Abstract
We present statistically convergent profile likelihood maps obtained via global fits of a phenomenological Minimal Supersymmetric Standard Model with 15 free parameters (the MSSM-15), based on over 250M points. We derive constraints on the model parameters from direct detection limits on dark matter, the Planck relic density measurement and data from accelerator searches. We provide a detailed analysis of the rich phenomenology of this model, and determine the SUSY mass spectrum and dark matter properties that are preferred by current experimental constraints. We evaluate the impact of the measurement of the anomalous magnetic moment of the muon (g − 2) on our results, and provide an analysis of scenarios in which the lightest neutralino is a subdominant component of the dark matter. The MSSM-15 parameters are relatively weakly constrained by current data sets, with the exception of the parameters related to dark matter phenomenology (M 1, M 2, μ), which are restricted to the sub-TeV regime, mainly due to the relic density constraint. The mass of the lightest neutralino is found to be < 1.5 TeV at 99% C.L., but can extend up to 3 TeV when excluding the g − 2 constraint from the analysis. Low-mass bino-like neutralinos are strongly favoured, with spin-independent scattering cross-sections extending to very small values, ~ 10−20 pb. ATLAS SUSY null searches strongly impact on this mass range, and thus rule out a region of parameter space that is outside the reach of any current or future direct detection experiment. The best-fit point obtained after inclusion of all data corresponds to a squark mass of 2.3 TeV, a gluino mass of 2.1 TeV and a 130 GeV neutralino with a spin-independent cross-section of 2.4 × 10−10 pb, which is within the reach of future multi-ton scale direct detection experiments and of the upcoming LHC run at increased centre-of-mass energy.
Highlights
T√he Large Hadron Collider (LHC) has delivered ∼ 20 fb−1 of integrated luminosity at s = 8 TeV, but evidence for new physics beyond the Standard Model (SM) is still lacking.In particular, the data contain no signature of Supersymmetry (SUSY), which is the most widely studied theory of physics beyond the SM, as it may offer a solution to the hierarchy problem and to the dark matter problem of the universe
This is motivated by the present lack of experimental evidence for SUSY: while highly constrained models as the constrained MSSM (cMSSM) are under pressure in the light of the recent negative sparticle searches at the LHC, there is no experimental indication that one requires the full freedom of the 19-dimensional phenomenological MSSM (pMSSM) at present
We present results for an analysis excluding the g − 2 constraint, in order to evaluate the impact of this controversial measurement on our profile likelihood results
Summary
If one applies a concrete mechanism that mediates SUSY breaking to the observable sector, the number of parameters can be reduced significantly This is for instance the case for models like the constrained MSSM (cMSSM) in which one demands universal scalar masses, gaugino masses and the trilinear couplings at a high energy scale. One exception is the focus point region where the weak scale is insensitive to variations in these parameters This region is becoming increasingly constrained by direct dark matter searches, such as the XENON100 and LUX experiments. We adopt a Bayesian approach to scanning (using a full likelihood function and an algorithm that generates samples from the posterior distribution), but derive profile likelihood maps — which are in principle prior-independent — for a more robust statistical interpretation. We describe our approach to approximating the likelihood for ATLAS 0-lepton and 3-lepton inclusive searches, and we demonstrate the statistical convergence of our profile likelihood maps
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