Publications [#304544] of Haiyan Gao

Papers Published
  1. 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; Sanctis, ED; Schepper, DD; Devitsin, E; Huberts, PKADW; Düren, M; Dvoredsky, A; Elbakian, G; Emerson, J et al., Measurement of angular distributions and R = σLT in diffractive electroproduction of ρ0 mesons, The European Physical Journal C - Particles and Fields, vol. 18 no. 2 (2000), pp. 303-316 .

    Abstract:
    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.