Multiple exchange and high-energy fixed-angle scattering

Abstract

For fcrmion-fermion elastic scattering with Abelian vector-gluon exchanges, some progress has recently been made in understanding the high-energy fixed-angle behaviour. CANDY (1) conjectured that, for generalized ladder exchanges, a suitable (( e ikonal , ansatz should give the correct leading asymptotic behaviour. In a subsequent work (2), the assumptions made by CARDY on what should be the dominant large-momentum flow were shown to be correct, order by order. A consequence of this ~( eikonalization ~) is that important cancellations take place between the leading contributions of ordinary ladder graphs and those of crossed ladder graphs. As a result of such cancellations, in the leading logarithm approximation, the dominant contribution to the sum of all graphs of a given order in the coupling constant g is due to vertex corrections to onegluon exchange. In the leading logarithm summation (LLS) to all orders in g, one then expects a behaviour, for the elastic-scattering amplitude ~#(s, 0) as s ~ oo with fixed centre-of-mass scattering angle 0,