Speaker
Description
A first measurement is presented of exclusive photoproduction of ρ0 mesons associated with leading neutrons at HERA. The data were taken with the H1 detector at a centre-of-mass energy of sqrt(s)=319 GeV and correspond to an integrated luminosity of 1.16 pb−1. The ρ mesons are reconstructed from their decays to charged pions, the neutrons are detected in the Forward Neutron Calorimeter. The photon virtuality is limited to Q²<2 GeV², the total energy of the photon-proton system 20<W<100 GeV and the polar angle of the leading neutron θ<0.75 mrad. The cross section of the reaction γp→ρnπ is measured as a function of several variables. The data are interpreted in terms of a double peripheral process. In the framework of one-pion-exchange dominance the elastic cross section of photon-pion scattering is also extracted. The observed value indicates significant absorptive corrections for the exclusive reaction γp→ρ0nπ+.
