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Proton-Positron Scattering at HERA-DESY Dr. Maurício Barbi McGill University The hadronic final state of events observed in Deep Inelastic Nucleon-Lepton Scattering is well described by models based on Quantum Chromodynamics (QCD). The struck quark and the proton remnant evolve into a system of gluons and partons which fragments into hadrons. However some peripherical processes are not taken into account in such models. The meson exchange is one of such processes where the incoming proton fluctuates into a state of a baryon and a meson. We study the process where the proton transforms into a neutron by emitting a pion which may interact with the incoming positron. The data used for this analysis corresponds to 3 inverse picobars collected in ZEUS experiment during the Spring 1999. A forward neutron calorimeter and a forward neutron tracker, FNC and FNT, are installed in a such way that allows to identify very energy neutrons at very small angles with good energy and position resolution. The neutron transverse momentum is measured and the slope of the distribution is obtained. This allows to test the different parametrisation models for one pion exchange.
Thursday, May 11th 2000, 15:30 |