LHC-7 supersymmetry search interpretation within the phenomenological MSSM

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.

“…The pMSSM has been studied in the past using random scans [6][7][8], as well as Bayesian methods [9][10][11][12]. Both approaches have limitations.…”

Section: Jhep09(2014)081mentioning

confidence: 99%

Profile likelihood maps of a 15-dimensional MSSM

Strege

Bertone

Besjes

et al. 2014

“…Several groups have advocated the use of the pMSSM for interpretation of LHC results [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52]. Most of these studies use estimated experimental efficiencies and acceptances for pMSSM points, and compare them to the model-independent limits from a selection of LHC searches to constrain the pMSSM parameter space.…”

Section: Jhep10(2015)134mentioning

confidence: 99%

Summary of the ATLAS experiment’s sensitivity to supersymmetry after LHC Run 1 — interpreted in the phenomenological MSSM

Aad

Bergeås

Brenner

et al. 2015

100

169

A summary of the constraints from the ATLAS experiment on R-parityconserving supersymmetry is presented. Results from 22 separate ATLAS searches are considered, each based on analysis of up to 20.3 fb −1 of proton-proton collision data at centre-of-mass energies of √ s = 7 and 8 TeV at the Large Hadron Collider. The results are interpreted in the context of the 19-parameter phenomenological minimal supersymmetric standard model, in which the lightest supersymmetric particle is a neutralino, taking into account constraints from previous precision electroweak and flavour measurements as well as from dark matter related measurements. The results are presented in terms of constraints on supersymmetric particle masses and are compared to limits from simplified models. The impact of ATLAS searches on parameters such as the dark matter relic density, the couplings of the observed Higgs boson, and the degree of electroweak fine-tuning is also shown. Spectra for surviving supersymmetry model points with low fine-tunings are presented. The ATLAS collaboration 58 Keywords: Hadron-Hadron Scattering IntroductionDuring the first run of the Large Hadron Collider (LHC), the ATLAS [1] and CMS [2] Collaborations performed a wide range of searches for supersymmetry (SUSY) [3][4][5][6][7][8][9][10][11], using proton-proton (pp) collision data at centre-of-mass energies ( √ s) of 7 and 8 TeV. SUSY, a theoretically favoured framework for extending the Standard Model (SM), is able to address some of its unanswered questions, particularly the hierarchy problem [12][13][14][15], which is related to the fine-tuning needed to obtain the correct mass for the observed Higgs boson. SUSY can also provide credible dark matter candidates [16,17] and can improve the unification of the electroweak and strong interactions [18][19][20][21][22][23][24][25][26].The minimal supersymmetric extension of the Standard Model (MSSM) [27][28][29][30][31] predicts partners for each of the SM states. It predicts a pair of scalar partners -one for each fermion chirality -for each of the SM quarks and leptons. These spin-zero partner particles are known as squarks (q) and sleptons (˜ ) respectively. In the first two generations the pair of chiral partners is largely unmixed, so the mass states can be labelledẽ L andẽ R , where the L and R subscripts denote the scalar partners of the left-and right-handed Standard Model fermion states respectively. In the third generation of quarks and leptons the mixing between the scalars is larger, and the mixed states are labelled by their mass indices e.g.t 1 and t 2 , wheret 1 is lighter by construction. Each state in the SM gluon colour octet has a spinhalf partner known as a gluinog. There are a total of eight spin-half partners of the electroweak gauge and Higgs bosons: the neutral bino (superpartner of the U(1) gauge field); the winos, which are a charged pair and a neutral particle (superpartners of the W bosons of the SU(2) L gauge fields); and the Higgsinos, which are two neutral particles and a charged pai...

“…However, from the latest global fit of pMSSM after the LHC results [60] (see also ref. [97,98] for an earlier global fit of pMSSM), the corresponding lower limit on squark mass is m q 500 GeV, and hence, we use this value to constrain our pMSSM parameter space.…”

Section: Jhep06(2013)113mentioning

confidence: 99%

Naturalness of light neutralino dark matter in pMSSM after LHC, XENON100 and Planck data

Bœhm

Dev²,

Mazumdar³

et al. 2013

Abstract:We examine the possibility of a light (below 46 GeV) neutralino dark matter (DM) candidate within the 19-parameter phenomenological Minimal Supersymmetric Standard Model (pMSSM) in the light of various recent experimental results, especially from the LHC, XENON100, and Planck. We also study the extent of electroweak fine-tuning for such a light neutralino scenario in view of the null results from the searches for supersymmetry so far. Using a Markov Chain Monte Carlo likelihood analysis of the full pMSSM parameter space, we find that a neutralino DM with mass 10 GeV can in principle still satisfy all the existing constraints. Our light neutralino solutions can be broadly divided into two regions: (i) The solutions in the 10-30 GeV neutralino mass range are highly finetuned and require the existence of light selectrons (below 100 GeV) in order to satisfy the observed DM relic density. We note that these are not yet conclusively ruled out by the existing LEP/LHC results, and a dedicated analysis valid for a non-unified gaugino mass spectrum is required to exclude this possibility. (ii) The solutions with low fine-tuning are mainly in the 30-46 GeV neutralino mass range. However, a major portion of it is already ruled out by the latest XENON100 upper limits on its spin-independent direct detection cross section, and the rest of the allowed points are within the XENON1T projected limit. Thus, we show that the allowed MSSM parameter space for a light neutralino DM below the LEP limit of 46 GeV, possible in supersymmetric models without gaugino mass unification, could be completely accessible in near future. This might be useful in view of the recent claims for positive hints of a DM signal in some direct detection experiments.