Impact of e^+ and e^- Beam Polarization on Chargino and Neutralino Production at a Linear Collider

Abstract

We study the production processes e^+ e^- -> chi^+_i chi^-_j, i,j=1,2, and e^+ e^- -> chi^0_m chi^0_n, m,n=1,...,4, working out the advantages of polarizing both beams. For e^+ e^- -> chi^+_1 chi^-_1 with chi^-_1 -> chi^0_1 e^- nu and e^+ e^- -> chi^0_1 chi^0_2 with chi^0_2 -> chi^0_1 e^+ e^- we perform a detailed analysis, including the complete spin correlations between production and decay. We analyze the forward--backward asymmetry of the decay electron for various beam polarizations. We also study polarization asymmetries in e^+ e^- -> chi^0_1 chi^0_2. These asymmetries strongly constrain the gaugino parameter M_1 and the masses m_{\tilde{e}_L}, m_{\tilde{e}_R}, m_{\tilde{nu}} also if m_{\tilde{e}_{L,R}}, m_{\tilde{nu}} > sqrt{s}/2. We give numerical predictions for three scenarios for a linear collider with sqrt{s}=500-1000 GeV.