We present an update of a search for supersymmetry in final states containing jets, missing transverse momentum, and one isolated electron or muon, using 1.04 fb^-1 of proton-proton collision data at sqrt{s} = 7 TeV recorded by the ATLAS experiment at the LHC in the first half of 2011. The analysis is carried out in four distinct signal regions with either three or four jets and variations on the (missing) transverse momentum cuts, resulting in optimized limits for various supersymmetry models. No excess above the standard model background expectation is observed. Limits are set on the visible cross-section of new physics within the kinematic requirements of the search. The results are interpreted as limits on the parameters of the minimal supergravity framework, limits on cross-sections of simplified models with specific squark and gluino decay modes, and limits on parameters of a model with bilinear R-parity violation.
Missing transverse energy after requiring one electron with pT>25 GeV, at least three jets with pT>60,25,25 GeV and dphi(jets,Etmiss)>0.2.
Missing transverse energy after requiring one muon with pT>20 GeV, at least three jets with pT>60,25,25 GeV and dphi(jets,Etmiss)>0.2.
Transverse mass after requiring one electron with pT>25 GeV, at least three jets with pT>60,25,25 GeV and dphi(jets,Etmiss)>0.2.
Results of a search for the electroweak associated production of charginos and next-to-lightest neutralinos, pairs of charginos or pairs of tau sleptons are presented. These processes are characterised by final states with at least two hadronically decaying tau leptons, missing transverse momentum and low jet activity. The analysis is based on an integrated luminosity of 20.3 fb$^{-1}$ of proton--proton collisions at $\sqrt{s}=8$ TeV recorded with the ATLAS experiment at the Large Hadron Collider. No significant excess is observed with respect to the predictions from Standard Model processes. Limits are set at 95% confidence level on the masses of the lighter chargino and next-to-lightest neutralino for various hypotheses for the lightest neutralino mass in simplified models. In the scenario of direct production of chargino pairs, with each chargino decaying into the lightest neutralino via an intermediate tau slepton, chargino masses up to 345 GeV are excluded for a massless lightest neutralino. For associated production of mass-degenerate charginos and next-to-lightest neutralinos, both decaying into the lightest neutralino via an intermediate tau slepton, masses up to 410 GeV are excluded for a massless lightest neutralino.
The stransverse mass distribution in the multi-jet CR-C1N2.
Mt(tau1)+Mt(tau2) distribution in the multi-jet CR C1C1.
Effective mass distribution in the multi-jet CR DS-highMass.
A search is presented for direct chargino production based on a disappearing-track signature using 20.3 fb-1 of proton-proton collisions at sqrt(s) = 8 TeV collected with the ATLAS experiment at the LHC. In anomaly-mediated supersymmetry breaking (AMSB) models, the lightest chargino is nearly mass-degenerate with the lightest neutralino and its lifetime is long enough to be detected in the tracking detectors by identifying decays that result in tracks with no associated hits in the outer region of the tracking system. Some models with supersymmetry also predict charginos with a significant lifetime. This analysis attains sensitivity for charginos with a lifetime between 0.1 ns and 10 ns, and significantly surpasses the reach of the LEP experiments. No significant excess above the background expectation is observed for candidate tracks with large transverse momentum, and constraints on chargino properties are obtained. In the AMSB scenarios, a chargino mass below 270 GeV is excluded at 95% confidence level.
The pT distribution of disappearing-track candidates.
Observed CLs contour in the ( M(CHARGINO), TAU(CHARGINO) ) space for tan(beta) = 5 and mu > 0.
Observed CLs contour with minus 1-sigma signal cross-section uncertainty in the ( M(CHARGINO), TAU(CHARGINO) ) space for tan(beta) = 5 and mu > 0.
Results from a search for supersymmetry in events with four or more leptons including electrons, muons and taus are presented. The analysis uses a data sample corresponding to 20.3 $fb^{-1}$ of proton--proton collisions delivered by the Large Hadron Collider at $\sqrt{s}$ = 8 TeV and recorded by the ATLAS detector. Signal regions are designed to target supersymmetric scenarios that can be either enriched in or depleted of events involving the production of a $Z$ boson. No significant deviations are observed in data from Standard Model predictions and results are used to set upper limits on the event yields from processes beyond the Standard Model. Exclusion limits at the 95% confidence level on the masses of relevant supersymmetric particles are obtained. In R-parity-violating simplified models with decays of the lightest supersymmetric particle to electrons and muons, limits of 1350 GeV and 750 GeV are placed on gluino and chargino masses, respectively. In R-parity-conserving simplified models with heavy neutralinos decaying to a massless lightest supersymmetric particle, heavy neutralino masses up to 620 GeV are excluded. Limits are also placed on other supersymmetric scenarios.
The ETmiss distribution in VR0Z.
The effective mass distribution in VR0Z.
The ETmiss distribution in VR2Z.
This letter reports the results of a search for top and bottom squarks from gluino pair production in 4.7 fb^-1 of pp collisions at sqrt(s) = 7 TeV using the ATLAS detector at the LHC. The search is performed in events with large missing transverse momentum and at least three jets identified as originating from a b-quark. Exclusion limits are presented for a variety of gluino-mediated models with gluino masses up to 1 TeV excluded.
Figure 2-a. Observed limit +1sigma-th.
Figure 2-a. Observed limit.
Figure 2-a. Observed limit -1sigma-th.
A search for diphoton events with large missing transverse momentum has been performed using proton-proton collision data at sqrt(s) = 7 TeV recorded with the ATLAS detector, corresponding to an integrated luminosity of 4.8 fb^-1. No excess of events was observed above the Standard Model prediction and model-dependent 95% confidence level exclusion limits are set. In the context of a generalised model of gauge-mediated supersymmetry breaking with a bino-like lightest neutralino of mass above 50 GeV, gluinos (squarks) below 1.07 TeV (0.87 TeV) are excluded, while a breaking scale Lambda below 196 TeV is excluded for a minimal model of gauge-mediated supersymmetry breaking. For a specific model with one universal extra dimension, compactification scales 1/R < 1.40 TeV are excluded. These limits provide the most stringent tests of these models to date.
Observeded limit on gluino mass as function of LSP mass for the GGM model.
Limit on squark mass as function of LSP mass for the GGM model.
Cross section limit for the SPS8 model.
Searches for heavy long-lived charged particles are performed using a data sample of 19.8 fb$^{-1}$ from proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 8 TeV collected by the ATLAS detector at the Large Hadron Collider. No excess is observed above the estimated background and limits are placed on the mass of long-lived particles in various supersymmetric models. Long-lived tau sleptons in models with gauge-mediated symmetry breaking are excluded up to masses between 440 and 385 GeV for $\tan\beta$ between 10 and 50, with a 290 GeV limit in the case where only direct tau slepton production is considered. In the context of simplified LeptoSUSY models, where sleptons are stable and have a mass of 300 GeV, squark and gluino masses are excluded up to a mass of 1500 and 1360 GeV, respectively. Directly produced charginos, in simplified models where they are nearly degenerate to the lightest neutralino, are excluded up to a mass of 620 GeV. $R$-hadrons, composites containing a gluino, bottom squark or top squark, are excluded up to a mass of 1270, 845 and 900 GeV, respectively, using the full detector; and up to a mass of 1260, 835 and 870 GeV using an approach disregarding information from the muon spectrometer.
Observed data, background estimate and expected signal in the slepton search for the lower of the two masses ($m$) in the two-candidate signal region (GMSB: $\tilde{\tau}_1$ masses of 344.5 and 437 GeV).
Observed data, background estimate and expected signal in the slepton search for the lower of the two masses ($m$) in the two-candidate signal region (GMSB: $\tilde{\tau}_1$ masses of 344.5 and 437 GeV).
Observed data, background estimate and expected signal in the slepton search for the one-candidate signal region (LeptoSUSY: $m_{\tilde q}$ = 2.0, 1.2 and 0.9 TeV with $m_{\tilde g}$ = 1.2 TeV).
This paper reviews and extends searches for the direct pair production of the scalar supersymmetric partners of the top and bottom quarks in proton-proton collisions collected by the ATLAS collaboration during the LHC Run 1. Most of the analyses use 20 fb$^{-1}$ of collisions at a centre-of-mass energy of $\sqrt{s}$ = 8 TeV, although in some case an additional 4.7 fb$^{-1}$ of collision data at $\sqrt{s}$ = 7 TeV are used. New analyses are introduced to improve the sensitivity to specific regions of the model parameter space. Since no evidence of third-generation squarks is found, exclusion limits are derived by combining several analyses and are presented in both a simplified model framework, assuming simple decay chains, as well as within the context of more elaborate phenomenological supersymmetric models.
Summary of the ATLAS Run 1 searches for direct stop pair production in models where no supersymmetric particle other than the $\tilde t_1$ and the $\tilde \chi_1^0$ is involved in the $\tilde t_1$ decay. Lines for $\Delta m(\tilde t_1, \chi_1^0 ) > m_{t}$ - t0L/t1L combined observed limit hepdata.cedar.ac.uk/view/ins1380183/d63 - t0L/t1L combined expected limit hepdata.cedar.ac.uk/view/ins1380183/d64 - t2L observed limit hepdata.cedar.ac.uk/view/ins1286444/d19 - t2L expected limit hepdata.cedar.ac.uk/view/ins1286444/d20 - SC observed limit $m_t< m_{\tilde t_1} < 198$ GeV - SC expected limit $m_t< m_{\tilde t_1} < 184$ GeV Lines for $m_b + m_W < \Delta m(\tilde t_1, \chi_1^0 ) < m_{t}$ - t1L observed limit hepdata.cedar.ac.uk/view/ins1304456/d22 - t1L expected limit hepdata.cedar.ac.uk/view/ins1304456/d23 - t2L observed limit hepdata.cedar.ac.uk/view/ins1286444/d22 - t2L expected limit hepdata.cedar.ac.uk/view/ins1286444/d23 - WW observed limit hepdata.cedar.ac.uk/view/ins1380183/d47 - WW expected limit hepdata.cedar.ac.uk/view/ins1380183/d48 Lines for $0 < \Delta m(\tilde t_1, \chi_1^0 ) < m_b + m_W $ - tc observed limit hepdata.cedar.ac.uk/view/ins1304459 (root macro) - tc expected limit hepdata.cedar.ac.uk/view/ins1304459 (root macro) - t1L observed limit hepdata.cedar.ac.uk/view/ins1304456/d22 - t1L expected limit hepdata.cedar.ac.uk/view/ins1304456/d23 - WW observed limit hepdata.cedar.ac.uk/view/ins1380183/d47 - WW expected limit hepdata.cedar.ac.uk/view/ins1380183/d48.
Upper limits on the stop pair production cross sections for different values of the branching ratios for the decays $\tilde{t}_1 \rightarrow c\tilde{\chi}_1^0$ and $\tilde{t}_1 \rightarrow ff'b\tilde{\chi}_1^0$, where BR$(\tilde{t}_1 \rightarrow c\tilde{\chi}_1^0)$ + BR$(\tilde{t}_1 \rightarrow ff'b\tilde{\chi}_1^0)$ = 1. Signal points with $\Delta m (\tilde{t}_1, \tilde{\chi}_1^0)$ of 10 GeV are shown. The limits quoted are taken from the best performing, based on expected exclusion CLs, signal regions from the tc-M, tc-C, t1L-bCa_low and WW analyses at each mass point. - Theoretical cross section from twiki.cern.ch/twiki/bin/view/LHCPhysics/SUSYCrossSections8TeVstopsbottom.
Upper limits on the stop pair production cross sections for different values of the branching ratios for the decays $\tilde{t}_1 \rightarrow c\tilde{\chi}_1^0$ and $\tilde{t}_1 \rightarrow ff'b\tilde{\chi}_1^0$, where BR$(\tilde{t}_1 \rightarrow c\tilde{\chi}_1^0)$ + BR$(\tilde{t}_1 \rightarrow ff'b\tilde{\chi}_1^0)$ = 1. Signal points with $\Delta m (\tilde{t}_1, \tilde{\chi}_1^0)$ of 80 GeV are shown. The limits quoted are taken from the best performing, based on expected exclusion CLs, signal regions from the tc-M, tc-C, t1L-bCa_low and WW analyses at each mass point. - Theoretical cross section from twiki.cern.ch/twiki/bin/view/LHCPhysics/SUSYCrossSections8TeVstopsbottom.
The ATLAS experiment has performed extensive searches for the electroweak production of charginos, neutralinos and staus. This article summarizes and extends the search for electroweak supersymmetry with new analyses targeting scenarios not covered by previously published searches. New searches use vector-boson fusion production, initial-state radiation jets, and low-momentum lepton final states, as well as multivariate analysis techniques to improve the sensitivity to scenarios with small mass splittings and low-production cross-sections. Results are based on 20 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}$=8 TeV recorded with the ATLAS experiment at the Large Hadron Collider. No significant excess beyond Standard Model expectations is observed. The new and existing searches are combined and interpreted in terms of 95% confidence-level exclusion limits in simplified models, where a single production process and decay mode is assumed, as well as within phenomenological supersymmetric models.
The missing transverse momentum ETmiss in the multi-jet validation region VR1 for the two-tau MVA analysis.
The effective mass meff in the multi-jet validation region VR2 for the two-tau MVA analysis.
The stransverse mass mT2 in the W+jets validation region VR1 for the two-tau MVA analysis.
Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. This article presents the results of a search for events containing at least one long-lived particle that decays at a significant distance from its production point into two leptons or into five or more charged particles. This analysis uses a data sample of proton-proton collisions at $\sqrt{s}$ = 8 TeV corresponding to an integrated luminosity of 20.3 fb$^{-1}$ collected in 2012 by the ATLAS detector operating at the Large Hadron Collider. No events are observed in any of the signal regions, and limits are set on model parameters within supersymmetric scenarios involving R-parity violation, split supersymmetry, and gauge mediation. In some of the search channels, the trigger and search strategy are based only on the decay products of individual long-lived particles, irrespective of the rest of the event. In these cases, the provided limits can easily be reinterpreted in different scenarios.
Vertex-level efficiency as a function of the vertex radial position for an RPV SUSY model of squark production with $\tilde{q}\to q[\tilde{\chi}_1^0\to\mu qq]$, where $m(\tilde{q}) = 700$ GeV, $m(\tilde{\chi}_1^0) = 494$ GeV and $c\tau(\tilde{\chi}_1^0)$ = 175 mm. This result is also represented in Figure 3b and Auxiliary Figure 1.
Vertex-level efficiency as a function of the vertex radial position for an RPV SUSY model of squark production with $\tilde{q}\to q[\tilde{\chi}_1^0\to\mu qq]$, where $m(\tilde{q}) = 700$ GeV, $m(\tilde{\chi}_1^0) = 108$ GeV and $c\tau(\tilde{\chi}_1^0)$ = 101 mm.
Vertex-level efficiency as a function of the vertex radial position for an RPV SUSY model of squark production with $\tilde{q}\to q[\tilde{\chi}_1^0\to\mu qb]$, where $m(\tilde{q}) = 700$ GeV, $m(\tilde{\chi}_1^0) = 494$ GeV and $c\tau(\tilde{\chi}_1^0)$ = 175 mm. The other SUSY model point in the figure is tabulated in http://hepdata.cedar.ac.uk/view/ins1362183/d1.
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