Contact interaction probes at the Linear Collider with polarized electron and positron beams

For contact-interaction searches at the Linear Collider, we discuss the advantages of polarizing both the electron and the positron beams as compared with polarizing only the electron beam. In particular, for the processes e+e−→μ+μ−, τ+τ−, bb̄ and cc̄ at a future e+e− collider with s=0.5 TeV we derive model-independent bounds on the four-fermion contact interaction parameters from studies of the helicity cross sections.