The Hunt for Supersymmetry at the Tevatron

During the Tevatron data-taking period from April 2001 to Se ptember 2011 (Run-II), several searches for supersymmetric particles w re performed. The results from searches by the CDF and DØ collaborations are concisely revi ew d. This includes results up to the summer conferences of 2013. Model-independent and mo del-dependent limits on new particle production are set, and interpretations in supers ymmetric models are given. Several limits from the Large Electron Positron (LEP) era have been e xtended. Specific results are placed into the context of the Tevatron performance expecta tions and a few of the current results from searches at the Large Hadron Collider (LHC).


Introduction
The search for supersymmetric particles was pioneered at the Super Proton Synchrotron (SPS) and Large Electron Positron (LEP) colliders at CERN (Conseil Européen pour la Recherche Nucléaire) and has been extensively advanced at the Tevatron (chiefly Run-II with data taken 2001-2011).A wide range of analyses is presented, illustrating major improvements in the analysis sensitivities.This review is not inclusive of all searches for supersymmetric particles, but rather, is intended to give an overview of several important results and relating them to the underlying theoretical framework.For details of specific experimental analysis techniques and the event selections of the individual search channels, the reader is referred to the publications by the CDF and DØ collaborations.After the first few years of data-taking with rather low instantaneous luminosity, the Tevatron collider achieved significantly higher collision rates in the second half of Run-II.The total delivered luminosity is about 12 fb −1 , of which about 10 fb −1 were recorded by each experiment.Figure 1 [1] shows the delivered Run-II luminosity between 2001 and 2011.The discovery of a supersymmetric particle would extend the Standard Model (SM) of particle physics and lead the way to a new level of understanding of the fundamental elements of our Universe.
Supersymmetric particle searches at the Tevatron are reviewed for di-photon signatures in the gauge-mediated supersymmetry breaking (GMSB) interpretation (Section 2.1), tri-lepton signatures (Section 2.2), gluinos and scalar quarks (Section 2.3), scalar tops (Section 2.4), scalar bottoms (Section 2.5) and charged massive particles (Section 2.6).In Section 3, first, LHC results [2] are compared with the Tevatron results, and a brief outlook is given.An overview of the reviewed analyses is given in the Appendix A.

Supersymmetric Particle Searches at the Tevatron
In the production of supersymmetric particles (sparticles), the lightest supersymmetric particle (LSP) is stable (if the so-called R-parity is conserved) and escapes detection, leading to missing momentum and missing energy in the recorded events.Examples of such events are shown in Figure 2 [3][4][5].The events reported by the DØ and CDF collaborations have jets and large missing energy (for DØ [3,4], large H T is defined as the sum of the transverse jet momenta, and for CDF [5], it is defined as the sum of the transverse jet energies).
Previous combined results from the LEP experiments have set limits on several sparticles with masses close to the kinematic reach.Figure 3 [6] shows the excluded region in the tan β versus LSP mass plane in the Minimal Supersymmetric extentions of the Standard Model (MSSM) and in the Gauge Mediated Symmetry Breaking (GMSB) model.The position in the GMSB parameter space of an intriguing CDF eeγγ candidate from the Tevatron Run-I is indicated (dashed line) [7].The GMSB interpretation for this event was later excluded at 95% Confidence Level (CL) by the LEP experiments.[6]; (b) Combined LEP exclusion in the (selectron mass, neutralino mass) plane from acoplanar photon searches [6].The CDF Run-I eeγγ candidate event is indicated in the excluded region [7].In the GMSB model, chargino-neutralino production has been searched for by the CDF and DØ collaborations.In the GMSB model, the lightest neutralino, χ0 1 , is the Next-to-Lightest Supersymmetric Particle (NLSP) and decays to a gravitino, G, and a photon.In this model, the LSP is the gravitino, which is a very light and weakly interacting particle.The production reaction is illustrated in Figure 4.The expected signal can be well separated from the background events [8].There is no indication of a signal in the early data, and combined limits on the chargino mass from CDF [9] and DØ [8] were given [10].Large progress has been made in recent years, and the results using 6.3 fb −1 for DØ and 2.6 fb −1 for CDF are shown in Figures 5 [11] and 6 [12].The experimental sensitivity on the production cross-section at 95% CL is now, below 7 fb.As a result, in the SPS8 (Snowmass Points and Slopes, parameters in scenario 8) benchmark, the DØ collaboration excluded an effective Supersymmetry breaking scale below 124 TeV at 95% CL, as well as the lightest neutralino and lightest chargino masses below 175 GeV and 330 GeV, respectively.A search for a long-lived particle that decays into a pair of photons resulted in a 95% CL lower mass limit of 101 GeV on the lightest neutralino at a 5-ns lifetime [13].Recently, updated results for searches for massive, long-lived particles that decay to photons in the exclusive photon and missing energy final state have been reported by the CDF collaboration [14].Figure 7 shows a simulated signal and the experimental measurement.No indication of a signal is observed.

Tri-Lepton Signatures
The sparticle production with a tri-lepton final state is illustrated in Figure 8.This scenario is called "Supersymmetry golden mode" because of the small expected background level.As an example, Figure 9a shows early results for the µµℓ final state [15][16][17][18].Furthermore, the other tri-lepton final states (eµℓ, eeℓ, eτ, µτ ) were studied.Good agreement between data and simulated background for the various final states with tri-lepton signatures was observed.The data does not show any indication of a supersymmetric signal above the background.
With increasing luminosities, the expectations from 2005 for the chargino mass reach were 170, 210, 235 and 265 GeV with one, two, four and 8 fb −1 , respectively, for a scenario with a maximal leptonic branching ratio, as shown in Figure 9b [19].
Examples of the updated DØ results with 2.3 fb −1 are shown in Figure 10 [20] and CDF results in Figure 11 [21,22].With 5.8 fb −1 CDF data, a chargino mass below 168 GeV is excluded at 95% CL in the minimal SUperGRAvity (mSUGRA) model.The CDF collaboration also searched for final states involving tau leptons.Results from these searches are shown in Figures 12 and 13 [23,24].[20].(a) The upper limit at the 95% CL on σ × BR(3ℓ) as a function of the χ± 1 mass from the tri-lepton searches and expectations for two Supersymmetry scenarios (3ℓ-max and large m 0 ); (b) The region in the m 0 -m 1/2 plane excluded by the combination of the DØ analyses (green), by LEP searches for charginos (light grey) and sleptons (dark grey) [6] and CDF searches based on 2.0 fb −1 data (black line) [21,22].The assumed mSUGRA parameters are tan β = 3, A 0 = 0 and µ > 0; (c) The upper limit at the 95% CL on σ × BR(3ℓ) as a function of tan β and a prediction for a chargino mass of 130 GeV with m τ − m χ0 2 = 1 GeV.

Gluinos and Scalar Quarks
Depending on the masses of squarks and gluinos, either qq , gg or qg could be produced.For gluinos heavier than squarks, squark pair-production dominates, leading to a signature of two acoplanar jets and missing energy from the escaping neutralino.If the squarks are heavier than the gluinos, gluino pair-production is expected, leading to four or more jets.If both masses are about equal, squark-gluino production is expected.Figure 14 [25] shows a summary of the production cross-sections for different reactions involving supersymmetric particles.The mass range for a cross-section of about 1 pb is largest for scalar quark pair-production.The figure also shows the mass limits from early results with 0.3 fb −1 [3,4] and sensitivity expectations for two, four and 8 fb −1 luminosity per experiment [19].
These expectations are compared to the results from analyses with higher data statistics.Results from DØ with 2.1 fb −1 are shown in Figures 15-17 [26], and results from CDF with 2.0 fb −1 are shown in Figures 18 and 19 [27].For both experiments, the achieved sensitivity for gluino masses is about 300 GeV at 95% CL for large squark masses.This is consistent with the expectations from 2005 (Figure 14b [19]).No indication of a signal is observed, and limits are set in the (m g, m q) and (m 0 , m 1/2 ) planes.
All cross-sections are given at the average mass scale of the massive final-state particles [25]; (b) DØ squark-gluino searches.Excluded regions at 95% CL in the gluino and squark mass plane by direct searches interpreted in the mSUGRA framework with tan β = 3, A 0 = 0, µ < 0. The region excluded by this analysis and previous DØ Run-II results [3,4] in the most conservative hypothesis (σ min ) is shown in dark shading.The thick (dotted) line is the limit of the observed (expected) excluded region.The band delimited by the two dashed lines shows the effect of the Parton Distribution Function (PDF) choice and of the variation of renormalization and factorization scale by a factor of two.Regions excluded by previous experiments are indicated in light shading [28][29][30][31][32][33][34].The two thin lines indicate the indirect limits inferred from the LEP2 chargino and slepton searches [35].The region where no mSUGRA solution can be found is shown as hatched.With 0.31 fb −1 , only a small region beyond the LEP limits near the diagonal was excluded.The sensitivity reach with larger luminosities is also shown [19].DØ squark-gluino searches, copyright (2008), with permission from Elsevier [26].Distributions of / E T after applying all analysis criteria except the one on / E T for the "di-jet" (a); "three-jets" (b); and "gluino" (c) analyses.The signal drawn corresponds to (m 0 , m 1/2 ) = (25, 175) GeV, m q = m g = 410 GeV and (m 0 , m 1/2 ) = (500, 110) GeV from left to right.The fitted Quantum ChromoDynamics (QCD) background contribution is also shown.
( DØ squark-gluino searches, copyright (2008), with permission from Elsevier [26].Upper limits at 95% CL on squark-gluino production cross-sections are shown for tan β = 3, A 0 = 0, µ < 0, observed (closed circles) and expected (opened triangles), combining the analyses for m 0 = 25 GeV (a); m q = m g (b); and m 0 = 500 GeV (c).The nominal production cross-sections are also shown.The shaded bands correspond to the uncertainties from the PDF, and renormalization and factorization scale uncertainties.DØ squark-gluino searches, copyright (2008), with permission from Elsevier [26].(a) Excluded regions at 95% CL in the gluino and squark mass plane by direct searches interpreted in the mSUGRA framework with the same mSUGRA model parameters, as in Figure 14, for 2.1 fb −1 data; (b) Region excluded at the 95% CL in the (m 0 , m 1/2 ) plane for the mSUGRA framework with tan β = 3, A 0 = 0, µ < 0 (dark shaded area).The thick line is the limit of the excluded region for the σ min hypothesis.The corresponding expected limit is the dashed line.The band delimited by the two dotted lines shows the effect of the PDF choice and of the variation of renormalization and factorization scale by a factor of two.Regions excluded by the LEP2 chargino and slepton searches are indicated in light shading [35].The region where there is no electroweak symmetry breaking is shown in black.

Gluino Mass (GeV
. CDF squark-gluino searches, copyright (2009), with permission by the American Physical Society [27].The exclusion plane at 95% CL as a function of squark and gluino masses in an mSUGRA scenario with A 0 = 0, µ < 0 and tan β = 5.The observed (solid line) and expected (dashed line) upper limits are compared to previous results from SPS and LEP experiments at CERN (shaded bands), and from the Run-I at the Tevatron (dashed-dotted line) [28][29][30][31][32][33][34].Unlike in Figure 17   Higher luminosity was required to reach sensitivity for the scalar top mass of up to about 160 to 180 GeV, as shown in Figure 21b [36,37].Scalar top results from the DØ collaboration with 1 fb −1 for the χ0 1 c mode are shown in Figure 22 [38].Results from the CDF collaboration with 2.6 fb −1 , including the development of the excluded stop-neutralino mass region, are shown in Figures 23 and 24 [39].
As seen in Figure 24b, a minimum stop-neutralino mass difference of at least about 35 GeV is required for sensitivity at 95% CL.This is in contrast to e + e − colliders, like the LEP [6] or the International Linear Collider (ILC) [40,41], which have also sensitivity for small mass differences.DØ scalar top searches in the χ0 1 c mode, copyright (2008), with permission from Elsevier [38].
(a) Distributions of H T for a signal with m t = 150 GeV and m χ0     2011), with permission from Elsevier [48].The observed (expected) 95% CL exclusion region is shown below the solid (dashed) line.The shaded band around the expected limit shows the effects of the scalar top quark pair production cross-section uncertainty.The kinematically forbidden region is represented in the upper left part of the plot.The regions excluded by LEP I and LEP II [6], by previous DØ searches [46,50] and by a previous CDF search [47] are also shown.The DØ collaboration searched for reactions involving τ leptons ( t1 t1 → b bµτ ν ν and t1 t1 → b bτ τ ν ν) using 7.3 fb −1 .Three neural networks are trained to identify tau decays corresponding to τ ± → π ± ν (τ 1 ), τ ± → π ± π 0 ν (τ 2 ), and τ ± → π ± π ± π ∓ (π 0 )ν (τ 3 ).Two signal points are chosen [m t1 ,m ν ] = (180,60) GeV and (120,80) GeV, labeled "Signal A" and "Signal B" in the following, to illustrate the impact of the selection criteria for large m t1 and ∆m (Signal A) and for low m t and ∆m (Signal B).The selection results are shown in Figure 30 for the higgsino scenario.Limits are shown in Figure 31 for the wino and higgsino scenarios [49].

Scalar Bottoms
In the kinematic reach under investigation, b1 → χ0 1 b decays are expected, leading to two b-jets and missing energy in the final state of sbottom pair-production.In order to demonstrate the progress at the Tevatron, first, the early results are shown.The DØ missing E T and mass limits in the sbottom-neutralino plane are shown in Figure 32 [52,53] for 0.31 fb −1 .Recent CDF results with 2.65 fb −1 are shown in Figure 33 [54], and results from the DØ collaboration with 5.2 fb −1 are shown in Figure 34 [55].The signal topology of two b-quarks and missing energy is identical to the one from the Higgs boson search pp → ZH → ν νb b [56][57][58].The increase of the sensitivity and the extension of the excluded region to higher sbottom masses are illustrated.Note that in Figure 34b for a 100 GeV sbottom mass, sensitivity is achieved for a mass difference m b −m χ0 1 of about 30 GeV, and for a 150 GeV sbottom for a mass difference of about 50 GeV.In contrast to these large values, the LEP e + e − collider achieved sensitivity over the whole kinematic reach for a mass difference close to m b − m χ0 1 = m b .

Charged Massive Particles
Many quasi-stable particles could appear in supersymmetric models (In particular, the next to lightest supersymmetric particle can have a long lifetime).Searches for quasi-stable particles were performed and interpretations given in several supersymmetric models.The production of stable scalar tau leptons would result in a signature in the detector similar to a pair of muons, but with mass and speed inconsistent with the production of muons.The speed β = v/c of these charged massive particles is expected to be significantly different compared to muons, as shown in Figure 35a [59].In the nearly mass-degenerate neutralino-chargino scenario, which occurs naturally in the anomaly-mediated symmetry breaking (AMSB) model, limits are shown on the chargino mass (Figure 35b).Figure 35c shows an example in the MSSM when the chargino is higgsino-like.
The scalar top quarks can have a distinct signature, since they appear in charged or neutral stop hadrons.These hadrons may flip their charge as they pass through the detector.In the simulation, approximately 60% of stop hadrons are charged following initial hadronization, i.e., 84% of the events will have at least one charged stop hadron.Furthermore, scalar top hadrons may flip their charge through nuclear interactions, as they pass through material.
It is assumed that stop hadrons have a probability of 2/3 of being charged after multiple nuclear interactions and anti-stop hadrons, a probability of 1/2 of being charged, consistent with the numbers of possible scalar top and anti-stop hadronic final states.CDF performed a search for long-lived charged massive particles produced in 1.0 fb −1 using a high transverse-momentum p T muon trigger.The search sets an upper bound on the production cross-section.Interpreting this result within the context of a stable scalar top-quark model resulted in a lower limit at 95% CL on the particle mass of 249 GeV, as shown in Figure 38 [62].
Higgsino-like Chargino Mass (GeV)   (b) Observed 95% CL limits on the production cross-section of a stable top-squark pair (points), compared to the theoretical NLO cross-section (curve).The band represents theoretical and parton distribution function uncertainties.The intersection of the band with the limit curve yields a lower mass limit for a stable top squark of 249 GeV.

LHC
In 2005, it was planned that the LHC would operate up to 14 TeV, which is about seven times the center-of-mass energy of the Tevatron.Sensitivity prospects for discovering supersymmetric particles were given for this LHC operation scenario.In the first stage, the LHC operated at 7 TeV center-of-mass energy in 2011, increasing to 8 TeV in 2012.Although the corresponding production cross-sections are reduced compared to the design center-of-mass energy, the increased LHC energy compared to the Tevatron greatly extends the reach to discover new particles.
In the search for supersymmetric particles, the LHC has great potential at 14 TeV for a discovery within a short period of data-taking.In order to compare the long-term expectations and the actual achieved sensitivities, an example from 2005 of the expectations at 14 TeV to discover supersymmetry is shown in Figure 39 [63], assuming the mSUGRA model.A variety of supersymmetric reactions are in reach of the LHC sensitivity.While a signature from supersymmetry cannot escape detection at the LHC, determining the precise model structure is a very challenging task.Further precision measurements would be possible at a linear collider, as reviewed, for example, in [64,65].It will be particular difficult for the LHC to determine the relevant scalar top parameters in the cosmologically interesting region of stop-neutralino co-annihilation, where a future linear collider can perform more precise measurements [40,41].
Figure 39.Squark-gluino 5σ discovery reach for a signal with jets plus missing energy in the mSUGRA model [63].In the forbidden region on the left (small m 0 ) the neutralino is not the LSP, and in the lower region (small m 1/2 ), there is no electroweak symmetry breaking.The cosmologically plausible region (co-annihilation) is close to the forbidden regions on the left bottom.This cosmological plausible region could be covered within the first period of LHC data-taking at 14 TeV.With the luminosity of 100 fb −1 , scalar quarks of up to 2500 GeV could be discovered.The first LHC results allow, in some cases, a direct comparison with the Tevatron results.Two examples of LHC search results are used for this comparison, first, searches with di-photons and, second, searches for scalar quarks.
As reviewed for the Tevatron (Section 2.1), the LHC results (ATLAS (A Toroidal LHC Apparatus) [66]) are also presented for a specific scenario in the framework of the supersymmetric model, the SPS8 benchmark for gauge-mediated supersymmetry breaking.Similar results were obtained by CMS (Compact Muon Solenoid) [67].Table 1 compares the limits on the excluded effective Supersymmetry breaking scale, the lightest neutralino mass and the lightest chargino mass between the DØ results (6.3 fb −1 data taken at 1.96 TeV) and the ATLAS results (1.07 fb −1 data taken at 7 TeV).It is interesting to note that the LHC superseded the limits with about 1/6 of the luminosity collected at the Tevatron.Figures 5 and 40 show the missing E T distributions, as well as the SPS8 limits for the Tevatron (DØ) and LHC (ATLAS), respectively.Table 1.Di-photon results for the SPS8 benchmark from the Tevatron (DØ with 6.3 fb −1 data taken at 1.96 TeV) and the LHC (ATLAS with 1.07 fb −1 data taken at 7 TeV).The limits on the effective Supersymmetry breaking scale, Λ, the lightest neutralino mass, m χ0   In the following, the Tevatron results for squark-gluino searches are compared with recent LHC results.The LHC results are also placed into the context of the 14 TeV sensitivity predictions (Figure 39).The squark-gluino searches presented here rely on the separation of QCD background and supersymmetric signal events with a multi-jet and missing energy characteristic.In order to achieve this, a so-called razor variable is defined by the CMS collaboration, which gives the name to this analysis [68].For the ATLAS collaboration, the ratio, E T / √ H T , is used for the separation of signal and background, where H T is the scalar sum of the jet momenta [69].It is a measure of the significance of the E T in the event.No indication of a signal was observed.The resulting limits in the (m 0 , m 1/2 ) plane are shown in Figure 41 in the framework of the mSUGRA model (constrained MSSM, CMSSM).The early result from ATLAS nicely displays the increase in sensitivity compared to the Tevatron results (as given in Figure 17 for DØ with 2.1 fb −1 and in Figure 19 for CDF with 2.0 fb −1 ).Recently, ATLAS and CMS published updated results with about 20 fb −1 data, each taken at 8 TeV [70,71].Thus, the lower Tevatron gluino mass limit increased from about 300 GeV (CDF [27], DØ [26]) to a current LHC mass limit above about 1.1 TeV (ATLAS [70], CMS [71]).The LHC has already largely extended the excluded parameter region of supersymmetric models compared to the Tevatron results.This extension is mostly due to the about 3.5-4.0times higher center-of-mass energy at the LHC.It is also remarkable that first LHC results with 4.7 fb −1 data taken at 7 TeV (2011 running period) excluded a parameter region quite similar to the sensitivity prediction for 1 fb −1 at 14 TeV (Figure 39).The search for scalar top quarks allows a direct comparison between the Tevatron and the first LHC results.At the Tevatron, a scalar top quark mass was excluded up to about 180 GeV (for example, CDF Figure 24 [39] 2.6 fb −1 at 2 TeV), while at the LHC for small mass values of the lightest supersymmetric particle, scalar top quark mass values up to around 650 GeV are excluded (for example, CMS Figure 42 [72] 19.5 fb −1 at 8 TeV).

Conclusions
The search at the Tevatron for supersymmetric particles was characterized as an era of sensitivity increases compared to the previous results at LEP and a preparation phase for the LHC operation.Results from the Tevatron are reviewed in the context of sensitivity improvements over the last, about, eight years (2005 to 2013).The sensitivity predictions from 2005 agree remarkably well with the achieved results using the full Tevatron dataset.The Tevatron results show impressive progress in sensitivity for supersymmetric signatures involving di-photons, tri-leptons, scalar quarks and gluinos, scalar top and scalar bottom quarks and for charged massive particles.These scientific advances are also based on many new and optimized search techniques and methods, which are directly applicable to current searches at the LHC.The first LHC results based on seven and 8 TeV center-of-mass energies are compared with the 14 TeV LHC predictions from 2005; and they agree well, taking into account the reduced operation energy in the first LHC stage.Examples of Tevatron and initial LHC results have been compared, and the LHC has much extended the sensitivity with respect to the Tevatron results from the 100 GeV scale to the terascale.The achieved experimental Tevatron results show that sensitivities can be reliably predicted for long-term planning of future performances at particle colliders.At the Tevatron, a major step towards discovering supersymmetry or ruling it out was made, and the LHC has taken over this exciting field of research.

Figure 2 .
Figure 2. Examples of events with large missing momentum and energy.The tracks result from charged particles produced at the interaction point.The height of the towers indicates the energy deposited in the calorimeters.In the CDF event display, the arrow indicates the direction of the missing momentum.(a) DØ H T = 410 GeV [3]; (b) CDF H T = 404 GeV [5].

Figure 10 .
Figure10.DØ tri-lepton searches[20].(a) The upper limit at the 95% CL on σ × BR(3ℓ) as a function of the χ± 1 mass from the tri-lepton searches and expectations for two Supersymmetry scenarios (3ℓ-max and large m 0 ); (b) The region in the m 0 -m 1/2 plane excluded by the combination of the DØ analyses (green), by LEP searches for charginos (light grey) and sleptons (dark grey)[6] and CDF searches based on 2.0 fb −1 data (black line)[21,22].The assumed mSUGRA parameters are tan β = 3, A 0 = 0 and µ > 0; (c) The upper limit at the 95% CL on σ × BR(3ℓ) as a function of tan β and a prediction for a chargino mass of 130 GeV with m τ − m χ0 2 = 1 GeV.

Figure 12 .Figure 13 .
Figure 12.CDF tri-lepton searches [23].(a) The summed missing p T and E T in the eτ channel; (b) The tau cluster, E T , in the µτ channel.(a) (b)

Figure 14 .
Figure 14.(a) The Next-to-Leading-Order (NLO) production cross-sections included in PROSPINO (PROduction of Supersymmetric Particles In Next-to-leading Order) as a function of the final state particle mass.The arrows indicate the SUGRA inspired scenario: m 1/2 = 150 GeV, m 0 = 100 GeV, A 0 = 300 GeV, tan β = 4, µ > 0. All cross-sections are Figure 15.DØ squark-gluino searches, copyright (2008), with permission from Elsevier[26].Distributions of / E T after applying all analysis criteria except the one on / E T Figure 16.DØ squark-gluino searches, copyright (2008), with permission from Elsevier[26].Upper limits at 95% CL on squark-gluino production cross-sections are shown for tan β = 3, A 0 = 0, µ < 0, observed (closed circles) and expected (opened triangles), combining the analyses for m 0 = 25 GeV (a); m q = m g (b); and m 0 = 500 GeV (c).The nominal production cross-sections are also shown.The shaded bands correspond to the uncertainties from the PDF, and renormalization and factorization scale uncertainties.

Figure 18 .
Figure18.CDF squark-gluino searches, copyright(2009), with permission by the American Physical Society[27].(a) Measured H T and / E T distributions (black dots) in events with at least two (bottom), three (middle), and four (top) jets in the final state compared to the Standard Model (SM) predictions (solid lines) and the SM + mSUGRA predictions (dashed lines).The shaded bands show the total systematic uncertainty in the SM predictions; (b) The observed (solid lines) and expected (dashed lines) 95% CL upper limits on the inclusive squark and gluino production cross-sections as a function of m q (left) and m g (right) in different squark and gluino mass relations, compared to NLO mSUGRA predictions (dashed-dotted lines).The shaded bands denote the total uncertainty in the theory.
Figure19.CDF squark-gluino searches, copyright(2009), with permission by the American Physical Society[27].The exclusion plane at 95% CL as a function of squark and gluino masses in an mSUGRA scenario with A 0 = 0, µ < 0 and tan β = 5.The observed (solid line) and expected (dashed line) upper limits are compared to previous results from SPS and LEP experiments at CERN (shaded bands), and from the Run-I at the Tevatron (dashed-dotted line)[28][29][30][31][32][33][34].Unlike in Figure17where the LEP2 chargino and slepton search results are shown for the given mSUGRA model point, here, only the limits from LEP squark searches are presented.The hatched area indicates the region in the plane with no mSUGRA solution.
Figure 22.DØ scalar top searches in the χ0 1 c mode, copyright (2008), with permission from Elsevier[38].(a)Distributions of H T for a signal with m t = 150 GeV and m χ0

1 = 70
GeV (hatched histogram); (b) The final distributions of / E T for the data (points with error bars), SM background (histogram) and a signal with m t = 150 GeV and m χ0 1 = 70 GeV (hatched histogram).

Figure 23 .Figure 24 .
Figure 23.CDF scalar top searches [39].(a) Neural network output to reject the heavy flavor (HF) QCD background.The arrow indicates the applied selection cut; (b) Neural network output for the final discriminant used to extract the limits.
[47] for the χ± 1 b mode.Recent results from DØ with 5.4 fb −1 are shown in Figures 28 and 29[48] for the eµ final state.

Figure 30 .
Figure 30.DØ scalar top searches, copyright (2012), with permission from Elsevier [49].Distributions of the Boosted Decision Trees (BDT) output discriminants in the higgsino scenario for the sample with N(jets) = 1, for Signal A (a); for Signal B (b); N(jets) = 2, for Signal A (c); for Signal B (d); N(jets) > 2, for Signal A (e); for Signal B (f); where Signal A and B are defined in the text.

Figure 31 .
Figure31.DØ scalar top searches, copyright (2012), with permission from Elsevier[49].(a) The contour of exclusion at 95% CL in the sneutrino versus scalar top quark mass plane obtained for the assumption B( t1 → bµν) = B( t1 → bτ ν) = 1/3 (wino scenario).The shaded areas represent the kinematically forbidden region and the LEP-I[51] and LEP-II[6] exclusions.The dashed and continuous lines represent the expected and observed 95% CL exclusion limits.The region excluded by a DØ search[48] for the t1 t1 → b beµν ν reaction in the wino scenario is indicated by the dotted line; (b) The contour of exclusion at 95% CL in the sneutrino versus scalar top quark mass plane obtained for the assumption B( t1 → bµν) = 0.1 and B( t1 → bτ ν) = 0.8 (higgsino scenario).

Figure 36 .Figure 37 .Figure 38 .
Figure 36.DØ searches for charged massive particles, copyright (2012), with permission by the American Physical Society [60].(a) Distributions of speed β; (b)The distribution of dE/dx for data, background and signal (gaugino-like charginos with a mass of 100 and 300 GeV) that pass the selection criteria.The histograms have been normalized in order to have the same number of events.The scale of the dE/dx measurements is scaled so that the dE/dx of muons from Z → µµ events peak at one.All entries exceeding the range of the histogram are added to the last bin.