Recent ATLAS data significantly extend the exclusion limits for supersymmetric particles. We examine the impact of such data on global fits of the constrained minimal supersymmetric standard model (CMSSM) to indirect and cosmological data. We calculate the likelihood map of the ATLAS search, taking into account systematic errors on the signal and on the background. We validate our calculation against the ATLAS determinaton of 95% confidence level exclusion contours. A previous CMSSM global fit is then re-weighted by the likelihood map, which takes a bite at the high probability density region of the global fit, pushing scalar and gaugino masses up.
We study to which extent SUSY extensions of the Standard Model can describe the excess of events of 3.0 standard deviations observed by ATLAS in the on-Z signal region, respecting constraints by CMS on similar signal channels as well as constraints from searches for jets and E^{miss}_T. GMSB-like scenarios are typically in conflict with these constraints, and do not reproduce well the shape of the E^{miss}_T distribution of the data. An alternative scenario with two massive neutralinos can improve fits to the total number of events as well as to the H_T and E^{miss}_T distributions. Such a scenario can be realised within the NMSSM.
This work explores the potential reach of the 7 TeV LHC to new colored states in the context of simplified models and addresses the issue of which search regions are necessary to cover an extensive set of event topologies and kinematic regimes. This article demonstrates that if searches are designed to focus on specific regions of phase space, then new physics may be missed if it lies in unexpected corners. Simple multiregion search strategies can be designed to cover all of kinematic possibilities. A set of benchmark models are created that cover the qualitatively different signatures and a benchmark multiregion search strategy is presented that covers these models.
We perform a systematic study of sneutrino production and decays in the Minimal Supersymmetric Standard Model (MSSM) with slepton generation mixing. We study bosonic decays like sneutrino to slepton^- + W^+/H^+ as well as fermionic ones. We show that the effect of slepton generation mixing on the sneutrino production and decays can be quite large in a significant part of the MSSM parameter space despite the very strong experimental limits on lepton flavour violating processes. This could have an important impact on the search for sneutrinos and the determination of the MSSM parameters at future colliders, such as LHC, ILC, CLIC and muon collider.
Recently ATLAS reported a $3.3sigma$ excess in the stop search with $ell+jets+E_T^{miss}$ channel. We try to interpret the signal by a light stop pair production in the MSSM. We find: (1) simple models where stop decays into a higgsino or a bino are not favored. (2) an extension of them can explain the data at $2sigma$ level without conflicting with the other search channels. A surviving possibility includes a light stop and a light higgsino, which is expected in a natural SUSY scenario.
We propose a rigorous and effective way to compare experimental and theoretical histograms, incorporating the different sources of statistical and systematic uncertainties. This is a useful tool to extract as much information as possible from the comparison between experimental data with theoretical simulations, optimizing the chances of identifying New Physics at the LHC. We illustrate this by showing how a search in the CMSSM parameter space, using Bayesian techniques, can effectively find the correct values of the CMSSM parameters by comparing histograms of events with multijets + missing transverse momentum displayed in the effective-mass variable. The procedure is in fact very efficient to identify the true supersymmetric model, in the case supersymmetry is really there and accessible to the LHC.
B.C. Allanach
,T.J. Khoo
,C.G. Lester
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(2011)
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"The impact of the ATLAS zero-lepton, jets and missing momentum search on a CMSSM fit"
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Ben Allanach PhD
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