Photoproduction at HERA detecting a scattered proton with the H1 forward proton spectrometer

140 pp. (1997).
In this thesis the measurement of the differential semi-inclusive cross section in Photoproduction with a leading proton is presented. The data were taken 1995 using the H1 detector at the HERA $ep$ storage ring, the corresponding integrated Luminosity is $\mathcal{L}$ = $2.05 pb^{-1}$. Protons were measured in the energy range of $580 GeV < E_{p\prime} < 740 GeV$ having a transverse momentum of $p\bot < 200MeV/c$. The cross section $d\sigma(\gamma p \to X p \prime)$/$dE_{p\prime}$, was calculated at $< W >$ = $$ = $90, 187 and 231 GeV$. The detection of leading protons with the H1 Forward Proton Spectometer (FPS) was possible for the first time in 1995. The FPS consists of two detector stations at 81 and 90 m and the proton magnets located between these stations and the interaction vertex. Using the measured proton track and the known beam optics, the proton energy $E_{p\prime}$ and the scattering angle $\vartheta_p \prime$, at vertex position are reconstructed. The resolution is $\Delta E_p \prime$ = $2 - 6 GeV, \Delta \vartheta_x$ = $5 - 10 \mu rad$ and $\Delta \vartheta_y$ = $5 - 100 \mu rad$ depending on the other quantities at a time. These values meet the design requirements.The selection efficiency and acceptance as well as corrections used for the cross section measurement are calculated. The differential cross section is of the order of $7 nb/GeV$ and does within errors not depend on $E_p \prime$ and $< W >$. A Regge fit shows the data to be compatible with $\pi^\circ$ exchange. To get information about the contribution from hard Photoproduction 2-jet events have been selected using a cone algorithm. The 2-jet cross section is of the order of $140 pb/GeV$. A comparison with predictions of the POMPYT model shows that the jet data can be described by Pion and Pomeron exchange within the Regge picture.