Searches for supersymmetry based on events with b jets and four W bosons in pp collisions at 8 TeV

Contents lists available atScienceDirect

Physics

Letters

B

www.elsevier.com/locate/physletb

Searches

for

supersymmetry

based

on

events

with

b

jets

and

four

W

bosons

in

pp

collisions

at

8 TeV

.

CMS

Collaboration



CERN,Switzerland

a

r

t

i

c

l

e

i

n

f

o

a

b

s

t

r

a

c

t

Articlehistory:

Received12December2014

Receivedinrevisedform18February2015 Accepted1April2015

Availableonline13April2015 Editor:M.Doser

Keywords:

CMS Physics Supersymmetry

Fivemutuallyexclusivesearchesforsupersymmetryarepresentedbasedoneventsinwhichb jets and fourW bosonsare producedinproton–protoncollisions at√s=8 TeV.Thedata,corresponding toan integratedluminosityof19.5 fb−1,werecollectedwiththeCMSexperimentattheCERNLHCin2012. ThefivestudiesdifferintheleptonicsignaturefromtheWbosondecays,andcorrespondtoall-hadronic, single-lepton,opposite-signdilepton,same-signdilepton,and≥3leptonfinalstates.Theresultsofthe fivestudiesarecombinedtoyield95%confidencelevellimitsforthegluinoandbottom-squarkmasses inthecontextofgluinoandbottom-squarkpairproduction,respectively.Inthelimitwhenthelightest supersymmetricparticleislight,gluinoandbottomsquarkmassesareexcludedbelow1280and570 GeV, respectively.

©2015CERNforthebenefitoftheCMSCollaboration.PublishedbyElsevierB.V.Thisisanopenaccess articleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

1. Introduction

TheStandardModel (SM)ofparticlephysics providesan accu-ratedescriptionofknownparticlepropertiesandinteractions.The discoveryofa HiggsbosonbytheATLAS

[1]

andCMS[2] Collab-orationsattheCERNLHCrepresentsthelatestmajormilestonein thevalidationoftheSM. Despiteits success,theSM isknownto beincompletebecause,forexample,itdoesnot offeran explana-tionfordark matter anditcontains ad-hocfeatures, such asthe fine-tuning[3–9]requiredtostabilizetheHiggsbosonmassatthe electroweakscale.ManyextensionstotheSMhavebeenproposed. Inparticular, supersymmetry(SUSY) mayprovide acandidate for darkmatterin

R-parity

conservingmodels[10]aswellasa natu-ralsolutiontothefine-tuningproblem[3–9].

The CMS and ATLAS Collaborations have performed many searchesfor physics beyond theSM. Thus far, no significant evi-dencefor new physics has been obtained. The search for super-symmetry is particularly interesting phenomenologically because of the large number of new particles expected. The LHC SUSY search program consists therefore of a wide array of searches

[11–22]. Any particular manifestation of SUSY in nature would likelyresultintopologiesthat aredetectableinavarietyof final-states.Individual searches can therefore be combined to provide complementarityandenhancedsensitivityintheglobalsearchfor newphysics.

 _{E-mailaddress:cms-publication-committee-chair@cern.ch.}

Naturalness arguments suggest that the supersymmetric part-nersofthegluon(gluino,



g)andthird-generationquarks(thetop andbottomsquarks,



t and



b)shouldnotbetooheavy[23–26]. Di-rectorcascadeproductionofthird-generationsquarkscanleadto final states with severalW bosons and bottom quarks,and con-siderable imbalance



pmiss_T intransverse momentum. The missing momentum arises from neutrinos in events where one or more W bosons decay leptonically, but also, for the R-parity conserv-ing models considered here, because the lightest SUSY particle (LSP), taken to be the lightest neutralino

χ



0

1, is weakly

interact-ing andstable,escaping withoutdetection. Thestudies presented herefocus on SUSY simplified modelscenarios [27,28] withfour W bosons. Eachof theW bosons candecay eitherintoa quark– antiquarkpairorintoachargedleptonanditsneutrino.Depending onthedecaymodesoftheW bosons,thefinalstatescontain0–4 leptons. Thismakescombiningthefinal stateswithdifferent lep-tonmultiplicitiesbeneficial.Thedileptonsignatureissplit accord-ing to the relative electric charges of the leptons, providing five mutually exclusive analyses for the combination: fully hadronic, single-lepton, opposite-sign dilepton,same-sign dilepton,and

≥

3 leptons(multilepton).Theresultsarebasedonproton–proton col-lision data collected at

√

s

=

8 TeV withthe CMSexperiment at theLHCduring 2012, andcorrespond toanintegratedluminosity of19.5 fb−1.

The first simplified model we consider describes gluino pair production,followedbythe decayofeachgluinotoa topquark– antiquark pair (t

¯

t) and the LSP. For cases where the top squark mass is larger than the gluino mass, the decay will proceed

http://dx.doi.org/10.1016/j.physletb.2015.04.002

0370-2693/©2015CERNforthebenefitoftheCMSCollaboration.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

Fig. 1. Feynmandiagramsforthesignalsfrom:(left) gluinopairproductionwithintermediatevirtualtopsquarks(T1tttt),(middle) gluinopairproductionwithintermediate on-shelltopsquarks(T5tttt),and(right) bottomsquarkpairproduction(T6ttWW).

through a virtual top squark (T1tttt model, Fig. 1 left). Alterna-tively,whenthetopsquarkmassissmallerthanthegluinomass and phase space allows, the decay will proceed through an on-shell top squark (T5tttt model, Fig. 1 middle). Each top quark decaysto a bottom quark anda W boson, leading to final states withfour W bosons, fourbottom-quark jets (b jets),and consid-erable



pmiss_T . The second simplified modelwe consider describes bottom–antibottomsquarkpairproduction,whereweassumethat each bottom squark decays to a top quark and a chargino (

χ



±), andthatthecharginothendecaystoyieldaWbosonandtheLSP (T6ttWWmodel,

Fig. 1

right).ThefinalstatethuscontainsfourW bosons,twob jets,andlarge



pmiss

T .

Thepaperisorganizedasfollows.Section2describestheCMS detector.The event simulation,trigger, and reconstruction proce-duresaredescribedinSection3.Section 4presentsdetails ofthe individualanalyses,withparticularemphasisontheopposite-sign dilepton search, which is presented here for the first time. The combinationmethodologyandresults arepresented inSection 5. Section6providesasummary.

2. Detector

The central feature ofthe CMS detector is a superconducting solenoid,of6 minternaldiameter,thatproducesanaxialmagnetic field of3.8 T.Withinthesolenoidvolume are asiliconpixel and strip tracker,a leadtungstatecrystalelectromagnetic calorimeter, anda brassandplasticscintillatorhadroncalorimeter.Muonsare detected in gasionization chambers embedded in the steel flux-return yoke outside the magnet. The tracking system covers the pseudorapidityrange

|

η

|

<

2.5,themuondetectors

|

η

|

<

2.4,and thecalorimeters

|

η

|

<

3.0.Steelandquartz-fiberforward calorime-terscover3

<

|

η

|

<

5.AdetaileddescriptionoftheCMSapparatus andcoordinatesystemaregiveninRef.[29].

3. Eventreconstruction,trigger,andsimulation

Therecordedeventsarereconstructed usingtheCMS particle-flow algorithm [30,31]. Electron candidates are reconstructed by associating tracks to energy clusters in the electromagnetic calorimeter [32,33]. Muon candidates are reconstructed by com-bininginformationfromthetrackerandthemuondetectors[34].

Particle-flow constituents are clustered into jets using the anti-kT clusteringalgorithmwithadistanceparameterof0.5[35].

Corrections are applied as a function of jet transverse momen-tum (pT) and

η

to account for non-uniform detector response [36,37]. Contributions from additional pp collisions overlapping withtheeventofinterest(pileup)areestimatedusingthejetarea method[38,39]andaresubtracted fromthejet pT.The total

vis-ible jet activity HT is definedasthe scalar sumof thejet pT in

theevent,and

H

miss

T asthe

p

T imbalanceofthereconstructedjets,

wherethe pT and

η

requirements foracceptedjetsare specified

fortheindividualsearchesinSection4.Theidentificationofb jets is performed using the combined secondary vertex algorithm at

the medium working point [40], which has a b-jet tagging effi-ciencyof70%andalight-flavorjetmisidentificationratebelow2% for jetswith pT values in the rangeof interest for thisanalysis.

The missingtransversemomentum vector



pmiss_T isdefinedasthe projectionontheplaneperpendiculartothebeamaxisofthe neg-ativevectorsumofthemomentaofallreconstructedparticles.Its magnitudeisreferredtoas

E

miss

T .

The data sample used for the fully hadronic analysis was recorded with trigger algorithms that required events to have

HT

>

350 GeV and EmissT

>

100 GeV. The single-lepton analysis

usestriple- ordouble-objecttriggers.Thetriple-objecttriggers re-quire a lepton with pT

>

15 GeV, together with HT

>

350 GeV

and Emiss_T

>

45 GeV. Thedouble-objecttriggershavethesame HT

requirement, no Emiss_T requirement, anda lepton pT thresholdof

40 GeV. Thedata samplesforthe dileptonandmultilepton anal-yses were collected withee, e

μ

, and

μμ

double-lepton triggers, whichrequireatleastone e orone

μ

with pT

>

17 GeV and

an-otherwith

p

T

>

8 GeV.

SimulatedMonteCarlo(MC)samplesofsignal eventsare pro-duced usingthe MadGraph 5.1.3.30 [41] generator, asare SM t

¯

t, Drell–Yan, W

+

jets,andsingletopquark events.Thet

¯

t events in-clude production in association with a photon, or with a W, Z, or H boson. The production of single top quarks in association with an additional quark and a Z boson is simulated with the mc@nlo_{2.0.0 [42,43]generator.ThePYTHIA6.4.24 [44]generator} is used to simulate the generic multijet QCD and diboson(WW, ZZ, and WZ)processes,aswell asto describe theparton shower andhadronizationforthe MadGraph samples.AllSMsamplesare processed withthe fullsimulation oftheCMSdetector,based on the Geant4 [45] package,while thesignal samplesare processed with the CMS fast simulation [46] program. The fast simulation is validated through comparisonof its predictions with those of the full simulation, and efficiency corrections based on data are applied[47].Theeffectofpileupinteractionsisincludedby super-imposing a numberofsimulatedminimumbias eventsontop of thehard-scatteringprocess,withthedistributionofthenumberof reconstructedverticesmatchingthatindata.

4. Searchchannels

This paperreportsthecombinationof fiveindividual searches fornewphysicsbyCMS.Thefullyhadronic[19],single-lepton[20], same-sign dilepton [21], and multilepton [22] searches have all beenpublished, andaresummarizedbriefly below.The opposite-sign dilepton search is presented here for the first time and is thereforedescribedingreaterdetail.

4.1. Fully hadronic analysis

ConsideringthatsignaleventscontainfourW bosons, thefully hadronicbranchingfractionisabout24%.Thefullyhadronic analy-sis[19]requiresatleastthreejetswith

p

T

>

50 GeV and

|

η

|

<

2.5,

pT

>

10 GeV and

|

η

|

<

2.5 (2.4) for electrons (muons). The HT

and Hmiss_T values are required to exceed 500 and 200 GeV, re-spectively. To render the analysis more sensitive to a variety of final-statetopologiesresultingfromlongercascadesofsquarksand gluinos, andtherefore a large number ofjets, theevents are di-vided into three exclusive jet-multiplicity regions: Njets

=

(3–5),

(6–7), and

≥

8. The events are further divided into exclusive re-gionsofHT andHmiss_T .Theexploitationofhigherjetmultiplicities

ismotivatedby natural SUSYmodels in whichthe gluinodecays intotopquarks[19].Thisanalysisdoesnotimposearequirement onthenumber Nbjetsoftaggedb jets,therebymaintainingahigh

signalefficiency.

ThemainSM backgroundsforthefullyhadronicchannel arise fromZ

+

jets eventsinwhichtheZ bosondecaystoa

νν

neutrino pair; from W

+

jets and t

¯

t events with a W boson that decays directly or through a

τ

lepton to an e or

μ

and the associated neutrino(s),withtheeor

μ

undetectedoroutsidetheacceptance oftheanalysis;fromW

+

jets and t

¯

t eventswithaW bosonthat decaystoahadronicallydecaying

τ

leptonanditsassociated neu-trino;andfromQCDmultijetevents.Forthefirstthreebackground categories,theneutrinosprovideasourceofgenuine

H

miss

T .Forthe

QCD multijet eventbackground, large values of Hmiss

T arise from

themismeasurementofjet pT orfromtheneutrinosproducedin

the semileptonicdecays of hadrons. All SM backgrounds are de-terminedfromcontrolregionsinthedata,andarefoundtoagree withtheobservednumbersofeventsinthesignalregions.

4.2. Single-lepton analysis

WithfourW bosons,thebranchingfractionofsignaleventsto stateswithasingleelectronormuonisabout42%,including con-tributionsfromleptonically decaying

τ

leptons. The single-lepton analysis[20] requires thepresence of an electron ormuon with

pT

>

20 GeV and nosecond electronormuonwith pT

>

15 GeV,

with the same

η

restrictions on the e and

μ

as in Section 4.1. Jetsarerequiredtohave pT

>

40 GeV and

|

η

|

<

2.4.The

S

lepT

vari-ableisevaluated, definedby thescalarsumof Emiss

T andthe

lep-ton pT.Eventsmustsatisfy

N

jets

≥

6,

N

bjets

≥

2,

H

T

>

400 GeV,and Slep_T

>

250 GeV.Afurthervariable,theazimuthal angle

φ (W,

)

betweenthe W bosoncandidateandthelepton,isevaluated.For thisvariable,the pT of theW boson candidateis definedby the

vectorsumofthelepton

p

Tandp



miss_T .Forsingle-leptont

¯

t events,

theanglebetweenthedirectionsoftheW boson andthecharged lepton hasa maximum value that isdetermined by themass of theW boson andits momentum. Therequirementof large Emiss_T

selectseventswithLorentz-boostedW bosons.Thisleadstoa nar-rowdistributionin

φ (W,

).

InSUSYdecaystherewillbenosuch maximum,sincethe

E

miss

T mostlyresultsfromthetwoneutralinos

andtheirdirectionsarelargelyindependentoftheleptondirection. Thereforethe

φ (W,

)

distributionisexpectedtobeflatforSUSY events.Theanalysisrequires

φ (W,

)

>

1.Thesearchisthen per-formedinexclusiveregionsof

S

lep_T for

N

bjets

=

2 and

N

bjets

≥

3.

The main SM backgrounds forthe single-lepton channel arise fromdileptont

¯

t eventsin whichone lepton isnot reconstructed orliesoutsidetheacceptanceoftheanalysis,fromresidual single-leptont

¯

t events,andfromeventswithsingle-topquarkproduction. The backgrounds are evaluated using data control samples. The totalnumberofbackgroundeventsisfoundtoagreewiththe ob-servednumberofeventsineachsignalregion.

4.3. Same-sign dilepton analysis

ThebranchingfractionforeventswithfourW bosonstoafinal state withatleast two same-sign leptons (ee,

μμ

,or e

μ

) is 7%,

includingthecontributionsof

τ

leptons.Forthepresentstudy,we makeuseofthehigh-pTselectionofthesame-signdilepton

analy-sisinRef.[21],whichrequiresatleasttwosame-signlightleptons (e,

μ

) with pT

>

20 GeV,

|

η

|

<

2.4, and invariant mass above

8 GeV. To prevent overlap between the same-sign dilepton and multilepton analyses, an explicit vetoon additionalleptons with

pT

>

10 GeV and

|

η

|

<

2.4 is added for the same-sign dilepton

analysis, asinthe searchfor



t2 productiondescribed inRef.[22].

Jetsarerequiredtosatisfy pT

>

40 GeV and

|

η

|

<

2.4.Eventsmust

have

N

jets

>

2, HT

>

200 GeV,and

E

miss_T

>

50 GeV.Theeventsare

examined in exclusive regions of HT and Emiss_T for 2

≤

Njets

≤

3

and

N

jets

≥

4,allfor

N

bjets

=

0,1,and

≥

2.

There are three main sources of SM backgroundin this anal-ysis: non-prompt leptons, rare SM processes, andelectrons with wrong charge assignments. Themain sources ofnon-prompt lep-tonsare leptonsfrombottom- and charm-quarkdecays, misiden-tifiedhadrons,muonsfromlight-mesondecaysinflight,and elec-tronsfromunidentifiedphotonconversions.Thebackgroundfrom non-prompt leptons isevaluatedfromdata controlregions. Dibo-son,t

¯

tW,andt

¯

tZ productionarethemostimportantrareSM back-ground sources. Their contributions are estimated fromMC sim-ulation. Opposite-sign dileptons can also contribute to the back-ground when the charge of an electron is misidentified because ofbremsstrahlung emitted inthe trackermaterial.This contribu-tionisestimatedusingatechnique basedon Z

→

e+e−data.No significantdeviationsareobservedfromtheSMexpectations.

4.4. Multilepton analysis

ThebranchingfractionforeventswithfourWbosonstodecay to a final state with three or more charged leptons (e or

μ

) is 6%,including

τ

leptoncontributions.Themultileptonsampleused in thepresent studycorresponds to the selection ofevents with three or more such leptons presented in Ref. [22]. The electrons ormuonsare requiredtohavepT

>

10 GeV and

|

η

|

<

2.4,except

atleastoneofthethreeleptons musthave pT

>

20 GeV.Jetsare

required tohave pT

>

30 GeV and

|

η

|

<

2.4.Events mustsatisfy Njets

≥

2,

N

bjets

≥

1,

H

T

>

60 GeV,andEmiss_T

>

50 GeV.Theevents

areexaminedinexclusiveregionsof

H

Tand

E

miss_T for2

≤

Njets

≤

3

and Njets

≥

4, both with Nbjets

=

1 and 2, andfor Njets

≥

3 with Nbjets

≥

3.

Comparedtothefullyhadronic,single-lepton,ordilepton signa-tures,themultileptonsearchtargetsfinalstateswithsmall branch-ing fractions, but provides good signal sensitivity because the three-leptonrequirementstronglysuppressesbackgrounds.Onlya few SMprocessesexhibit such signatures.Background from dibo-sonproductionishighlysuppressedbythe

N

bjetsrequirement.The

mainbackgroundsarisefromeventswithacombinationoft

¯

t pro-ductionandnon-promptleptons,aswellasfromrareSMprocesses like t

¯

tW andt

¯

tZ production.The non-prompt lepton background is evaluated using data control regions and the rare SM back-groundfromsimulation.Thereisnostatisticallysignificantexcess ofeventsfoundinthesignalregionsabovetheSMexpectations.

4.5. Opposite-sign dilepton analysis

ThebranchingfractionforeventswithfourW bosonstoafinal statewithatleastoneopposite-signleptonpair(e or

μ

)is14%, in-cludingthecontributionsof

τ

leptons. Theopposite-signdilepton search requiresthepresence ofexactlytwo opposite-signleptons (eor

μ

),eachwith

p

T

>

20 GeV and

|

η

|

<

2.4.Eventswithathird

leptonsatisfying pT

>

20 GeV and

|

η

|

<

2.4 are vetoed.Jetsmust

satisfy pT

>

30 GeV and

|

η

|

<

2.5.ThisanalysistargetstheT1tttt

Table 1

Selectioncriteriaforthesignalregionintheopposite-signdileptonanalysis.

Variable Description Criterion

ETmiss Missing transverse momentum >30 GeV

Njets Number of jets >4

Nbjets Number of b-tagged jets >2

|ηj1| Pseudorapidity for jet with largest pT <1

|ηj2| Pseudorapidity for jet with next-to-largest pT <1

Manyvariablesareexaminedinordertodefineasignalregion (SR)that maximizessignal content whileminimizing the contri-butionsofSMevents.Wechoosethosevariablesthatdemonstrate thegreatest discriminatingpowerbetweensignal andSM events, andthat exhibit the smallestlevel of correlation amongst them-selves: Njets, Nbjets, EmissT ,and the

η

values of thetwo jets with

largest pT. The criteria that yield the highest sensitivity in the

parameterspace ofthe T1ttttmodel, summarizedin

Table 1

,are optimized using simulated events. Events are divided into bins of Emiss_T .ThebinwithhighestEmiss_T (>180 GeV)isthemost sen-sitive for the bulk of the signal phase space, but the bins with lower Emiss

T are importantfor compressed spectra,i.e., for signal

scenarioswithsmallmassdifferencesbetweentheSUSYparticles. Afterapplyingtheselectioncriteriasummarizedin

Table 1

,the re-maining SMbackground isprimarily composedofeventswith t

¯

t, Drell–Yan,andW

+

jets production.

Acontrol region (CR) isdefined bythe sumof thetwo event samplesobtainedby separatelyinverting the

η

j1

<

1 and

η

j2

<

1

requirements.Thecontributionof signaleventsto thecontrol re-gion dependson the gluino mass (m_g) and theLSP mass (mLSP)

andcanbe aslarge as10%. Thecontributions ofsignal eventsto theCRaretakenintoaccountintheinterpretationoftheresults.

An extrapolation factor Rext is defined asa function of EmissT

and Nbjets, as the ratio of the number of SM events in the SR

tothat intheCR. Insimulatedeventsthe Rext factorisobserved

to change slowly as a function of Emiss_T , asshown in Fig. 2. The

Rextratioissimilarlyfoundtobeindependentof

N

bjets,makingit

possibleto extract its value directlyfrom datausingevents with

Nbjets

=

2, withoutalteringthe othersignal andcontrol selection

criteria.Thecontributionofsignaleventstothe

N

bjets

=

2 regionis

smallcompared tothestatistical uncertaintyintheextrapolation factorandisthereforeneglected.Thusthebackgroundestimateis derivedentirelyfromdata,minimizingsystematicuncertainties.

TheSMbackgroundpredictionfortheSRisobtainedby multi-plying RextwiththenumberofdataeventsintheCR:

NSR_predicted

=

RextNCRdata

.

(1)

Theperformanceofthebackgroundestimationmethodis stud-iedboth inthe SR, usingsimulation, andina cross-checkregion definedby 2

≤

Njets

≤

4, usingdata andsimulation.Forboth

re-gions, the SM background consistsprimarily oft

¯

t events, witha smallcontributionfromW

+

jets production.Fig. 3 shows agree-mentbetweenthepredictedandactual

E

miss

T distributionsforthe

SRandcross-checkregions.

The systematic uncertainty in the background prediction is basedon the statisticaluncertainties in thedata, usedto extract the Rext factors, andonthelevel ofagreementbetweenthe

pre-dictedandactual resultsfoundusingsimulation intheSR(Fig. 3

right).Nosignificantbiasinthemethodisobservedinsimulation, andan additionalsystematicuncertaintyof25–50%isassignedto accountforthestatisticalprecisionofthelatterterm.

Thepredictedandobserved

E

miss

T distributionsforthesignal

re-gionareshownin

Fig. 4

andlistedin

Table 2

.Noexcessofevents is observed with respect to the SM prediction.For the interpre-tationof results(Section 5),all four Emiss

T bins are used.Besides

Fig. 2. Extrapolationfactorsfromthecontrolregiontothesignalregion,Rext,asa functionofEmissT ,forsimulatedeventswithNbjets=2 (blacktriangles)andNbjets≥ 3 (redpoints).Alltheothersignalselectioncriteriahavebeenapplied.Thelower panelshowstheratiooftheNbjets≥3 totheNbjets=2 results.(Forinterpretation ofthereferencestocolorinthisfigure,thereaderisreferredtothewebversionof thisarticle.)

their useinthecombination,wepresentin

Appendix A

the inter-pretationoftheT1ttttandT5ttttscenariosbasedontheresultsof theopposite-sidedileptonanalysisalone.

5. Combinationofanalyses

The results from the five analyses are combined to provide more stringentconclusions. The combinedresults are interpreted inthecontext oftheSUSY scenariosillustratedin

Fig. 1

.The 95% confidence level (CL) upper limits(UL) on the cross sections are calculated using the LHC-style CLS method [48–50]. Because of

theirlargebranchingfractions,thefullyhadronicandsingle-lepton analyses aremostsensitiveinthelargestpartofthephasespace. However, the analyses based on higher lepton multiplicities be-come important for the more compressed mass spectra and for modelswithfewerb jets.

Systematic uncertainties in the signal selection efficiency are evaluated using the same techniques for all analyses. They are evaluatedseparatelyforthedifferentsignalmodels,searchregions, andforeachhypothesisfortheSUSYparticlemasses.The system-atic uncertainties in the signal modeling are taken to be 100% correlated among the mass hypotheses. As an example, a sum-mary ofsystematicuncertainties forthe T1tttt modelis givenin

Table 3.Thetotalsystematicuncertaintyvariesbetween7and35% dependingonthedecaymodesconsidered,thesearchregions,and themasspoints.Animportantsourceofsystematicuncertaintyfor the analyses that requiremultiple leptons arises fromthe lepton identification and isolation efficiencies, which are evaluated us-ing Z

→

+

− events. Theuncertainty intheenergyscale ofjets

Fig. 3. Emiss

T distributionpredictedforSMbackgroundsbyextrapolationfromthecontrolregionwiththestatisticalandsystematicuncertainties(redbands),comparedto actualdistribution(blackpoints)for(left) simulatedeventsinthecross-checkregion,(middle) dataeventsinthecross-checkregion,and(right) simulatedeventsinthe searchregion.Thelowerpanelsshowtheratiosoftheactualtopredicteddistributions.(Forinterpretationofthereferencestocolorinthisfigure,thereaderisreferredto thewebversionofthisarticle.)

Fig. 4. Emiss

T distributioninthe signalregion(blackpoints)comparedtotheSM backgroundpredictionwithitsstatisticalandsystematicuncertainties(redband). TheexpectedsignalfortheT1ttttmodelwithagluinomassof1150 GeV andan LSPmassof300 GeV,multipliedbyafactorof3forbettervisibility,isindicated bythebluecurve.(Forinterpretationofthereferencestocolorinthisfigure,the readerisreferredtothewebversionofthisarticle.)

gives rise to a 1–15% systematicuncertainty that increases with more stringent kinematic requirements. For compressed spectra, the modeling of initial-state radiation (ISR) [18] is an important sourceofuncertainty.The PDF4LHCrecommendations

[51,52]

are usedtoevaluatetheuncertaintyassociatedwiththeparton distri-butionfunctions(PDFs).Formostoftheanalyses thebackground evaluationmethodsdiffer,andsothesystematicuncertainties are treatedasuncorrelated.Theoverlapbetweenmostcontrolregions isstudied and found to be negligible. The only exception occurs

Table 2

PredictedSMbackgroundandobserveddatayieldsasafunctionofEmiss

T forthe

opposite-signdileptonanalysis.Theuncertaintiesinthetotalbackground predic-tionsincludeboththestatisticalandthesystematiccomponents.

Emiss

T requirement Background prediction Observed data yields

30<Emiss T <80 GeV 19.9±3.7 17 80<EmissT <130 GeV 11.8±3.0 10 130<Emiss T <180 GeV 5.7±2.2 5 Emiss T >180 GeV 1.2±1.1 1

forthesame-signdileptonandmultileptonanalyses,whichusethe samemethodstopredictthebackgroundfromnon-promptleptons andrareSM processes.Forthiscase, thesystematicuncertainties aretakentobefullycorrelated.

5.1. Gluino-mediated top squark production with virtual top squarks

Theresultsarefirstinterpretedinthecontextof



g



g production with



g

→

t

¯

t

χ



0

1 throughavirtual



t,theprocessreferredtoasT1tttt.

The signaturecontains fourtop quarksandhassignificantjet ac-tivity (Fig. 1 left). The fully hadronic and single-lepton analyses are thereforeexpectedtobe especiallysensitive, becauseoftheir largersignalefficiencies.

Fig. 5

(left)showsthe95%CLupperlimits onthe productofthecross sectionandbranching fractioninthe (m_χ0

1, mg) plane. The exclusion curves are evaluated by

compar-ing the crosssection upperlimitswiththe next-to-leading-order (NLO) plusnext-to-leading-logarithm(NLL)theoretical production crosssections[54–58].Thethickreddashedlineindicatesthe95% CL expected limit, which is definedas the median of the upper limitdistributionobtainedusingpseudo-experimentsanda likeli-hood model.The

±

1 standard deviation experimental systematic uncertainties

σ

experimentareshownbythethinredlinearoundthe

Table 3

Relative(%)systematicuncertaintiesinthesignalefficiencyoftheT1ttttmodelforthefullyhadronic(0 ),single-lepton(1 ),opposite-signdilepton(2OS ),same-sign dilepton(2SS ),andmultilepton(≥3 )analyses.ThegivenrangesreflectthevariationacrossthedifferentsearchregionsandfordifferentvaluesoftheSUSYparticle masses.

Source 0 1 2 OS 2 SS ≥3

Integrated luminosity[53] 2.6

Pileup <5

Lepton identification and isolation efficiency <1 3 4 10 12

Trigger efficiency 2 4 6 6 5

Parton distribution functions 1–8 10–30 2 2 4

Jet energy scale 2–8 2–7 8 1–10 5–15

b-tagged jet identification n/a 1–15 14 2–10 5–20

Initial-state radiation 3–22 2–18 1–18 3–15 3–15

Total 7–28 14–35 17–25 18–25 15–30

line,wheretheuncertaintyband(thinblacklines)indicatesthe

±

1 standarddeviationuncertainty

σ

theoryinthetheoreticalcross

sec-tion.Thetheoretical uncertaintyismainlyduetouncertainties in therenormalizationandfactorizationscales,andintheknowledge ofthePDFs.Toquotethegluinomassexclusion,weconservatively consider the observed upper limit minus

σ

theory. It is seen that

gluinosbelow1280 GeV areexcluded for

m

_χ0

1

≈

0 GeV.Assuming

agluinomassof1000 GeV,anLSPwithamassbelow600 GeV is excluded.

Theexclusioncurvesforeachindividual analysisare shownin

Fig. 5(right). As expected, forlow LSP masses, the single-lepton andfullyhadronicanalysesprovidethemoststringentresults.For

m_χ0

1

≈

0 GeV,thecombinationisseen toextendthegluino mass

exclusionbyabout35 GeV comparedtothesingle-leptonanalysis, whichprovidesthemoststringentcorrespondingindividualresult. Largevaluesof

m

_χ0

1 leadtomorecompressedmassspectra,softer

decayproducts,andtherefore smaller Emiss_T . Asa result,the fully hadronic and single-lepton analyses become less sensitive, since theyrequirehigh-pT jetsandlarge Emiss_T .Thedileptonand

multi-leptonanalysesdepend lessonthe pT spectrumofthefinal-state

particles,andtheirsensitivitydecreaseslessforsmallermass split-tings.Thustheanalyses requiringtwo ormoreleptons contribute mosttotheoverall sensitivitywhenthedifference

m

g

−

m_χ0

1

be-comes small. For

m

g

≈

1000 GeV, the exclusion limit on m_χ0

1 is

extended byabout 60 GeV becauseofthe addition ofthe multi-leptonchannels.

5.2. Gluino-mediated top squark production with on-shell top squarks

If the top squarks are light enough, the gluino can decay through an intermediate on-shell top squark. In this model, re-ferred to as T5tttt, the values of m_χ0

1, mt, and mg function as

independent parameters. Results are presented for a fixed mass

m_χ0

1

=

50 GeV and scanned over the massesof the on-shell top

squarkandgluino.The 95%CLupperlimitsontheproductofthe crosssectionandthebranchingfractioninthe

m

t versus

m

gplane

areshownin

Fig. 6

,top.InthecontextoftheT5ttttmodel,gluinos withmassesbelowaround1300 GeV areexcluded fortop squark massesaround700 GeV.

Fig. 6

,bottom,showsthe resultsforthe individualstudies.Thecontributionfromthefullyhadronic analy-sisremains importantevenforrelativelysmalltopsquarkmasses

m_t

≈

200 GeV becauseofthehigh

H

Tsearchregions:signalevents

in this case contain smaller Emiss_T but larger HT. However, for m_t

<

150 GeV, the fully hadronic analysis loses sensitivity. The single-lepton analysis provides the most stringent individual re-sults,butloses sensitivityasm_t decreases. Thesensitivity ofthe

dileptonandmultileptonsearchesdependslessstronglyon

m

t,but

theirsensitivityeveninthecompressedregionisrathersmall,

al-Fig. 5. (Top)The95%CLcrosssectionupperlimitsforgluino-mediatedsquark pro-ductionwithvirtualtopsquarks,based onanNLO+NLLreferencecrosssection forgluinopairproduction.Thesolidanddashedlinesindicate,respectively,the ob-servedandexpectedexclusioncontours forthecombinationofthefiveanalyses. Thethincontoursindicatethe±1standarddeviationregions.(Bottom)Exclusion contours(EC)fortheindividualsearches,plusthecombination.

though they contribute tothe combinationatvery smallm_t. The

combination improvesthe exclusionreach in thegluino massby about50 GeV forsmall

m

t.

5.3. Bottom squark pair production

We alsoconsiderbottom squarkpairproductionwiththe bot-tom squarks decayingas



b1

→

t

χ



₁− and



χ

₁−

→

W−

χ



₁0,knownas

T6ttWW(Fig. 1right).Thesingle-leptonandopposite-signdilepton analyseshaveverylittlesensitivitytosuchamodelbecauseofthe stringent

N

bjetsand

N

jetsrequirements,andarenotincludedinthe

combination.Thefullyhadronicanalysis,whichdoesnotimposea requirementon

N

bjets,contributessomesensitivity.Themain

sen-Fig. 6. (Top) The95%CLcrosssectionupperlimitsforgluino-mediatedsquark pro-ductionwithon-shelltopsquarks,assuminganLSPmassofm_χ0

1=50 GeV,based onanNLO+NLLreferencecrosssectionforgluinopairproduction.Thesolidand dashedlinesindicate,respectively, theobservedandexpectedexclusioncontours forthecombinationofthefiveanalyses.Thethincontoursindicatethe±1standard deviationregions.(Bottom) Exclusioncontours(EC)fortheindividualsearches,plus thecombination.

sitivitycomes fromthesame-sign andmultilepton searches with eitherNbjets

=

1 or 2.

FortheT6ttWWmodel,theLSPmassissetto50 GeV.The re-sulting95%CLupperlimitsontheproductofthecrosssectionand branchingfractioninthe

m

_χ± versus

m

bplaneareshownin

Fig. 7

,

top. In the context of this model, bottom squark masses up to 570 GeV areexcludedforLSPmassesaround150–300 GeV.

Fig. 7

, bottom,showstheexclusionlimitsforthe individualanalyses as-suming a fixed bottom squark mass of 600 GeV. The same-sign dileptonanalysisprovidesthebestsensitivityforcharginomasses below400 GeV, andthe combinationwiththe multilepton anal-ysisleadsto a15% improvementinthe crosssection upperlimit andevenupto35%improvementintheexpectedcrosssection up-perlimit,whichrepresentsanimprovementintheexpected sbot-tommass exclusionlimitsof around 50 GeV.For largerchargino masses,the fullyhadronicanalysisis moresensitive becausejets fromW bosondecaysbecomemoreenergetic.

6. Summary

Five searches for supersymmetry with non-overlapping event samples are combined to obtain more stringent exclusion limits onmodels inwhichb jets and fourW bosons areproduced. The resultsarebasedondatacorrespondingtoanintegrated luminos-ityof19.5 fb−1 ofpp collisions,collected withtheCMSdetector at

√

s

=

8 TeV in2012. Becauseoftheir largebranchingfractions,

Fig. 7. (Top)The95%CLcrosssectionupperlimitsforbottom-squarkpair produc-tion,assuminganLSPmassofm_χ0

1 =50 GeV,based onanNLO+NLLreference crosssection.Thesolidanddashed linesindicate,respectively,the observedand expectedexclusioncontoursforthecombination ofthefullyhadronic,same-sign dilepton,andmultileptonanalyses.Thethincontoursindicatethe±1standard de-viationregions.(Bottom)Exclusioncontours(EC)fortheindividualsearches,plus thecombination,assumingabottomsquarkmassof600 GeV.

thesingle-leptonandfullyhadronicanalyseshavethelargest sen-sitivity for mostof the range ofthe supersymmetric mass spec-tra, whereas the analyses with higher lepton multiplicities have higher sensitivity for models withmore compressed mass spec-tra. The complementarity ofthe searches is exploited to provide comprehensivecoverageacross awideregionofparameterspace. Thecombinedsearchesyield95%confidencelevelexclusionsofup to 1280 and 570 GeV for the gluino and bottom-squark masses in the context of gluino and bottom-squark pair production, re-spectively. The increase in sensitivity that arises from the com-bination ofthe fiveanalyses corresponds to an increase ofabout 50 GeV intheSUSYmassreachcomparedtotheindividual analy-ses.

Acknowledgements

WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the technicalandadministrative staffsatCERN andatother CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcentersand personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythe computinginfrastructureessential to ouranalyses. Finally, we acknowledge the enduring support for the construc-tionandoperation oftheLHC andtheCMSdetectorprovidedby thefollowingfundingagencies:BMWFWandFWF(Austria);FNRS

and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES(Bulgaria);CERN;CAS,MOST,andNSFC(China);COLCIENCIAS (Colombia);MSESandCSF(Croatia);RPF(Cyprus);MoER,ERCIUT andERDF(Estonia);Academy ofFinland,MEC,andHIP(Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); LAS (Lithuania); MOE and UM(Malaysia); CINVESTAV, CONACYT,SEP,andUASLP-FAI(Mexico);MBIE(NewZealand);PAEC (Pakistan);MSHEandNSC(Poland);FCT(Portugal);JINR(Dubna); MON,RosAtom,RASandRFBR(Russia);MESTD(Serbia);SEIDIand CPAN(Spain);SwissFundingAgencies(Switzerland);MST(Taipei); ThEPCenter,IPST,STARandNSTDA(Thailand);TUBITAKandTAEK (Turkey);NASUandSFFR(Ukraine); STFC(United Kingdom);DOE andNSF(USA).

Individuals have received support from the Marie-Curie pro-gramme and the European Research Council and EPLANET (Eu-ropean Union); the Leventis Foundation; the A.P. Sloan Founda-tion; the Alexander von Humboldt Foundation; the Belgian Fed-eral Science Policy Office; the Fonds pour la Formation à la Recherchedansl’Industrieetdansl’Agriculture(FRIA-Belgium);the AgentschapvoorInnovatiedoorWetenschapenTechnologie (IWT-Belgium);the Ministry ofEducation,Youth andSports (MEYS) of theCzechRepublic;theCouncilofScienceandIndustrialResearch, India; the HOMING PLUS programme of Foundation For Polish Science, cofinanced from European Union, Regional Development Fund;the CompagniadiSan Paolo(Torino); theConsorzio per la Fisica (Trieste);MIUR project20108T4XTM(Italy); the Thalisand Aristeia programmes cofinanced by EU-ESF andthe Greek NSRF; andtheNationalPrioritiesResearchProgrambyQatarNational Re-searchFund.

Appendix A. Additionalplotsfortheopposite-signdilepton search

Thisappendixpresentsadditionalresultsfortheopposite-sign dilepton search. The results of this analysis alone for the T1tttt (Fig. 1 left) andT5tttt(Fig. 1 middle) modelsare shown, respec-tively, in Figs. A.1, top and bottom. In the context of the T1tttt model,gluinos withmassesbelowaround 980 GeV are excluded forLSPmassesbelow400 GeV.Inthe T5ttttmodel,gluinos with massesbelow1000 GeV areprobedfortopsquarkmassesaround 650 GeV.

References

[1] ATLASCollaboration,Observationofanewparticleinthesearchforthe Stan-dardModelHiggsbosonwiththeATLASdetectorattheLHC,Phys.Lett.B716 (2012)1,http://dx.doi.org/10.1016/j.physletb.2012.08.020,arXiv:1207.7214. [2] CMSCollaboration,Observationofanewboson atamassof125 GeVwith

theCMSexperimentattheLHC,Phys.Lett.B716(2012)30,http://dx.doi.org/ 10.1016/j.physletb.2012.08.021,arXiv:1207.7235.

[3] R. Barbieri,G.F. Giudice,Upper boundson supersymmetricparticle masses, Nucl.Phys.B306(1988)63,http://dx.doi.org/10.1016/0550-3213(88)90171-X. [4] A.Romanino,A.Strumia,Areheavyscalarsnaturalinminimalsupergravity?

Phys.Lett.B487(2000)165,http://dx.doi.org/10.1016/S0370-2693(00)00806-6, arXiv:hep-ph/9912301.

[5] J.L. Feng, K.T. Matchev, T. Moroi, Multi-TeV scalars are natural in mini-malsupergravity, Phys.Rev.Lett. 84(2000) 2322, http://dx.doi.org/10.1103/ PhysRevLett.84.2322,arXiv:hep-ph/9908309.

[6] R. Kitano, Y. Nomura, A solution to the supersymmetric fine-tuning prob-lemwithintheMSSM,Phys.Lett.B631(2005)58,http://dx.doi.org/10.1016/ j.physletb.2005.10.003,arXiv:hep-ph/0509039.

[7] G.F.Giudice,R.Rattazzi,Livingdangerouslywithlow-energysupersymmetry, Nucl.Phys.B757(2006)19,http://dx.doi.org/10.1016/j.nuclphysb.2006.07.031, arXiv:hep-ph/0606105.

[8] R.Barbieri,D.Pappadopulo,S-particlesattheirnaturalnesslimits,J.High En-ergyPhys.0910(2009)061,http://dx.doi.org/10.1088/1126-6708/2009/10/061, arXiv:0906.4546.

Fig. A.1. (Top) The95%CLcrosssection upperlimitsforgluino-mediated squark productionwithvirtualtopsquarks,basedonanNLO+NLLreferencecrosssection for gluinopairproduction,derivedfromthe opposite-signdileptonanalysis.The solidanddashedlinesindicate,respectively,theobservedandexpectedexclusion contours.Thethincontoursindicatethe±1standarddeviationregions.(Bottom) Thecorrespondingresultsforgluino-mediatedsquarkproductionwithon-shelltop squarks.

[9] D.Horton,G.G.Ross,Naturalnessandfocuspointswithnon-universal gaug-inomasses,Nucl.Phys.B830(2010)221,http://dx.doi.org/10.1016/j.nuclphysb. 2009.12.031,arXiv:0908.0857.

[10] G.R.Farrar,P.Fayet,Phenomenologyoftheproduction,decay,anddetectionof newhadronicstatesassociatedwithsupersymmetry,Phys.Lett.B76(1978) 575,http://dx.doi.org/10.1016/0370-2693(78)90858-4.

[11] ATLASCollaboration,Searchfornewphenomenainfinalstateswithlargejet multiplicitiesandmissingtransversemomentumat√s=8 TeV proton–proton collisionsusingtheATLASexperiment,J.HighEnergyPhys.1310(2013)130,

http://dx.doi.org/10.1007/JHEP10(2013)130,arXiv:1308.1841.

[12] ATLASCollaboration,Searchfordirectthird-generationsquarkpairproduction infinalstates withmissingtransversemomentumandtwobjetsin√s=

8 TeV ppcollisionswiththeATLASdetector,J.HighEnergyPhys.1310(2013) 189,http://dx.doi.org/10.1007/JHEP10(2013)189,arXiv:1308.2631.

[13] ATLASCollaboration,Searchfordirectproductionofcharginosandneutralinos ineventswiththreeleptonsandmissingtransversemomentumin√s=8 TeV ppcollisionswiththeATLASdetector,J.HighEnergyPhys.1404(2014)169,

http://dx.doi.org/10.1007/JHEP04(2014)169,arXiv:1402.7029.

[14] ATLAS Collaboration, Search for direct top-squark pair production in final states with two leptons in pp collisions at √s=8 TeV with the ATLAS detector, J. High Energy Phys. 1406 (2014) 124, http://dx.doi.org/10.1007/ JHEP06(2014)124,arXiv:1403.4853.

[15] ATLASCollaboration,Searchfordirectproductionofcharginos,neutralinosand sleptonsinfinalstateswithtwoleptonsandmissingtransversemomentumin ppcollisionsat√s=8 TeV withtheATLASdetector,J.HighEnergyPhys.1405 (2014)071,http://dx.doi.org/10.1007/JHEP05(2014)071,arXiv:1403.5294. [16] ATLASCollaboration,Searchfor supersymmetryineventswithfourormore

leptonsin√s=8 TeV ppcollisions withthe ATLASdetector, Phys.Rev.D, Part.Fields 90(2014) 052001, http://dx.doi.org/10.1103/PhysRevD.90.052001, arXiv:1405.5086.

[17] CMSCollaboration,Searchforgluinomediatedbottom- andtop-squark produc-tioninmultijetfinalstatesinppcollisionsat8 TeV,Phys.Lett.B725(2013) 243,http://dx.doi.org/10.1016/j.physletb.2013.06.058,arXiv:1305.2390.

[18] CMSCollaboration,Searchfortop-squarkpairproductioninthesingle-lepton finalstateinppcollisionsat√s=8 TeV,Eur.Phys.J.C73(2013)2677,http:// dx.doi.org/10.1140/epjc/s10052-013-2677-2,arXiv:1308.1586.

[19] CMSCollaboration,Searchfornewphysicsinthemultijetandmissing trans-versemomentumfinalstateinproton–protoncollisionsat√s=8 TeV,J.High Energy Phys. 1406 (2014) 055, http://dx.doi.org/10.1007/JHEP06(2014)055, arXiv:1402.4770.

[20] CMSCollaboration,Searchforsupersymmetryinppcollisionsat√s=8 TeV in eventswith a single lepton, large jet multiplicity, and multiple b jets, Phys.Lett.B733(2013)328,http://dx.doi.org/10.1016/j.physletb.2014.04.023, arXiv:1311.4937.

[21] CMSCollaboration,Searchfornewphysicsineventswithsame-signdileptons andjetsinppcollisionsat√s=8 TeV,J.HighEnergyPhys.1401(2014)163,

http://dx.doi.org/10.1007/JHEP01(2014)163,arXiv:1311.6736.

[22] CMSCollaboration,Searchfortop-squarkpairsdecayingintoHiggsorZbosons inppcollisionsat√s=8 TeV,Phys.Lett.B736(2014)371,http://dx.doi.org/ 10.1016/j.physletb.2014.07.053,arXiv:1405.3886.

[23] N.Sakai,NaturalnessinsupersymmetricGUTS,Z.Phys.C11(1981)153,http:// dx.doi.org/10.1007/BF01573998.

[24] S.Dimopoulos, G.F. Giudice,Naturalnessconstraintsinsupersymmetric the-ories with nonuniversal soft terms, Phys. Lett. B 357 (1995) 573, http:// dx.doi.org/10.1016/0370-2693(95)00961-J,arXiv:hep-ph/9507282.

[25] M.Papucci,J.T.Ruderman,A.Weiler,NaturalSUSYendures,J.HighEnergyPhys. 1209(2012)035,http://dx.doi.org/10.1007/JHEP09(2012)035,arXiv:1110.6926. [26] C.Brust, A.Katz,S. Lawrence,R.Sundrum,SUSY,theThird Generationand the LHC, J. High Energy Phys. 1203 (2012) 103, http://dx.doi.org/10.1007/ JHEP03(2012)103,arXiv:1110.6670.

[27] J.Alwall,P.Schuster, N.Toro,Simplified modelsfor afirstcharacterization ofnewphysicsattheLHC,Phys.Rev.D79(2009)075020,http://dx.doi.org/ 10.1103/PhysRevD.79.075020,arXiv:0810.3921.

[28] D.Alves,et al.,Simplifiedmodelsfor LHCnewphysicssearches,J. Phys.G 39 (2012) 105005, http://dx.doi.org/10.1088/0954-3899/39/10/105005, arXiv: 1105.2838.

[29] CMSCollaboration,TheCMSexperimentattheCERNLHC,J.Instrum.3(2008) S08004,http://dx.doi.org/10.1088/1748-0221/3/08/S08004.

[30] CMSCollaboration,ParticlefloweventreconstructioninCMSandperformance forjets,tausandMET,CMSPhysicsAnalysisSummaryCMS-PAS-PFT-09-001, 2009,https://cdsweb.cern.ch/record/1194487.

[31] CMS Collaboration, Commissioning of the particle-flow event reconstruc-tion with the first LHC collisions recorded in the CMS detector, CMS PhysicsAnalysisSummaryCMS-PAS-PFT-10–001,2010,http://cdsweb.cern.ch/ record/1247373.

[32] CMSCollaboration,Electron reconstructionand identificationat√s=7 TeV, CMSPhysicsAnalysis SummaryCMS-PAS-EGM-10–004, 2010,http://cdsweb. cern.ch/record/1299116.

[33] CMSCollaboration,EnergycalibrationandresolutionoftheCMS electromag-neticcalorimeterinppcollisionsat√s=7 TeV,J.Instrum.8(2013)P09009,

http://dx.doi.org/10.1088/1748-0221/8/09/P09009,arXiv:1306.2016.

[34] CMS Collaboration, Performance of CMS muon reconstruction in pp colli-sion eventsat √s=7 TeV, J. Instrum. 7(2012) P10002, http://dx.doi.org/ 10.1088/1748-0221/7/10/P10002.

[35] M.Cacciari,G.P.Salam,G.Soyez,Theanti-ktjetclusteringalgorithm,J. High Energy Phys. 0804 (2008) 063, http://dx.doi.org/10.1088/1126-6708/2008/ 04/063,arXiv:0802.1189.

[36] CMS Collaboration, Determination of jet energy calibration and trans-verse momentum resolution in CMS, J. Instrum. 6 (2011) P11002,

http://dx.doi.org/10.1088/1748-0221/6/11/P11002,arXiv:1107.4277.

[37] CMSCollaboration, Missing transverseenergy performanceof theCMS de-tector,J.Instrum.6(2011)P09001,http://dx.doi.org/10.1088/1748-0221/6/09/ P09001,arXiv:1106.5048.

[38] M.Cacciari,G.P.Salam,Pileupsubtractionusingjetareas,Phys. Lett.B659 (2007)119,http://dx.doi.org/10.1016/j.physletb.2007.09.077,arXiv:0707.1378.

[39] M. Cacciari,G.P. Salam,G. Soyez, The catchment area ofjets, J. High En-ergyPhys.0704(2007)005,http://dx.doi.org/10.1088/1126-6708/2008/04/005, arXiv:0802.1188.

[40] CMS Collaboration,Identificationofb-quarkjetswith the CMSexperiment, J.Instrum.8(2013)P04013,http://dx.doi.org/10.1088/1748-0221/8/04/P04013, arXiv:1211.4462.

[41] J.Alwall,P.Demin,S.deVisscher,R.Frederix,M.Herquet,F.Maltoni,T. Plehn, D.L.Rainwater, T.Stelzer,MadGraph/MadEventv4:thenewwebgeneration, J. High Energy Phys. 0709 (2007) 028,http://dx.doi.org/10.1088/1126-6708/ 2007/09/028,arXiv:0706.2334.

[42] S. Frixione, B.R. Webber, Matching NLO QCD computations and parton shower simulations,J.HighEnergyPhys.0206(2002)029,http://dx.doi.org/ 10.1088/1126-6708/2002/06/029,arXiv:hep-ph/0204244.

[43] S. Frixione, P. Nason, B.R. Webber, Matching NLO QCD and parton show-ers in heavy flavor production, J. High Energy Phys. 0308 (2003) 007,

http://dx.doi.org/10.1088/1126-6708/2003/08/007,arXiv:hep-ph/0305252. [44] T.Sjöstrand,S.Mrenna,P.Skands,PYTHIA6.4physicsandmanual,J.High

En-ergyPhys.0605(2006)026,http://dx.doi.org/10.1088/1126-6708/2006/05/026, arXiv:hep-ph/0603175.

[45] S.Agostinelli,et al., GEANT4Collaboration, GEANT4—asimulation toolkit, Nucl. Instrum. Methods Phys. Res., Sect. A,Accel. Spectrom. Detect. Assoc. Equip.506(2003)250,http://dx.doi.org/10.1016/S0168-9002(03)01368-8. [46] CMS Collaboration, The fast simulation of the CMS detector at LHC, J.

Phys.Conf.Ser.331(2011)032049,http://dx.doi.org/10.1088/1742-6596/331/3/ 032049.

[47] R.Rahmat, R. Kroeger,A.Giammanco, The fastsimulation ofthe CMS ex-periment, J. Phys. Conf. Ser. 396 (2012) 062016, http://dx.doi.org/10.1088/ 1742-6596/396/6/062016.

[48] A.L.Read,Presentationofsearchresults:theC Lstechnique,J.Phys.G28(2002) 2693,http://dx.doi.org/10.1088/0954-3899/28/10/313.

[49] T.Junk,Confidencelevelcomputationforcombiningsearcheswithsmall statis-tics, Nucl.Instrum.MethodsPhys.Res., Sect.A,Accel.Spectrom.Detect. As-soc.Equip.434(1999)435,http://dx.doi.org/10.1016/S0168-9002(99)00498-2, arXiv:hep-ex/9902006.

[50] ATLAS Collaboration, CMS Collaboration, LHC Higgs Combination Group, Procedure for the LHC Higgs boson search combination in Summer 2011, TechnicalReport ATL-PHYS-PUB 2011-11, CMSNOTE2011/005, 2011,

http://cdsweb.cern.ch/record/1379837.

[51]S.Alekhin,etal.,ThePDF4LHCWorkingGroupinterimreport,arXiv:1101.0536, 2011.

[52]M.Botje,etal.,ThePDF4LHCWorkingGroupinterimrecommendations,arXiv: 1101.0538,2011.

[53] CMSCollaboration,CMSluminositybasedonpixelclustercounting— Sum-mer2013update,CMSPhysicsAnalysisSummaryCMS-PAS-LUM-13–001,2013,

http://cdsweb.cern.ch/record/1598864.

[54]M. Krämer,A. Kulesza,R. vanderLeeuw, M. Mangano, S. Padhi,T. Plehn, X.Portell,Supersymmetryproductioncrosssectionsinppcollisionsat√s= 7 TeV,arXiv:1206.2892,2012.

[55] W. Beenakker, R. Höpker, M. Spira, P.M. Zerwas, Squark and gluino pro-duction at hadron colliders,Nucl. Phys. B 492(1997) 51, http://dx.doi.org/ 10.1016/S0550-3213(97)80027-2,arXiv:hep-ph/9610490.

[56] A. Kulesza, L. Motyka, Threshold resummation for squark–antisquark and gluino-pair production at the LHC, Phys. Rev. Lett. 102 (2009) 111802,

http://dx.doi.org/10.1103/PhysRevLett.102.111802,arXiv:0807.2405.

[57] A.Kulesza,L.Motyka,Softgluonresummationfortheproductionofgluino– gluinoandsquark–antisquarkpairsattheLHC,Phys.Rev.D80(2009)095004,

http://dx.doi.org/10.1103/PhysRevD.80.095004,arXiv:0905.4749.

[58] W. Beenakker, S. Brensing, M. Krämer, A. Kulesza, E. Laenen, I. Niessen, Soft-gluon resummationforsquark andgluinohadroproduction,J. High En-ergyPhys.0912(2009)041,http://dx.doi.org/10.1088/1126-6708/2009/12/041, arXiv:0909.4418.

CMSCollaboration

V. Khachatryan,

A.M. Sirunyan,

A. Tumasyan

YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam,

T. Bergauer,

M. Dragicevic,

J. Erö,

M. Friedl,

R. Frühwirth

1

,

V.M. Ghete,

C. Hartl,

N. Hörmann,

J. Hrubec,

M. Jeitler

1

,

W. Kiesenhofer,

V. Knünz,

M. Krammer

1

,

I. Krätschmer,

D. Liko,

I. Mikulec,

D. Rabady

2

,

B. Rahbaran,

H. Rohringer,

R. Schöfbeck,

J. Strauss,

W. Treberer-Treberspurg,

W. Waltenberger,

C.-E. Wulz

1

V. Mossolov,

N. Shumeiko,

J. Suarez Gonzalez

NationalCentreforParticleandHighEnergyPhysics,Minsk,Belarus

S. Alderweireldt,

S. Bansal,

T. Cornelis,

E.A. De Wolf,

X. Janssen,

A. Knutsson,

J. Lauwers,

S. Luyckx,

S. Ochesanu,

R. Rougny,

M. Van De Klundert,

H. Van Haevermaet,

P. Van Mechelen,

N. Van Remortel,

A. Van Spilbeeck

UniversiteitAntwerpen,Antwerpen,Belgium

F. Blekman,

S. Blyweert,

J. D’Hondt,

N. Daci,

N. Heracleous,

J. Keaveney,

S. Lowette,

M. Maes,

A. Olbrechts,

Q. Python,

D. Strom,

S. Tavernier,

W. Van Doninck,

P. Van Mulders,

G.P. Van Onsem,

I. Villella

VrijeUniversiteitBrussel,Brussel,Belgium

C. Caillol,

B. Clerbaux,

G. De Lentdecker,

D. Dobur,

L. Favart,

A.P.R. Gay,

A. Grebenyuk,

A. Léonard,

A. Mohammadi,

L. Perniè

2

,

A. Randle-conde,

T. Reis,

T. Seva,

L. Thomas,

C. Vander Velde,

P. Vanlaer,

J. Wang,

F. Zenoni

UniversitéLibredeBruxelles,Bruxelles,Belgium

V. Adler,

K. Beernaert,

L. Benucci,

A. Cimmino,

S. Costantini,

S. Crucy,

S. Dildick,

A. Fagot,

G. Garcia,

J. Mccartin,

A.A. Ocampo Rios,

D. Poyraz,

D. Ryckbosch,

S. Salva Diblen,

M. Sigamani,

N. Strobbe,

F. Thyssen,

M. Tytgat,

E. Yazgan,

N. Zaganidis

GhentUniversity,Ghent,Belgium

S. Basegmez,

C. Beluffi

3

,

G. Bruno,

R. Castello,

A. Caudron,

L. Ceard,

G.G. Da Silveira,

C. Delaere,

T. du Pree,

D. Favart,

L. Forthomme,

A. Giammanco

4

,

J. Hollar,

A. Jafari,

P. Jez,

M. Komm,

V. Lemaitre,

C. Nuttens,

L. Perrini,

A. Pin,

K. Piotrzkowski,

A. Popov

5

,

L. Quertenmont,

M. Selvaggi,

M. Vidal Marono,

J.M. Vizan Garcia

UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium

N. Beliy,

T. Caebergs,

E. Daubie,

G.H. Hammad

UniversitédeMons,Mons,Belgium

W.L. Aldá Júnior,

G.A. Alves,

L. Brito,

M. Correa Martins Junior,

T. Dos Reis Martins,

J. Molina,

C. Mora Herrera,

M.E. Pol,

P. Rebello Teles

CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

W. Carvalho,

J. Chinellato

6

,

A. Custódio,

E.M. Da Costa,

D. De Jesus Damiao,

C. De Oliveira Martins,

S. Fonseca De Souza,

H. Malbouisson,

D. Matos Figueiredo,

L. Mundim,

H. Nogima,

W.L. Prado Da Silva,

J. Santaolalla,

A. Santoro,

A. Sznajder,

E.J. Tonelli Manganote

6

,

A. Vilela Pereira

UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

C.A. Bernardes

b

,

S. Dogra

a

,

T.R. Fernandez Perez Tomei

a

,

E.M. Gregores

b

,

P.G. Mercadante

b

,

S.F. Novaes

a

,

Sandra S. Padula

a

a_{UniversidadeEstadualPaulista,SãoPaulo,Brazil} b_{UniversidadeFederaldoABC,SãoPaulo,Brazil}

A. Aleksandrov,

V. Genchev

2

,

R. Hadjiiska,

P. Iaydjiev,

A. Marinov,

S. Piperov,

M. Rodozov,

S. Stoykova,

G. Sultanov,

M. Vutova

InstituteforNuclearResearchandNuclearEnergy,Sofia,Bulgaria

A. Dimitrov,

I. Glushkov,

L. Litov,

B. Pavlov,

P. Petkov

J.G. Bian,

G.M. Chen,

H.S. Chen,

M. Chen,

T. Cheng,

R. Du,

C.H. Jiang,

R. Plestina

7

,

F. Romeo,

J. Tao,

Z. Wang

InstituteofHighEnergyPhysics,Beijing,China

C. Asawatangtrakuldee,

Y. Ban,

S. Liu,

Y. Mao,

S.J. Qian,

D. Wang,

Z. Xu,

L. Zhang,

W. Zou

StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

C. Avila,

A. Cabrera,

L.F. Chaparro Sierra,

C. Florez,

J.P. Gomez,

B. Gomez Moreno,

J.C. Sanabria

UniversidaddeLosAndes,Bogota,Colombia

N. Godinovic,

D. Lelas,

D. Polic,

I. Puljak

UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia

Z. Antunovic,

M. Kovac

UniversityofSplit,FacultyofScience,Split,Croatia

V. Brigljevic,

K. Kadija,

J. Luetic,

D. Mekterovic,

L. Sudic

InstituteRudjerBoskovic,Zagreb,Croatia

A. Attikis,

G. Mavromanolakis,

J. Mousa,

C. Nicolaou,

F. Ptochos,

P.A. Razis,

H. Rykaczewski

UniversityofCyprus,Nicosia,Cyprus

M. Bodlak,

M. Finger,

M. Finger Jr.

8

CharlesUniversity,Prague,CzechRepublic

Y. Assran

9

,

A. Ellithi Kamel

10

,

M.A. Mahmoud

11

,

A. Radi

12

,

13

AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt

M. Kadastik,

M. Murumaa,

M. Raidal,

A. Tiko

NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia

P. Eerola,

M. Voutilainen

DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland

J. Härkönen,

V. Karimäki,

R. Kinnunen,

M.J. Kortelainen,

T. Lampén,

K. Lassila-Perini,

S. Lehti,

T. Lindén,

P. Luukka,

T. Mäenpää,

T. Peltola,

E. Tuominen,

J. Tuominiemi,

E. Tuovinen,

L. Wendland

HelsinkiInstituteofPhysics,Helsinki,Finland

J. Talvitie,

T. Tuuva

LappeenrantaUniversityofTechnology,Lappeenranta,Finland

M. Besancon,

F. Couderc,

M. Dejardin,

D. Denegri,

B. Fabbro,

J.L. Faure,

C. Favaro,

F. Ferri,

S. Ganjour,

A. Givernaud,

P. Gras,

G. Hamel de Monchenault,

P. Jarry,

E. Locci,

J. Malcles,

J. Rander,

A. Rosowsky,

M. Titov

DSM/IRFU,CEA/Saclay,Gif-sur-Yvette,France

S. Baffioni,

F. Beaudette,

P. Busson,

E. Chapon,

C. Charlot,

T. Dahms,

M. Dalchenko,

L. Dobrzynski,

N. Filipovic,

A. Florent,

R. Granier de Cassagnac,

L. Mastrolorenzo,

P. Miné,

I.N. Naranjo,

M. Nguyen,

C. Ochando,

G. Ortona,

P. Paganini,

S. Regnard,

R. Salerno,

J.B. Sauvan,

Y. Sirois,

C. Veelken,

Y. Yilmaz,

A. Zabi

J.-L. Agram

14

,

J. Andrea,

A. Aubin,

D. Bloch,

J.-M. Brom,

E.C. Chabert,

C. Collard,

E. Conte

14

,

J.-C. Fontaine

14

,

D. Gelé,

U. Goerlach,

C. Goetzmann,

A.-C. Le Bihan,

K. Skovpen,

P. Van Hove

InstitutPluridisciplinaireHubertCurien,UniversitédeStrasbourg,UniversitédeHauteAlsaceMulhouse,CNRS/IN2P3,Strasbourg,France

S. Gadrat

CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France

S. Beauceron,

N. Beaupere,

C. Bernet

7

,

G. Boudoul

2

,

E. Bouvier,

S. Brochet,

C.A. Carrillo Montoya,

J. Chasserat,

R. Chierici,

D. Contardo

2

,

B. Courbon,

P. Depasse,

H. El Mamouni,

J. Fan,

J. Fay,

S. Gascon,

M. Gouzevitch,

B. Ille,

T. Kurca,

M. Lethuillier,

L. Mirabito,

A.L. Pequegnot,

S. Perries,

J.D. Ruiz Alvarez,

D. Sabes,

L. Sgandurra,

V. Sordini,

M. Vander Donckt,

P. Verdier,

S. Viret,

H. Xiao

UniversitédeLyon,UniversitéClaudeBernardLyon1,CNRS–IN2P3,InstitutdePhysiqueNucléairedeLyon,Villeurbanne,France

Z. Tsamalaidze

8

InstituteofHighEnergyPhysicsandInformatization,TbilisiStateUniversity,Tbilisi,Georgia

C. Autermann,

S. Beranek,

M. Bontenackels,

M. Edelhoff,

L. Feld,

A. Heister,

K. Klein,

M. Lipinski,

A. Ostapchuk,

M. Preuten,

F. Raupach,

J. Sammet,

S. Schael,

J.F. Schulte,

H. Weber,

B. Wittmer,

V. Zhukov

5

RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany

M. Ata,

M. Brodski,

E. Dietz-Laursonn,

D. Duchardt,

M. Erdmann,

R. Fischer,

A. Güth,

T. Hebbeker,

C. Heidemann,

K. Hoepfner,

D. Klingebiel,

S. Knutzen,

P. Kreuzer,

M. Merschmeyer,

A. Meyer,

P. Millet,

M. Olschewski,

K. Padeken,

P. Papacz,

H. Reithler,

S.A. Schmitz,

L. Sonnenschein,

D. Teyssier,

S. Thüer,

M. Weber

RWTHAachenUniversity,III.PhysikalischesInstitutA,Aachen,Germany

V. Cherepanov,

Y. Erdogan,

G. Flügge,

H. Geenen,

M. Geisler,

W. Haj Ahmad,

F. Hoehle,

B. Kargoll,

T. Kress,

Y. Kuessel,

A. Künsken,

J. Lingemann

2

,

A. Nowack,

I.M. Nugent,

O. Pooth,

A. Stahl

RWTHAachenUniversity,III.PhysikalischesInstitutB,Aachen,Germany

M. Aldaya Martin,

I. Asin,

N. Bartosik,

J. Behr,

U. Behrens,

A.J. Bell,

A. Bethani,

K. Borras,

A. Burgmeier,

A. Cakir,

L. Calligaris,

A. Campbell,

S. Choudhury,

F. Costanza,

C. Diez Pardos,

G. Dolinska,

S. Dooling,

T. Dorland,

G. Eckerlin,

D. Eckstein,

T. Eichhorn,

G. Flucke,

J. Garay Garcia,

A. Geiser,

A. Gizhko,

P. Gunnellini,

J. Hauk,

M. Hempel

15

,

H. Jung,

A. Kalogeropoulos,

O. Karacheban

15

,

M. Kasemann,

P. Katsas,

J. Kieseler,

C. Kleinwort,

I. Korol,

D. Krücker,

W. Lange,

J. Leonard,

K. Lipka,

A. Lobanov,

W. Lohmann

15

,

B. Lutz,

R. Mankel,

I. Marfin

15

,

I.-A. Melzer-Pellmann,

A.B. Meyer,

G. Mittag,

J. Mnich,

A. Mussgiller,

S. Naumann-Emme,

A. Nayak,

E. Ntomari,

H. Perrey,

D. Pitzl,

R. Placakyte,

A. Raspereza,

P.M. Ribeiro Cipriano,

B. Roland,

E. Ron,

M.Ö. Sahin,

J. Salfeld-Nebgen,

P. Saxena,

T. Schoerner-Sadenius,

M. Schröder,

C. Seitz,

S. Spannagel,

A.D.R. Vargas Trevino,

R. Walsh,

C. Wissing

DeutschesElektronen-Synchrotron,Hamburg,Germany

V. Blobel,

M. Centis Vignali,

A.R. Draeger,

J. Erfle,

E. Garutti,

K. Goebel,

M. Görner,

J. Haller,

M. Hoffmann,

R.S. Höing,

A. Junkes,

H. Kirschenmann,

R. Klanner,

R. Kogler,

T. Lapsien,

T. Lenz,

I. Marchesini,

D. Marconi,

J. Ott,

T. Peiffer,

A. Perieanu,

N. Pietsch,

J. Poehlsen,

T. Poehlsen,

D. Rathjens,

C. Sander,

H. Schettler,

P. Schleper,

E. Schlieckau,

A. Schmidt,

M. Seidel,

V. Sola,

H. Stadie,

G. Steinbrück,

D. Troendle,

E. Usai,

L. Vanelderen,

A. Vanhoefer

UniversityofHamburg,Hamburg,Germany

C. Barth,

C. Baus,

J. Berger,

C. Böser,

E. Butz,

T. Chwalek,

W. De Boer,

A. Descroix,

A. Dierlamm,

A. Kornmayer

2

,

P. Lobelle Pardo,

M.U. Mozer,

T. Müller,

Th. Müller,

A. Nürnberg,

G. Quast,

K. Rabbertz,

S. Röcker,

H.J. Simonis,

F.M. Stober,

R. Ulrich,

J. Wagner-Kuhr,

S. Wayand,

T. Weiler,

R. Wolf

InstitutfürExperimentelleKernphysik,Karlsruhe,Germany

G. Anagnostou,

G. Daskalakis,

T. Geralis,

V.A. Giakoumopoulou,

A. Kyriakis,

D. Loukas,

A. Markou,

C. Markou,

A. Psallidas,

I. Topsis-Giotis

InstituteofNuclearandParticlePhysics(INPP),NCSRDemokritos,AghiaParaskevi,Greece

A. Agapitos,

S. Kesisoglou,

A. Panagiotou,

N. Saoulidou,

E. Stiliaris

UniversityofAthens,Athens,Greece

X. Aslanoglou,

I. Evangelou,

G. Flouris,

C. Foudas,

P. Kokkas,

N. Manthos,

I. Papadopoulos,

E. Paradas,

J. Strologas

UniversityofIoánnina,Ioánnina,Greece

G. Bencze,

C. Hajdu,

P. Hidas,

D. Horvath

16

,

F. Sikler,

V. Veszpremi,

G. Vesztergombi

17

,

A.J. Zsigmond

WignerResearchCentreforPhysics,Budapest,Hungary

N. Beni,

S. Czellar,

J. Karancsi

18

,

J. Molnar,

J. Palinkas,

Z. Szillasi

InstituteofNuclearResearchATOMKI,Debrecen,Hungary

A. Makovec,

P. Raics,

Z.L. Trocsanyi,

B. Ujvari

UniversityofDebrecen,Debrecen,Hungary

S.K. Swain

NationalInstituteofScienceEducationandResearch,Bhubaneswar,India

S.B. Beri,

V. Bhatnagar,

R. Gupta,

U. Bhawandeep,

A.K. Kalsi,

M. Kaur,

R. Kumar,

M. Mittal,

N. Nishu,

J.B. Singh

PanjabUniversity,Chandigarh,India

Ashok Kumar,

Arun Kumar,

S. Ahuja,

A. Bhardwaj,

B.C. Choudhary,

A. Kumar,

S. Malhotra,

M. Naimuddin,

K. Ranjan,

V. Sharma

UniversityofDelhi,Delhi,India

S. Banerjee,

S. Bhattacharya,

K. Chatterjee,

S. Dutta,

B. Gomber,

Sa. Jain,

Sh. Jain,

R. Khurana,

A. Modak,

S. Mukherjee,

D. Roy,

S. Sarkar,

M. Sharan

SahaInstituteofNuclearPhysics,Kolkata,India

A. Abdulsalam,

D. Dutta,

V. Kumar,

A.K. Mohanty

2

,

L.M. Pant,

P. Shukla,

A. Topkar

BhabhaAtomicResearchCentre,Mumbai,India

T. Aziz,

S. Banerjee,

S. Bhowmik

19

,

R.M. Chatterjee,

R.K. Dewanjee,

S. Dugad,

S. Ganguly,

S. Ghosh,

M. Guchait,

A. Gurtu

20

,

G. Kole,

S. Kumar,

M. Maity

19

,

G. Majumder,

K. Mazumdar,

G.B. Mohanty,

B. Parida,

K. Sudhakar,

N. Wickramage

21

TataInstituteofFundamentalResearch,Mumbai,India

S. Sharma