70 research outputs found

    Refining light stop exclusion limits with W+Wβˆ’W^+W^- cross sections

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    If light supersymmetric top (stop) quarks are produced at the LHC and decay via on- or off-shell WW-bosons they can be expected to contribute to a precision W+Wβˆ’W^+W^- cross section measurement. Using the latest results of the CMS experiment, we revisit constraints on the stop quark production and find that this measurement can exclude portions of the parameter space not probed by dedicated searches. In particular we can exclude light top squarks up to 230~GeV along the line separating three- and four-body decays, t~1β†’Ο‡~10W(βˆ—)b\tilde{t}_1 \to \tilde{\chi}_1^0 W^{(*)} b. We also study the exclusion limits in the case when the branching ratio for these decays is reduced and we show significant improvement over previously existing limits.Comment: 5 pages, 2 figures; references updated, minor changes; to appear in Phys. Lett.

    Can R-parity violation hide vanilla supersymmetry at the LHC?

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    Current experimental constraints on a large parameter space in supersymmetric models rely on the large missing energy signature. This is usually provided by the lightest neutralino which stability is ensured by the R-parity. However, if the R-parity is violated, the lightest neutralino decays into the standard model particles and the missing energy cut is not efficient anymore. In particular, the UDD type R-parity violation induces the neutralino decay to three quarks which potentially leads to the most difficult signal to be searched at hadron colliders. In this paper, we study the constraints on the R-parity violating supersymmetric model using a same-sign dilepton and a multijet signatures. We show that the gluino and squarks lighter than a TeV are already excluded in constrained minimal supersymmetric standard model with R-parity violation if their masses are approximately equal. We also analyze constraints in a simplified model with R-parity violation. We compare how R-parity violation changes some of the observables typically used to distinguish a supersymmetric signal from standard model backgrounds.Comment: 14 pages, 4 figure

    Neutralinos betray their singlino nature at the ILC

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    It is one of the most challenging tasks at the Large Hadron Collider and at a future Linear Collider not only to observe physics beyond the Standard Model, but to clearly identify the underlying new physics model. In this paper we concentrate on the distinction between two different supersymmetric models, the MSSM and the NMSSM, as they can lead to similar low energy spectra. The NMSSM adds a singlet superfield to the MSSM particle spectrum and simplifies embedding a SM-like Higgs candidate with the measured mass of about 125.5 GeV. In parts of the parameter space the Higgs sector itself does not provide sufficient indications for the underlying model. We show that exploring the gaugino/higgsino sectors could provide a meaningful way to distinguish the two models. Assuming that only the lightest chargino and neutralino masses and polarized cross sections e+eβˆ’β†’Ο‡~i0Ο‡~j0e^+e^-\to \tilde{\chi}^0_i\tilde{\chi}^0_j, Ο‡~i+Ο‡~jβˆ’\tilde{\chi}^+_i\tilde{\chi}^-_j are accessible at the linear collider, we reconstruct the fundamental MSSM parameters M1M_1, M2M_2, ΞΌ\mu, tan⁑β\tan\beta and study whether a unique model distinction is possible based on this restricted information. Depending on the singlino admixture in the lightest neutralino states, as well as their higgsino or gaugino nature, we define several classes of scenarios and study the prospects of experimental differentiation.Comment: 20 pages, 11 figure
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