Speaker
Aleksander Filip Zarnecki
(University of Warsaw)
Description
The exclusive photoproduction reaction $\gamma p \to \psi(2S) p$ 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$^2$ - the photon virtuality and t – four-momentum transfer at the proton vertex. The $\psi(2S)$ mesons were identified via the decay channels: $\psi(2S) \to \mu^+\mu^-$ and $J/\psi \pi^+\pi^-$ with $J/\psi \to \mu^+\mu^-$. 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.
Authors
Matthew Wing
(University College London)
Aleksander Filip Zarnecki
(University of Warsaw)
Grzegorz Grzelak
