We explore the potential of a e+e- linear collider to disentangle
new physics scenarios on μ+ μ- - pair production. R-parity violation
and extensions of the Standard Model gauge structure offer two
non-minimal realizations ofsupersymmetry at low energies that can
lead to similar new physics signatures at e+ e- linear collider. We
discuss the center-edge asymmetry which is useful for discriminating
amongst these two new physics scenarios.

A method of studying target mass effects based on the Jost-Lehmann-Dyson integral representation for structure functions of the inelastic lepton-hadron scattering is elaborated. It is shown that, in accordance with general principles of local quantum field theory, expressions obtained for the physical structure functions depending on the target mass have a correct spectral property.