HELICITY AMPLITUDES FOR COLLIDING BEAM SCATTERING OF 2 SPIN 1 2 PARTICLES/

As a generalization and extension of the extensive tables of polarizat ion asymmetries given in a previous work,1 we present here tables of h elicity amplitudes for the scattering of two spin 1/2 particles in the colliding beam system (i.e. two incoming particles with opposite dire ctions but not necessarily of equal momenta). The particles belonging to the same current may have different masses in order to describe par ticle excitations. The amplitudes are given for six different basic co uplings connecting two vector vertices, a vector vertex at the one cur rent and a derivative vector vertex at the other current, two derivati ve vector vertices, two tensor vertices, and two scalar vertices. The vertices include axial couplings by factors of type 1 + cgamma5. The a mplitudes are written as expressions with 16 components in the six dif ferent reaction channels, namely the scattering of two fermions, of tw o antifermions, and of a fermion and an antifermion, the pair creation by pair annihilation, as well as the exchange scattering for two iden tical fermions or antifermions. The formulas may be used for an analys is which extracts the invariant coupling functions from the experiment al data obtained in the colliding beam system directly without an inte rmediate transformation to the center of mass system.