PROJECTION SCHEME FOR HANDLING LARGE-NUMBER CANCELLATION RELATED TO GAUGE-INVARIANCE

A scheme, the so-called ''projection,'' for handling singularities in processes such as e(+)e(-) --> t(b) over bare$(-)<(nu)over bar> (or e( +)e(-) --> u(d) over bare$(-)<(nu)over bar>) is proposed. In the schem e, with the help of gauge invariance, the large power quantities (s/m( e)(2))(n) (n greater than or equal to 1; s --> infinity) are removed f rom the calculation totally, while in the usual schemes the large quan tities appear and only will be canceled at last. The advantages of the scheme in numerical calculations are obvious; thus, we focus our disc ussions mainly on the advantages of the scheme in the special case whe re the absorptive part for some propagators relevant to the process co uld not be ignored, and a not satisfactory but widely adopted approxim ation is made; i.e., a finite constant ''width'' is introduced to appr oximate the absorptive part of the propagators phenomenologically even though QED gauge invariance is violated.