Reconstructing the chargino and neutralino systems at linear colliders

In most supersymmetric theories, charginos χ tildei± (i=1-2) and neutralinos χ tildei0 (i=1-4) are within the reach of future linear colliders. By measuring the total cross sections and the asymmetries with polarized beams in e+e- → χ tildei+ χ tildej- [i, j=1, 2], the chargino masses and the gaugino-higgsino mixing angles of these states can be determined very accurately. If only the lightest charginos χ tilde1± are kinematically accessible, transverse beam polarization is needed to determine the mixing angles unambiguously. From these observables the SU(2) gaugino mass M2, the modulus and the cosine of the CP-violating phase of the higgsino mass parameter μ, and than β=v2/v1, can be derived. Supposed that the chargino system has already been reconstructed through chargino production, the U(1) gaugino mass M1 also can be unambiguously by measuring three neutralino masses or two neutralino masses and one neutralino pair production cross section. In addition, the threshold behavior of the excitation curves of neutralino pair production enables us to investigate CP violation in the neutralino system. The sum rules for the couplings at asymptotic energies enable us to check the closure of two-chargino and four-neutralino systems in the minimal supersymmetric extension of the standard model. (author)