A NEW METHOD FOR HELICITY CALCULATIONS

We propose a new helicity formalism based on the insertion in spinor l ines of a complete set of states built up with appropriate unphysical spinors, which are eigenstates of ($) over bar p, where p is the momen tum flowing in a fermion propagator. The corresponding eigenvalues can be real (p(2) > 0) or imaginary (p(2) < 0). The method is developed b oth for massless and massive fermions for which it turns out to be par ticularly fast. All relevant formulae are given.