Search for new phenomena in final states with large jet multiplicities and missing transverse momentum at sqrt(s)=8 TeV proton-proton collisions using the ATLAS experiment

A search is presented for new particles decaying to large numbers (7 to greater or equal to 10) of jets, missing transverse momentum and no isolated electrons or muons. This analysis uses 20.3/fb of pp collision data at sqrt(s)=8 TeV collected by the ATLAS experiment at the Large Hadron Collider. The sensitivity of the search is enhanced by considering the number of b-tagged jets and the scalar sum of masses of large-radius jets in an event. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of various simplified supersymmetry-inspired models where gluinos are pair produced, as well as a mSUGRA/CMSSM model.


Introduction
Many extensions of the Standard Model of particle physics predict the presence of TeVscale strongly interacting particles that decay to weakly interacting descendants. In the context of R-parity-conserving supersymmetry (SUSY) [1][2][3][4][5], the strongly interacting parent particles are the partners of the quarks (squarks,q) and gluons (gluinos,g), and are produced in pairs. The lightest supersymmetric particle (LSP) is stable, providing a candidate that can contribute to the relic dark-matter density in the universe [6,7]. If they are kinematically accessible, the squarks and gluinos could be produced in the proton-proton interactions at the Large Hadron Collider (LHC) [8].
Such particles are expected to decay in cascades, the nature of which depends on the mass hierarchy within the model. The events would be characterised by significant missing transverse momentum from the unobserved weakly interacting descendants, and by a large number of jets from emissions of quarks and/or gluons. Individual cascade decays may include gluino decays to a top squark (stop,t) and an anti-top quark, g →t +t (1.1a) followed by the top-squark decay to a top quark and a neutralino LSP,χ (1.1b) Alternatively, if the top squark is heavier than the gluino, the three-body decay, g → t +t +χ In this paper we consider final states with large numbers of jets together with significant missing transverse momentum in the absence of isolated electrons or muons, using the pp collision data recorded by the ATLAS experiment [9] during 2012 at a centre-of-mass energy of √ s = 8 TeV. The corresponding integrated luminosity is 20.3 fb −1 . Searches for new phenomena in final states with large jet multiplicities -requiring from at least six to at least nine jets -and missing transverse momentum have previously been reported by the ATLAS Collaboration using LHC pp collision data corresponding to 1.34 fb −1 [10] and to 4.7 fb −1 [11] at √ s = 7 TeV. Searches with explicit tagging of jets from bottom quarks (b-jets) in multi-jet events were also performed by ATLAS [12] and CMS [13][14][15]. These searches found no significant excess over the Standard Model expectation and provide limits on various supersymmetric models, including decays such as that in eq. (1.2) and an mSUGRA/CMSSM [16][17][18][19][20][21] model that includes strong production processes. The analysis presented in this paper extends previous analyses by reaching higher jet multiplicities and utilizing new sensitive variables.
-2 -Events are first selected with large jet multiplicities, with requirements ranging from at least seven to at least ten jets, reconstructed using the anti-k t clustering algorithm [22,23] and jet radius parameter R = 0.4. Significant missing transverse momentum is also required in the event. The sensitivity of the search is further enhanced by the subdivision of the selected sample into several categories using additional information. Event clasification based on the number of b-jets gives enhanced sensitivity to models which predict either more or fewer b-jets than the Standard Model background. In a complementary stream of the analysis, the R = 0.4 jets are clustered into large (R = 1.0) composite jets to form an event variable, the sum of the masses of the composite jets, which gives additional discrimination in models with a large number of objects in the final state [24]. Events containing isolated, high transverse-momentum (p T ) electrons or muons are vetoed in order to reduce backgrounds involving leptonic W boson decays. The previous analyses [10,11] had signal regions with smaller jet multiplicities; those are now omitted since the absence of significant excesses in earlier analyses places stringent limits on models with large cross sections.
Searches involving final states with many jets and missing transverse momentum have been confirmed to have good sensitivity to decays such as those in eqs. (1.1) and (1.2) [11], but they also provide sensitivity to any model resulting in final states with large jet multiplicity in association with missing transverse momentum. Such models include the pair production of gluinos, each of them decaying via an off-shell squark, as g →q + q +χ ± 1 →q + q + W ± +χ 0 1, (1.3a) or alternativelỹ g →q + q +χ ± 1 →q + q + W ± +χ 0 2 →q + q + W ± + Z 0 +χ 0 1.

(1.3b)
Another possibility is the pair production of gluinos which decay as in eq. (1.1a) and the subsequent decay of thet-squark viat using both calorimeter and tracker information. The magnitude of p miss T , conventionally denoted by E miss T , is used to distinguish signal and background regions.

Event selection
Following the physics object reconstruction described in section 3, events are discarded if they contain any jet that fails quality criteria designed to suppress detector noise and non-collision backgrounds, or if they lack a reconstructed primary vertex with five or more associated tracks. Events containing isolated electron or muon candidates are also vetoed as described in section 3. The remaining events are then analysed in two complementary analysis streams, both of which require large jet multiplicities and significant E miss T . The selections of the two streams are verified to have good sensitivity to decays such as those in eqs. (1.1) -(1.4), but are kept generic to ensure sensitivity in a broad set of models with large jet multiplicity and E miss T in the final state.

The multi-jet + flavour stream
In the multi-jet + flavour stream the number of jets with |η| < 2 and p T above the threshold p min T = 50 GeV is determined. Events with exactly eight or exactly nine such jets are selected, and the sample is further subdivided according to the number of the jets (0, 1 or ≥2) with p T > 40 GeV and |η| < 2.5 which satisfy the b-tagging criteria. The b-tagged jets may belong to the set of jets with p T greater than p min T , but this is not a requirement. Events with ten or more jets are retained in a separate category, without any further subdivision.
A similar procedure is followed for the higher jet-p T threshold of p min T = 80 GeV. Signal regions are defined for events with exactly seven jets or at least eight jets. Both categories are again subdivided according to the number of jets (0, 1 or ≥2) that are b-tagged. Here again, the b-tagged jets do not necessarily satisfy the p min Two background categories are considered in this search: (1) multi-jet production, including purely strong interaction processes and fully hadronic decays of tt, and hadronic decays of W and Z bosons in association with jets, and (2) processes with leptons in the final states, collectively referred to as leptonic backgrounds. The latter consist of semileptonic and fully leptonic decays of tt, including tt production in association with a boson; leptonically decaying W or Z bosons produced in association with jets; and single top quark production.
The major backgrounds (multi-jet, tt, W + jets, and Z + jets) are determined with the aid of control regions, which are defined such that they are enriched in the background process(es) of interest, but nevertheless remain kinematically close to the signal regions. The multi-jet background determination is fully data-driven, and the most significant of the other backgrounds use data control regions to normalise simulations. The normalisations of the event yields predicted by the simulations are adjusted simultaneously in all the control regions using a binned fit described in section 6, and the simulation is used to extrapolate the results into the signal regions. The methods used in the determination of the multi-jet and leptonic backgrounds are described in sections 5.2 and 5.4, respectively.

Monte Carlo simulations
Monte Carlo simulations are used as part of the leptonic background determination process, and to assess the sensitivity to specific SUSY signal models. Most of the leptonic backgrounds are generated using Sherpa-1.4.1 [35] with the CT10 [36] set of parton distribution functions (PDF). For tt production, up to four additional partons are modelled --> 340 and > 420 for each case -8 -in the matrix element. Samples of W + jets and Z + jets events are generated with up to five additional partons in the matrix element, except for processes involving b-quarks for which up to four additional partons are included. In all cases, additional jets are generated via parton showering. The leptonic W + jets, Z + jets and tt backgrounds are normalised according to their inclusive theoretical cross sections [37,38]. In the case of tt production, to account for higher-order terms which are not present in the Sherpa Monte Carlo simulation, the fraction of events initiated by gluon fusion, relative to other processes, is modified to improve the agreement with data in tt-enriched validation regions described in section 5.4. This corresponds to applying a scale factor of 1.37 to the processes initiated by gluon fusion and a corresponding factor to the other processes to keep the total tt cross section the same. The estimation of the leptonic backgrounds in the signal regions is described in detail in section 5.4. Smaller background contributions are also modelled for the following processes: single top quark production in association with a W boson in the s-channel (MC@NLO 4.06 [39][40][41][42] / Herwig 6.520 [43] / Jimmy 4.31 [44]), t-channel single top quark production (AcerMC3.8 [45] / Pythia-6.426 [46]), and tt production in association with a W or Z boson (Madgraph-5.1.4.8 [47] / Pythia-6.426).
For each process, the nominal cross section and its uncertainty are taken from an envelope of cross-section predictions using different PDF sets and factorisation and renormalisation scales, as described in ref. [55]. All Monte Carlo simulated samples also include simulation of pile-up and employ a detector simulation [56] based on GEANT4 [57]. The simulated events are reconstructed with the same algorithms as the data.

Multi-jet background
The dominant background at intermediate values of E miss T is multi-jet production including purely strong interaction processes and fully hadronic decays of tt. The contribution from these processes is determined using collision data and the selection criteria were designed such that multi-jet processes can be accurately determined from supporting measurements.
The background determination method is based on the observation that the E miss T resolution of the detector is approximately proportional to √ H T and almost independent of the jet multiplicity in events dominated by jet activity, including hadronic decays of top quarks and gauge bosons [10,11]. The distribution of the ratio E miss T / √ H T therefore has a shape that is almost invariant under changes in the jet multiplicity. The multi-jet backgrounds can be determined using control regions with lower E miss T / √ H T and/or lower jet multiplicity than the signal regions. The control regions are assumed to be dominated by Standard Model processes, and that assumption is corroborated by the agreement with Standard Model predictions of multi-jet cross-section measurements for up to six jets [58].
Events containing heavy quarks show a different E miss T / √ H T distribution than those containing only light-quark or gluon jets, since semileptonic decays of heavy quarks contain -9 -neutrinos. The dependence of E miss T / √ H T on the number of heavy quarks is accounted for in the multi-jet + flavour signal regions by using a consistent set of control regions with the same b-jet multiplicity as the target signal distribution. The E miss T / √ H T distribution is also found to be approximately independent of the M Σ J event variable, so a similar technique is used to obtain the expected multi-jet background contributions to the multi-jet + M Σ J signal regions.
The leading source of variation in E miss T / √ H T under changes in the jet multiplicity comes from a contribution to E miss T from calorimeter energy deposits not associated with jets and hence not contributing to H T . The effect of this 'soft' energy is corrected for by reweighting the E miss T / √ H T distribution separately for each jet multiplicity in the signal region, to provide the same E CellOut is the scalar sum of E T over all clusters of calorimeter cells not associated with jets having p T > 20 GeV or electron, or muon candidates.
For example, to obtain the multi-jet contribution to the multi-jet + flavour stream 9j50 signal region with exactly one b-jet, the procedure is as follows. A template of the shape of the E miss T / √ H T distribution is formed from events which have exactly six jets with p T > 50 GeV, and exactly one b-jet (which is not required to be one of the six previous jets). The expected contribution from leptonic backgrounds is then subtracted, so that the template provides the expected distribution resulting from the detector resolution, together with any contribution to the resolution from semileptonic b-quark decays. The nine-jet background prediction for the signal region (E miss T / √ H T > 4 GeV 1/2 ) with exactly one b-jet is then given by H T > 4 GeV 1/2 , and each of the counts N is determined after requiring the same b-jet multiplicity as for the target signal region (i.e. exactly one b-jet in this example). Equation 5.1 is applied separately to each of ten bins (of width 0.1) in E CellOut        For all cases in the multi-jet + M Σ J stream the E miss T / √ H T template shape is determined from a sample which has exactly six jets with p T > 50 GeV.
Variations in the shape of the E miss T / √ H T distribution under changes in the jet multiplicity are later used to quantify the systematic uncertainty associated with the method, as described in section 5.3.

Systematic uncertainties in the multi-jet background determination
The multi-jet background determination method is validated by measuring the accuracy of the predicted E miss T / √ H T template for regions with jet multiplicities and/or E miss T / √ H T smaller than those chosen for the signal regions. The consistency of the prediction with the number of observed events (closure) is tested in regions with E miss T / √ H T [ GeV 1/2 ] in the ranges (1.5, 2.0), (2.0, 2.5), and (2.5, 3.5) for jet multiplicities of exactly seven, eight and nine, and in the range (1.5, 2.0) and (2.0, 3.5) for ≥10 jets. The tests are performed separately for 0, 1 and ≥ 2 b-tagged jets. In addition, the method is tested for events with exactly six (five) jets with p min T = 50 GeV (80 GeV) across the full range of E miss T / √ H T in this case using a template obtained from events with exactly five (four) jets. The five-jet (four-jet) events are obtained using a prescaled trigger for which only a fraction of the total luminosity is available. Agreement is found both for signal region jet multiplicities at intermediate values of E miss T / √ H T and also for the signal region E miss T / √ H T selection at lower multiplicity. A symmetrical systematic uncertainty on each signal region is constructed by taking the largest deviation in any of the closure regions with the same jet multiplicity or lower, for the same b-tagging requirements. Typical closure uncertainties are in the range 5% to 15%; they can grow as large as ∼50% for the tightest signal regions, due to larger statistical variations in the corresponding control regions.
Additional systematic uncertainties result from modelling of the heavy-flavour content (25%), which is assessed by using combinations of the templates of different b-tagged jet multiplicity to vary the purity of the different samples. The closure in simulation of samples with high heavy-flavour content is also tested. The leptonic backgrounds that are subtracted when forming the template have an uncertainty associated with them (5-20%, depending on the signal region). Furthermore, other uncertainties taken into account are due to the scale choice of the cutoff for the soft energy term, E CellOut T , (3-15%) and the trigger efficiency (<1%) in the region where the template is formed.

Leptonic backgrounds
The leptonic backgrounds are defined to be those which involve the leptonic decays W → ν or Z → νν. Contributions are determined for partly hadronic (i.e. semileptonic or dileptonic) tt, single top, W and Z production, and diboson production, each in association with jets. The category excludes semileptonic decays of charm and bottom quarks, which are considered within the multi-jet category (section 5.2). The leptonic backgrounds which contribute most to the signal regions are tt and W + jets. In each case, events can evade the lepton veto, either via hadronic τ decays or when electrons or muons are produced but not reconstructed.
The predictions employ the Monte Carlo simulations described in section 5.1. When predictions are taken directly from the Monte Carlo simulations, the leptonic background event yields are subject to large theoretical uncertainties associated with the use of a leading-order Monte Carlo simulation generator. These include scale variations as well as changes in the number of partons present in the matrix element calculation, and uncertainties in the response of the detector. To reduce these uncertainties the background predictions are, where possible, normalised to data using control regions and cross-checked against data in other validation regions. These control regions and validation regions are designed to be distinct from, but kinematically close to, the signal regions, and orthogonal to them by requiring an identified lepton candidate.
The validation and control regions for the tt and W + jets backgrounds are defined in table 2. In single-lepton regions, a single lepton (e or µ) is required, with sufficient p T to allow the leptonic trigger to be employed. Modest requirements on E miss T and E miss T / √ H T reduce the background from fake leptons. An upper limit on where p T is the transverse momentum vector of the lepton, decreases possible contamination from non-Standard-Model processes.
Since it is dominantly through hadronic τ decays that W bosons and tt pairs contribute to the signal regions, the corresponding control regions are created by recasting the muon -13 -     or electron as a jet. If the electron or muon has sufficient p T (without any additional calibration), it is considered as an additional 'jet' and it can contribute to the jet multiplicity count, as well as to H T and hence to the selection variable E miss T / √ H T . The same jet multiplicity as the signal region is required for the equivalent control regions. Additionally, -14 -       consistent with that of the Z boson. To create control regions that emulate the signal regions, the lepton transverse momenta are added to the missing momentum two-vector and then the requirement E miss T / √ H T > 4 GeV 1/2 is applied. This emulates the situation expected for the Z → νν background. The details of the selection criteria are given in table 3. This selection, but with relaxed jet multiplicity criteria, is used to validate the Monte Carlo simulation description of this process; however, insufficient events remain at high jet multiplicity, so the estimation of this background is taken from Monte Carlo simulations.  -16 -

Systematic uncertainties in the leptonic background determination
Systematic uncertainties on the leptonic backgrounds originate from both detector-related and theoretical sources from the Monte Carlo simulation modelling. Experimental uncertainties are dominated by those on the jet energy scale, jet energy resolution and, in the case of the flavour stream, b-tagging efficiency. Other less important uncertainties result from the modelling of the pile-up, the lepton identification and the soft energy term in the E miss T calculation; these make negligible contributions to the total systematic uncertainty. The ATLAS jet energy scale and resolution are determined using in-situ techniques [28,59]. The jet energy scale uncertainty includes uncertainties associated with the quarkgluon composition of the sample, the heavy-flavour fraction and pile-up uncertainties. The uncertainties are derived for R = 0.4 jets and propagated to all objects and selections used in the analysis. The sources of the jet energy scale uncertainty are treated as correlated between the various Standard Model backgrounds as well as with the signal contributions when setting exclusion limits. The uncertainties on the yields due to those on the jet energy scale and resolution range typically between 20% and 30%. The b-tagging efficiency uncertainties are treated in a similar way when setting limits and have typical values of ≈ 10%. They are derived from data samples tagged with muons associated with jets, using techniques described in refs. [31,32].
For the tt background, theoretical uncertainties are evaluated by comparing the particlelevel predictions of the nominal Sherpa samples with additional samples in which some of the parameter settings were varied. These include variations of the factorisation scale, the matching scale of the matrix element to the parton shower, the number of partons in the matrix element and the PDFs. Alpgen [60] samples are also generated with the renormalisation scale associated with α S in the matrix element calculation varied up and down by a factor of two relative to the original scale k t between two partons [61]. Finally, samples with and without weighting of events initiated by gluon fusion relative to other processes are used to provide a systematic uncertainty on this procedure. The two latter sources of systematic uncertainty are the dominant ones with typical values of 25-30% each, leading to a total theoretical uncertainty on the tt background of ≈ 40%.
Alternative samples are generated similarly for the other smaller backgrounds with different parameters and/or generators to assess the associated theoretical uncertainties, which are found to be similar to those for the tt background. if there are at least two expected events associated with it. The fits differ significantly between the two analysis streams, as described in the following sections.

Results
When evaluating a supersymmetric signal model for exclusion, any signal contamination in the control regions is taken into account for each signal point in the control-region fits performed for each signal hypothesis. Separately, each signal region (one at a time), along with all control regions, is also fitted under the background-only hypothesis. This fit is used to characterise the agreement in each signal region with the background-only hypothesis, and to extract visible cross-section limits and upper limits on the production of events from new physics. For these limits, possible signal contamination in the control regions is neglected. The fit considers several independent background components: • tt and W + jets. One control region is defined for each signal region, as described in table 2; the normalisation of each background component is allowed to vary freely in the fit.
• Less significant backgrounds (Z + jets, tt + W , tt + Z, and single top) are determined using Monte Carlo simulations. These are individually allowed to vary within their uncertainties.
• Multi-jet background. Being data-driven, it is not constrained in the fit by any control region. It is constrained in the signal regions by its uncertainties, which are described in section 5.3.
The systematic effects, described in sections 5.3 and 5.5, are treated as nuisance parameters in the fit. For the signal, the dominant systematic effects are included in the fit; these are the jet energy scale and resolution uncertainties, the b-tagging efficiency uncertainties, and the theoretical uncertainties.

Simultaneous fit in the multi-jet + M Σ
J stream For the multi-jet + M Σ J signal regions, a separate fit is performed on each signal region to adjust the normalisation of the tt and W + jets backgrounds using control regions, as defined in table 2.
The systematic uncertainties affecting the background, described in sections 5.3 and 5.5, and signal predictions are treated as nuisance parameters in the fit. The dominant sources of uncertainty are considered for the signal predictions: the jet energy scale, the jet energy resolution, and the theoretical uncertainties.

Fit results
Tables 4-7 summarise the fit results; the number of events observed in each of the signal regions, as well as their Standard Model background expectations, are reported before and after the fit to the control regions. In each of the signal regions, agreement is found between the Standard Model prediction and the data. The fit results are checked for stability and consistency with the background modelling based on the predictions described in sections 5.2 and 5.4. There is no indication of a systematic mis-modelling of any of the major backgrounds; the fitted values are in all cases consistent with the Monte Carlo simulation predictions.
In addition to the event yields, the probability (p 0 -value) that a background-only pseudo-experiment is more signal-like than the observed data is given for each individual signal region. To obtain these p 0 -values, the fit in the signal region proceeds in the same way as the control-region-only fit, except that the number of events observed in the signal region is included as an input to the fit. Then, an additional parameter for the non-Standard-Model signal strength, constrained to be non-negative, is fitted. The significance (σ) of the agreement between data and the Standard Model prediction is given. No significant deviations from the Standard Model prediction are found. The 95% confidence level (CL) upper limit on the number of events (N 95% BSM ) and the cross section times acceptance times efficiency (σ 95% BSM,max · A · ) from non-Standard-Model production are also provided, neglecting in the fit possible signal contamination in the control regions.

Interpretation
In the absence of significant discrepancies, exclusion limits at 95% CL are set in the context of several simplified supersymmetric models and an mSUGRA/CMSSM model, all described in section 1. Theoretical uncertainties on the SUSY signals are estimated as described in section 5.1. Combined experimental systematic uncertainties on the signal yield from the jet energy scale, resolution, and b-tagging efficiency in the case of the flavour stream, range from 15% to 25%. Acceptance and efficiency values, uncertainties and other information per signal region are tabulated in HepData [63].
The limit for each signal region is obtained by comparing the observed event count with that expected from Standard Model background plus SUSY signal processes. All uncertainties on the Standard Model expectation are used, including those which are correlated between signal and background (for instance jet energy scale uncertainties) and all but theoretical cross-section uncertainties (PDF and scale) on the signal expectation. The resulting exclusion regions are obtained using the CL s prescription [64]. For the multi-jet + flavour stream a simultaneous fit is performed in all the signal regions for each of the two values of p min T , and the two fit results are combined using the better expected limit per point in the parameter space, as described in section 6.1. For the multi-jet + M Σ J stream the signal region with the best expected limit at each point in parameter space is used. The stream with the better expected limit at each point in parameter space is chosen when combining the two streams. The multi-jet + flavour stream typically has stronger expected exclusion limits than the multi-jet + M Σ J stream. However, in models with large -19 -numbers of objects in the final state, and more so in boosted topologies, the multi-jet + M Σ J stream becomes competitive. Limits on sparticle masses quoted in the text are those from the lower edge of the 1σ signal cross-section band rather than the central value of the observed limit.
As shown in the rest of this section, the analysis substantially extends previous published exclusion limits on various models, from ATLAS [11, 12] and CMS [13,65].
The analysis result is interpreted in a simplified model that contains only a gluino octet and a neutralinoχ 0 1 within kinematic reach, and decaying with unit probability according to Eq. 1.2, via an off-shellt-squark. The results are presented in the (mg, mχ0 1 ) plane in figure 9, which shows the combined exclusion. Within the context of this simplified model, the 95% CL exclusion bound on the gluino mass is 1.1 TeV for the lightest neutralino mass up to 350 GeV.   In this simplified model, each gluino of a pair decays promptly via an off-shell squark as g →q + q +χ ± 1 →q + q + W ± +χ 0 2 →q + q + W ± + Z 0 +χ 0 1 . The intermediate particle masses, mχ± 1 and mχ0 2 , are set to (mg + mχ0 1 )/2 and (mχ± 1 + mχ0 1 )/2, respectively. The results are presented in the (mg, mχ0 1 ) plane in figure 12, which shows the combined exclusion limits for this model. Gluino masses are excluded below 1.1 TeV at 95% CL, for χ 0 1 masses below 300 GeV.

mSUGRA/CMSSM
An mSUGRA/CMSSM model with parameters tan β = 30, A 0 = −2m 0 and µ > 0 is also used to interpret the analysis results. The exclusion limits are presented in the (m 0 , m 1/2 ) plane in figure 13. For large universal scalar mass m 0 , gluino masses smaller than 1.1 TeV are excluded at 95% CL.

'Gluino-stop (RPV)' model
In this simplified model, each gluino of a pair decays asg →t +t; and thet-squark decays via the R-parity-and baryon-number-violating decayt →s +b. The results are presented in the (mg, mt) plane in figure 14. Within the context of this simplified model, the 95% CL exclusion bound on the gluino mass is 900 GeV fort-squark masses ranging from 400 GeV to 1 TeV.                           Table 7: As for table 4 but for the signal regions in the multi-jet + M Σ J stream for which the number of events in the control regions did not allow background determination using a fit and therefore the leptonic background is extracted directly from Monte Carlo simulations. : 95% CL exclusion curve for the simplified gluino-stop (off-shell) model. The dashed grey and solid red curves show the 95% CL expected and observed limits, respectively, including all uncertainties except the theoretical signal cross-section uncertainty (PDF and scale). The shaded yellow band around the expected limit shows the ±1σ result. The ±1σ lines around the observed limit represent the result produced when moving the signal cross section by ±1σ (as defined by the PDF and scale uncertainties). The diagonal dashed line is the kinematic limit for this decay channel.    [13] CMS Collaboration, Search for supersymmetry in hadronic final states with missing transverse energy using the variables α t and b-quark multiplicity in pp collisions at √ s = 8 tev, arXiv:1303.2985. Submitted to EPJC.

Conclusion
[14] CMS Collaboration, Inclusive search for supersymmetry using the razor variables in pp collisions at √ s = 7 tev, arXiv:1212.6961. Submitted to Phys. Rev. Lett.