Inclusive spin–momentum analysis and new physics at a polarized electron–positron collider

We consider the momentum distribution and the polarization of an inclusive heavy fermion in a process assumed to arise from standard-model (SM) s-channel exchange of a virtual $$\gamma $$ or Z with a further contribution from physics beyond the standard model involving s-channel exchanges. The interference of the new-physics amplitude with the SM $$\gamma $$ or Z exchange amplitude is expressed entirely in terms of the space-time signature of such new physics. Transverse as well as longitudinal polarizations of the electron and positron beams are taken into account. Similarly, we consider the cases of the polarization of the observed final-state fermion along longitudinal and two transverse spin-quantization axes, which are required for a full reconstruction of the spin dependence of the process. We show how these model-independent distributions can be used to deduce some general properties of the nature of the interaction and some of their properties in prior work which made use of spin–momentum correlations