Understanding amplitudes from an s-channel approach

Abstract

The systematics of inelastic two-body reactions at high energies is discussed on the basis of a geometrical s-channel approach which we proposed recently. The amplitudes are given in terms of an asymptotically universal s-(and u-) channel trajectory representating the peripheral resonances. Its imaginary part is responsible for the amount of shrink-age, its real part for the structure in differential cross sections, polarizations and density matrix elements. An approximation, valid for |t| ⪆ 0.25 ( GeV/c) 2 , allows for a very simple, qualitative understanding of these structures in a large sample of reactions. The predictions are confronted with many experimental examples, among these the amplitude analysis for π −p→ π°n at 6 GeV/ c. The agreement is good in all cases. As characteristic features for |t| ⪆ 0.25 ( GeV/c) 2 emerge a certain universality of inelastic reactions and the regularity of all structures with −t instead of − t.