Spin Correlations in Production and Decay of Charginos

Abstract

We study the production of charginos e^+ e^- -> chi^+_i chi^-_j, (i,j=1,2) with polarized beams and the subsequent decays chi^+_i -> chi^0_k ell^+ nu and chi^-_j -> chi^0_l ell^- nu, (k,l=1,...,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 chi^+_1 into the lightest neutralino 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.

20 pages, 13 postscript figures, latex using epsf.sty; misprints in (12),(61),(82) corrected, minor changes in text and in some numerical results; version to appear in Eur.Phys.J.C