/ Experiment-HEP hep-ex/0603038

Diffractive photoproduction of rho mesons with large momentum transfer at HERA

Aktas, A. ; Andreev, V. ; Anthonis, T. ; Antunovic, B. ; Aplin, S. ; Asmone, A. ; Astvatsatourov, A. ; Babaev, A. ; Backovic, S. ; Baghdasaryan, A. ; Baranov, P. ; Barrelet, E. ; Bartel, W. ; Baudrand, S. ; Baumgartner, S. ; Becker, J. ; Beckingham, M. ; Behnke, O. ; Behrendt, O. ; Belousov, A. ; Berger, N. ; Bizot, J.C. ; Boenig, M.-O. ; Boudry, V. ; Bracinik, J.

Published in: Phys.Lett.
Year: 2006
Vol.: B638
Page No: 422-431
Pages: 19

Abstract: The diffractive photoproduction of rho mesons, e p \to e rho Y, with large momentum transfer squared at the proton vertex, |t|, is studied with the H1 detector at HERA using an integrated luminosity of 20.1 pb^{-1}. The photon-proton centre of mass energy spans the range 75 < W < 95 GeV, the photon virtuality is restricted to Q^2 < 0.01 GeV^2 and the mass M_Y of the proton remnant is below 5 GeV. The t dependence of the cross section is measured for the range 1.5 < |t| < 10.0 GeV^2 and is well described by a power law, dsigma/ d|t| \propto |t|^{-n}. The spin density matrix elements, which provide information on the helicity structure of the interaction, are extracted using measurements of angular distributions of the rho decay products. The data indicate a violation of s-channel helicity conservation, with contributions from both single and double helicity-flip being observed. The results are compared to the predictions of perturbative QCD models.

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