Model-independent limits on four-fermion contact interactions at LC with polarization

Fermion compositeness, and other types of new physics that can be described by the exchange of very massive particles, can manifest themselves as the result of an effective four-fermion contact interaction. In the case of the processes e+e− → μ+μ−, τ+τ−, b̄b and c̄c at future e+e− colliders with √s = 0.5 − 1 TeV, we examine the sensitivity to four-fermion contact interactions of two new integrated observables, σ+ and σ−, conveniently defined for such kind of analysis. We find that, if longitudinal polarization of the electron beam were available, these observables would offer the opportunity to separate the helicity cross sections and, in this way, to derive model-independent bounds on the relevant parameters. Permanent address: Department of Physics, Polytechnical Institute, Gomel, 246746 Belarus. E-mail: [email protected] Also supported by the Italian Ministry of University, Scientific Research and Technology (MURST).