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\begin{document} 

\title{Probing small x dynamics in hard vector meson production phenomena}
\author {M. ~Strikman\\
\it Department of Physics,
Pennsylvania State University,\\
\it University Park, PA  16802, USA}
\date{}
\maketitle
Study of production of exclusive and semiexclusive production of $J/\psi$ and $\Upsilon$ production at LHC will allow to study  elastic and inelastic interactions of small dipoles protons and nuclei
in the a kinematic range  $30\, GeV \ge W_{\gamma N}\ge 1\, TeV$ with . 
The  coherent channel provides an effective method to probe the leading twist hard QCD regimes of color transparency and perturbative color opacity as well as the onset of black disk regime (BDR) in the soft and hard QCD interactions 
\cite{Frankfurt:2001db,Frankfurt:2002wc,Frankfurt:2003qy}. Study of UPC pA collisions will allow to study both exclusive onium production off protons and nuclei at much larger energy interval than for AA collisions \cite{Frankfurt:2006tp}.


 The use of the neutron tagging will allow to 
select photon interactions at higher energies away from zero rapidity and will test dynamics of inelastic interactions of small dipoles\cite{Strikman:2005ze}.

We demonstrate that study of large t vector meson photoproduction with rapidity gaps in ultraperipheral proton-ion and ion-ion collisions at LHC would allow to investigate the energy dependence of cross section of elastic scattering of a small dipole off the parton over a wide range of energies $10^3 < s_{dipole - parton} < 10^6 GeV^2$ where this cross section is expected to change by a factor $\ge 20$. The accessible energy range exceeds the one reached at HERA by a factor of 10 both in $\gamma p$ and in $\gamma A$ scattering. In addition, study of A-dependence of this process will allow to determine the t range where interaction of small dipoles gives the dominant contribution and to investigate effects of absorption for the propagation of ultrarelativistic small $q\bar q$ dipoles through the nuclear media and probe in a novel way onset of the BDR\cite{Frankfurt:2006wg}.

\begin{thebibliography}{99}

\bibitem{Frankfurt:2001db}
  L.~Frankfurt, M.~Strikman and M.~Zhalov,
  %``Fading out of J/psi color transparency in high energy heavy ion  peripheral
  %collisions,''
  Phys.\ Lett.\ B {\bf 540}, 220 (2002)
  [arXiv:hep-ph/0111221].
\bibitem{Frankfurt:2002wc}
  L.~Frankfurt, M.~Strikman and M.~Zhalov,
  %``Signals for black body limit in coherent ultraperipheral heavy ion
  %collisions,''
  Phys.\ Lett.\ B {\bf 537}, 51 (2002)
  [arXiv:hep-ph/0204175].
  \bibitem{Frankfurt:2003qy}
  L.~Frankfurt, V.~Guzey, M.~Strikman and M.~Zhalov,
  %``Onset of perturbative color opacity at small x and Upsilon coherent
  %photoproduction off heavy nuclei at LHC,''
  JHEP {\bf 0308}, 043 (2003)
  [arXiv:hep-ph/0304218].
  \bibitem{Frankfurt:2006tp}
  L.~Frankfurt, M.~Strikman and M.~Zhalov,
  %``Elastic and large t rapidity gap vector meson production in
  %ultraperipheral proton ion collisions,''
  Phys.\ Lett.\ B {\bf 640}, 162 (2006)
  [arXiv:hep-ph/0605160].
  \bibitem{Strikman:2005ze}
  M.~Strikman, M.~Tverskoy and M.~Zhalov,
  %``Neutron tagging of quasielastic J/psi photoproduction off nucleus in
  %ultraperipheral heavy ion collisions at RHIC energies,''
  Phys.\ Lett.\ B {\bf 626}, 72 (2005)
  [arXiv:hep-ph/0505023].
  \bibitem{Frankfurt:2006wg}
  L.~Frankfurt, M.~Strikman and M.~Zhalov,
  %``Large t diffractive rho-meson photoproduction with target dissociation in
  %ultraperipheral p A and A A collisions at LHC,''
  arXiv:hep-ph/0612072.
 
      \end{thebibliography}

  
  
\end{document}