Spin Correlations in Production and Subsequent Decay of Neutralinos

Abstract

We study the process e^{-} e^{+} -> chi^0_1 chi^0_2 with the subsequent decay chi^0_2 -> chi^0_1 l^{+} l^{-} taking into account the complete spin correlations. We give the analytical formulae for the differential cross section and present numerical results for the lepton angular distribution and the distribution of the opening angle between the outgoing leptons for the LEP2 energy of sqrt{s}=193 GeV and for sqrt{s}=500 GeV. We examine three representative mixing scenarios in the MSSM and also study the influence of the common scalar mass parameter m_0 on the shape of the distributions. For the lepton angular distribution the effect of the spin correlations amounts to up to 20% for lower energies. We find that the opening angle distribution is suitable for distinguishing between higgsino-like and gaugino-like neutralinos. The shape of the lepton angular distribution is very sensitive to the mixing in the gaugino sector and to the value of m_0. For higher energies it is also suitable for distinguishing between higgsino-like and gaugino-like neutralino.