40 research outputs found

    CP-odd observables in neutralino production with transverse e+ and e- beam polarization

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    We consider neutralino production and decay e^+e^ --> chi^0_i chi^0_j, chi^0_j --> chi^0_1 f \bar{f} at a linear collider with transverse e^+ and e^- beam polarization. We propose CP asymmetries by means of the azimuthal distribution of the produced neutralinos and of that of the final leptons, while taking also into account the subsequent decays of the neutralinos. We include the complete spin correlations between production and decay. Our framework is the Minimal Supersymmetric Standard Model with complex parameters. In a numerical study we show that there are good prospects to observe these CP asymmetries at the International Linear Collider and estimate the accuracy expected for the determination of the phases in the neutralino sector.Comment: 30 pages, minor changes in the introduction, references adde

    Towards Measuring the Stop Mixing Angle at the LHC

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    We address the question of how to determine the stop mixing angle and its CP-violating phase at the LHC. As an observable we discuss ratios of branching ratios for different decay modes of the light stop ~t_1 to charginos and neutralinos. These observables can have a very strong dependence on the parameters of the stop sector. We discuss in detail the origin of these effects. Using various combinations of the ratios of branching ratios we argue that, depending on the scenario, the observable may be promising in exposing the light stop mass, the mixing angle and the CP phase. This will, however, require a good knowledge of the supersymmetric spectrum, which is likely to be achievable only in combination with results from a linear collider.Comment: 30 pages, 11 figures, version to appear in EPJ

    Towards discrimination of MSSM and NMSSM scenarios at colliders

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    One of the challenging tasks at future experiments is the clear identification of the underlying new physics model. In this study we concentrate on the distinction between different supersymmetric models, the MSSM and the NMSSM, exploring the gaugino/higgsino sector as an alternative to the Higgs sector. Under the assumption that only the light chargino and neutralino masses and polarized cross sections e+eχ~i0χ~j0e^+e^-\to \tilde{\chi}^0_i\tilde{\chi}^0_j, χ~i+χ~j\tilde{\chi}^+_i\tilde{\chi}^-_j have been measured, we perform a fit of the fundamental MSSM parameters M1M_1, M2M_2, μ\mu and tanβ\tan\beta and study whether a model distinction is possible. We focus here on the challenging cases of scenarios with a relatively heavy singlino and address two classes of neutralino mixing, χ~10\tilde{\chi}^0_1\simhiggsino-like versus χ~10\tilde{\chi}^0_1\simgaugino-like
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