# ICHEP 2010

22-28 July 2010
Palais des Congrès de Paris
Europe/Paris timezone

## Exclusive Processes at HERA

23 Jul 2010, 11:20
25m
Salle 252B ()

### Salle 252B

Parallel Session Talk 03 - Perturbative QCD, Jets and Diffractive Physics

### Speaker

Armen Bunyatyan (DESY)

### Description

Diffractive cross sections of electroproduction of rho and phi mesons is measured at HERA with the H1 detector in the elastic and proton dissociative channels. The data correspond to an integrated luminosity of 51 pb^-1. Based on data collected with the H1 detector at HERA in 2005, cross sections or elastic rho photoproduction have been measured at momentum transfer |t| < 0.58 GeV^2 and photon-proton center-of-mass energies 20 < W < 90 GeV. This data has been combined with cross sections published previously by the Omega and ZEUS collaborations in a global fit to determine the pomeron trajectory alpha(t) in 13 bins of t by from the W-dependence of the elastic rho production cross section. Exclusive diffractive photoproduction of J/psi mesons is measured with the H1 detector at the electron-proton collider HERA. At the end of the HERA operation in 2007 the nominal proton beam energy was reduced from 920 GeV to 575 and 460 GeV, respectively. The reduced proton beam energy allows diffractive J/psi measurements in an extended phase space towards lower photon-proton centre of mass energies W_gammap. Differential cross sections are presented as a function of t, the squared four-momentum transfer at the proton vertex, and of W_gammap in the kinematical range of low photon virtualities of Q^2 < 2.5 GeV^2. The exclusive photoproduction reaction gamma p -> Upsilon p has been studied with the ZEUS detector in ep collisions at HERA using an integrated luminosity of 468 pb-1. The measurement covers the kinematic range 60 < W < 220 GeV and Q^2 < 1 GeV^2, where W is the photon-proton centre-of-mass energy and Q^2 is the photon virtuality. The gamma-p cross section for Upsilon photoproduction is presented as a function of W and |t|, where t is negative transverse momentum square at the proton vertex. These results, which represent the analysis of the full ZEUS data sample for dimuon decay channel, are compared to predictions based on perturbative QCD. The proton-dissociative diffractive photoproduction of J/psi mesons has been studied in ep collisions with the ZEUS detector at HERA using an integrated luminosity of 112 pb. The cross section is presented as a function of the photon-proton centre-of-mass energy and of the squared four-momentum transfer at the proton vertex. The results are compared to perturbative QCD calculations. The J/Psi decay angular distributions have been measured in inelastic photoproduction in ep collisions with the ZEUS detector at HERA, using an integrated luminosity of 468 pb-1. The range in photon-proton centre-of-mass energy, W, was 50 < W < 180 GeV. The J/Psi mesons were identied through their decays into muon pairs. The polar and azimuthal angles of the muon+ were measured in the J/Psi rest frame and compared to theoretical predictions at leading and next-to-leading order in QCD.

### Primary authors

Dr Katja Krueger (DESY/Heidelberg) Dr Tobias Haas (DESY)

 Slides