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Measurement of diffractive photoproduction of vector mesons at large momentum transfer at HERA

  • The ZEUS Collaboration
  • J. Breitweg et al.
Experimental physics

Abstract.

Elastic and proton–dissociative photoproduction of \(\rho^0\), \(\phi\) and \(J/\psi\) vector mesons (\(\gamma p\rightarrow Vp\), \(\gamma p\rightarrow VN\), respectively) have been measured in \(e^+p\) interactions at HERA up to \(-t=3\) GeV\(^2\), where t is the four-momentum transfer squared at the photon–vector–meson vertex. The analysis is based on a data sample in which photoproduction reactions were tagged by detection of the scattered positron in a special-purpose calorimeter. This limits the photon virtuality, \(Q^2\), to values less than 0.01 GeV\(^2\), and selects a \(\gamma p\) average center-of-mass energy of \(\langle W\rangle\) = 94 GeV. Results for the differential cross sections, \(\mbox{d}\sigma/\mbox{d}t\), for \(\rho^0\), \(\phi\) and \(J/\psi\) mesons are presented and compared to the results of recent QCD calculations. Results are also presented for the t-dependence of the pion-pair invariant-mass distribution in the \(\rho^0\) mass region and of the spin-density matrix elements determined from the decay-angle distributions. The Pomeron trajectory has been derived from measurements of the W dependence of the elastic differential cross sections \(\mbox{d}\sigma/\mbox{d}t\) for both \(\rho^0\) and \(\phi\) mesons.

Keywords

Matrix Element Momentum Transfer Differential Cross Section Vector Meson Differential Cross 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • The ZEUS Collaboration
  • J. Breitweg et al.
    • 1
  1. 1.Argonne National Laboratory, Argonne, IL, USA US

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