Spin correlations in production and decay of charginos

Abstract.

We study the production of charginos $e^+ e^- \to\tilde{\chi}^{+}_i\tilde{\chi}^{-}_j, (i,j=1,2)$ with polarized beams and the subsequent decays $\tilde{\chi}^{+}_{i} \to \tilde{\chi}^0_k \ell^{+}\nu_\ell$ and $\tilde{\chi}^{-}_{j} \to \tilde{\chi}^0_l \ell^{-}\bar{\nu}_\ell, (k,l=1,\ldots,4)$, including the complete spin correlations between production and decay. Analytical formulae are presented for the joint spin-density matrix of the charginos, for the chargino decay matrix and for the differential cross section of the combined processes of production and decays. We present numerical results for pair production of the lighter chargino with unpolarized beams and the leptonic decay of $\tilde{\chi}_1^-$ into the lightest neutralino $\tilde{\chi}^0_1$. The lepton angular distribution and the forward-backward asymmetry are studied in four representative scenarios for $\sqrt{s}=192$ GeV and $\sqrt{s}=200$ GeV.