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Elastic and inelastic φ photoproduction
Authors:H.-J. Behrend  J. Bodenkamp  W.P. Hesse  W.A. McNeely  T. Miyachi  D.C. Fries  P. Heine  H. Hirschmann  A. Markou  E. Seitz
Affiliation:1. Institut für Kernphysik des Kernforschungszentrum, Germany;2. Institut für Experimentelle Kernphysik der Universität Karlsruhe, Germany
Abstract:The differential cross section of the reaction (γp → pφ) has been measured in the t range 0 ? t ? 0.4 GeV2 and for photon energies from 3.0 to 6.7 GeV. In particular for the small t region the measurement accuracy was better than 10%. We obtained for the slope parameter B in an exponential parametrization of the differential cross section dσ/dt = Ae?Bt values of B ? 6 ± 0.5 GeV?2 which are significantly larger than the slopes obtained by most other experiments at higher t values. This indicates a t dependence of B particularly in the small t region.An energy dependence of the optical point (dσ/dt)t=0, observed in our measurements, has been explained as a kinematic effect due to the VDM relation. A fit of our measurements is in excellent agreement with all other published values of (dσ/dt)t=0(γp → φp), this implies that σtot(φp) must be essentially energy independent in this energy range.Spin density matrix elements of the φ have been evaluated and an analysis of the helicity amplitudes has been carried out. This analysis confirmed s-channel helicity conservation. Moments of spherical harmonics of the KK angular decay distribution have been computed for 10 MeV KK mass-bins from threshold to 1.3 GeV. The mass dependence of the normalized moments is generally smooth. Contributing amplitudes have essentially only even moments. The moment 〈Y20〉/〈Y00〉 changes sign above the φ mass.Differential cross sections for the inelastic φ production γp → φX have been evaluated for the first time both with respect to t?tmin and MK. The integrated inelastic cross sections are comparable in size with the elastic ones. The slopes of the differential cross sections dσ/dt appear to become flatter with increasing MX.
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