Measurement of angular distributions and R = σLT in diffractive electroproduction of ρ0 mesons

K. Ackerstaff, A. Airapetian, N. Akopov, M. Amarian, E. C. Aschenauer, H. Avakian, R. Avakian, A. Avetissian, B. Bains, M. Beckmann, S. Belostotski, J. E. Belz, Th Benisch, S. Bernreuther, N. Bianchi, S. Blanchard, J. Blouw, H. Böttcher, A. Borissov, J. BrackB. Braun, B. Bray, W. Brückner, A. Brüll, E. E.W. Bruins, H. J. Bulten, G. P. Capitani, P. Carter, E. Cisbani, G. R. Court, P. P.J. Delheij, E. De Sanctis, D. De Schepper, E. Devitsin, P. K.A. de Witt Huberts, M. Düren, A. Dvoredsky, G. Elbakian, J. Emerson, A. Fantoni, A. Fechtchenko, M. Ferstl, K. Fiedler, B. W. Filippone, H. Fischer, B. Fox, J. Franz, S. Frullani, M. A. Funk, Y. Gärber, N. D. Gagunashvili, P. Galumian, H. Gao, F. Garibaldi, G. Gavrilov, P. Geiger, V. Gharibyan, A. Golendukhin, G. Graw, O. Grebeniouk, P. W. Green, L. G. Greeniaus, C. Grosshauser, A. Gute, V. Gyurjyan, J. P. Haas, W. Haeberli, O. Häusser, J. O. Hansen, D. Hasch, R. Henderson, Th Henkes, R. Hertenberger, Y. Holler, R. J. Holt, H. Ihssen, M. Iodice, A. Izotov, H. E. Jackson, A. Jgoun, C. Jones, R. Kaiser, E. Kinney, M. Kirsch, A. Kisselev, P. Kitching, K. Königsmann, M. Kolstein, H. Kolster, W. Korsch, V. Kozlov, L. H. Kramer, B. Krause, V. G. Krivokhijine, M. Kückes, G. Kyle, W. Lachnit, W. Lorenzon, A. Lung, N. C.R. Makins, S. I. Manaenkov, F. K. Martens, J. W. Martin, A. Mateos, K. Mcllhany, R. D. McKeown, F. Meissner, F. Menden, D. Mercer, A. Metz, N. Meyners, O. Mikloukho, C. A. Miller, M. A. Miller, R. Milner, V. Mitsyn, A. Most, R. Mozzetti, V. Muccifora, A. Nagaitsev, Y. Naryshkin, A. M. Nathan, F. Neunreither, J. M. Niczyporuk, W. D. Nowak, M. Nupieri, P. Oelwein, H. Ogami, T. G. O'Neill, R. Openshaw, J. Ouyang, S. F. Pate, M. Pitt, H. R. Poolman, S. Potashov, D. H. Potterveld, G. Rakness, R. Redwine, A. R. Reolon, R. Ristinen, K. Rith, G. Röper, H. O. Roloff, P. Rossi, M. Ruh, D. Ryckbosch, Y. Sakemi, I. Savin, K. P. Schüler, A. Schwind, T. A. Shibata, T. Shin, A. Simon, K. Sinram, W. R. Smythe, J. Sowinski, M. Spengos, E. Steffens, J. Stenger, J. Stewart, F. Stock, U. Stösslein, M. Sutter, H. Tallini, S. Taroian, A. Terkulov, D. M. Thiessen, B. Tipton, A. Trudel, M. Tytgat, G. M. Urciuoli, J. F.J. van den Brand, G. van der Steenhoven, R. van de Vyver, M. C. Vetterli, M. G. Vincter, E. Volk, W. Wander, T. P. Welch, S. E. Williamson, T. Wise, K. Zapfe, H. Zohrabian

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish (US)
Pages (from-to)303-316
Number of pages14
JournalEuropean Physical Journal C
Issue number2
StatePublished - 2000
Externally publishedYes

ASJC Scopus subject areas

  • Engineering (miscellaneous)
  • Physics and Astronomy (miscellaneous)


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