| Popis: |
The European Muon Collaboration reports that in exclusive ϱ 0 production in deep-inelastic muon scattering from hydrogen and nitrogen targets, the ϱ 0 is found predominately in a longitudinally polarised state. The t -dependence is typical of a hard scattering process. The ϱ 0 's are claimed to be mainly produced by transverse photons. The cross section decreases as ( Q 2 ) −2 . While the latter is expected in a vector dominance model, the dominance of helicity flip is inconsistent with such a model. We show that it is possible to reconcile these experimental results in a simple hard scattering model. However, we must suppose the photons mainly longitudinal, in agreement with Donnachie and Landshoff. |
