Search for pair production of third-generation scalar leptoquarks and top squarks in proton-proton collisions at √s=8 TeV

Contents lists available atScienceDirect

Physics

Letters

B

www.elsevier.com/locate/physletb

Search

for

pair

production

of

third-generation

scalar

leptoquarks

and

top

squarks

in

proton–proton

collisions

at

√

s

=

8 TeV

.CMSCollaboration

CERN,Switzerland

a r t i c l e i n f o a b s t ra c t

Articlehistory:

Received4August2014

Receivedinrevisedform1October2014 Accepted26October2014

Availableonline30October2014 Editor:M.Doser Keywords: CMS Physics Leptoquark Topsquark

A search for pair production of third-generation scalar leptoquarks and supersymmetric top quark partners, topsquarks,infinal statesinvolvingtauleptonsand bottomquarksis presented.Thesearch useseventsfromadata sampleofproton–proton collisionscorresponding toanintegratedluminosity of19.7 fb−1_{,collected withthe CMSdetector atthe LHCwith} √_{s=8 TeV. The numberof observed} events is found to be inagreement with the expected standard model background. Third-generation scalarleptoquarkswithmassesbelow740 GeVareexcludedat95%confidencelevel,assuminga100% branchingfractionfortheleptoquarkdecaytoatauleptonand abottomquark.Inaddition,thismass limitapplies directlytotop squarks decayingviaan R-parityviolatingcoupling λ₃₃₃.The searchalso considersasimilarsignaturefromtopsquarksundergoingachargino-mediateddecayinvolvingthe R-parityviolatingcoupling λ_{3 jk}.Each topsquark decaysto atau lepton,abottomquark, andtwo light quarks.Top squarksinthismodel withmassesbelow 580 GeVare excluded at95% confidencelevel. Theconstraintontheleptoquarkmassisthemoststringenttodate,andthisisthefirstsearchfortop squarksdecayingvia λ

3 jk.

©2014TheAuthors.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/3.0/).FundedbySCOAP3.

1. Introduction

Manyextensionsofthestandardmodel(SM)predictnewscalar or vector bosons, called leptoquarks (LQ), which carry non-zero leptonand baryon numbers,aswell as colorandfractional elec-triccharge. Examplesof suchSM extensionsincludeSU(5)grand unification[1],Pati–SalamSU(4)[2],compositemodels[3], super-strings [4], andtechnicolor models [5].Leptoquarks decayinto a quarkandalepton,withamodel-dependentbranchingfractionfor eachpossibledecay.Experimentallimitsonflavor-changingneutral currentsandother rareprocessessuggestthatsearchesshould fo-cus onleptoquarks that coupleto quarks andleptons within the sameSM generation,for leptoquark masses accessibleto current colliders[3,6].

The dominantpair production mechanisms forleptoquarks at theCERNLHC wouldbe gluon–gluonfusion andquark–antiquark annihilation via quantum chromodynamic (QCD) couplings. The crosssectionsfortheseprocesses dependonly onthe leptoquark massforscalarleptoquarks.InthisLetter,a searchwiththeCMS detectorforthird-generationscalarleptoquarks,eachdecayingtoa tauleptonandabottomquark,ispresented.

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

Similarsignaturesarisingfromsupersymmetricmodelsarealso coveredbythissearch.Supersymmetry(SUSY)[7,8]isanattractive extension oftheSM becauseitcanresolvethehierarchyproblem withoutunnaturalfine-tuning,ifthemassesofthe supersymmet-ricpartner ofthetop quark(topsquark)andthesupersymmetric partnersoftheHiggsboson(higgsinos)arenottoolarge[9,10].In manynatural SUSY modelsthe top squark andthe higgsinosare substantiallylighterthantheotherscalarSUSYparticles.Thislight top squark scenario can be realized in both R-parity conserving (RPC)andR-parityviolating(RPV)SUSYmodels,whereR-parityis anewquantumnumber[11]thatdistinguishesSMandSUSY parti-cles.InthecontextofanRPCdecayofthetopsquark,thepresence ofanundetectedparticle(thelightestSUSYparticle)isexpectedto generatea signature withlargemissingtransverse momentum.If R-parity is violated, however,SUSY particles can decayinto final statescontainingonlySMparticles.TheRPVtermsinthe superpo-tentialare: W1 2λi jkLiLjE c k+ λi jkLiQjDck+ 1 2λ  i jkUciDcjDkc+μiLiHu (1) where W is thesuperpotential; L is theleptondoubletsuperfield;

E is thelepton singletsuperfield; Q is the quark doublet super-field; U and D are thequark singletsuperfields; Hu is theHiggs

http://dx.doi.org/10.1016/j.physletb.2014.10.063

0370-2693/©2014TheAuthors.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/3.0/).Fundedby SCOAP3_.

doublet superfield that couples to up-type quarks; λ, λ, and λ

arecouplingconstants;and i, j, and k are generationindices. AttheLHC,topsquarks(˜t)wouldbedirectlypair-producedvia stronginteractions.Inthissearch,twodifferentdecaychannelsof directlyproducedtopsquarksareconsidered.Bothscenariosrelate tosimplifiedmodelsinwhichalloftheotherSUSYparticleshave massestoolargetoparticipateintheinteractions.Inthefirstcase westudythetwo-bodyleptonnumberviolatingdecay˜t→τb[11] withacouplingconstantλ₃₃₃ allowedbythetrilinearRPV opera-tors.The final-statesignature andkinematicdistributions ofsuch a signal areidentical to thosefromthe pairproduction of third-generationscalarleptoquarks.Whenthemassesofthe supersym-metricpartnersofthegluonandquarks,excludingthetopsquark, arelarge,thetopsquarkpairproductioncrosssectionisthesame asthatof thethird generationLQ. Thus,the resultsofthe lepto-quarksearchcanbedirectlyinterpretedinthecontextofRPVtop squarks.

InsomenaturalSUSYmodels[12],ifthehiggsinos(χ˜0_,χ˜±_)are

lighterthanthetopsquark,oriftheRPVcouplingsthatallow di-rect decays to SM particles are sufficiently small, the top squark decaymaypreferentiallyproceedviasuperpartners.Inthesecond partofthesearchwe focusonascenarioinwhichthedominant RPC decayof thetop squark is t˜→ ˜χ±b. Thisrequires themass splittingbetweenthetopsquarkandthecharginotobe lessthan the mass of the top quark, so it is chosen to be 100 GeV. The chargino isassumed to be a pure higgsino andto be nearly de-generateinmasswiththeneutralino.Weconsiderthecasewhen

˜

χ±→ ˜ντ±→qqτ±. The decay of the sneutrino occurs accord-ing toan RPV operatorwitha couplingconstant λ_{3 jk},wherethe cases j,k =1,2 are considered. Such signal models can only be probed by searches that do not require large missingtransverse momentum, asthe other decayof the chargino, χ˜±→ντ˜, does notcontributetoscenarios involvingtheλ_{3 jk}couplingbecauseof chiral suppression.From such a signal process, we expect events withtwo tau leptons, two jets originatingfrom hadronization of thebottomquarks,andatleastfouradditionaljets.

InthisLetter,thesearchforscalarleptoquarksandtopsquarks decaying through the coupling λ₃₃₃ is referred to as the lepto-quark search. The search for thechargino-mediated decay oftop squarksinvolvingtheλ_{3 jk} couplingisreferredtoasthetopsquark search.Thedatasampleusedinthissearchhasbeenrecordedwith the CMSdetectorin proton–protoncollisions at a center-of-mass energy of 8 TeV and corresponds to an integrated luminosity of 19.7 fb−1.Oneofthe tauleptons inthefinal state isrequiredto decayleptonically: τ→ ¯νντ , where canbe eitheranelectron ora muon,denotedasa light lepton.The othertau leptonis re-quiredtodecaytohadrons(τh): τ→hadrons+ντ .Thesedecays

resultintwopossiblefinalstateslabeledbelowaseτhand μτh,or

collectivelyτhwhentheleptonflavorisunimportant.The

lepto-quarksearchisperformedinamassrangefrom200to1000 GeV usinga sample ofevents containing one light lepton,a hadroni-callydecayingtaulepton,andatleasttwojets,withatleastoneof thejetsidentifiedasoriginatingfrombottomquarkhadronization (b-tagged). The top squark search is performed in a mass range from 200 to 800 GeV using a sample of events containing one light lepton, a hadronically decayingtau lepton,and atleast five jets,withatleastoneofthejetsb-tagged.

No evidence for third-generation leptoquarks or top squarks decayingtotauleptonsandbottomquarkshasbeenfoundin pre-vious searches[13,14].The moststringentlower limit todateon themassofascalarthirdgenerationleptoquarkdecayingtoatau leptonandabottomquarkwitha100%branchingfractionisabout 530 GeV fromboth the CMSandATLAS experiments. ThisLetter alsopresents the firstsearch for thechargino-mediated decayof thetopsquarkthroughtheRPVcouplingλ_{3 jk}.

2. TheCMSdetector

The central feature of the CMS apparatus is a superconduct-ing solenoid, of6 minternal diameter, providinga field of3.8 T. Within the field volume are several subdetectors. A silicon pixel and strip tracker allows the reconstruction of the trajectories of charged particles within the pseudorapidity range |η|<2.5. The calorimetry system consists of a lead tungstate crystal electro-magnetic calorimeter (ECAL) anda brass and scintillator hadron calorimeter,andmeasures particleenergydepositionsfor|η|<3. The CMS detector also has extensive forward calorimetry (2.8<

|η|<5.2).Muonsaremeasuredingas-ionizationdetectors embed-ded inthe steel flux-returnyoke of themagnet. Collisionevents are selected using a two-tiered trigger system[15]. A more de-tailed description ofthe CMSdetector,together witha definition ofthecoordinatesystemusedandtherelevantkinematicvariables, canbefoundinRef.[16].

3. Objectandeventselection

Candidate LQ or top squark events were collected using a set of triggers requiring the presence of either an electron or a muonwithtransversemomentum(pT)aboveathresholdof27or

24 GeV,respectively.

Both electrons and muons are required to be reconstructed within the range |η|<2.1 and to have pT>30 GeV. Electrons,

reconstructed using information from the ECAL and the tracker, are required tohave an electromagneticshower shape consistent with that of an electron, and an energy deposition in ECALthat is compatiblewith thetrack reconstructedin the tracker.Muons arerequiredtobereconstructedbyboththetrackerandthemuon spectrometer. A particle-flow (PF) technique [17–19] is used for thereconstruction ofhadronicallydecayingtauleptoncandidates. InthePFapproach,informationfromallsubdetectorsiscombined toreconstructandidentifyallfinal-stateparticlesproducedinthe collision. The particles are classified as either charged hadrons, neutralhadrons,electrons, muons,orphotons.Theseparticles are usedwiththe“hadronplusstrips”algorithm[20]toidentify τh

ob-jects.Hadronicallydecayingtauleptonswithoneorthreecharged pions andup totwo neutral pions are reconstructed.The recon-structed τh isrequiredto havevisible pT>50 GeV and|η|<2.3.

Electrons,muons,andtauleptonsarerequiredtobeisolatedfrom other reconstructed particles.The identified electron (muon) and τharerequiredtooriginatefromthesamevertexandbeseparated

by R =( η)2_{+ ( φ)}2_{>0.5.The light lepton andthe τ} h are

alsorequiredtohaveoppositeelectriccharge.Eventsarevetoedif anotherlightleptonisfound,passingthekinematic,identification, andisolationcriteriadescribedabove,thathasanoppositeelectric chargefromtheselectedlightlepton.

Jetsarereconstructedusingtheanti-kT algorithm[21,22]with

a sizeparameter 0.5usingparticlecandidates reconstructedwith thePFtechnique.Jetenergiesarecorrectedbysubtractingthe av-eragecontributionfromparticlescomingfromotherproton–proton collisionsinthesamebeamcrossing(pileup)andbyapplyingajet energy calibration, determined empirically [23]. Jets are required to bewithin |η|<2.4,have pT>30 GeV, andbeseparatedfrom

boththelightleptonandthe τhby R >0.5.Theminimumjet pT

requirementeliminatesmostjetsfrompileupinteractions.Jetsare b-taggedusingthecombinedsecondaryvertexalgorithmwiththe looseoperatingpoint [24].In theleptoquarksearch, theb-tagged jetwiththehighest pTisselected,andthentheremainingjetwith

thehighestpTisselectedwhetherornotitisb-tagged.Inthetop

squark search, the b-tagged jet with the highest pT is selected,

andthentheremainingfourjetswiththehighest pT areselected

Todiscriminate betweensignal and background in the lepto-quarksearch, themassofthe τh andajet,denoted M(τh,jet),is

requiredtobe greaterthan250 GeV.Therearetwopossible pair-ingsofthe τhwiththetworequiredjets.Thepairingischosento

minimize thedifference betweenthemass ofthe τh andone jet

andthemass ofthe light lepton andanother jet.According to a simulation,thecorrectpairingisselectedinapproximately70%of events.

The ST distribution afterthe final selection is used to extract

thelimitsonboththeleptoquark andtopsquarksignal scenarios, whereSTisdefinedasthescalarsumofthe pTofthelightlepton,

the τh,andthetwo jets(fivejets) forthe leptoquark search(top

squarksearch).

4. Backgroundandsignalmodels

SeveralSM processes can mimic thefinal-state signatures ex-pectedfromleptoquark ortop squarkpair productionanddecay. Forthis analysis, the backgrounds are divided into three groups, which are denoted as tt irreducible, major reducible, and other. Thett irreduciblebackground comesfromthe pairproductionof top quarks (tt) when both the light lepton and τh are genuine,

each produced from the decay of a W boson. In this case, the lightleptoncan originateeitherdirectlyfromtheWbosondecay orfroma decaychain W→τ ντ→ νντντ . Themajor reducible

background consists of events in which a quark or gluon jet is misidentifiedasa τh.Theprocessescontributingtothemajor

re-ducible backgroundare associatedproductionof aW or Zboson withjets, andtt.Additionally, asmallcontribution fromthe QCD multijet process is included, in which both the light lepton and the τh are misidentifiedjets. Thethird group,other backgrounds,

consistsofprocessesthatmakesmallcontributionsandmay con-taineithergenuineormisidentifiedtauleptons.Thisincludesthe dibosonand single-top-quark processes, the tt and Z+jets pro-cesseswhenalightleptonismisidentifiedasa τh,andtheZ+jets

process when the Z boson decays to a pair of tau leptons. The other backgrounds are estimated from the simulation described below, whilethe tt irreducible andmajor reducible backgrounds areestimatedusingobserveddata.Themajorreducibleandother backgrounds includeevents withboth genuine and misidentified lightleptons.

The pythia v6.4.24generator[25] is usedto modelthe signal anddiboson processes.The leptoquark signal samples are gener-ated with masses ranging from 200 to 1000 GeV, and the top squark signal samples are generated with masses ranging from 200 to 800 GeV and the sneutrino mass set to 2000 GeV. The MadGraphv5.1.3.30 generator [26] is usedto model thett, W+ jets,andZ+jets processes.Thisgenerationincludescontributions fromheavy-flavor andextrajets. The singletop-quarkproduction ismodeledwiththe powheg 1.0r138[27–29]generator.Boththe MadGraphand powheg generatorsareinterfacedwith pythia for hadronizationandshowering.The tauola program[30]isusedfor taulepton decays in the leptoquark, tt, W+jets, Z+jets, dibo-son,andsingletop-quarksamples.Eachsampleispassedthrough a full simulationof the CMSdetectorbased on Geant4 [31] and the complete set of reconstruction algorithms is used to ana-lyze collision data. Cross sections for the leptoquark signal and diboson processes are calculated to next-to-leading order (NLO) [32,33].Thecrosssectionsforthetopsquarksignalarecalculated atNLO in the strong couplingconstant, including the resumma-tionofsoftgluonemissionatnext-to-leading-logarithmicaccuracy (NLO+NLL)[34–38].Thenext-to-next-to-leading-orderor approx-imatenext-to-next-to-leading-order[39,40]crosssectionsareused fortherestofthebackgroundprocesses.

The efficiencies of the trigger and final selection criteria for signal processes are estimated from thesimulation. The efficien-ciesforlightleptonsandb jetsarecalculatedfromdataandused where necessaryto correct theevent selection efficiency estima-tions from thesimulation. No correction is requiredfor hadroni-callydecayingtauleptons.

The tt irreducible background is estimated froman eμ sam-plethat is87%purein tt eventsaccordingtothe simulation.The contributions from other processes are simulated andsubtracted from the observed data. This sample comprises events withone electron andone muon that satisfy the remaining final selection criteria,exceptthata τhisnotrequired.Thepotential signal

con-taminationofthissamplehasbeenfoundtobe negligibleforany signalmasshypothesis.Thefinal yieldoftheeμsampleisscaled bytherelativedifferenceintheselectionefficienciesbetweenthe

τhandeμsamples.Theselectionefficienciesaremeasuredinthe

simulation andare corrected to matchthose from collision data. Theestimationofthefinalyieldbasedontheobserveddataagrees withboththedirectpredictionfromthesimulationandtheyield obtainedafterapplyingthesamemethodtotheMonte Carlo(MC) samples. The ST distribution for the tt irreducible background is

obtained froma simulated tt sample that consists exclusively of fullyleptonicdecaysoftopquarks.

Themajorreduciblebackgroundfromtt,W+jets,andZ+jets events in which a jet is misidentified as a hadronically decay-ingtauleptonisestimatedfromobserveddata.Theprobability of misidentificationismeasured usingeventsrecordedwitha Z bo-son produced in association withjets and decaying to a pair of muons(Z→μμ).Theinvariantmassofthemuonpairisrequired to be greater than50 GeV and eventsare requiredto contain at leastonejetthatisincorrectly identifiedasa τh andmayormay

notpasstheisolationrequirement. Themisidentification probabil-ity f(pT(τ)) is calculated as the fraction of these τh candidates

thatpasstheisolation requirementanddependsonthe pT ofthe

candidates. The background yield is estimated from a sample of eventssatisfyingthefinalselectioncriteria,exceptthatall τh

can-didates inthe events mustfail the isolation requirement. Eq. (2) relates the yield of these “anti-isolated” events to the yield of eventspassingthefinalselection,usingthemisidentification prob-ability: NmisIDτ = (anti-iso)_ events 1−_τ[1−f(pT(τ))]  τ[1−f(pT(τ))] . (2)

Theestimationofthefinalyieldbasedontheobserveddataagrees withboththe directpredictionfromthesimulationandthe esti-mationperformedusingthesameapproachonsimulatedsamples. The STdistributionforthemajorreduciblebackgroundisobtained

using simulatedsamples for the W+jets and Z+jets processes andthett processwithexclusivelysemi-leptonicdecays.

The QCD multijetprocess contributes onlyin the eτh channel

intheleptoquark search andcorresponds to16% ofthereducible background. The contribution from multijet events is estimated fromasampleofobservedeventssatisfyingthefinalselection cri-teria for the eτh channel except that the electron and τh must

havethesameelectriccharge.TheQCDcomponentisincludedin thedistributionoftherestofthemajorreduciblebackground, de-scribedabove.

5. Systematicuncertainties

Thereareanumberofsystematicuncertaintiesassociatedwith boththebackgroundestimationandthesignalefficiency.The un-certainty in the total integrated luminosity is 2.6% [41]. The un-certainty in the trigger and lepton efficiencies is 2%, while the

Table 1

Theestimatedbackgrounds,observedeventyields,andexpectednumberofsignal eventsfor theleptoquarksearch. Forthesimulation-based entries,the statistical andsystematicuncertaintiesareshownseparately,inthatorder.

eτh μτh tt irreducible 105.6±18.1 66.7±12.6 Major reducible 147.8±33.0 117.3±18.9 Z(/τ τ)+jets 21.4±7.4±4.9 7.5±4.6±0.2 Single t 16.0±2.8±4.4 17.3±2.8±4.7 VV 4.1±0.6±1.3 2.6±0.5±0.8 Total exp. bkg. 294.9±7.9±39.1 211.4±5.4±23.4 Observed 289 216 MLQ=500 GeV 57.7±1.4±5.9 51.6±1.3±5.3 MLQ=600 GeV 20.1±0.5±1.9 17.7±0.4±1.6 MLQ=700 GeV 7.1±0.2±6.3 6.2±0.1±5.5 MLQ=800 GeV 2.7±0.1±0.2 2.3±0.1±0.2

uncertaintyassigned tothe τh identification efficiencyis 6%.The

uncertainties intheb-taggingefficiencyandmistagging probabil-itydepend onthe η andpT ofthejetandare onaverage4%and

10%,respectively[42].

Systematic uncertainties, totaling 19–22% depending on the channel andthe search,are assignedto the normalizationofthe tt irreducible background based on statistical uncertainty in the control samples and the propagation of the uncertainties in the acceptances,efficiencies,andsubtractionofthecontributionsfrom otherprocessesintheeμsample.Systematicuncertaintiesinthe major reducible background are driven by statistical uncertainty inthemeasuredmisidentificationprobability andvariationinthe misidentification probability based on the event topology. These uncertainties amount to 16–24%, depending on the channel and thesearch.

Because of the limited number of events in the simulation, uncertainties in the small backgrounds range between 20–50%. Uncertaintydueto theeffectofpileupmodelingintheMC is es-timated to be 3%. A 4% uncertainty, due to modeling of initial-andfinal-stateradiationinthesimulation,isassignedtothesignal acceptance. The uncertainty in the initial- and final-state radia-tionwas foundtohavea negligibleeffectonthesimulated back-grounds.A7–32%uncertaintyfromknowledgeofparton distribu-tionfunctionsanda14–80%uncertaintyfromQCDrenormalization andfactorizationscalesareassignedtothetheoreticalsignal cross-section.Finally,jet energyscaleuncertainties(2–4%dependingon ηand pT) andenergyresolution uncertainties (5–10% depending

on η),aswellasenergyscale(3%)andresolution(10%) uncertain-tiesfor τh,affectboththe STdistributionsandtheexpectedyields

fromthesignalandbackgroundprocesses.

6. Results

Thenumbersofobservedeventsandexpectedsignaland back-groundeventsafterthefinalselection fortheleptoquarkandtop squarksearchesarelisted inTables 1 and2,respectively,andthe selection efficiencies for the two signals are listed in Tables 3 and 4. The ST distributions of the selected events fromthe

ob-served dataandfromthe backgroundpredictions,combiningeτh

and μτh channels, are shownin Fig. 1forthe leptoquark search

and Fig. 2 for the top squark search. The distribution from the 500 GeV(300 GeV)signal hypothesis isaddedtothe background inFig. 1(Fig. 2)to illustratehowahypotheticalsignalwould ap-pearabove the backgroundprediction. The data agree well with theSMbackgroundprediction.

An upper bound at95% confidence level (CL) is set on σB2_,

where σisthecrosssectionforpairproductionofthird-generation LQs(topsquarks)andBisthebranchingfractionfortheLQdecay

Table 2

Theestimatedbackgrounds,observedeventyields,andexpectednumberofsignal eventsforthetopsquarksearch.Forthesimulation-basedentries,thestatistical andsystematicuncertaintiesareshownseparately,inthatorder.

eτh μτh tt irreducible 88.3±13.7 55.0±9.5 Major reducible 65.7±16.4 59.8±13.8 Z(/τ τ)+jets 4.9±2.5±1.1 11.6±5.5±2.7 Single t 3.9±1.5±1.1 3.5±1.3±0.9 VV 0.6±0.2±0.2 0.4±0.2±0.1 Total exp. bkg. 163.4±2.9±21.5 130.3±5.6±17.1 Observed 156 123 M˜t=300 GeV 94.3±8.5±13.2 82.8±8.0±11.7 M˜t=400 GeV 43.9±2.6±4.3 38.3±2.3±3.8 M˜t=500 GeV 19.4±0.8±1.8 15.4±0.7±1.5 M˜t=600 GeV 6.9±0.9±0.7 5.7±0.3±0.5 Table 3

Selectionefficienciesin%forthesignalintheleptoquark search,estimatedfromthesimulation.

MLQ(GeV) eτh μτh 200 0.1 0.1 250 0.3 0.2 300 1.0 0.8 350 1.9 1.5 400 2.4 2.3 450 3.0 2.9 500 3.6 3.2 550 4.0 3.3 600 4.4 3.8 650 4.5 4.0 700 4.7 4.1 750 4.9 4.2 800 5.1 4.3 850 5.4 4.4 900 5.1 4.4 950 5.4 4.3 1000 5.5 4.4 Table 4

Selectionefficienciesin%forthesignalinthetopsquark search,estimatedfromthesimulation.

M˜t(GeV) eτh μτh 200 0.02 0.02 300 0.3 0.2 400 0.7 0.6 500 1.2 1.0 600 1.5 1.2 700 1.8 1.4 800 1.8 1.3 900 1.5 1.1

to a tau lepton anda bottom quark (the top squark decay to a ˜

χ± andabottomquark, withasubsequentdecayofthechargino via χ˜±→ ˜ντ±→qqτ±). The symbol MLQ is usedforthe

lepto-quark mass andthe symbol M_˜t isused forthe top squarkmass. The modified-frequentistconstructionCLs [43–45]is usedforthe

limit calculation. A maximum likelihood fit is performed to the

ST spectrum simultaneously for the eτh and μτh channels,

tak-ingintoaccountcorrelationsbetweenthesystematicuncertainties. Expected andobservedupper limitson σB2 _{asafunction ofthe}

signalmassareshowninFig. 3fortheleptoquarksearchandFig. 4 forthetopsquarksearch.

We extend the current limits and exclude scalar leptoquarks andtop squarksdecayingthrough thecouplingλ₃₃₃ withmasses below 740 GeV,in agreementwith a limitat 750 GeV,expected in theabsence ofa signal. Weexclude top squarks undergoing a

Fig. 1. ThefinalST distributionfortheleptoquark searchwiththeeτh and μτh

channelscombined.A signalsampleforleptoquarks withthe massof500 GeV isaddedontopofthebackgroundprediction.Thelastbincontainstheoverflow events.Thehorizontalbaroneachobserveddatapointindicatesthewidthofthe bininST.

Fig. 2. ThefinalST distributionforthetopsquarksearchwiththe eτh and μτh

channelscombined.Asignalsamplefor topsquarkswith themass of300 GeV isaddedontopofthebackgroundprediction.Thelastbincontainstheoverflow events.Thehorizontalbaroneachobserveddatapointindicatesthewidthofthe bininST.

chargino-mediateddecayinvolvingthecouplingλ_{3 jk} withmasses intherange200–580 GeV,inagreementwiththeexpected exclu-sionlimit in therange 200–590 GeV.Theseupper limitsassume

B =100%. Similar results are obtained when calculating upper boundsusingaBayesianmethodwithauniformpositivepriorfor thecrosssection.

Theupperboundsfortheleptoquarksearchasafunctionofthe leptoquarkbranchingfractionandmassareshowninFig. 5.Small

Bvaluesarenotconstrainedbythissearch.ResultsfromtheCMS experimenton a search fortop squarks decaying to a top quark anda neutralino[46] areusedtofurther constrainB.Ifthe neu-tralinoismassless,thefinalstatekinematicdistributionsforsucha signalarethesameasthoseforthepairproductionofleptoquarks decayingto a tauneutrinoanda top quark. Limits cantherefore beplacedonthissignal,whichmusthaveabranchingfractionof 1−B ifthe leptoquarkonly decaysto third-generationfermions. Thisreinterpretation isincluded inFig. 5. The unexcludedregion

Fig. 3. Theexpectedandobservedcombinedupperlimitsonthethird-generationLQ pairproductioncrosssection σ timesthesquareofthebranchingfraction,B2_,at

95%CL,asafunctionoftheLQmass.Theselimitsalsoapplytotopsquarksdecaying directlyviathecouplingλ333.Thegreen(darker)andyellow(lighter)uncertainty

bandsrepresent68%and95%CLintervalsontheexpectedlimit.Thedarkbluecurve andthehatchedlightbluebandrepresentthetheoreticalLQpairproductioncross section,assumingB=100%,andtheuncertaintiesduetothechoiceofPDFand renormalization/factorizationscales.(Forinterpretationofthereferencestocolorin thisfigurelegend,thereaderisreferredtothewebversionofthisarticle.)

Fig. 4. Theexpectedandobservedcombinedupperlimitsonthetopsquarkpair productioncrosssection σ timesthesquareofthebranchingfraction,B2_,at95%

CL,asafunctionofthetopsquarkmass.Theselimitsapplytotopsquarkswith achargino-mediateddecaythroughthecouplingλ3kj.The green(darker)and

yel-low(lighter)uncertaintybandsrepresent68%and95%CLintervalsontheexpected limit.Thedarkbluecurveandthehatchedlightbluebandrepresentthetheoretical topsquarkpairproductioncrosssection,assumingB=100%,andtheuncertainties duetothechoiceofPDFandrenormalization/factorizationscales.(For interpreta-tionofthereferencestocolorinthisfigurelegend,thereaderisreferredtothe webversionofthisarticle.)

at MLQ=200–230 GeV corresponds to a portion of phase space

whereit istopologically verydifficult todistinguish betweenthe topsquarksignalandthett process,owingtosmallmissing trans-versemomentum.Atopsquarkexcessinthisregionwouldimply anexcessinthemeasuredtt crosssectionof∼10%.

7. Summary

A search for pair production of third-generation scalar lep-toquarks and top squarks has been presented. The search for

Fig. 5. Theexpected(dashedblack)andobserved(greensolid)95%CLupper lim-itsonthebranchingfractionfortheleptoquarkdecaytoatauleptonandabottom quark,asafunctionoftheleptoquarkmass.Asearchfortopsquarkpairproduction

[46]hasthesamekinematicsignatureastheleptoquarkdecaytoatauneutrino andatopquark.Thissearchisreinterpretedtoprovidetheexpected(bluehatched) andobserved(blueopen)95%CLupperlimitsforlowvaluesofB,assumingthe leptoquarkonlydecaystothird-generationfermions.(Forinterpretationofthe ref-erencestocolorinthisfigurelegend,thereaderisreferredtothewebversionof thisarticle.)

leptoquarks and top squarks decaying through the R-parity vio-lating coupling λ₃₃₃ is performed in final states that include an electron or a muon, a hadronically decaying tau lepton, and at least two jets, at leastone of which is b-tagged. The search for top squarks undergoing a chargino-mediated decay involvingthe R-parity violating coupling λ_{3 jk} is performed in events contain-ing an electron or a muon, a hadronically decaying tau lepton, and at least five jets, at least one of which is b-tagged. No ex-cesses above the standard model background prediction are ob-servedinthe ST distributions.Assuminga100%branchingfraction

for the decay to a tau lepton and a bottom quark, scalar lepto-quarksandtopsquarksdecayingthroughλ₃₃₃withmassesbelow 740 GeVareexcludedat95%confidencelevel.Topsquarks decay-ingthroughλ_{3 jk} withmassesbelow580 GeVareexcludedat95% confidencelevel, assuming a 100% branching fractionforthe de-cay to a tau lepton, a bottom quark, and two light quarks. The constraint on the third-generation leptoquark mass is the most stringentto date, andthisis the firstsearch fortop squarks de-cayingthroughλ_{3 jk}.

Acknowledgements

WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the technicalandadministrativestaffs atCERN andatother CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcenters and personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythe computinginfrastructureessential to ouranalyses. Finally, we acknowledge the enduring support for the construc-tionandoperation oftheLHCandthe CMSdetectorprovidedby 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); NRF and WCU (Republic of Korea); LAS (Lithuania); MOE andUM (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);TUBITAK andTAEK (Turkey);NASU andSFFR (Ukraine);STFC(United Kingdom);DOE andNSF(USA).

Individuals have received support from the Marie-Curie pro-gramme andtheEuropean Research Council andEPLANET (Euro-peanUnion);theLeventisFoundation;theAlfredP.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 MinistryofEducation, Youth andSports(MEYS) of theCzechRepublic;theCouncilofScienceandIndustrialResearch, India; the HOMING PLUS programme of Foundation For Polish Science, cofinanced from European Union, Regional Development Fund; theCompagniadi SanPaolo (Torino);the Consorzioper la Fisica (Trieste); MIURproject20108T4XTM (Italy); theThalisand Aristeia programmes cofinanced by EU-ESF and the Greek NSRF; andtheNationalPrioritiesResearchProgrambyQatarNational Re-searchFund.

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CMSCollaboration

V. Khachatryan,A.M. Sirunyan, A. Tumasyan

YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam, T. Bergauer, M. Dragicevic,J. Erö,C. Fabjan1,M. Friedl,R. Frühwirth1, V.M. Ghete, C. Hartl,

N. Hörmann, J. Hrubec, M. Jeitler1,W. Kiesenhofer, V. Knünz,M. Krammer1, I. Krätschmer,D. Liko,

I. Mikulec,D. Rabady2, B. Rahbaran,H. Rohringer, R. Schöfbeck, J. Strauss, A. Taurok,

W. Treberer-Treberspurg,W. Waltenberger, C.-E. Wulz1

InstitutfürHochenergiephysikderOeAW,Wien,Austria

V. Mossolov,N. Shumeiko,J. Suarez Gonzalez

NationalCentreforParticleandHighEnergyPhysics,Minsk,Belarus

S. Alderweireldt, M. Bansal, S. Bansal,T. Cornelis, E.A. De Wolf,X. Janssen,A. Knutsson, S. Luyckx,

S. Ochesanu,B. Roland, R. Rougny, M. Van De Klundert,H. Van Haevermaet, P. Van Mechelen,

N. Van Remortel,A. Van Spilbeeck

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. Perniè2, T. Reis,T. Seva, L. Thomas, C. Vander Velde, P. Vanlaer, J. Wang

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. Ryckbosch, S. Salva Diblen, M. Sigamani,N. Strobbe, F. Thyssen,

M. Tytgat, E. Yazgan, N. Zaganidis

GhentUniversity,Ghent,Belgium

S. Basegmez, C. Beluffi3,G. Bruno,R. Castello, A. Caudron, L. Ceard, G.G. Da Silveira, C. Delaere,

T. du Pree,D. Favart, L. Forthomme,A. Giammanco4,J. Hollar, P. Jez, M. Komm, V. Lemaitre, C. Nuttens,

D. Pagano,L. Perrini, A. Pin, K. Piotrzkowski, A. Popov5, 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, C. Mora Herrera,

M.E. Pol

CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

W. Carvalho,J. Chinellato6,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 Manganote6,A. Vilela Pereira

UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

C.A. Bernardesb, S. Dograa,T.R. Fernandez Perez Tomeia,E.M. Gregoresb, P.G. Mercadanteb,

S.F. Novaesa, Sandra S. Padulaa

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

A. Aleksandrov, V. Genchev2,P. Iaydjiev, A. Marinov, S. Piperov,M. Rodozov, S. Stoykova, G. Sultanov,

V. Tcholakov, M. Vutova

InstituteforNuclearResearchandNuclearEnergy,Sofia,Bulgaria

A. Dimitrov, I. Glushkov,R. Hadjiiska, V. Kozhuharov, L. Litov,B. Pavlov, P. Petkov

UniversityofSofia,Sofia,Bulgaria

J.G. Bian, G.M. Chen,H.S. Chen, M. Chen, R. Du,C.H. Jiang, S. Liang,R. Plestina7,J. Tao, X. Wang,Z. Wang

InstituteofHighEnergyPhysics,Beijing,China

C. Asawatangtrakuldee, Y. Ban, Y. Guo, Q. Li, W. Li, S. Liu, Y. Mao,S.J. Qian, H. Teng, D. Wang,W. Zou

StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

C. Avila,L.F. Chaparro Sierra, C. Florez, J.P. Gomez, B. Gomez Moreno,J.C. Sanabria

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

UniversityofCyprus,Nicosia,Cyprus

M. Bodlak,M. Finger,M. Finger Jr.8

CharlesUniversity,Prague,CzechRepublic

Y. Assran9,S. Elgammal10,M.A. Mahmoud11,A. Radi10,12

AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt

M. Kadastik, M. Murumaa, M. Raidal, A. Tiko

NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia

P. Eerola,G. Fedi, 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, C. Charlot, T. Dahms,M. Dalchenko, L. Dobrzynski, N. Filipovic,

A. Florent,R. Granier de Cassagnac, L. Mastrolorenzo, P. Miné, C. Mironov, I.N. Naranjo, M. Nguyen,

C. Ochando, P. Paganini,S. Regnard, R. Salerno,J.B. Sauvan, Y. Sirois, C. Veelken, Y. Yilmaz,A. Zabi

LaboratoireLeprince-Ringuet,EcolePolytechnique,IN2P3–CNRS,Palaiseau,France

J.-L. Agram13,J. Andrea, A. Aubin,D. Bloch, J.-M. Brom,E.C. Chabert, C. Collard,E. Conte13,

J.-C. Fontaine13,D. Gelé, U. Goerlach,C. Goetzmann, A.-C. Le Bihan, P. Van Hove

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

S. Gadrat

CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France

S. Beauceron,N. Beaupere, G. Boudoul2,E. Bouvier, S. Brochet,C.A. Carrillo Montoya, J. Chasserat,

T. Kurca, M. Lethuillier, L. Mirabito,S. Perries, J.D. Ruiz Alvarez,D. Sabes, L. Sgandurra,V. Sordini,

M. Vander Donckt, P. Verdier, S. Viret,H. Xiao

UniversitédeLyon,UniversitéClaudeBernardLyon 1,CNRS–IN2P3,InstitutdePhysiqueNucléairedeLyon,Villeurbanne,France

Z. Tsamalaidze8

InstituteofHighEnergyPhysicsandInformatization,TbilisiStateUniversity,Tbilisi,Georgia

C. Autermann, S. Beranek,M. Bontenackels, M. Edelhoff,L. Feld, O. Hindrichs, K. Klein, A. Ostapchuk,

A. Perieanu, F. Raupach, J. Sammet, S. Schael, H. Weber, B. Wittmer, V. Zhukov5

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, A. Heister, F. Hoehle,

B. Kargoll, T. Kress, Y. Kuessel,J. Lingemann2, A. Nowack,I.M. Nugent, L. Perchalla, O. Pooth,A. Stahl

RWTHAachenUniversity,III.PhysikalischesInstitutB,Aachen,Germany

I. Asin, N. Bartosik, J. Behr, W. Behrenhoff,U. Behrens, A.J. Bell,M. Bergholz14, A. Bethani,K. Borras,

A. Burgmeier,A. Cakir, L. Calligaris,A. Campbell, S. Choudhury, F. Costanza, C. Diez Pardos,S. Dooling,

T. Dorland,G. Eckerlin, D. Eckstein, T. Eichhorn, G. Flucke, J. Garay Garcia, A. Geiser, P. Gunnellini,

J. Hauk, G. Hellwig, M. Hempel, D. Horton, H. Jung,A. Kalogeropoulos, M. Kasemann,P. Katsas,

J. Kieseler, C. Kleinwort,D. Krücker, W. Lange, J. Leonard, K. Lipka,A. Lobanov, W. Lohmann14,B. Lutz,

R. Mankel, I. Marfin, I.-A. Melzer-Pellmann,A.B. Meyer, J. Mnich, A. Mussgiller, S. Naumann-Emme,

A. Nayak,O. Novgorodova, F. Nowak, E. Ntomari,H. Perrey,D. Pitzl, R. Placakyte, A. Raspereza,

P.M. Ribeiro Cipriano, E. Ron,M.Ö. Sahin, J. Salfeld-Nebgen,P. Saxena, R. Schmidt14,

T. Schoerner-Sadenius,M. Schröder, C. Seitz, S. Spannagel, A.D.R. Vargas Trevino, R. Walsh,C. Wissing

DeutschesElektronen-Synchrotron,Hamburg,Germany

M. Aldaya Martin,V. Blobel, M. Centis Vignali, A.r. Draeger, J. Erfle,E. Garutti, K. Goebel, M. Görner,

J. Haller, M. Hoffmann,R.S. Höing, H. Kirschenmann,R. Klanner, R. Kogler, J. Lange,T. Lapsien, T. Lenz,

I. Marchesini, J. Ott, T. Peiffer, 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,

M. Feindt,F. Frensch, M. Giffels,F. Hartmann2,T. Hauth2,U. Husemann, I. Katkov5, A. Kornmayer2,

E. Kuznetsova, P. Lobelle Pardo, M.U. Mozer, Th. Müller, A. Nürnberg, G. Quast, K. Rabbertz,F. Ratnikov,

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

S. Kesisoglou, A. Panagiotou, N. Saoulidou, E. Stiliaris

X. Aslanoglou,I. Evangelou, G. Flouris,C. Foudas, P. Kokkas, N. Manthos, I. Papadopoulos,E. Paradas

UniversityofIoánnina,Ioánnina,Greece

G. Bencze,C. Hajdu, P. Hidas,D. Horvath15, F. Sikler,V. Veszpremi, G. Vesztergombi16, A.J. Zsigmond

WignerResearchCentreforPhysics,Budapest,Hungary

N. Beni,S. Czellar, J. Karancsi17,J. Molnar, J. Palinkas, Z. Szillasi

InstituteofNuclearResearchATOMKI,Debrecen,Hungary

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, 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, S. Kailas,V. Kumar, A.K. Mohanty2,L.M. Pant, P. Shukla, A. Topkar

BhabhaAtomicResearchCentre,Mumbai,India

T. Aziz,S. Banerjee, S. Bhowmik18, R.M. Chatterjee, R.K. Dewanjee,S. Dugad, S. Ganguly, S. Ghosh,

M. Guchait,A. Gurtu19, G. Kole, S. Kumar, M. Maity18,G. Majumder, K. Mazumdar, G.B. Mohanty,

B. Parida,K. Sudhakar, N. Wickramage20

TataInstituteofFundamentalResearch,Mumbai,India

H. Bakhshiansohi,H. Behnamian,S.M. Etesami21, A. Fahim22, R. Goldouzian, A. Jafari,M. Khakzad,

M. Mohammadi Najafabadi,M. Naseri, S. Paktinat Mehdiabadi, F. Rezaei Hosseinabadi, B. Safarzadeh23,

M. Zeinali

InstituteforResearchinFundamentalSciences(IPM),Tehran,Iran

M. Felcini,M. Grunewald

UniversityCollegeDublin,Dublin,Ireland

M. Abbresciaa,b, L. Barbonea,b,C. Calabriaa,b,S.S. Chhibraa,b,A. Colaleoa,D. Creanzaa,c,

N. De Filippisa,c, M. De Palmaa,b, L. Fiorea, G. Iasellia,c, G. Maggia,c, M. Maggia,S. Mya,c,S. Nuzzoa,b, A. Pompilia,b, G. Pugliesea,c,R. Radognaa,b,2,G. Selvaggia,b,L. Silvestrisa,2,G. Singha,b,R. Vendittia,b,

P. Verwilligena,G. Zitoa

a_{INFNSezionediBari,Bari,Italy} b_{UniversitàdiBari,Bari,Italy} c_{PolitecnicodiBari,Bari,Italy}

G. Abbiendia,A.C. Benvenutia, D. Bonacorsia,b_{, S. Braibant-Giacomelli}a,b_{,L. Brigliadori}a,b_, R. Campaninia,b,P. Capiluppia,b,A. Castroa,b, F.R. Cavalloa,G. Codispotia,b, M. Cuffiania,b,

G.M. Dallavallea,F. Fabbria, A. Fanfania,b, D. Fasanellaa,b,P. Giacomellia,C. Grandia,L. Guiduccia,b, S. Marcellinia, G. Masettia,2,A. Montanaria,F.L. Navarriaa,b, A. Perrottaa,F. Primaveraa,b,A.M. Rossia,b, T. Rovellia,b,G.P. Sirolia,b,N. Tosia,b,R. Travaglinia,b

a_{INFNSezionediBologna,Bologna,Italy} b_{UniversitàdiBologna,Bologna,Italy}

S. Albergoa,b,G. Cappelloa, M. Chiorbolia,b, S. Costaa,b, F. Giordanoa,c,2, R. Potenzaa,b, A. Tricomia,b, C. Tuvea,b

a_{INFNSezionediCatania,Catania,Italy} b_{UniversitàdiCatania,Catania,Italy} c_{CSFNSM,Catania,Italy}

G. Barbaglia, V. Ciullia,b,C. Civininia, R. D’Alessandroa,b,E. Focardia,b,E. Galloa,S. Gonzia,b, V. Goria,b,2,P. Lenzia,b, M. Meschinia, S. Paolettia,G. Sguazzonia,A. Tropianoa,b

a_{INFNSezionediFirenze,Firenze,Italy} b_{UniversitàdiFirenze,Firenze,Italy}

L. Benussi, S. Bianco, F. Fabbri,D. Piccolo

INFNLaboratoriNazionalidiFrascati,Frascati,Italy

F. Ferroa, M. Lo Veterea,b, E. Robuttia,S. Tosia,b

a_{INFNSezionediGenova,Genova,Italy} b_{UniversitàdiGenova,Genova,Italy}

M.E. Dinardoa,b,S. Fiorendia,b,2,S. Gennaia,2,R. Gerosa2, A. Ghezzia,b, P. Govonia,b, M.T. Lucchinia,b,2,

S. Malvezzia, R.A. Manzonia,b,A. Martellia,b,B. Marzocchi,D. Menascea, L. Moronia, M. Paganonia,b,

D. Pedrinia,S. Ragazzia,b,N. Redaellia, T. Tabarelli de Fatisa,b

a_{INFNSezionediMilano-Bicocca,Milano,Italy} b_{UniversitàdiMilano-Bicocca,Milano,Italy}

S. Buontempoa, N. Cavalloa,c_{, S. Di Guida}a,d,2_{, F. Fabozzi}a,c_{,A.O.M. Iorio}a,b_{,L. Lista}a_{, S. Meola}a,d,2_,

M. Merolaa, P. Paoluccia,2

a_{INFNSezionediNapoli,Napoli,Italy} b_{UniversitàdiNapoli‘FedericoII’,Napoli,Italy} c_{UniversitàdellaBasilicata(Potenza),Napoli,Italy} d_{UniversitàG. Marconi(Roma),Napoli,Italy}

P. Azzia,N. Bacchettaa,D. Biselloa,b,A. Brancaa,b,R. Carlina,b, P. Checchiaa,M. Dall’Ossoa,b,T. Dorigoa, U. Dossellia,M. Galantia,b,F. Gasparinia,b,U. Gasparinia,b, P. Giubilatoa,b,A. Gozzelinoa,

K. Kanishcheva,c,S. Lacapraraa,M. Margonia,b,A.T. Meneguzzoa,b, J. Pazzinia,b, N. Pozzobona,b, P. Ronchesea,b,F. Simonettoa,b, E. Torassaa,M. Tosia,b, P. Zottoa,b, A. Zucchettaa,b,G. Zumerlea,b

a_{INFNSezionediPadova,Padova,Italy} b_{UniversitàdiPadova,Padova,Italy} c_{UniversitàdiTrento(Trento),Padova,Italy}

M. Gabusia,b, S.P. Rattia,b,C. Riccardia,b,P. Salvinia,P. Vituloa,b

a_{INFNSezionediPavia,Pavia,Italy} b_{UniversitàdiPavia,Pavia,Italy}

M. Biasinia,b, G.M. Bileia,D. Ciangottinia,b,L. Fanòa,b,P. Laricciaa,b, G. Mantovania,b, M. Menichellia, F. Romeoa,b_{, A. Saha}a_{, A. Santocchia}a,b_{,A. Spiezia}a,b,2

a_{INFNSezionediPerugia,Perugia,Italy} b_{UniversitàdiPerugia,Perugia,Italy}

K. Androsova,24,P. Azzurria,G. Bagliesia,J. Bernardinia,T. Boccalia,G. Broccoloa,c,R. Castaldia,

T. Lomtadzea, L. Martinia,b,A. Messineoa,b,C.S. Moona,25,F. Pallaa,2,A. Rizzia,b,A. Savoy-Navarroa,26, A.T. Serbana, P. Spagnoloa,P. Squillaciotia,24, R. Tenchinia,G. Tonellia,b, A. Venturia, P.G. Verdinia, C. Vernieria,c,2

a_{INFNSezionediPisa,Pisa,Italy} b_{UniversitàdiPisa,Pisa,Italy}

c_{ScuolaNormaleSuperiorediPisa,Pisa,Italy}

L. Baronea,b, F. Cavallaria,G. D’imperioa,b,D. Del Rea,b, M. Diemoza,M. Grassia,b,C. Jordaa, E. Longoa,b, F. Margarolia,b, P. Meridiania,F. Michelia,b,2,S. Nourbakhsha,b, G. Organtinia,b, R. Paramattia,S. Rahatloua,b, C. Rovellia,F. Santanastasioa,b,L. Soffia,b,2,P. Traczyka,b

a_{INFNSezionediRoma,Roma,Italy} b_{UniversitàdiRoma,Roma,Italy}

N. Amapanea,b,R. Arcidiaconoa,c, S. Argiroa,b,2,M. Arneodoa,c,R. Bellana,b, C. Biinoa, N. Cartigliaa, S. Casassoa,b,2, M. Costaa,b,A. Deganoa,b,N. Demariaa, L. Fincoa,b, C. Mariottia, S. Masellia,

E. Migliorea,b,V. Monacoa,b, M. Musicha, M.M. Obertinoa,c,2,G. Ortonaa,b,L. Pachera,b,N. Pastronea, M. Pelliccionia, G.L. Pinna Angionia,b,A. Potenzaa,b, A. Romeroa,b,M. Ruspaa,c,R. Sacchia,b,

A. Solanoa,b,A. Staianoa, U. Tamponia

a_{INFNSezionediTorino,Torino,Italy} b_{UniversitàdiTorino,Torino,Italy}

c_{UniversitàdelPiemonteOrientale(Novara),Torino,Italy}

S. Belfortea,V. Candelisea,b, M. Casarsaa,F. Cossuttia,G. Della Riccaa,b,B. Gobboa,C. La Licataa,b, M. Maronea,b, D. Montaninoa,b, A. Schizzia,b,2, T. Umera,b,A. Zanettia

a_{INFNSezionediTrieste,Trieste,Italy} b_{UniversitàdiTrieste,Trieste,Italy}

S. Chang,A. Kropivnitskaya, S.K. Nam

KangwonNationalUniversity,Chunchon,RepublicofKorea

D.H. Kim,G.N. Kim, M.S. Kim, D.J. Kong, S. Lee, Y.D. Oh,H. Park, A. Sakharov,D.C. Son

KyungpookNationalUniversity,Daegu,RepublicofKorea

T.J. Kim

ChonbukNationalUniversity,Jeonju,RepublicofKorea

J.Y. Kim,S. Song

ChonnamNationalUniversity,InstituteforUniverseandElementaryParticles,Kwangju,RepublicofKorea

S. Choi, D. Gyun,B. Hong,M. Jo, H. Kim, Y. Kim,B. Lee, K.S. Lee, S.K. Park,Y. Roh

KoreaUniversity,Seoul,RepublicofKorea

M. Choi,J.H. Kim, I.C. Park, S. Park, G. Ryu, M.S. Ryu

UniversityofSeoul,Seoul,RepublicofKorea

Y. Choi,Y.K. Choi,J. Goh, D. Kim, E. Kwon, J. Lee, H. Seo,I. Yu

SungkyunkwanUniversity,Suwon,RepublicofKorea

A. Juodagalvis

VilniusUniversity,Vilnius,Lithuania

J.R. Komaragiri, M.A.B. Md Ali

H. Castilla-Valdez, E. De La Cruz-Burelo,I. Heredia-de La Cruz27,R. Lopez-Fernandez, A. Sanchez-Hernandez

CentrodeInvestigacionydeEstudiosAvanzadosdelIPN,MexicoCity,Mexico

S. Carrillo Moreno, F. Vazquez Valencia

UniversidadIberoamericana,MexicoCity,Mexico

I. Pedraza, H.A. Salazar Ibarguen

BenemeritaUniversidadAutonomadePuebla,Puebla,Mexico

E. Casimiro Linares, A. Morelos Pineda

UniversidadAutónomadeSanLuisPotosí,SanLuisPotosí,Mexico

D. Krofcheck

UniversityofAuckland,Auckland,NewZealand

P.H. Butler,S. Reucroft

UniversityofCanterbury,Christchurch,NewZealand

A. Ahmad, M. Ahmad, Q. Hassan,H.R. Hoorani, S. Khalid, W.A. Khan, T. Khurshid, M.A. Shah, M. Shoaib

NationalCentreforPhysics,Quaid-I-AzamUniversity,Islamabad,Pakistan

H. Bialkowska, M. Bluj,B. Boimska, T. Frueboes,M. Górski, M. Kazana, K. Nawrocki,

K. Romanowska-Rybinska, M. Szleper,P. Zalewski

NationalCentreforNuclearResearch,Swierk,Poland

G. Brona, K. Bunkowski, M. Cwiok,W. Dominik, K. Doroba, A. Kalinowski, M. Konecki,J. Krolikowski,

M. Misiura, M. Olszewski, W. Wolszczak

InstituteofExperimentalPhysics,FacultyofPhysics,UniversityofWarsaw,Warsaw,Poland

P. Bargassa,C. Beirão Da Cruz E Silva, P. Faccioli, P.G. Ferreira Parracho, M. Gallinaro,F. Nguyen,

J. Rodrigues Antunes, J. Seixas,J. Varela, P. Vischia

LaboratóriodeInstrumentaçãoeFísicaExperimentaldePartículas,Lisboa,Portugal

S. Afanasiev,P. Bunin,M. Gavrilenko, I. Golutvin,I. Gorbunov, A. Kamenev, V. Karjavin,V. Konoplyanikov,

A. Lanev,A. Malakhov,V. Matveev28, P. Moisenz, V. Palichik,V. Perelygin, S. Shmatov, N. Skatchkov,

V. Smirnov, A. Zarubin

JointInstituteforNuclearResearch,Dubna,Russia

V. Golovtsov, Y. Ivanov,V. Kim29, P. Levchenko, V. Murzin,V. Oreshkin, I. Smirnov, V. Sulimov, L. Uvarov,

S. Vavilov, A. Vorobyev,An. Vorobyev

PetersburgNuclearPhysicsInstitute,Gatchina(St.Petersburg),Russia

Yu. Andreev,A. Dermenev, S. Gninenko, N. Golubev, M. Kirsanov,N. Krasnikov, A. Pashenkov, D. Tlisov,

A. Toropin

InstituteforNuclearResearch,Moscow,Russia

V. Epshteyn, V. Gavrilov, N. Lychkovskaya,V. Popov, G. Safronov, S. Semenov, A. Spiridonov, V. Stolin,

E. Vlasov, A. Zhokin

V. Andreev,M. Azarkin, I. Dremin, M. Kirakosyan, A. Leonidov, G. Mesyats,S.V. Rusakov, A. Vinogradov

P.N.LebedevPhysicalInstitute,Moscow,Russia

A. Belyaev,E. Boos,V. Bunichev, M. Dubinin30,L. Dudko, A. Ershov, V. Klyukhin, O. Kodolova, I. Lokhtin,

S. Obraztsov,S. Petrushanko,V. Savrin, A. Snigirev

SkobeltsynInstituteofNuclearPhysics,LomonosovMoscowStateUniversity,Moscow,Russia

I. Azhgirey,I. Bayshev,S. Bitioukov, V. Kachanov, A. Kalinin, D. Konstantinov,V. Krychkine, V. Petrov,

R. Ryutin, A. Sobol,L. Tourtchanovitch, S. Troshin, N. Tyurin, A. Uzunian,A. Volkov

StateResearchCenterofRussianFederation,InstituteforHighEnergyPhysics,Protvino,Russia

P. Adzic31,M. Ekmedzic, J. Milosevic,V. Rekovic

UniversityofBelgrade,FacultyofPhysicsandVincaInstituteofNuclearSciences,Belgrade,Serbia

J. Alcaraz Maestre,C. Battilana, E. Calvo,M. Cerrada, M. Chamizo Llatas, N. Colino, B. De La Cruz,

A. Delgado Peris,D. Domínguez Vázquez, A. Escalante Del Valle, C. Fernandez Bedoya,

J.P. Fernández Ramos,J. Flix, M.C. Fouz, P. Garcia-Abia,O. Gonzalez Lopez, S. Goy Lopez, J.M. Hernandez,

M.I. Josa,G. Merino, E. Navarro De Martino, A. Pérez-Calero Yzquierdo,J. Puerta Pelayo,

A. Quintario Olmeda,I. Redondo, L. Romero,M.S. Soares

CentrodeInvestigacionesEnergéticasMedioambientalesyTecnológicas(CIEMAT),Madrid,Spain

C. Albajar, J.F. de Trocóniz,M. Missiroli, D. Moran

UniversidadAutónomadeMadrid,Madrid,Spain

H. Brun, J. Cuevas,J. Fernandez Menendez, S. Folgueras, I. Gonzalez Caballero,L. Lloret Iglesias

UniversidaddeOviedo,Oviedo,Spain

J.A. Brochero Cifuentes,I.J. Cabrillo, A. Calderon, J. Duarte Campderros, M. Fernandez, G. Gomez,

A. Graziano,A. Lopez Virto, J. Marco, R. Marco,C. Martinez Rivero, F. Matorras,F.J. Munoz Sanchez,

J. Piedra Gomez,T. Rodrigo, A.Y. Rodríguez-Marrero,A. Ruiz-Jimeno, L. Scodellaro, I. Vila,

R. Vilar Cortabitarte

InstitutodeFísicadeCantabria(IFCA),CSIC–UniversidaddeCantabria,Santander,Spain

D. Abbaneo, E. Auffray, G. Auzinger, M. Bachtis,P. Baillon, A.H. Ball, D. Barney, A. Benaglia,J. Bendavid,

L. Benhabib,J.F. Benitez, C. Bernet7, G. Bianchi, P. Bloch, A. Bocci, A. Bonato, O. Bondu,C. Botta,

H. Breuker, T. Camporesi, G. Cerminara, S. Colafranceschi32,M. D’Alfonso, D. d’Enterria, A. Dabrowski,

A. David,F. De Guio, A. De Roeck, S. De Visscher, M. Dobson, M. Dordevic, N. Dupont-Sagorin,

A. Elliott-Peisert,J. Eugster, G. Franzoni, W. Funk, D. Gigi,K. Gill, D. Giordano, M. Girone, F. Glege,

R. Guida,S. Gundacker, M. Guthoff, J. Hammer, M. Hansen,P. Harris, J. Hegeman, V. Innocente, P. Janot,

K. Kousouris,K. Krajczar,P. Lecoq, C. Lourenço,N. Magini, L. Malgeri,M. Mannelli, J. Marrouche,

L. Masetti,F. Meijers, S. Mersi, E. Meschi, F. Moortgat, S. Morovic, M. Mulders, P. Musella,L. Orsini,

L. Pape,E. Perez, L. Perrozzi,A. Petrilli, G. Petrucciani, A. Pfeiffer,M. Pierini,M. Pimiä, D. Piparo,

M. Plagge,A. Racz, G. Rolandi33, M. Rovere,H. Sakulin, C. Schäfer, C. Schwick,A. Sharma,P. Siegrist,

P. Silva,M. Simon, P. Sphicas34,D. Spiga, J. Steggemann,B. Stieger, M. Stoye,Y. Takahashi, D. Treille,

A. Tsirou,G.I. Veres16, J.R. Vlimant, N. Wardle, H.K. Wöhri, H. Wollny, W.D. Zeuner

CERN,EuropeanOrganizationforNuclearResearch,Geneva,Switzerland

W. Bertl,K. Deiters,W. Erdmann, R. Horisberger, Q. Ingram,H.C. Kaestli, D. Kotlinski, U. Langenegger,

D. Renker, T. Rohe

F. Bachmair, L. Bäni, L. Bianchini, M.A. Buchmann,B. Casal, N. Chanon, A. Deisher,G. Dissertori,

M. Dittmar, M. Donegà, M. Dünser,P. Eller, C. Grab,D. Hits, W. Lustermann,B. Mangano, A.C. Marini,

P. Martinez Ruiz del Arbol, D. Meister,N. Mohr, C. Nägeli35, F. Nessi-Tedaldi, F. Pandolfi, F. Pauss,

M. Peruzzi,M. Quittnat, L. Rebane, M. Rossini, A. Starodumov36,M. Takahashi, K. Theofilatos, R. Wallny,

H.A. Weber

InstituteforParticlePhysics,ETHZurich,Zurich,Switzerland

C. Amsler37, M.F. Canelli,V. Chiochia,A. De Cosa, A. Hinzmann, T. Hreus, B. Kilminster, C. Lange,

B. Millan Mejias, J. Ngadiuba,P. Robmann, F.J. Ronga, S. Taroni, M. Verzetti, Y. Yang

UniversitätZürich,Zurich,Switzerland

M. Cardaci, K.H. Chen,C. Ferro, C.M. Kuo, W. Lin, Y.J. Lu, R. Volpe,S.S. Yu

NationalCentralUniversity,Chung-Li,Taiwan

P. Chang, Y.H. Chang,Y.W. Chang,Y. Chao, K.F. Chen, P.H. Chen, C. Dietz,U. Grundler, W.-S. Hou,K.Y. Kao,

Y.J. Lei, Y.F. Liu, R.-S. Lu,D. Majumder, E. Petrakou, Y.M. Tzeng,R. Wilken

NationalTaiwanUniversity(NTU),Taipei,Taiwan

B. Asavapibhop, N. Srimanobhas,N. Suwonjandee

ChulalongkornUniversity,FacultyofScience,DepartmentofPhysics,Bangkok,Thailand

A. Adiguzel, M.N. Bakirci38, S. Cerci39,C. Dozen, I. Dumanoglu, E. Eskut, S. Girgis, G. Gokbulut,

E. Gurpinar,I. Hos, E.E. Kangal, A. Kayis Topaksu,G. Onengut40,K. Ozdemir, S. Ozturk38, A. Polatoz,

D. Sunar Cerci39,B. Tali39, H. Topakli38,M. Vergili

CukurovaUniversity,Adana,Turkey

I.V. Akin, B. Bilin,S. Bilmis, H. Gamsizkan, G. Karapinar41, K. Ocalan,S. Sekmen, U.E. Surat,M. Yalvac,

M. Zeyrek

MiddleEastTechnicalUniversity,PhysicsDepartment,Ankara,Turkey

E. Gülmez,B. Isildak42,M. Kaya43,O. Kaya44

BogaziciUniversity,Istanbul,Turkey

K. Cankocak, F.I. Vardarlı

IstanbulTechnicalUniversity,Istanbul,Turkey

L. Levchuk,P. Sorokin

NationalScientificCenter,KharkovInstituteofPhysicsandTechnology,Kharkov,Ukraine

J.J. Brooke,E. Clement, D. Cussans, H. Flacher,R. Frazier, J. Goldstein,M. Grimes, G.P. Heath, H.F. Heath,

J. Jacob, L. Kreczko,C. Lucas, Z. Meng, D.M. Newbold45,S. Paramesvaran, A. Poll, S. Senkin,V.J. Smith,

T. Williams

UniversityofBristol,Bristol,UnitedKingdom

K.W. Bell, A. Belyaev46, C. Brew, R.M. Brown, D.J.A. Cockerill, J.A. Coughlan, K. Harder, S. Harper,

E. Olaiya,D. Petyt, C.H. Shepherd-Themistocleous, A. Thea, I.R. Tomalin, W.J. Womersley, S.D. Worm

RutherfordAppletonLaboratory,Didcot,UnitedKingdom

M. Baber, R. Bainbridge,O. Buchmuller, D. Burton,D. Colling, N. Cripps, M. Cutajar,P. Dauncey,

G. Davies, M. Della Negra, P. Dunne,W. Ferguson, J. Fulcher, D. Futyan, A. Gilbert,G. Hall, G. Iles,