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We consider NLO chargino production and decays at the ILC. For this, we present an NLO extension of the Monte Carlo Event Generator Whizard including the NLO production. For photonic corrections, we use both a fixed order and a resummation approach. The latter method evades the problem of negative event weights and automatically includes leading higher order corrections. We present results for cross sections and event generation for both methods. As a first step towards a full NLO Monte Carlo, we consider a LO implementation of the chargino production and subsequent leptonic decay and investigate the precision of the sneutrino mass determination by means of lepton energy distributions in chargino decays. The SM and SUSY backgrounds are included in our study using full matrix elements as well as smearing effects from ISR and beamstrahlung. Without using energy distribution fits, the sneutrino mass can be determined with an error in the percent regime.
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We discuss the pair production of charginos in collisions of polarized photons $gammagamma to tilde{chi}_i^+ tilde{chi}_i^-$, ($i=1,2$) and the subsequent leptonic decay of the lighter chargino $tilde{chi}_1^+ to tilde{chi}_1^0 e^+ u_e$ including the complete spin correlations. Analytical formulae are given for the polarization and the spin-spin correlations of the charginos. Since the production is a pure QED process the decay dynamics can be studied separately. For high energy photons from Compton backscattering of polarized laser pulses off polarized electron beams numerical results are presented for the cross section, the angular distribution and the forward-backward asymmetry of the decay positron. Finally we study the dependence on the gaugino mass parameter $M_1$ and on the sneutrino mass for a gaugino-like MSSM scenario.
We study CP violation in chargino production and decay in the Minimal Supersymmetric Standard Model (MSSM) with complex parameters at an e^+ e^- linear collider with longitudinally polarized beams. We investigate CP-sensitive asymmetries by means of triple product correlations and study their dependence on the complex parameters M_1 and mu. We give numerical predictions for the asymmetries and their measurability at the future International Linear Collider. Our results show that the CP asymmetries can be measured in a large region of the MSSM parameter space.
A Monte-Carlo analysis on production and decay of supersymmetric charginos at a future photon-collider is presented. A photon collider offers the possibility of a direct branching-ratio measurement. In this study, the process gamma,gamma -> chi_1^+,chi_1^- -> W+W-chi_1^0chi_1^0 -> 4-jets,chi_1^0chi_1^0 has been considered for a specific mSUGRA scenario. Various backgrounds and parameterised detector simulation have been included. Depending on the centre-of-mass energy, a statistical error for the directly measurable branching ratio BR(chi}_1^+ ->chi}_1^0 W^+) of up to 3.5% can be reached.
Previously, in the context of the minimal supersymmetric standard model (without {em a priori} assumptions of parameter unification), we studied the constraints on weak-scale SUSY parameters from chargino production at LEP II, using as observables $mch$, $mLSP$, the cross section and the leptonic branching fraction. Here, exploiting the high degree of polarization in chargino production, we add to our earlier work the forward-backward asymmetries of the visible hadrons and leptons in chargino decays. For a chargino that is mostly gaugino, the parameter space can now be restricted to a small region; $tanb$ is constrained, the soft electroweak gaugino and electron sneutrino masses are determined to about 10%, and the sign of $mu$ may be determined. Constraints for a chargino that is mostly Higgsino are much weaker, but still disfavor the hypothesis that the chargino is mostly gaugino. For a chargino which is a roughly equal mixture of Higgsino and gaugino, we find intermediate results.
We study chargino pair production on the heavy Higgs resonances at a muon collider in the MSSM. At $sqrt{s} approx 350$ GeV cross sections up to 2 pb are reached depending on the supersymmetric scenario and the beam energy spread. The resonances of the scalar and pseudoscalar Higgs bosons may be separated for $tanbeta <8$. Our aim is to determine the ratio of the chargino couplings to the heavy scalar and pseudoscalar Higgs boson independently of the specific chargino decay characteristics. The precision of the measurement depends on the energy resolution of the muon collider and on the error in the measurement of the cross sections of the non-Higgs channels including an irreducible standard model background. With a high energy resolution the systematic error can be reduced to the order of a few percent.
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