Speaker
Aleksander Zarnecki
(University of Warsaw (PL))
Description
The exclusive photoproduction reaction $\gamma p -> \psi(2S) p$ has been studied with the ZEUS detector in $ep$ collisions at HERA using an integrated luminosity of 350 pb$^{-1}$, in the kinematic range 30 $< W <$ 180 GeV, $Q^2$ < 1 GeV$^2$, $|t|$ < 5 GeV$^2$, where $W$ is the photon proton centre-of-mass energy, $Q^2$ is the photon virtuality and t is the four-momentum transfer at the proton vertex. The $\psi(2S)$ mesons were identified via the decay channels: $\psi(2S) -> \mu^+\mu^-$ and $J/\psi \pi^+\pi^-$ with $J/\psi -> \mu^+\mu^-$. The ratio of the production cross sections $R = \sigma(\psi(2S)) / \sigma(J/\psi)$ was measured as a function of $W$ and compared to predictions of the perturbative QCD.
Author
Aleksander Zarnecki
(University of Warsaw (PL))
