Chr. Geweniger

PION PRODUCTION WITH POLARIZED PHOTONS AND TEST OF VECTOR DOMINANCE MODEL.

Abstract Cross section asymmetries for the sum of single π+ and π- production with polarized photons of 3.4 GeV have been measured. The results disagree with calculations based on the vector dominance model using experimental data of vector meson production in π beams.

π+ production with linearly polarized photons

Abstract Single π+ production on protons by linearly polarized photons of 2.5 to 5 GeV was measured at squared four momentum transfers t between −0.01 and −0.6 (GeV/c)2. The results show that the differential cross section d σ ⊥ d t with the electric vector of the photon perpendicular to the reaction plane is much larger than d σ ‖ d t with the electric vector parallel to the reaction plane. The predictions of Regge models and of the vector meson dominance model are briefly discussed.

Small momentum transfer π+ production with linearly polarized photons

Abstract Previous measurements of the cross section asymmetry for single π + production on protons with linearly polarized photons of 3.4 GeV have been extended to momentum transfers within the forward peak, i.e. − = 0.0026, 0.006 and 0.01 (GeV/ c ) 2 . The results are in good agreement with pion exchange models.

MEASUREMENT OF PROTON COMPTON SCATTERING AT 6 GeV AND SMALL MOMENTUM TRANSFERS.

Abstract Compton scattering on protons has been measured at a mean photon energy of 6 GeV and four-momentum transfers − t between 0.06 and 0.60 (GeV/ c ) 2 . The differential cross section shows a diffraction-like behaviour. The cross section extrapolated to t =0 is in fair agreement with the optical point. Discrepancies with the vector meson dominance model are pointed out.

π− production with linearly polarized photons at 3.4 GeV

Abstract The asymmetry of the reaction γ d π − p ( p S ) with linearly polarized photons has been measured at 3.4 GeV and momentum transfers √− t between 0.2 and 0.8 GeV/ c . As in π + production, the asymmetry is large and positive at small momentum transfers but drops rapidly with increasing √− t , crossing zero around √− t = 0.55 GeV/ c .