The properties of a single-peripheral model of the Deck effect are presented as a proto-type diffraction-dissociation process, using $\pi N\to \pi \rho N$ as an example. The $\pi -\rho$ mass spectrum, angular distributions, and the $N-N$ momentum-transfer distribution are investigated. We evaluate the effects on these distributions due to three major components of the model, namely, the dissociation vertex, the propagation, and the diffraction scattering of the virtual particle. It is found that many "expected" properties (usually derived for asymptotic energies) of the diffraction-dissociation process do not obtain at finite energies. In particular, there is considerably more structure in the momentum-transfer and angular distributions. The mass dependence in the momentum-transfer slope found by others is reproduced in this model. Structure in the angular distributions is seen to imply some uncertainty over tests of helicity conservation for $A_1$ production. The peak in the mass spectrum (the Deck effect) is found to have an undesirable dependence on incident momentum. This difficulty is traced to the presence of spin in the model. Explicit numerical calculations and qualitative considerations lead us to believe that many Reggeized calculations of the Deck effect share the same difficulty. Their prediction of a sharp and $s$-independent peak is unjustified due to neglect of external spin.

Close

PrevNext

View figure in article