Measurement of the Elastic ρ-meson Photoproduction Cross Section using the Forward Proton Spectrometer at the H1 Detector at HERA DISSERTATION

A measurement of the elastic ρ-meson photoproduction cross section is presented. The data are collected by the H1 experiment in scattering of electrons off protons at the HERA collider in January–April 1999. In the current analysis the absolute value of the proton momentum transfer at the proton vertex |t| is measured by the horizontal stations of the Forward Proton Spectrometer (FPS) which have started stable operation in January 1999. The FPS horizontal stations cover the kinematic region of low proton momentum transfer t. The cross section of elastic ρ-meson photoproduction is measured in the following kinematic region: 1) proton momentum transfer of 0.08 ≤ |t| ≤ 0.38 GeV , 2) γ p centre of mass energy W of 20 < W < 78 GeV (inelasticity y kinematic range of 0.004 < y < 0.06), 3) ρ decay pions invariant mass Mππ interval of 0.5 < Mππ < 1.1 GeV . The logarithmical slope parameter of the differential cross section dσ/dt is found to be: b = 10.11± 1.54 (stat.)± 1.25 (syst.) GeV −2. The observed γp → ρp cross section value extrapolated to the full kinematic region, is found to be: σγ p → ρo p = 9.88± 0.93 (stat.) ± 1.30 (syst.) μb.