2018 Impact factor 4.843
Particles and Fields
Eur. Phys. J. C 26, 389-409 (2003)
DOI: 10.1140/epjc/s2002-01079-0

Measurement of proton-dissociative diffractive photoproduction of vector mesons at large momentum transfer at HERA

The ZEUS Collaboration


(Received: 22 May 2002 / Published online: 9 December 2002)

Abstract
Diffractive photoproduction of vector mesons, $\gamma p \to V Y$, where Y is a proton-dissociative system, has been measured in e+p interactions with the ZEUS detector at HERA using an integrated luminosity of 25 $\,\text{pb}^{-1}$. The differential cross section, ${\rm d}\sigma/{\rm d}t$, is presented for 1.2<-t<12 GeV2, where t is the square of the four-momentum transferred to the vector meson. The data span the range in photon-proton centre-of-mass energy, W, from 80 GeV to 120 GeV. The t distributions are well fit by a power law, ${\rm d}\sigma/{\rm d}t \propto (-t)^{-n}$. The slope of the effective Pomeron trajectory, measured from the W dependence of the $\rho^0$ and $\phi$ cross sections in bins of t, is consistent with zero. The ratios ${\rm d}\sigma_{\gamma p \to \phi Y}/{\rm d}t$ to ${\rm d}\sigma_{\gamma p \to \rho^0 Y}/{\rm d}t$ and ${\rm d}\sigma_{\gamma p \to J/\psi Y}/{\rm d}t$ to ${\rm d}\sigma_{\gamma p \to \rho^0 Y}/{\rm d}t$ increase with increasing -t. Decay-angle analyses for $\rho^0$, $\phi$ and $J/\psi$ mesons have been carried out. For the $\rho^0$ and $\phi$ mesons, contributions from single and double helicity flip are observed. The results are compared to expectations of theoretical models.



© Società Italiana di Fisica, Springer-Verlag 2003