, LH; Krause, B; Krivokhijine, VG; Kückes, M; Kyle, G; Lachnit, W; Lorenzon, W; Lung, A; Makins, NCR

Published Date

  • January 1, 2000

Published In

Volume / Issue

  • 18 / 2

Start / End Page

  • 303 - 316

International Standard Serial Number (ISSN)

  • 1434-6044

Digital Object Identifier (DOI)

  • 10.1007/s100520000536

Citation Source

  • Scopus