Dark matter interpretations of ATLAS searches for the electroweak production of supersymmetric particles in s = 8 $$ \sqrt{s}=8 $$ TeV proton-proton collisions

Abstract

A selection of searches by the ATLAS experiment at the LHC for the electroweak production of SUSY particles are used to study their impact on the constraints on dark matter candidates. The searches use 20 fb −1 of proton-proton collision data at √ s = 8 TeV. A likelihood-driven scan of a five-dimensional effective model focusing on the gaugino-higgsino and Higgs sector of the phenomenological minimal supersymmetric Standard Model is performed. This scan uses data from direct dark matter detection experiments, the relic dark matter density and precision flavour physics results. Further constraints from the ATLAS Higgs mass measurement and SUSY searches at LEP are also applied. A subset of models selected from this scan are used to assess the impact of the selected ATLAS searches in this five-dimensional parameter space. These ATLAS searches substantially impact those models for which the mass m(χ 0 1 ) of the lightest neutralino is less than 65 GeV, excluding 86% of such models. The searches have limited impact on models with larger m(χ 0 1 ) due to either heavy electroweakinos or compressed mass spectra where the mass splittings between the produced particles and the lightest supersymmetric particle is small. 4 Signal simulation and evaluation of ATLAS constraints 10 5 Impact of the ATLAS electroweak SUSY searches 12 5.1 Impact on the electroweakino masses 12 5.2 Impact on the EWKH model parameters 13 5.3 Impact on dark matter observables 14 Conclusions 19The ATLAS collaboration 27 IntroductionSupersymmetry, or SUSY [1][2][3][4][5][6], is a popular candidate for physics beyond the Standard Model. It provides an elegant solution to the hierarchy problem, which, in the Standard Model, demands high levels of fine tuning to counteract large quantum corrections to the mass of the Higgs boson [7][8][9][10]. R-parity-conserving supersymmetric models can also provide a candidate for dark matter, in the form of the lightest supersymmetric particle (LSP) [11,12]. The ATLAS and CMS experiments performed a large number of searches for SUSY during Run-1 of the LHC and, in the absence of a significant excess in any channel, exclusion limits on the masses of SUSY particles (sparticles) were calculated in numerous scenarios, usually in the context of the minimal supersymmetric Standard Model (MSSM) [13,14]. These scenarios include "high-scale" SUSY models such as mSUGRA [15][16][17] or GMSB [18][19][20], both of which specify a particular SUSY-breaking mechanism. Most searches also considered specific "simplified models", which attempt to capture the behaviour of a small number of kinematically accessible SUSY particles, often through considering one particular SUSY production process with a fixed decay chain.Although the high-scale and simplified model exclusions provide an easily interpretable picture of the sensitivity of analyses to specific areas of parameter space, they are far from -1 - JHEP09(2016)175a full exploration of the MSSM, which contains about 120 free parameters. The number of parameters is reduced i...

Probing compressed mass spectra in electroweak supersymmetry with Recursive Jigsaw Reconstruction

“…Herein, one assumes the lightest neutralino is the LSP and focuses on cases with small mass difference between it and theχ ± 1 and/orχ 0 2 . Compressed scenarios involving electroweakinos have been studied in detail elsewhere in the literature [12][13][14][15][16][17][18], and they are common in supersymmetric theory. For example, in naturalness-inspired models [19], the higgsino components are light, hence extremely small mass splittings are expected for the lower eigenstates of mass of higgsino-like charginos and neutralinos.…”

Electroweak and Higgs boson internal bremsstrahlung. General considerations for Majorana dark matter annihilation and application to MSSM neutralinos

“…Another advantage is that the WIMP hypothesis can be tested in multiple ways: at colliders, where the signature consists in missing energy, in direct detection experiments aiming to observe DM particles recoiling off the nuclei of deep underground detectors, and in indirect searches for the debris of DM annihilation in cosmic regions with large DM densities. Direct detection experiments have become extremely competitive in constraining smaller and smaller scattering rates [5,6], and collider searches have pushed the scale of new physics to TeV energies in many popular models [7,8]. It is worth stressing, however, that only 'indirect' searches would eventually allow to test the WIMP DM hypothesis in situ, i.e.…”

“…As an application, we consider electroweak corrections to the annihilation cross section of the lightest supersymmetric neutralino -one of the most often discussed DM prototypes [28] and still a leading candidate despite null searches for supersymmetry at ever higher energies and luminosities at the LHC [7,8] -though our main findings can be extended in an analogous way to other DM candidates that couple to the SM via the electroweak or Higgs sector. Concretely, we provide a comprehensive analysis, both analytically and numerically, of all 3-body final states from neutralino annihilation that contain a fermion pair and either an electroweak gauge boson or one of the five Higgs bosons contained in the minimal supersymmetric standard model (MSSM), for a neutralino that can be an arbitrary admixture of Wino, Bino and Higgsino.…”

Analysing parameter space correlations of recent 13 TeV gluino and squark searches in the pMSSM

“…However, its sensitivity is greatly altered in richer dark sectors of the pMSSM, shaped by the composition of the neutralinoχ 0 1 lightest SUSY particle (LSP) [68][69][70][71][72] being dominantly bino, Higgsino or wino (defined in Table 2 of Appendix A.1). Furthermore, studies of neutralino DM often combine exclusions of multiple analyses [48,53] or only focus on the electroweakino sector [52,[73][74][75], omitting potentially important coannihilation roles of other sparticles. Section 2 addresses question (a) by directly correlating the most sensitive of the six analyses considered with the masses of the gluino, LSP and lightest squark.…”