Combination of CMS searches for heavy resonances decaying to pairs of bosons or leptons

Contents lists available atScienceDirect

Physics

Letters

B

www.elsevier.com/locate/physletb

Combination

of

CMS

searches

for

heavy

resonances

decaying

to

pairs

of

bosons

or

leptons

Receivedinrevisedform14August2019 Accepted16September2019

Availableonline23September2019 Editor:M.Doser Keywords: CMS B2G Diboson Dilepton HVT Graviton

A statistical combinationof searches for heavy resonances decaying to pairs ofbosons orleptons is presented.Thedata correspondtoanintegratedluminosity of35.9 fb−1 _{collectedduring2016bythe}

CMSexperimentattheLHCinproton-protoncollisionsatacenter-of-mass energyof13 TeV.Thedata arefoundtobeconsistentwithexpectationsfromthestandardmodelbackground.Exclusionlimitsare set in the context ofmodels ofspin-1 heavy vectortriplets and ofspin-2 bulkgravitons. For mass-degenerateW andZ resonancesthatpredominantlycoupletothestandard modelgaugebosons, the massexclusionat95% confidencelevel ofheavy vectorbosonsisextendedto4.5 TeVascomparedto 3.8 TeVdetermined fromthe bestindividual channel.Thisexcluded massincreases to5.0 TeV if the resonancescouplepredominantlytofermions.

©2019TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

1. Introduction

Overthe past half century, successivesearches for heavy res-onancesintwo-bodydecayshaveoftenled todiscoveriesofnew states.AttheCERNLHC,searchesforWandZresonances (collec-tivelyreferredtoasV)thatcouplethroughtheelectroweak(EW) interactiontostandardmodel(SM)particleshavebeenperformed by ATLAS and CMS in final states with two SM bosons [1–18], two leptons [19–22], andtwo light-flavor [23,24] or heavy-flavor quarks [25–29].Thesenewstateswouldcouplepredominantlyto either SM fermions, as in the case of minimal W andZ mod-els [30–32],orSMbosons,asinstronglycoupledcompositeHiggs and little Higgs models [33–39]. In addition, models based on warpedextradimensionsprovideacandidatefora massive reso-nance,suchasthespin-2firstKaluza-Kleinexcitationofthe gravi-ton(G) [40–42].Inbulkgravitonmodels [43],theSMfermionsand gaugebosons are locatedin thebulk five-dimensionalspacetime, andthegravitonhasasizablebranchingfractiontopairsofW,Z, andHbosons.

ThisLetter describesa statisticalcombinationofCMSsearches for heavy resonances that decay to pairs of bosons or leptons [1–10,19,20].Theeventselection,thesimulatedsamples,the back-groundestimation,andthesystematicuncertaintiesofthe individ-ualanalyses areunchanged. Theresults areused tosetexclusion

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

limits on models that invoke heavy vector resonances and on a modelwithabulkgraviton.

The SM bosons produced in the decay of resonances X with massesmX thatexceed1 TeVareexpectedtohavealargeLorentz boost [44]. The decay products of the SM bosons are therefore highly collimated, requiring dedicated techniques for their iden-tification andreconstruction. In the case ofhadronic decays, the pair of quarks produce a single large-cone jet with a two-prong structure.Inaddition,Higgsbosons canalsobe identifiedby tag-gingthebquarksoriginatingfromtheirdecays.Inmodels where heavy vector bosonscouple predominantlytofermions, the com-binedcontributionfromtheleptonicdecaysW→ ν andZ→  dominates, and thesechannels [19,20] are included in the com-bination, providing complementary sensitivity to the searches in dibosonchannels. TheanalysesconsideredinthisLetterarebased on a datasample ofproton-proton(pp)collisions ata center-of-mass energyof1 TeV collected by the CMSexperiment in2016, andcorrespondingtoanintegratedluminosityof35.9 fb−1.A sim-ilarcombinationperformedonacomparablesetofdatahasbeen recentlypublishedbyATLAS [45].

2. TheCMSdetectorandeventreconstruction

The CMS detector features a silicon pixel and strip tracker, a lead tungstatecrystalelectromagneticcalorimeter(ECAL), anda brassandscintillatorhadroncalorimeter(HCAL),eachcomposedof abarrelandtwo endcapsections.Thesedetectorsresidewithina

https://doi.org/10.1016/j.physletb.2019.134952

0370-2693/©2019TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).Fundedby SCOAP3_.

superconductingsolenoid,whichprovidesamagneticfieldof3.8 T. Forward calorimeters extend the pseudorapidity coverage up to |η| <5.2.Muonsaremeasuredingas-ionizationdetectors embed-dedinthesteel flux-returnyokeoutsidethe solenoid.A detailed descriptionoftheCMSdetector,together withadefinitionofthe coordinate system and the kinematic variables, can be found in Ref. [46].

The information from various elements of the CMS detector is used by a particle-flow (PF) algorithm [47] to identify stable particles reconstructed in the detectoras electrons, muons, pho-tons, and chargedor neutralhadrons. The energyof electrons is determined from a combination of the electron momentum, as determined inthe tracker,the energyof the corresponding ECAL cluster,andtheenergysumofallbremsstrahlungphotonsspatially compatiblewithoriginatingfromtheelectrontrack.Thedielectron mass resolution for Z→ee decays ranges from1.9% when both electrons areintheECALbarrel, to2.9% whenboth electronsare in the endcaps [48]. The momentum of muonsis obtained from thecurvatureofthecorrespondingtrack.The pT resolutioninthe barrelisbetterthan7% formuonswith pT upto 1 TeV [49].The τ leptons that decayto hadrons anda neutrino (labeled τh) are reconstructed by combining one or three charged PF candidates withuptotwoneutralpioncandidates [50].Thee, μ,and τhwith largemomentaarerequiredtobeisolatedfromotherhadronic ac-tivityin theevent. The energyofchargedhadrons isdetermined fromacombinationoftheirmomentameasuredinthetrackerand thematchingECALandHCALenergydeposits.Finally,the energy of neutralhadrons is obtainedfrom the corresponding corrected ECALandHCALenergies.

Jets are reconstructed from PF candidates clustered with the anti-kT algorithm [51], witha distance parameter 0.4 (AK4 jets) or0.8(AK8jets), usingthe FastJet 3.0package [52,53]. The geo-metricaloverlapsbetweenjetsandisolatedleptons, andbetween AK4jetsandtheAK8jet,arehandledbyassigningtheoverlapping four-momentum tothe lepton, andtheAK8 jet,respectively. The four-momentaoftheAK4andAK8jetsareobtainedbyclustering candidatespassingthecharged-hadronsubtractionalgorithm [54]. The contribution of neutral particles originating from additional pp interactions within the same or neighboring bunch crossings (pileup)isproportionaltothejetarea,andisestimatedusingthe medianareamethodimplementedin FastJet,andthensubtracted fromthejetenergy.Thejetenergyresolution,aftertheapplication ofcorrectionsto thejet energy, is4% at1 TeV [55]. The missing transverse momentum vector pmiss_T is computed asthe negative vectorsumofthetransversemomenta ofall thePFcandidatesin anevent, anditsmagnitudeisdenotedaspmiss

T [56].The pmissT is correctedforadjustmentstotheenergyscaleofthereconstructed AK4jetsintheevent.

WhileAK4jetsareusedforsinglequarks,AK8jetsareadopted toreconstruct largemomentum SM bosons that decaytoquarks. Reconstructing the AK8 jet mass (mj) and substructure relieson thepileup-per-particleidentificationalgorithm [54,57].The contri-butionsfromsoftradiationandadditionalinteractionsareremoved usingthesoft-dropalgorithm [58,59], withparameters β=0 and zcut=0.1. Dedicated mass corrections, obtained fromsimulation anddatainaregionenrichedwithtt events¯ withmergedW(qq¯)

decays,are applied tothe jet massto reduce anyresidualjet pT dependence [6,60],andtomatchthejetmassscaleandresolution observedindata.Themeasuredsoft-dropjetmassresolutionis ap-proximatelyconstantat10%intheconsideredrangeofjet pT[60]. ExclusivemjintervalslabeledmW,mZ,andmH,whichrangefrom 65to85,85to105,and105to135 GeV,respectively,aredefined accordingtotheSMbosonmassesandthejetmassresolution.

Hadronic decays of W and Z bosons are identified using the ratiobetween2-subjettinessand1-subjettiness [61], τ21=τ2/τ1.

Thevariablesmjand τ21arecalibratedusingatopquark-antiquark sample enrichedinhadronically decayingW bosons [62].The de-cay ofaHiggsbosontoapairofbquarksisidentified usingone of two btagging algorithms, depending onthe background com-position.The firstconsistsofa dedicatedbtaggingdiscriminator, specifically designed to identify a pair of b quarks clustered in a single jet [63]. The second relies on splitting the AK8 jet into two subjets, then applying the combined secondary vertex algo-rithm [63] tothesubjets.The latterisalsoappliedto AK4jetsto identifyisolatedbquarksintheevent.

3. Signalmodeling

The response of the CMS detector to the production and de-cay of heavy resonances is evaluated through simulated events, whicharereconstructedusingthesamealgorithmsasusedin col-lision data.Thespin-1 gaugebosons, W andZ,aresimulatedat leading order (LO) using the MadGraph5_amc@nlo 2.4.2 matrix element generator [64], in the heavy vector triplet (HVT) frame-work [65,66], which introduces a triplet of heavy vector bosons withsimilar mass,ofwhichoneis neutral(Z)andtwo are elec-trically charged(W±). Thecouplingstrength ofthe heavyvector bosonstoSMbosonsandfermionsisdeterminedfromthe combi-nations gH=gVcH and gf=g2cF/gV,respectively. The parameter gV is the strength of the new interaction; cH characterizes the interaction betweentheHVTbosons,the Higgsboson,and longi-tudinally polarizedSMvector bosons;cF representsthedirect in-teractionbetweentheVbosonsandtheSMfermions; g istheSM SU(2)L gaugecouplingconstant.The HVTframework ispresented intwoscenarios, henceforthreferredtoasmodel Aandmodel B, dependingonthecouplingstotheSMparticles [66].Intheformer, thecouplingstrengthstotheSM bosonsandfermionsare compa-rable, and the new particles decay primarily to fermions. In the latter,thecouplingstotheSMfermionsaresmall,andthe branch-ingfractiontotheSMbosonsisnearly100%.Eventsaresimulated withdifferentmX hypothesesfrom800to4500 GeV forXdecays to bosons, and800to 5500 GeVforX decaysto leptons, assum-ing a negligible resonance width compared to the experimental resolution (3–20%). The kinematic distributions of the signal do notdependonthechoiceofbenchmarkscenario,andthesamples arereweightedaccordingonlytothecrosssectionsandbranching fractions.

The bulk graviton events are also simulated at LO using the same MadGraph5_amc@nlo generator. The crosssection andthe widthofthebulkgravitonmainlydependonitsmassandthe ra-tioκ≡κ/MPl,where κisacurvaturefactorofthemodelandMPl is thereducedPlanckmass [43,67].The gravitonsignalsare gen-erated assumingκ=0.5,which guaranteesthat thewidthofthe gravitonissmallerthantheexperimentalresolution.

Thesignal eventsaregeneratedusingtheNNPDF3.0 [68] par-ton distribution functions (PDFs), and are interfaced to pythia 8.205 [69] forparton showeringand hadronization,adopting the MLMmatchingscheme [70].Simulatedpileupinteractionsare su-perimposedon thehard process,andtheir frequencydistribution isweightedtomatchthenumberofinteractionsperbunch cross-ing observedindata.Generatedeventsareprocessedthroughthe CMSdetectorsimulation,basedon Geant4 [71].

4. Searchchannels

Thesearch strategiesfortheanalysescontributingtothe com-binationaresummarizedinthisSection.Moredetailsareprovided intherelevantpublications [1–10,19,20].

4.1.Fullyhadronicdibosonchannels

Diboson resonances have been searched for in several final states, depending on the decay modes of the bosons. The final statestargeted were VV→qqq¯ q [¯ 1], VH→qqb¯ b [¯ 6], andHH→ bbb¯ b final¯ states [9,10]. Each boson is reconstructed as a two-prong,large-conejet,sothatfordibosonresonances,thetwo jets wouldrecoilagainst each other. The presenceof a diboson reso-nancewouldbeobservedinthedijetinvariantmassspectrummjj. TheW and Z bosonsare identified(V tagged)viathemj and τ21 variables, andb tagging is used to identify b quarks fromHiggs bosons in addition to mj. Although the signal yield is large, be-causeofthelargefractionofHiggsbosondecaystobquarks,these channelsaresubjectto anoverwhelming backgroundfrom quan-tumchromodynamics(QCD)multijetproduction.

IntheVVandVH analyses,thebackgroundisestimateddirectly from data, assuming that the invariant mass distribution of the backgroundcanbedescribedbyasmooth,parameterizable, mono-tonicallydecreasingfunctionofmjj.Thesignal template,basedon aGaussiancore,isfittedtothedatasimultaneouslywiththe back-ground function. The HH analyses also use an additional region in the fit, obtained by inverting the b tagging selection on the H candidates,whichconstrains theparametersofthebackground function.

4.2.Semi-leptonicdibosonchannels

SearchesforVV,VH,andHH resonanceshavebeenperformed inchannelswhereoneoftheSMbosonsdecaystoleptonsandthe otherto quarks(ZV→ννqq [¯ 2], WV→ νqq [¯ 3],ZV→ qq [¯ 4], ZH→ννbb [¯ 7], WH→ νbb [¯ 7], ZH→ bb [¯ 7], VH→qq¯τ τ [8] and HH→bb¯τ τ [8]). These final states represent an attractive alternativeto all-jetfinal states, thanks tothe large selection ef-ficiencies and naturaldiscrimination against multijet background stemmingfromthepresenceinthesignalofenergeticandisolated leptonsorneutrinos.

Thedecayofa Z bosontoneutrinoscanbe identifiedthrough itslarge pmiss_T ,andthe resonancemass canbe inferred fromthe transverse mass between the pmiss_T and the jet originating from the hadronic decay of the other boson. For the W→ ν decay, thereisasingle,isolatedleptonassociatedwithamoderatepmiss

T , andthe vectorbosoncan thereforebereconstructedby imposing a constraintfrom the W boson mass to recover the longitudinal momentumoftheneutrino. InZ→  decays,twoopposite-sign, same-flavor leptons with a combined invariant mass compatible with the Z boson mass are used to determine accurately the Z boson four-momentum. A Higgs boson decaying to τ leptons is identified from dedicated τh decay reconstruction and isolation techniques [8], and its mass is estimated through the measured momentaof thevisible decayproducts of the τ leptons andthe 

pmiss_T ,with the SVfit algorithm [72]. The boson that decays to a pairofquarksisreconstructedasanAK8jet.TheAK8jetmassis requiredtobecompatiblewitheithertheW andZ bosonmasses, denoted as mV (65 <mj<105 GeV), or the Higgs boson mass (105 <mj<135 GeV).

Inthesemi-leptonicanalyses,themainV+jetsbackgroundis estimatedfromafittodatainthemjsidebandsofthehadronicjet, andextrapolatedtothesignalregionusingatransferfunction(“α function”)obtained from simulation.The top quark pair produc-tionisestimatedfromsimulation,butitsnormalizationisrescaled tomatchthedataincontrol regionsobtainedbyrequiringan ad-ditionalb-taggedAK4jetintheevent [2,7,8].

Inaddition,the WV→ νqq analysis¯ introducesa novelsignal extractionmethodbasedonatwo-dimensional(2D)fittodata [3]. The backgrounds are separated into non-resonant and resonant

categoriesdependingonthepresenceorabsenceofW bosonsand topquarksinthejetmassspectrum,andarefittedsimultaneously in the space ofmj and mWV, accounting forthe correlation be-tweenthetwovariables.

4.3. Fullyleptonicdibosonchannels

SearchesfordibosonresonancesdecayingtoapairofZ bosons havebeenperformedinfullyleptonic finalstates,withoneboson undergoingthedecayZ→ andtheotherZ→νν[5].The pres-enceoftheleptons andneutrinosdefinesa verycleanfinal state withreducedbackgrounds,butthesmallbranchingfractionmakes thischannelcompetitiveonlyforsmallresonantmassvalues.

4.4. Decaystoapairoffermions

The decay ofa heavy resonance to a pair offermions can be sizablewhen thecouplingstoSM fermions arelarge.Ifthe reso-nanceis electricallycharged, asin thecaseofW±,thedecay to a neutrinoandan electronormuon yields a broadexcessin the

ν transversemass spectrum [19]. Ifthenew state isneutral, as inthecaseofZ,a narrowresonancewouldemergefromthe di-electronordimuon() invariantmassspectra [20].Theanalyses ofthesefermionicdecaysextendtomassesabove5 TeV,and em-ployselection techniquesoptimizedtoidentifyandmeasurevery energeticelectronsandmuonsinthedetector [19,20].

5. Eventselection

The search regions of the analyses entering in the combina-tion are statistically independent because of mutually exclusive selections on the number of leptons and their flavor, number of AK8 jets, and jet mass intervals. Analyses with hadronic fi-nal statesreject eventswithisolated leptons orwith large pmiss_T . Overlaps between channels that share the same lepton multi-plicity are avoided by selecting different jet mass ranges. The W→ ν search doesnot share any events with the W→VW and W→WH analyses because of therequirements on the an-gular separation φ (, pmiss

T ) between the pmissT and the lepton direction. The Z→  analysis includes events with a dilepton invariant mass m >120 GeV, which is incompatible with the 70 <m<110 GeV selection used in the diboson channels, in whichthe Z bosonison-shell.The twosearchesforresonant HH bosons thatdecaytob quarkshavecommoneventsexplicitly re-moved [10].

IntheWV→ νqq channel [¯ 3] thebackgroundisestimated us-ing a2D fittingtechnique that scansthefull jet massrange,and isthereforenotindependentoftheWH→ νbb channel.¯ Forthis reason, in the W, Z, andV interpretations, wherethe two sig-nals might be present simultaneously, the “α function” is used to estimate the background instead. This method considers only eventsinthemj regionsoftheW andZ bosons,thereby prevent-ingdoublecountingofeventsintheHiggsbosonmassregion.The resultsof thealternativebackground estimationmethodare con-sistentwiththoseobtainedinthe2Dfit,butthemethodisabout 10% lesssensitive. Themain selectionsthat define theexclusivity oftheanalysesaresummarizedinTable1.

6. Systematicuncertainties

The systematic uncertainties originating fromthe background estimationintheindividualchannelsareconsidereduncorrelated, because the backgrounds are determined from statistically inde-pendentcontrolregions.Theuncertaintiesarisingfromthe recon-structionandcalibrationareinsteadcorrelatedamongthedifferent

Table 1

Summaryofthemainselectionsthatguaranteetheexclusivitybetweenindividualfinalstates.Thesymbolrepresentsanelectronoramuon;τleptonsareconsidered separately.Ifanentryisnotprecededby“≥”,theexactvalueisrequired.TheAK4bjetsareadditionalbtaggedAK4jetsthatdonotgeometricallyoverlapwithAK8jets. Thesymbol“–”impliesthatnoselectionisapplied.

Ref. Channel Final state  τh AK8 jets AK8 jet mass AK4 b jets

[1] WW, WZ, ZZ q¯qq¯q 0 0 ≥2 2[mW,mZ] – [2] WZ, ZZ ννqq¯ 0 0 ≥1 mV 0 [3] WW, WZ νqq¯ 1 – ≥1 see Sec.5 0 [4] WZ, ZZ q¯q ≥2 – ≥1 mV – [5] ZZ νν ≥2 – – – – [6] WH, ZH q¯qb¯b 0 0 ≥2 [mW,mZ], mH – [7] ZH ννb¯b 0 0 ≥1 mH 0 [7] WH νb¯b 1 0 ≥1 mH 0 [7] ZH b¯b ≥2 0 ≥1 mH – [8] WH, ZH q¯qτ τ – ≥2 ≥1 [mW,mZ] 0 [8] HH τ τb¯b – ≥2 ≥1 mH 0 [9] HH b¯bb¯b – – ≥2 2 mH – [10] HH b¯bb¯b – – 1 mH ≥2 [19] ν 1 – – – – [20]  ≥2 – – – – Table 2

Summaryofthemainsystematicuncertainties.Thesecondcolumnreportswhetherasystematicuncertaintyisconsideredfullycorrelatedornotacrossdifferentchannels. Thethirdcolumnindicateswhethertheuncertaintyaffectstheyield,theshapeofthedistributions,orboth,orifitinducesmigration(migr.)effectsacrosssearchregions. Thefourthcolumnreportsthesmallestandlargesteffectoftheuncertainty,amongtheyield,themigration,andthesignalshapeparameters.Thesymbols“s”,“b”indicate thattheuncertaintyaffectsthesignal,themainbackgroundsoftheanalysis,respectively.Thetreatmentofnon-dominantbackgroundsisoftendifferentandnotreported here.Thesymbol“f”indicatesthattheparametersarenotconstrained,orassociatedwithlargeuncertaintiesasinthecaseofmulti-dimensionalfits.Theentrieslabeled with“t”aretreateddifferentlydependingontheinterpretationoftheexclusionlimit,asdiscussedinSection7.Uncertaintiesmarkedwith“–”arenotapplicableorare negligible. Cor relation Type Variation ¯qqq ¯q[ 1 ] νν q ¯ q[ 2 ]  ν q ¯q( 2 D fi t)[ 3 ]  q ¯ q[ 4 ] νν  [ 5 ] q ¯qb ¯b[ 6 ] ( νν , ν , ) b ¯b[ 7 ] ( q ¯ q , b ¯b)ττ [ 8 ] b ¯bb ¯b[ 9 , 10 ]  ν [ 19 ]  [ 20 ] Bkg. modeling no shape – f b f b b f b b b b b Bkg. normalization no yield 2–30% f b f b b f b b b b b

Jet energy scale yes yield, shape 1–2% s s s, b s – s s s s – –

Jet energy resolution yes yield, shape 3–7% s s s, b s – s s s s – –

Jet mass scale yes yield, migr. 1–36% s s s, b s – s s s s – –

Jet mass resolution yes yield, migr. 5–25% s s s, b s – s s s s – –

Jet triggers yes yield 1–15% s – – – – s – – s – –

e,μid., iso., trigger yes yield, shape 1–3% – – s s s, b – s s – s, b s, b

e,μscale and res. yes yield, shape 1–6% – – s s s, b – s – – s, b s, b

τhreco., id., iso. yes yield 6–13% – s – – – – s s – – –

τhenergy scale yes yield, shape 1–5% – – – – – – – s – – –

τhhigh-pTextr. yes yield, shape 18–30% – – – – – – – s – – –

pmissT scale and res. yes yield 1–2% – s s – s, b – s s – s, b –

pmiss

T triggers yes yield 1–2% – s – – – – s s – – –

b quark identification yes yield, migr. 1–9% – s s, b – – s s s s – –

τ21identification yes yield, migr. 11–33% s s s, b s – s – s s – –

V tagging high-pTextr. yes yield, migr. 2–40% s s s, b s – s – s s – –

mHselection yes yield 6% – – – – – s s s s – –

pp cross section yes yield 1–2% s s – s – s s s s s, b –

Luminosity yes yield 2.5% s s s s s, b s s s s s, b s, b

PDF and QCD accept. yes yield 1–2% s – s s s, b s s s s – s, b

PDF and QCD norm. yes yield 2–78% t t t t t, b t t t t t, b t, b

channels. These include the uncertainties in jet energy and res-olution, and in the e, μ, and τh lepton energy, reconstruction, andidentification.TheuncertaintiesintheidentificationoftheSM bosonsthat decaytoquarksare dominantinfinalstates contain-ing atleastone such decay, andoriginate fromthemj scale and resolution,the τ21 selection,andthebtagging.The uncertainties in the V tagging extrapolation to large jet pT and the selection of events in the jet mass window of the Higgs boson are esti-mated by comparing the results with those obtained using the alternative herwig++ [73] shower model. These uncertainties af-fect the signal distribution,selection efficiency, andinduce event migrationeffectsbetweensearchregions.Theuncertainties inthe

proton-protoninelasticcrosssection [74], theintegrated luminos-ityduringthe2016data-taking [75] andthekinematicacceptance of final-state particles, whichaffect the signal normalization, are also considered ascorrelated among channels. Theoretical uncer-taintiesinthecrosssectionandinthesignalgeometricacceptance relatedtothechoiceofPDFsusedintheeventgenerators [76],and the uncertainties in the factorization and renormalizationscales, are evaluated according to the PDF4LHC recommendations [76]. The impact oftheseuncertainties onthe signalcross section can be aslarge as78%, depending on thesignal mass andthe initial state (qq or¯ gg).Asummary ofthe mainsystematicuncertainties isgiveninTable2.

7.Statisticalcombination

NosignificantexcessisobservedabovetheSMbackground ex-pectations.Upperlimitsaresetat95%confidencelevel(CL) [77,78] onthecrosssectionofa heavyresonance,whichisrescaledby a signalstrengthmodifierparameter μwithuniformprior. System-aticuncertainties are represented by nuisance parameters θ, and affect both signal and background expectations [79]. Systematic uncertainties are considered fully (anti-)correlated when related toacommonnuisanceparameter,oruncorrelatedwhendifferent nuisanceparametersareused.Thepriorontheseparametersis ei-therflat(representedbythesymbol“f” inTable2)orlog-normal distributed(identifiedwith“s”, “b”,“t”inTable 2).Thestatistical procedureisbasedonalikelihoodconstructedas:

L(data|μ, θ )=  c  i Pdata|μsc,i(θ )+bc,i(θ )   j pj( ˜θj|θj), (1)

whereP represents the Poissonprobability, and pj( ˜θj|θj) is the frequentistpdf ofthenuisanceparameter θj anditsdefaultvalue ˜θj associated with the jth uncertainty. The values sc,i(θ ) and bc,i(θ ) representthe numberof signal andbackground eventsin thechannel c andbini,respectively.Theteststatisticisbasedon theprofilelikelihoodratioq:˜

˜

q(μ)= −2 logL(data|μ, ˆθμ)

L(data| ˆμ, ˆθ_μˆ), (2) andthequantities μˆ, ˆθμ, ˆθμ areˆ fixed to their best-fit value, and the rangeof μ is limitedin the 0≤ ˆμ≤μ interval. The uncer-taintiesthataffectthesignalnormalization(PDFsandfactorization andrenormalizationscales,markedwith“t”inTable2)aretreated differentlydependingonhowtheexclusionispresented.When de-rivingupperlimitsonthecrosssection,theseuncertaintiesarenot variedinthefit,butarereportedseparatelyastheuncertaintyof thetheoreticalcrosssectionsfromthemodel.Whenplacinglimits onthemodel parameters,thesenuisanceparameters are fixedat thebest-fitvalues,inthesamemannerastotheother systematic uncertainties.

The upper limit on μ is derived from the 95% CLs criterion, defined as CLs(μ) =p(μ)/(1−p(0)), such that CLs(μ) =0.05. The quantities p(μ) and 1−p(0) represent the probabilities to havea value ofq equal˜ to, orlarger than the observed value in thesignalorbackground(μ=0) hypotheses,respectively,andare derivedfromanalyticalfunctionsusingtheasymptotic approxima-tion [80]. This approximation leads to limitsthat are up to 30% strongerinregionswithasmallnumberofdataevents,compared to those obtained from the Monte Carlo generation of pseudo-experiments [79].

8. Resultsandinterpretation

Thedataareinagreementwiththeexpectedbackgroundfrom SM processes. The largest deviation from the expected limit is observed in the V model A at a mass of 1.3 TeV, with a local significanceof 2.7standard deviations,corresponding toa global significanceof1.6standard deviations.The localsignificances are obtainedintheasymptoticapproximation [80],andtheglobal sig-nificancesareevaluatedusingthetrialfactorsmethod [81].

Theexclusionlimitonthecrosssectionofeachdibosonchannel (WW,WZ,ZZ,WH,ZH,HH)isdepictedinFig.1forthe combina-tionofallcontributingchannels,reportedinTable1,accordingto thespinofthenewresonance.Thegeneratedsignal canbeeither

Fig. 1. Observedandexpected95%CL upperlimitsontheproductofthecross sec-tionandbranchingfractionofaspin-1(upper)orspin-2resonance(lower)decaying toapairofSMbosons.

aspin-1heavyvector(W orZ,asintheHVTmodel)oraspin-2 boson (as in the bulk graviton model). In fact, the spin and po-larizationoftheheavyresonancedoesaffectthefinalstate,signal acceptance,andselectionefficiencies. Theexclusionlimitsarenot presentedabove4.5 TeV,sinceatlargermassesthebackground es-timationprocedureusedindibosonanalysesbecomeslessreliable becauseofthelackofeventsindata.

Thecombinedexclusionlimitsforthespin-1singlethypotheses (W orZ) inthe HVTmodel B framework, where thebranching fractionsto SMbosons aredominant, are showninFig.2.Inthis scenario, the contribution of the dilepton channels is negligible because their branching fraction isof the orderof a few permil. In theVV analyses,the V→VH signal isadded tothe V→VV signal becausethe fractionof H jets passingthe mW andmZ se-lectionsisnotnegligibleandcancontributeupto30%tothetotal signalyield.ThepredictionsoftheHVTmodel Baresuperimposed on theexclusion limits,showing that a W boson ofmass below 4.3 TeV,anda Z bosonwithmassbelow3.7 TeVare excludedat 95%CL.

TheHVThypothesisistestedinFig.3bycombiningalldiboson channels, showingthata mass-degeneratestate withmassbelow 4.5 TeVcanbeexcludedinHVTmodel B,andextendingthe exclu-sionwithrespecttothebestindividualchannel byapproximately 700 GeV [1].Thisresultsignificantlyimprovestheprevious√s=8 and 13 TeV CMS combination [82], which excluded a triplet of

Fig. 2. Observedandexpected95%CL upperlimitsontheW(upper)andZcross section(lower)asafunctionoftheWandZresonancemass.Theinnergreenand outeryellowbandsrepresentthe±1 and±2 standarddeviationvariationsonthe expectedlimitsofthestatisticalcombinationoftheVV andVH channelsconsidered. Theexpectedlimitsinindividualchannelsarerepresentedbythecoloreddashed lines.Thesolidcurvessurroundedbythe shadedareasshow thecross sections predictedbytheHVTmodel Bandtheiruncertainties.

heavy resonanceswithmassesup to 2.4 TeV inthesame model. Thedileptonresonancesprovidethemoststringentresultswithin theHVTmodel Aframework,andarecombinedwiththediboson searchesinFig.3.Aheavytriplet ofV resonancesisexcludedup toamassof5.0 TeV.

Theexclusionlimitsontheresonancecross sectionsshownin Fig. 3 are also interpreted as limits in the [gH,gf] plane of the HVTparameters.Theexcluded regionofparameterspacefor nar-rowresonancesobtainedfromthecombinationofallthechannels isshowninFig.4.Thedileptonanddibosonsearchesconstrain dif-ferentregionsoftheparameterspace,asthedileptonsearchescan probetheregionwherethecouplingtotheSMbosonsapproaches zero.In the triplet interpretation,the ratioof the W toZ cross sectionsisassumedtobedeterminedbytheratioofthepartonic luminosities,andtodependonlyweaklyonthemodelparameters. The fraction of the parameter space where the natural width of theresonancesis largerthantheaverage experimentalresolution of5%,andthenarrow-widthapproximationisthusinvalid,isalso indicatedinFig.4.

Inthespin-2bulkgravitonmodel,theWW,ZZ, andHH chan-nelsarecombined,settingupperlimitsofupto1.1 fbonthecross sectionofagravitonwithmassupto4.5 TeV.Intheκ=0.5

sce-Fig. 3. Observedandexpected95%CL upperlimitsoncrosssectionsasafunction oftheHVTtripletmassforthecombinationofallchannelsintheHVTmodel B (upper)andmodel A(lower).Theinnergreenandouteryellowbandsrepresentthe ±1 and±2 standarddeviationvariationsontheexpectedlimit.Thesolidcurves surroundedbytheshadedareasshowthecrosssectionspredictedbyHVTmodels A andBandtheiruncertainties.

nario,agravitonwithamasssmallerthan850 GeVisexcludedat 95% CL, asshownin Fig.5.Larger κ valuesincrease the produc-tioncrosssections,butalsothegraviton naturalwidth,whichcan becomparableorlargerthantheexperimentalresolution.Inthese cases,thenarrow-widthapproximationisnolongervalid.

Theseresultsrepresentthemoststringentlimitsonheavy vec-tor models set by CMS and are comparable at large V mass to the limits obtained the ATLAS in the combination of similar channels [45]. At lower masses, the ATLAS combinationexcludes smallercrosssectionsbecauseoftheinclusionoffinal stateswith three ormore leptons. The exclusion limits in the bulk graviton modelarenotdirectlycomparablebecauseofthelargeκ=1.0 pa-rameteradopted by ATLAS,which increasesthecross sectionbut alsoimpliesanon-negligiblenaturalwidth.

9. Summary

A statisticalcombinationof searchesforheavy resonances de-caying into pairs of vector bosons, a vector boson and a Higgs boson,two Higgsbosons,orpairsofleptons,hasbeenpresented. TheresultsarebasedondatacollectedbytheCMSexperimentat √

s=13 TeVduring2016correspondingtoanintegrated luminos-ityof 35.9 fb−1_{.Inmodels withwarpedextradimensions, upper}

Fig. 4. Observedexclusion limitsonthecouplingsofheavyvectorresonancesto fermionsandSMvectorbosonsandtheHiggsbosonfor thestatistical combina-tion(solidlines)ofthedilepton(dottedlines)anddibosonchannels(dashedlines). Threeresonancemasseshypotheses (3.0,4.0, and 4.5 TeV) areconsidered. The hatchedbandsindicatetheregionsexcluded.Theareasboundedbythethingray contourlinescorrespondtoregionswheretheresonancewidths( V)arepredicted tobelargerthantheaverageexperimentalresolution(5%).

Fig. 5. Observedandexpected95%CL upperlimitonthecrosssectionofthespin-2 bulkgravitonasafunctionofitsmassforthestatisticalcombinationoftheWW, ZZ,andHH channels.Theinnergreenand outeryellowbandsrepresentthe ±1 and±2 standarddeviationvariationsontheexpectedlimit.Thesolidcurveandits shadedarearepresentthecrosssectionderivedwiththeparameterκ=0.5 andthe associateduncertainty.

limitsofup to1.1 fb areset at95% confidencelevel onthe pro-ductioncrosssectionofthespin-2bulkgraviton.Formodelswith a triplet of narrow spin-1 resonances, heavy vector bosons with massesbelow5.0and4.5 TeVareexcludedat95%confidencelevel inmodels where theW and Z bosons couplepredominantly to fermionsandbosons,respectively.Inthelatter,thestatistical com-binationextends the exclusionlimit by 700 GeV ascompared to thebestindividualchannel.

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,wegratefullyacknowledgethecomputingcentersand personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythe computinginfrastructureessential to ouranalyses. Finally, we acknowledge the enduring support for the construc-tionandoperation oftheLHC andtheCMSdetectorprovidedby thefollowing fundingagencies:BMBWF andFWF(Austria); FNRS and FWO(Belgium); CNPq,CAPES, FAPERJ, FAPERGS, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MOST, and NSFC (China); COLCIENCIAS (Colombia); MSES andCSF (Croatia); RPF (Cyprus); SENESCYT (Ecuador); MoER, ERC IUT, PUT and ERDF (Estonia); AcademyofFinland,MEC,andHIP(Finland);CEAandCNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); NK-FIA (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN(Italy);MSIPandNRF(RepublicofKorea);MES(Latvia);LAS (Lithuania);MOEandUM(Malaysia);BUAP,CINVESTAV,CONACYT, LNS,SEP,andUASLP-FAI(Mexico);MOS(Montenegro);MBIE(New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portu-gal);JINR (Dubna);MON, RosAtom, RAS, RFBR,and NRCKI (Rus-sia);MESTD(Serbia);SEIDI,CPAN,PCTI,andFEDER(Spain);MoSTR (Sri Lanka); Swiss Funding Agencies(Switzerland); MST (Taipei); ThEPCenter,IPST,STAR,andNSTDA(Thailand);TUBITAKandTAEK (Turkey);NASUandSFFR(Ukraine); STFC(United Kingdom);DOE andNSF(USA).

Individuals have received support from the Marie-Curie pro-gramandtheEuropeanResearchCouncilandHorizon2020Grant, contract Nos. 675440, 752730, and 765710 (European Union); the Leventis Foundation; the A.P. Sloan Foundation; the Alexan-der von Humboldt Foundation; the Belgian Federal Science Pol-icy Office; the Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the F.R.S.-FNRSand FWO(Belgium) underthe “Excellence of Sci-ence – EOS” – be.h project n. 30820817; the Beijing Municipal Science & Technology Commission, No. Z181100004218003; the Ministry of Education, Youth and Sports (MEYS) of the Czech Republic; the Lendület (“Momentum”) Program and the János Bolyai Research Scholarship of the Hungarian Academy of Sci-ences, the New National Excellence Program ÚNKP, the NK-FIA research grants 123842, 123959, 124845, 124850, 125105, 128713, 128786, and 129058 (Hungary); the Council of Science and Industrial Research, India; the HOMING PLUS program of the Foundation for Polish Science, cofinanced from European Regional Development Fund, the Mobility Plus program of the Ministry of Science and Higher Education, the National Science Center (Poland), contracts Harmonia 2014/14/M/ST2/00428, Opus 2014/13/B/ST2/02543, 2014/15/B/ST2/03998, and 2015/19/B/ST2/ 02861,Sonata-bis2012/07/E/ST2/01406;theNationalPriorities Re-search Programby QatarNationalResearchFund;the Ministryof Science and Education, grant no. 3.2989.2017 (Russia); the Pro-gramaEstatalde Fomento delaInvestigación CientíficayTécnica de Excelencia María de Maeztu, grant MDM-2015-0509 and the Programa Severo Ochoa del Principado de Asturias; the Thalis andAristeiaprogramscofinancedbyEU-ESF andtheGreek NSRF; theRachadapisekSompotFundforPostdoctoralFellowship, Chula-longkornUniversityandtheChulalongkornAcademic intoIts2nd CenturyProjectAdvancementProject(Thailand);TheWelch Foun-dation,contractC-1845;andtheWestonHavensFoundation(USA). References

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TheCMSCollaboration

A.M. Sirunyan†,A. Tumasyan

YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam, F. Ambrogi, T. Bergauer,J. Brandstetter, M. Dragicevic,J. Erö, A. Escalante Del Valle,M. Flechl,

R. Frühwirth1, M. Jeitler1, N. Krammer,I. Krätschmer, D. Liko,T. Madlener, I. Mikulec,N. Rad,

J. Schieck1, R. Schöfbeck, M. Spanring, D. Spitzbart,W. Waltenberger, J. Wittmann, C.-E. Wulz1,

M. Zarucki

InstitutfürHochenergiephysik,Wien,Austria

V. Drugakov,V. Mossolov,J. Suarez Gonzalez

M.R. Darwish,E.A. De Wolf, D. Di Croce, X. Janssen,J. Lauwers, A. Lelek,M. Pieters, H. Rejeb Sfar,

H. Van Haevermaet,P. Van Mechelen, S. Van Putte, N. Van Remortel

UniversiteitAntwerpen,Antwerpen,Belgium

F. Blekman, E.S. Bols,S.S. Chhibra, J. D’Hondt,J. De Clercq, D. Lontkovskyi, S. Lowette,I. Marchesini,

S. Moortgat, L. Moreels,Q. Python, K. Skovpen, S. Tavernier, W. Van Doninck, P. Van Mulders,

I. Van Parijs

VrijeUniversiteitBrussel,Brussel,Belgium

D. Beghin, B. Bilin,H. Brun, B. Clerbaux, G. De Lentdecker,H. Delannoy, B. Dorney, L. Favart,

A. Grebenyuk,A.K. Kalsi, J. Luetic, A. Popov, N. Postiau,E. Starling, L. Thomas, C. Vander Velde,

P. Vanlaer,D. Vannerom, Q. Wang

UniversitéLibredeBruxelles,Bruxelles,Belgium

T. Cornelis,D. Dobur, I. Khvastunov2,C. Roskas, D. Trocino, M. Tytgat, W. Verbeke,B. Vermassen, M. Vit,

N. Zaganidis

GhentUniversity,Ghent,Belgium

O. Bondu,G. Bruno, C. Caputo,P. David, C. Delaere, M. Delcourt,A. Giammanco, G. Krintiras,V. Lemaitre,

A. Magitteri,K. Piotrzkowski,J. Prisciandaro, A. Saggio, M. Vidal Marono, P. Vischia,J. Zobec

UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium

F.L. Alves,G.A. Alves, G. Correia Silva,C. Hensel, A. Moraes,P. Rebello Teles

CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

E. Belchior Batista Das Chagas, W. Carvalho,J. Chinellato3,E. Coelho, E.M. Da Costa, G.G. Da Silveira4,

D. De Jesus Damiao,C. De Oliveira Martins, S. Fonseca De Souza, L.M. Huertas Guativa, H. Malbouisson,

J. Martins5,D. Matos Figueiredo, M. Medina Jaime6,M. Melo De Almeida, C. Mora Herrera,L. Mundim,

H. Nogima,W.L. Prado Da Silva, L.J. Sanchez Rosas, A. Santoro, A. Sznajder,M. Thiel,

E.J. Tonelli Manganote3,F. Torres Da Silva De Araujo, A. Vilela Pereira

UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

S. Ahujaa, C.A. Bernardesa, L. Calligarisa, T.R. Fernandez Perez Tomeia,E.M. Gregoresb,D.S. Lemos,

P.G. Mercadanteb,S.F. Novaesa,Sandra S. Padulaa

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

A. Aleksandrov, G. Antchev, R. Hadjiiska,P. Iaydjiev, A. Marinov, M. Misheva, M. Rodozov,M. Shopova,

G. Sultanov

InstituteforNuclearResearchandNuclearEnergy,BulgarianAcademyofSciences,Sofia,Bulgaria

A. Dimitrov, L. Litov,B. Pavlov, P. Petkov

UniversityofSofia,Sofia,Bulgaria

W. Fang7, X. Gao7,L. Yuan

BeihangUniversity,Beijing,China

M. Ahmad, G.M. Chen, H.S. Chen, M. Chen,C.H. Jiang, D. Leggat, H. Liao, Z. Liu, S.M. Shaheen8,

A. Spiezia,J. Tao, E. Yazgan, H. Zhang, S. Zhang8, J. Zhao

A. Agapitos,Y. Ban, G. Chen, A. Levin,J. Li, L. Li,Q. Li, Y. Mao, S.J. Qian, D. Wang

StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

Z. Hu, Y. Wang

TsinghuaUniversity,Beijing,China

C. Avila,A. Cabrera, L.F. Chaparro Sierra, C. Florez,C.F. González Hernández, M.A. Segura Delgado

UniversidaddeLosAndes,Bogota,Colombia

D. Giljanovi ´c, N. Godinovic, D. Lelas,I. Puljak, T. Sculac

UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia

Z. Antunovic,M. Kovac

UniversityofSplit,FacultyofScience,Split,Croatia

V. Brigljevic,S. Ceci, D. Ferencek,K. Kadija,B. Mesic, M. Roguljic, A. Starodumov9,T. Susa

InstituteRudjerBoskovic,Zagreb,Croatia

M.W. Ather,A. Attikis, E. Erodotou, A. Ioannou,M. Kolosova, S. Konstantinou, G. Mavromanolakis,

J. Mousa,C. Nicolaou, F. Ptochos, P.A. Razis,H. Rykaczewski, D. Tsiakkouri

UniversityofCyprus,Nicosia,Cyprus

M. Finger10,M. Finger Jr.10,A. Kveton, J. Tomsa

CharlesUniversity,Prague,CzechRepublic

E. Ayala

EscuelaPolitecnicaNacional,Quito,Ecuador

E. Carrera Jarrin

UniversidadSanFranciscodeQuito,Quito,Ecuador

Y. Assran11,12, S. Elgammal12

AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt

S. Bhowmik, A. Carvalho Antunes De Oliveira,R.K. Dewanjee, K. Ehataht,M. Kadastik, M. Raidal,

C. Veelken

NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia

P. Eerola,L. Forthomme, H. Kirschenmann,K. Osterberg, J. Pekkanen,M. Voutilainen

DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland

F. Garcia, J. Havukainen, J.K. Heikkilä, T. Järvinen,V. Karimäki, R. Kinnunen, T. Lampén, K. Lassila-Perini,

S. Laurila, S. Lehti,T. Lindén, P. Luukka, T. Mäenpää,H. Siikonen, E. Tuominen, J. Tuominiemi

HelsinkiInstituteofPhysics,Helsinki,Finland

T. Tuuva

LappeenrantaUniversityofTechnology,Lappeenranta,Finland

M. Besancon,F. Couderc, M. Dejardin, D. Denegri,B. Fabbro, J.L. Faure, F. Ferri, S. Ganjour, A. Givernaud,

P. Gras, G. Hamel de Monchenault,P. Jarry, C. Leloup,E. Locci, J. Malcles,J. Rander, A. Rosowsky,

M.Ö. Sahin,A. Savoy-Navarro13, M. Titov

C. Amendola, F. Beaudette, P. Busson, C. Charlot, B. Diab, R. Granier de Cassagnac,I. Kucher, A. Lobanov,

C. Martin Perez, M. Nguyen,C. Ochando, P. Paganini, J. Rembser,R. Salerno, J.B. Sauvan, Y. Sirois, A. Zabi,

A. Zghiche

LaboratoireLeprince-Ringuet,Ecolepolytechnique,CNRS/IN2P3,UniversitéParis-Saclay,Palaiseau,France

J.-L. Agram14, J. Andrea, D. Bloch,G. Bourgatte, J.-M. Brom,E.C. Chabert, C. Collard,E. Conte14,

J.-C. Fontaine14,D. Gelé, U. Goerlach, M. Jansová, A.-C. Le Bihan, N. Tonon,P. Van Hove

UniversitédeStrasbourg,CNRS,IPHCUMR7178,Strasbourg,France

S. Gadrat

CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France

S. Beauceron,C. Bernet, G. Boudoul, C. Camen, N. Chanon, R. Chierici,D. Contardo, P. Depasse,

H. El Mamouni, J. Fay, S. Gascon,M. Gouzevitch, B. Ille, Sa. Jain, F. Lagarde, I.B. Laktineh, H. Lattaud,

M. Lethuillier, L. Mirabito,S. Perries, V. Sordini,G. Touquet, M. Vander Donckt, S. Viret

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

T. Toriashvili15

GeorgianTechnicalUniversity,Tbilisi,Georgia

Z. Tsamalaidze10

TbilisiStateUniversity,Tbilisi,Georgia

C. Autermann, L. Feld, M.K. Kiesel, K. Klein, M. Lipinski, D. Meuser, A. Pauls,M. Preuten, M.P. Rauch,

C. Schomakers,J. Schulz, M. Teroerde,B. Wittmer

RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany

A. Albert, M. Erdmann,S. Erdweg, T. Esch,B. Fischer, R. Fischer,S. Ghosh, T. Hebbeker, K. Hoepfner,

H. Keller, L. Mastrolorenzo, M. Merschmeyer,A. Meyer, P. Millet,G. Mocellin, S. Mondal, S. Mukherjee,

D. Noll, A. Novak, T. Pook, A. Pozdnyakov,T. Quast, M. Radziej, Y. Rath, H. Reithler,M. Rieger,

A. Schmidt, S.C. Schuler, A. Sharma, S. Thüer, S. Wiedenbeck

RWTHAachenUniversity,III.PhysikalischesInstitutA,Aachen,Germany

G. Flügge, W. Haj Ahmad16,O. Hlushchenko, T. Kress, T. Müller,A. Nehrkorn, A. Nowack, C. Pistone,

O. Pooth,D. Roy, H. Sert, A. Stahl17

RWTHAachenUniversity,III.PhysikalischesInstitutB,Aachen,Germany

M. Aldaya Martin,C. Asawatangtrakuldee, P. Asmuss, I. Babounikau, H. Bakhshiansohi, K. Beernaert,

O. Behnke,U. Behrens, A. Bermúdez Martínez, D. Bertsche, A.A. Bin Anuar, K. Borras18,V. Botta,

A. Campbell,A. Cardini, P. Connor,S. Consuegra Rodríguez, C. Contreras-Campana, V. Danilov,A. De Wit,

M.M. Defranchis, C. Diez Pardos,D. Domínguez Damiani, G. Eckerlin,D. Eckstein, T. Eichhorn, A. Elwood,

E. Eren, E. Gallo19,A. Geiser, J.M. Grados Luyando, A. Grohsjean, M. Guthoff, M. Haranko,A. Harb,

N.Z. Jomhari, H. Jung,A. Kasem18,M. Kasemann, J. Keaveney, C. Kleinwort,J. Knolle, D. Krücker,

W. Lange, T. Lenz,J. Leonard, J. Lidrych, K. Lipka,W. Lohmann20, R. Mankel, I.-A. Melzer-Pellmann,

A.B. Meyer, M. Meyer, M. Missiroli, G. Mittag, J. Mnich, A. Mussgiller, V. Myronenko,D. Pérez Adán,

S.K. Pflitsch, D. Pitzl,A. Raspereza, A. Saibel,M. Savitskyi,V. Scheurer, P. Schütze, C. Schwanenberger,

R. Shevchenko, A. Singh,H. Tholen, O. Turkot, A. Vagnerini,M. Van De Klundert, G.P. Van Onsem,

R. Walsh, Y. Wen,K. Wichmann, C. Wissing,O. Zenaiev, R. Zlebcik

DeutschesElektronen-Synchrotron,Hamburg,Germany

R. Aggleton,S. Bein, L. Benato, A. Benecke, V. Blobel, T. Dreyer, A. Ebrahimi, A. Fröhlich, C. Garbers,

R. Kogler,N. Kovalchuk, S. Kurz, V. Kutzner, J. Lange,T. Lange, A. Malara, D. Marconi,J. Multhaup,

M. Niedziela, C.E.N. Niemeyer,D. Nowatschin, A. Perieanu, A. Reimers, O. Rieger,C. Scharf, P. Schleper,

S. Schumann,J. Schwandt,J. Sonneveld, H. Stadie,G. Steinbrück, F.M. Stober, M. Stöver,B. Vormwald,

I. Zoi

UniversityofHamburg,Hamburg,Germany

M. Akbiyik, C. Barth,M. Baselga,S. Baur, T. Berger, E. Butz,R. Caspart, T. Chwalek, W. De Boer,

A. Dierlamm,K. El Morabit, N. Faltermann, M. Giffels,P. Goldenzweig, M.A. Harrendorf,F. Hartmann17,

U. Husemann,S. Kudella, S. Mitra, M.U. Mozer, Th. Müller, M. Musich, A. Nürnberg, G. Quast,

K. Rabbertz,M. Schröder, I. Shvetsov,H.J. Simonis, R. Ulrich, M. Weber, C. Wöhrmann, R. Wolf

KarlsruherInstitutfuerTechnologie,Karlsruhe,Germany

G. Anagnostou,P. Asenov, G. Daskalakis, T. Geralis,A. Kyriakis, D. Loukas,G. Paspalaki

InstituteofNuclearandParticlePhysics(INPP),NCSRDemokritos,AghiaParaskevi,Greece

M. Diamantopoulou,G. Karathanasis,P. Kontaxakis, A. Panagiotou, I. Papavergou, N. Saoulidou, A. Stakia,

K. Theofilatos,K. Vellidis

NationalandKapodistrianUniversityofAthens,Athens,Greece

G. Bakas, K. Kousouris,I. Papakrivopoulos,G. Tsipolitis

NationalTechnicalUniversityofAthens,Athens,Greece

I. Evangelou,C. Foudas, P. Gianneios, P. Katsoulis, P. Kokkas, S. Mallios,K. Manitara, N. Manthos,

I. Papadopoulos,J. Strologas, F.A. Triantis,D. Tsitsonis

UniversityofIoánnina,Ioánnina,Greece

M. Bartók21,M. Csanad, P. Major, K. Mandal, A. Mehta, M.I. Nagy, G. Pasztor, O. Surányi,G.I. Veres

MTA-ELTELendületCMSParticleandNuclearPhysicsGroup,EötvösLorándUniversity,Budapest,Hungary

G. Bencze,C. Hajdu, D. Horvath22, F. Sikler,T.Á. Vámi, V. Veszpremi, G. Vesztergombi†

WignerResearchCentreforPhysics,Budapest,Hungary

N. Beni,S. Czellar, J. Karancsi21,A. Makovec,J. Molnar, Z. Szillasi

InstituteofNuclearResearchATOMKI,Debrecen,Hungary

P. Raics,D. Teyssier, Z.L. Trocsanyi, B. Ujvari

InstituteofPhysics,UniversityofDebrecen,Debrecen,Hungary

T.F. Csorgo, W.J. Metzger, F. Nemes, T. Novak

EszterhazyKarolyUniversity,KarolyRobertCampus,Gyongyos,Hungary

S. Choudhury,J.R. Komaragiri, P.C. Tiwari

IndianInstituteofScience(IISc),Bangalore,India

S. Bahinipati23,C. Kar, P. Mal, V.K. Muraleedharan Nair Bindhu, A. Nayak24, S. Roy Chowdhury,

D.K. Sahoo23, S.K. Swain

NationalInstituteofScienceEducationandResearch,HBNI,Bhubaneswar,India

S. Bansal,S.B. Beri, V. Bhatnagar, S. Chauhan,R. Chawla, N. Dhingra, R. Gupta, A. Kaur, M. Kaur, S. Kaur,

P. Kumari,M. Lohan, M. Meena, K. Sandeep, S. Sharma, J.B. Singh, A.K. Virdi, G. Walia

A. Bhardwaj,B.C. Choudhary, R.B. Garg, M. Gola,S. Keshri, Ashok Kumar, S. Malhotra,M. Naimuddin,

P. Priyanka, K. Ranjan,Aashaq Shah, R. Sharma

UniversityofDelhi,Delhi,India

R. Bhardwaj25,M. Bharti25,R. Bhattacharya,S. Bhattacharya, U. Bhawandeep25,D. Bhowmik, S. Dey,

S. Dutta, S. Ghosh, M. Maity26,K. Mondal, S. Nandan, A. Purohit, P.K. Rout, A. Roy,G. Saha, S. Sarkar,

T. Sarkar26, M. Sharan, B. Singh25, S. Thakur25

SahaInstituteofNuclearPhysics,HBNI,Kolkata,India

P.K. Behera, P. Kalbhor,A. Muhammad, P.R. Pujahari, A. Sharma,A.K. Sikdar

IndianInstituteofTechnologyMadras,Madras,India

R. Chudasama, D. Dutta, V. Jha, V. Kumar, D.K. Mishra,P.K. Netrakanti, L.M. Pant, P. Shukla

BhabhaAtomicResearchCentre,Mumbai,India

T. Aziz, M.A. Bhat,S. Dugad,G.B. Mohanty, N. Sur,Ravindra Kumar Verma

TataInstituteofFundamentalResearch-A,Mumbai,India

S. Banerjee, S. Bhattacharya, S. Chatterjee,P. Das, M. Guchait, S. Karmakar,S. Kumar, G. Majumder,

K. Mazumdar,N. Sahoo, S. Sawant

TataInstituteofFundamentalResearch-B,Mumbai,India

S. Chauhan,S. Dube, V. Hegde, A. Kapoor, K. Kothekar, S. Pandey, A. Rane, A. Rastogi, S. Sharma

IndianInstituteofScienceEducationandResearch(IISER),Pune,India

S. Chenarani27, E. Eskandari Tadavani,S.M. Etesami27,M. Khakzad, M. Mohammadi Najafabadi,

M. Naseri, F. Rezaei Hosseinabadi

InstituteforResearchinFundamentalSciences(IPM),Tehran,Iran

M. Felcini,M. Grunewald

UniversityCollegeDublin,Dublin,Ireland

M. Abbresciaa,b, C. Calabriaa,b,A. Colaleoa,D. Creanzaa,c, L. Cristellaa,b,N. De Filippisa,c,

M. De Palmaa,b, A. Di Florioa,b, L. Fiorea, A. Gelmia,b, G. Iasellia,c,M. Incea,b,S. Lezkia,b,G. Maggia,c,

M. Maggia,G. Minielloa,b, S. Mya,b, S. Nuzzoa,b, A. Pompilia,b, G. Pugliesea,c,R. Radognaa, A. Ranieria,

G. Selvaggia,b, L. Silvestrisa,R. Vendittia, P. Verwilligena

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

G. Abbiendia,C. Battilanaa,b,D. Bonacorsia,b,L. Borgonovia,b,S. Braibant-Giacomellia,b,

R. Campaninia,b, P. Capiluppia,b,A. Castroa,b,F.R. Cavalloa, C. Cioccaa, G. Codispotia,b, M. Cuffiania,b,

G.M. Dallavallea,F. Fabbria, A. Fanfania,b, E. Fontanesi, P. Giacomellia,C. Grandia, L. Guiduccia,b,

F. Iemmia,b_{, S. Lo Meo}a,28_{, S. Marcellini}a_{, G. Masetti}a_{, F.L. Navarria}a,b_{,A. Perrotta}a_{, F. Primavera}a,b_,

A.M. Rossia,b, T. Rovellia,b, G.P. Sirolia,b,N. Tosia

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

S. Albergoa,b,29,S. Costaa,b,A. Di Mattiaa, R. Potenzaa,b,A. Tricomia,b,29,C. Tuvea,b

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