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SISTEMA DE BIBLIOTECAS DA UNICAMP

REPOSITÓRIO DA PRODUÇÃO CIENTIFICA E INTELECTUAL DA UNICAMP

Versão do arquivo anexado / Version of attached file:

Versão do Editor / Published Version

Mais informações no site da editora / Further information on publisher's website:

https://www.sciencedirect.com/science/article/pii/S0370269315002853

DOI: 10.1016/j.physletb.2015.04.042

Direitos autorais / Publisher's copyright statement:

©2015 by Elsevier. All rights reserved.

DIRETORIA DE TRATAMENTO DA INFORMAÇÃO Cidade Universitária Zeferino Vaz Barão Geraldo

CEP 13083-970 – Campinas SP Fone: (19) 3521-6493 http://www.repositorio.unicamp.br

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Contents lists available atScienceDirect

Physics

Letters

B

www.elsevier.com/locate/physletb

Search

for

quark

contact

interactions

and

extra

spatial

dimensions

using

dijet

angular

distributions

in

proton–proton

collisions

at

s

=

8 TeV

.CMS Collaboration CERN,Switzerland a r t i c l e i n f o a b s t ra c t Articlehistory: Received10November2014 Receivedinrevisedform19April2015 Accepted21April2015

Availableonline24April2015 Editor:M.Doser Keywords: CMS Physics QCD Electroweakcorrections Contactinteractions Extradimensions

A search is presented for quark contact interactions and extra spatial dimensions in proton–proton collisionsat√s=8 TeV usingdijetangulardistributions.Thesearchisbasedonadatasetcorresponding to an integrated luminosity of 19.7 fb−1 collected by the CMS detector at the CERN LHC. Dijet

angulardistributionsarefoundtobeinagreementwiththeperturbativeQCDpredictionsthatinclude electroweak corrections. Limitson the contact interaction scale from avariety of models at next-to-leading orderinQCDcorrections are obtained.A benchmarkmodelinwhichonlyleft-handedquarks participateisexcluded uptoascale of9.0(11.7) TeVfordestructive(constructive)interferenceat95% confidence level.Lower limits between5.9and 8.4 TeVonthe scale ofvirtualgraviton exchangeare extractedfortheArkani-Hamed–Dimopoulos–Dvalimodelofextraspatialdimensions.

©2015CERNforthebenefitoftheCMSCollaboration.PublishedbyElsevierB.V.Thisisanopenaccess articleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3.

1. Introduction

Highmomentum-transferproton–protoncollisionsattheCERN LHCprobethedynamicsoftheunderlyinginteractionatdistances below10−19m.Oftenthesecollisions producea pairof jets (di-jets)approximately balanced in transverse momentum pT.These dijeteventsprovidean idealtestinggroundto probethe validity ofperturbative quantum chromodynamics andto search fornew phenomenasuch asquark compositenessoradditional, compacti-fiedspatial dimensions.Aparticularlysuitable observable forthis purpose is the dijet angular distribution [1] expressed in terms of χdijet=exp(|y1−y2|), where y1 and y2 are therapidities of thetwojetswiththehighesttransversemomenta.Rapidityis de-finedas y=ln [(E+pz) / (Epz)]/2 with E beingthejetenergy

and pz the projection ofthejet momentum onto thebeamaxis.

Forthescatteringofmassless partons, χdijet is relatedtothe po-larscatteringangleθ∗ inthepartoniccenter-of-mass(c.m.)frame by χdijet= (1+ |cosθ|)/(1− |cosθ|).Thechoiceofthevariable

χdijet is motivated by the fact that for Rutherford scattering the angulardistributionisapproximatelyindependentof χdijet.In per-turbativeQCDthedijetangulardistributionatsmallc.m.scattering

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

angles is approximately independent of the underlying partonic level process andexhibits behavior similar to Rutherford scatter-ing, characteristic of spin-1 particle exchange. Signatures of new physics(NP),such asquark contactinteractions(CI)orvirtual ex-changeofKaluza–Klein[2]excitationsofthegraviton,thatexhibit angulardistributionsthat aremoreisotropicthanthosepredicted byQCD,couldappearasanexcessofeventsatlowvaluesof χdijet. Models of quark compositeness [3–5] postulate interactions between quark constituents at a characteristic scale  that is much larger than the quark masses. At energies well below , theseinteractions canbeapproximatedby aCIcharacterizedbya four-fermioncoupling.The effectiveLagrangianforflavor-diagonal color-singletcouplingsbetweenquarkscanbewrittenas[4,5]:

Lqq= 2π 2  ηLL(qLγμqL)(qLγμqL) +ηR R(qRγμqR)(qRγμqR)+2ηR L(qRγμqR)(qLγμqL)  ,

where the subscripts L and R refer to the left and right chi-ral projections ofthe quark fieldsrespectively and ηLL, ηR R,and

ηR L are taken to be 0, +1, or −1. The various combinations of

(ηLL,ηR R,ηR L) correspond to different CI models. The following

CI scenarios withcolor-singlet couplings between quarks are in-vestigated:

http://dx.doi.org/10.1016/j.physletb.2015.04.042

0370-2693/©2015CERNforthebenefitoftheCMSCollaboration.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3.

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 (ηLL,ηR R,ηR L) ±LL (±1, 0, 0) ±R R ( 0,±1, 0) ±V V (±1,±1,±1) ±A A (±1,±1,∓1) ±(VA) ( 0, 0,±1)

Notethat themodels withpositive(negative) ηLL or ηR R leadto

destructive (constructive) interferencewith theQCD terms anda lower(higher)crosssectioninthelimitofhighpartonicc.m. ener-gies.InallCImodelsdiscussedinthisLetter,next-to-leading-order (NLO) QCD corrections are employed to calculate the cross sec-tions.Inproton–protoncollisionsthe ±LL and±R R modelsresult inidenticaltree-levelcrosssectionsandNLOcorrections,and con-sequentlyleadtothesamesensitivity.For±V V and±A A,aswell asfor±(VA),theCIpredictionsareidenticalattree-level,but ex-hibitdifferentNLOcorrectionsandyielddifferentsensitivity.

Measurements of dijet angular distributions at the Fermilab TevatronhavebeenreportedbytheCDF[6]andD0[7,8] Collabora-tions,andattheLHCbytheCMS[9–11]andATLAS[12,13] Collab-orations.ThemoststringentlimitstodateonCImodelscalculated at tree-levelhave been obtained by the CMS Collaboration from theinclusivejet pT spectrum[14],whichexcludes+LL<9.9 TeV

and LL<14.3 TeV. Constraints on CI models with NLO correc-tions have been previously obtained from a search in the dijet angulardistributions[9],excludinginparticular+LL<7.5 TeV and

LL<10.5 TeV.

Dijet angular distributions are also sensitive to signatures from the Arkani-Hamed–Dimopoulos–Dvali (ADD) model [15,16] of compactified extra dimensions (EDs) that provides a possible solution to the hierarchy problem of the standard model (SM). In the ADD model, gravity is assumed to propagate in the en-tire higher-dimensional space, while SM particles are confined to a (3+1) dimensional subspace. As a result, the fundamen-tal Planck scale MD in the ADD model is much smaller than the (3+1) dimensional Planck energy scale MPl, which may leadtophenomenologicaleffects thatcanbe testedwithproton– proton collisions at the LHC. The coupling of the graviton in higher-dimensional space to the SM fields can be described by a(3+1)-dimensionaltower ofKaluza–Klein(KK) graviton excita-tions, each coupled to the energy–momentum tensor of the SM field with gravitationalstrength. The effects ofa virtual graviton exchangecan thereforebe approximatedatleading-order(LO) by an effective (3+1)-dimensional theory that sums over KK exci-tationsof avirtual graviton. Thissum isdivergent, andtherefore hastobe truncatedatacertain energyscaleoforder MD,where the effective theory is expected to break down. Such a theory predicts a non-resonant enhancement ofdijet production,whose angulardistributiondiffers fromtheQCDprediction.Two param-eterizations for virtual graviton exchange in the ADD model are considered, namely the Giudice–Rattazzi–Wells (GRW) [17] and the Han–Lykken–Zhang (HLZ) [18] conventions. Thoughnot con-sidered in this paper, another convention by Hewett [19] exists. In the GRW convention the sum over the KK states is regulated by a single cutoff parameter T. The HLZ convention describes

the effectivetheory in terms oftwo parameters, thecutoff scale MS andthenumberofextraspatialdimensionsnED.The

parame-ters MS andnED canbe directlyrelatedto T [20].Weconsider

scenarios with2to 6EDs. The caseofnED=1 isnot considered since it would requirean ED ofthe size of the order ofthe so-lar system; the gravitational potential at these distances would be noticeably modified and this case is therefore excluded. The caseofnED=2 isspecial inthe sense that therelation between

MS andT also depends onthe parton–parton c.m. energy

√ ˆ

s. Signatures from virtual graviton exchange have previously been soughtindilepton[21,22],diphoton[23,24],anddijet[7,25,26] fi-nalstates,wherethemoststringentlimitscomefromthedilepton searchesandrangefrom3.5to4.9 TeV.

InthisLetter,we extendprevious searchesforcontact interac-tions tohigherCIscales, forawiderangeofmodels thatinclude the exact NLO QCD corrections to dijet production. In addition, we explore variousmodels ofcompactifiedextradimensions. Us-ing a data sample corresponding to an integrated luminosity of 19.7 fb−1 at√s=8 TeV,themeasureddijetangulardistributions, unfolded fordetectoreffects,are comparedtoQCD predictionsat NLO,includingforthefirsttimeelectroweak(EW)corrections. 2. Eventselection

AdetaileddescriptionoftheCMSdetector,togetherwitha def-inition ofthecoordinatesystemsusedandtherelevantkinematic variables,canbefoundinRef.[27].ThecentralfeatureoftheCMS apparatusisasuperconductingsolenoidof6 m internaldiameter, providinganaxialfieldof3.8 T.Withinthesolenoidarethesilicon pixelandstrip trackers,whichcoverthe regionofpseudorapidity

|η|<2.5,andthe lead tungstate crystalelectromagneticand the brass and scintillator hadronic calorimeters, which surround the tracking volume and cover |η|<3. Muons are measured in gas-ionizationdetectorsembeddedinthesteelflux-returnyokeofthe solenoidwithacoverageof|η|<2.4.

Eventsarereconstructedusingaparticle-flowtechnique[28,29] whichcombinesinformationfromallCMSsubdetectorstoidentify and reconstruct inan optimalway the individual particle candi-dates (charged hadrons, neutral hadrons, electrons, muons, and photons)ineachevent.Theseparticlecandidatesareclusteredinto jetsusingtheanti-kTalgorithm[30]asimplementedinthe FastJet package [31] withasize parameter R=0.5.Jet energyscale cor-rections [32]derived fromdataandMonteCarlo(MC) simulation are appliedto accountforthe responsefunctionof the calorime-tersforhadronicshowers.

TheCMStriggersystemusesatwo-tieredsystemcomprisinga level-1trigger(L1)andahigh-leveltrigger(HLT)toselectphysics eventsofinterestforfurtheranalysis.Theselectioncriteriausedin thisanalysisaretheinclusivesingle-jettriggers,whichrequireone L1 jet andone HLT jet withvarious thresholds on the jet pT,as well astriggerpathswiththresholdsonthedijetmassandscalar sumofthejet pT.The pT ofjetsiscorrected forthe responseof thedetectoratbothL1andtheHLT.Theefficiencyofeach single-jettriggerismeasuredasafunctionofdijetmassMj jusingevents

selectedbyalower-thresholdtrigger.

Eventswithatleasttworeconstructedjetsareselectedfroman inclusivejetsampleandthetwohighest-pT jetsareusedto mea-surethedijetangulardistributions fordifferentrangesin Mj j.In

unitsofTeVtheMj j rangesare(1.9,2.4),(2.4,3.0),(3.0,3.6),(3.6,

4.2),and>4.2.ThelowestMj j rangeischosensuchthatthe

trig-ger efficiencyexceeds 99% in all bins of χdijet considered inthis analysis.ThetwohighestMj j rangeswerechosentomaximizethe

expectedsensitivitytothenewphysics signalsconsidered.Events with spurious jets from noise and noncollision backgrounds are rejected by applying loose quality criteria [33] to jet properties and requiring a reconstructed primary vertex within ±24 cm of the detector centeralong the beam lineand within 2 cm of the detectorcenterintheplanetransversetothebeam.Themain pri-mary vertexis defined as the one with the largest summed p2T of its associated tracks. The phase space for this analysis is de-finedbyselectingeventswith χdijet<16 and yboost<1.11,where yboost= 12|y1+y2|. This choice of values restricts the two jets

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within |y|<2.5.The highest value of Mj j observed in thisdata

sampleis5.2 TeV.

3. Crosssectionunfoldinganduncertainties

Themeasured χdijet distributions, definedas(1dijet)(dσdijet/ dχdijet),arecorrectedformigrationeffectsduetothefinitejet en-ergy andposition resolutions ofthe detector. Fluctuationsin the jet response cause event migrations in χdijet as well as in dijet mass.Therefore,atwo-dimensionalunfoldinginthesevariablesis performed using the D’Agostini method [34] as implemented in the RooUnfold package[35].Theunfoldingcorrectionsare deter-minedfroma response matrixthat mapsthetrue Mj j and χdijet distributions onto the measured ones. This matrixis derived us-ingparticle-leveljetsfrom herwig++ version2.5.0[36,37]withthe tuneofversion2.4.ThejetsaresmearedinpTwithadouble-sided Crystal-Ballparameterization[38]oftheresponse,whichtakesinto accountthe fulljet energyresponseincludingnon-Gaussian tails. Theunfolding correction factors asa function of χdijet vary from lessthan3%inthelowestMj j rangetolessthan20%inthe

high-estMj j range.

Themain experimental systematic uncertainties inthis analy-sis are caused by the jet energy scale, thejet energyresolution, andthe unfolding modeling anddetector simulation. The overall jetenergyscale uncertaintyvariesbetween1%and2% andhasa dependenceon pseudorapidityoflessthan1%per unitof η [32]. The jet energy scale uncertainty is divided into 21 uncorrelated sources [39].The effect ofeach source ispropagated to thedijet angulardistributionsandthensummedinquadraturetotakeinto accountuncorrelatedpT- and η-dependentsourcesthatcould can-celifvariedsimultaneously.Theresultinguncertaintyinthe χdijet distributionsduetothe jetenergyscale uncertaintiesis foundto belessthan2.0%(2.6%)atlow(high) Mj j overall χdijet bins,and themaximumuncertaintyinagivenMj j binistypicallyfoundto

beinthelowest χdijetbin.

Thejet energyresolution isknown to within 10%of its value inthephasespaceconsideredinthisanalysis[32].Thesystematic uncertaintyinthe χdijetdistributionsduetothiseffectwas evalu-atedby varyingthewidthoftheGaussiancoreoftheCrystal-Ball parameterizationoftheresponseby ±10% andcomparingthe re-sultant unfoldingcorrections beforeandafter thesechanges. The resultinguncertaintyinthe χdijetdistributionsis0.5%(1.5%)inthe lowest (highest) Mj j range. In addition, a systematicuncertainty

inthetailsofthejetresponse functionisevaluatedby determin-ingacorrectionfactorusingaGaussianansatz[32]ratherthanthe double-sidedCrystal-Ball(Gaussianwithtails)functionto parame-terizetheresponse.SincetheGaussianassumptioncorrespondsto theextremecaseofthecompleteabsenceofatail,theassociated uncertaintyhas been takento be 50% ofthe difference between thiscorrection andthe nominal correction basedon the Crystal-Ballfunction. Thiscoverstheuncertaintyinthe understandingof thetailsfromjetresolutiontailmeasurements.Thesizeofthis un-certaintyvariesfromlessthan1% inthelowestMj j rangetoless

than13%inthehighestMj j range.

Asystematicuncertaintyin theunfolding dueto theuseof a parameterizedmodelofthejet pT andpositionresolutionsto de-terminetheunfoldingcorrectionfactorsisestimatedbycomparing thesmeared χdijet distributionstotheonesfroma detailed simu-lationoftheCMSdetectorusing Geant4[40].Thisuncertaintyis foundtobelessthan0.4%(5%)inthelowest(highest) Mj j range.

Afurthersystematicuncertaintyintheunfoldingforthemodeling ofthedijetspectrawith herwig++ [0.1%(1.2%)inthelowest (high-est) Mj j range],is estimatedfromacomparisonofthe unfolding

correctionsfrom herwig++ withthoseobtainedfrom pythia 8 ver-sion 8.165[41]withtune4C[42].

Theuncertaintyfromadditionalinteractionsinthesameproton bunch crossingasthe interactionofinterest, calledpileup,is de-terminedinsimulationbyvaryingtheminimumbiascrosssection within its measured uncertainty of 6% [43]. No significant effect isobserved.Thoughinthe statisticalanalysisofthe datathe un-certaintiesaretreatedseparately,fordisplayintablesandfigures, the total experimental systematicuncertainty in the χdijet distri-butionsiscalculatedasthequadraticsumofthecontributionsdue totheuncertaintiesinthejetenergycalibration,jet pT resolution, andunfoldingcorrection.Thetotaluncertaintyincludingstatistical uncertainties isless than2.5% (49%)for thelowest (highest) Mj j

range.Experimentaluncertainties are evaluatedforboth theQCD background andsignal predictions, however,the resulting uncer-taintiesdonotdiffersignificantly.

4. Theoreticalpredictions

Thenormalizeddijetangulardistributionsarecomparedtothe predictions ofperturbative QCD. The NLO calculation isprovided by NLOJet++ version 4.1.3 [44,45] within the fastNLO framework version 2[46,47].Thefactorization(μF)andrenormalization(μR)

scales are defined to be the average pT of the two jets, pT1,2. Electroweak corrections for dijet production have been derived in Ref. [48], the authors of which provided us with the corre-spondingcorrectionsforthe χdijet distributions.Thesecorrections change the predictions of the normalized χdijet distributions by up to 4% (14%) at low (high) Mj j. Since fast re-evaluation

tech-niquesfordifferentchoicesofPDFsorscalesarenotyetavailable fortheelectroweakcorrectionpartofthetheory,thefactorshave beenappliedherewithoutadditionaluncertainties.Afigure show-ing thesecorrectionscanbe found inAppendix A. Theimpact of non-perturbative effects such ashadronization andmultiple par-toninteractions isestimatedusing pythia 8and herwig++.These effectsarefoundtobenegligible.

ThedominantuncertaintyintheQCD predictionsisassociated withthechoiceofthe μR and μF scales andisevaluated

follow-ingtheproposalinRef.[49]byvaryingthedefaultchoiceofscales in the following six combinations: (μF/pT1,2, μR/pT1,2)=

(1/2,1/2), (1/2,1), (1,1/2), (2,2), (2,1), and(1,2). These scale variations change the QCD predictions of the normalized

χdijetdistributionsbylessthan9%(18%)atlow(high)Mj j.The

un-certainty duetothechoice ofpartondistributionfunctions(PDF) is determined fromthe 22uncertainty eigenvectorsof CT10[50] usingtheproceduredescribedinRef.[50],andisfoundtobeless than 0.6%(1.0%)atlow (high) Mj j.A summaryof thesystematic

uncertainties inthetheoretical predictionsisgiveninTable 1 to-gether withtheexperimental ones. Inthehighest Mj j range,the

dominant experimental contribution is the statistical uncertainty whilethe dominanttheoreticalcontributionis theQCD scale un-certainty.

ForcalculatingtheCItermsaswellastheinterferencebetween theCItermsandQCDtermsatLOandNLOinQCDthe cijet pro-gramversion1.0[51]hasbeenemployed.TheCImodelsatLOare cross-checkedwiththeimplementationin pythia 8 andfound to beconsistent.TheADDpredictionsarecalculatedwith pythia 8. 5. Results

InFig. 1themeasured χdijetdistributions,correctedfor instru-mental effects and normalized by their respective event counts, for all Mj j ranges, are compared to theoretical predictions. The

data are well described by NLO calculationsthat incorporateEW corrections. No significant deviation from the SM predictions is observed. The distributions are also compared to predictions for

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Table 1

Summaryoftheexperimentalandtheoreticaluncertaintiesinthenormalizedχdijet

distributions.Forthelowest,secondhighestandhighest Mj j ranges,therelative

shift(in%)ofthelowestχdijetbinfromitsnominalvalueisquoted.Whileinthe

statisticalanalysiseachsystematicuncertaintyisrepresentedbyachangeofthe χdijetdistributioncorrelatedamongallχdijetbins,thistablesummarizeseach

un-certaintybyarepresentativenumbertodemonstratetherelativecontributions. Uncertainty 1.9<Mj j<2.4 TeV(%) 3.6<Mj j<4.2 TeV(%) Mj j>4.2 TeV(%) Statistical 1.0 2.3 47

Jetenergyscale 2.0 2.1 2.5

Jetenergyresolution (tails)

1.0 2.0 13

Jetenergyresolution (core) 0.5 0.6 1.5 Unfolding,modeling 0.1 1.2 1.2 Unfolding,detector simulation 0.4 1.0 5.0 Pileup <0.1 <0.1 <1.0 Totalexperimental 2.5 4.1 49 QCDNLOscale (6 variationsofμRand μF) +9.0 −3.4 + 11 −4.0 + 18 −6.3 PDF(CT10eigenvectors) 0.6 0.7 1.0 Non-perturbativeeffects <1.0 <1.0 <0.2 Totaltheoretical 9 11 18

Fig. 1. Normalized χdijet distributions for 19.7 fb−1 ofintegrated luminosity at

s=8 TeV.ThecorrecteddatadistributionsarecomparedtoNLOpredictionswith EWcorrections(blackdottedline).Forclaritytheindividualdistributionsareshifted verticallybyoffsetsindicatedinparentheses.Theoreticaluncertaintiesareindicated asagrayband. Theerrorbarsrepresentstatisticaland experimentalsystematic uncertaintiescombinedinquadrature.Theticksontheerrorbarsrepresent exper-imentalsystematicuncertaintiesonly.Thehorizontalbarsindicatethebinwidths. TheNLOQCDpredictionwithoutEWcorrectionsisalsoshown(purpledashed dot-ted).ThepredictionforSM+CIwithLL+ (NLO)=10 TeV isshown(redsolidline),

andsoisthepredictionforSM+ADDwithT(GRW)=7 TeV (bluedashedline).

(Forinterpretationofthereferencestocolorinthisfigurelegend,thereaderis re-ferredtothewebversionofthisarticle.)

SM+CIwith+LL (NLO)=10 TeV andpredictionsforSM+ADD withT (GRW)=7 TeV.

Themeasured χdijet distributionsareusedto determine exclu-sionlimitsonCImodelsthat includefullNLOQCD correctionsto dijet production induced by contact interactions calculated with cijet.LimitsarealsoextractedforCImodelscalculatedatLOwith cijetandADDmodels implementedin pythia 8.To takeinto ac-count theNLO QCD andEW correctionsintheseLO models,the

Fig. 2. Normalized χdijetdistributionsinthetwohighestMj jranges.Thecorrected

data distributions arecomparedto NLOpredictionswith EW corrections(black dottedline).Theoreticaluncertaintiesareindicatedasgraybands.Theerrorbars representstatisticalandexperimentalsystematicuncertaintiescombinedin quadra-ture. Theticksontheerrorbarsrepresentexperimentalsystematicuncertainties only.Thehorizontalbarsindicatethebinwidths.ThepredictionsforthevariousCI andADDmodelsareoverlaid.

crosssection difference σNLOQCD+EW corrσLOQCD isevaluatedforeach

Mj j and χdijet bin and added to the pythia 8+ADD and LO

QCD+CIpredictions.Withthisprocedure,anSM+CI(SM+ADD) predictionisobtainedwheretheQCDtermsarecorrectedtoNLO with EW corrections while the CI (ADD) terms are calculated at LO. Thevariationsduetotheoreticaluncertainties associatedwith scales and PDFs are applied only to the QCD terms of the pre-diction, thereby treating the effectivenewphysics termsasfixed benchmarkterms.

InFig. 2,the χdijetdistributionsforthetwohighestMj j ranges

arecomparedtovariousCIandADDmodels.Onlythetwohighest Mj j rangesareusedtodeterminelimitsofCIandADDmodel

pa-rameterssincetheaddedsensitivityfromthelower Mj j rangesis

negligible.

We quantify the significance of an NP signal with respect to the SM-only hypothesis by means of the likelihood for the SM-only,LSM,andthelikelihoodfortheSMwithnewphysics,LSM+NP.

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Table 2

Observedandexpectedexclusionlimitsat95%CLforvariousCImodels.The uncer-taintiesintheexpectedlimitsconsideringstatisticalandsystematiceffectsforthe SM-onlyhypothesisarealsogiven.

Model Observed (TeV) Expected (TeV) +LL/R R(LO) 10.3 9.8±1.0 LL/R R(LO) 12.9 12.4±2.2 +LL/R R(NLO) 9.0 8.7±0.8 LL/R R(NLO) 11.7 11.4±1.8 +V V(NLO) 11.3 10.8±1.1 V V(NLO) 15.2 14.6±2.6 +A A(NLO) 11.4 10.9±1.1 A A(NLO) 15.1 14.5±2.6 +(VA)(NLO) 8.8 8.5±1.1 (VA)(NLO) 8.9 8.6±1.2 Table 3

Observedandexpectedexclusionlimitsat95%CLforvariousADDmodelsinLO. Theuncertaintiesintheexpectedlimitsconsideringstatisticalandsystematic ef-fectsfortheSM-onlyhypothesisarealsogiven.

Model Observed (TeV) Expected (TeV) ADDT(GRW) 7.1 6.8±0.5 ADD MS(HLZ) nED=2 6.9 6.6±0.4 ADD MS(HLZ) nED=3 8.4 8.0±0.6 ADD MS(HLZ) nED=4 7.1 6.8±0.5 ADD MS(HLZ) nED=5 6.4 6.1±0.5 ADD MS(HLZ) nED=6 5.9 5.7±0.4

The LSM and LSM+NP are defined as products of Poisson likeli-hood functionsfor each binin χdijet for the two highest ranges ofMj j.Thepredictions foreach Mj j rangeare normalizedtothe

number of observed events in that range. The p-values for the twohypotheses, pSM+NP(qqobs)andpSM(qqobs),arebasedon thelog-likelihoodratioq= −2ln(LSM+NP/LSM).Theyareevaluated fromensembles of pseudo-experiments, inwhich systematic un-certaintiesare takenintoaccount via nuisanceparameters which affectthe χdijet distribution, varied within their Gaussian uncer-taintieswhengeneratingthedistributionsofq [52].

Wenote thatthereisan observeddifference betweentheNLO QCDcalculationswithEWcorrectionsandtheNLOQCD-only hy-pothesisintheabove definedlikelihoodratio,which corresponds toasignificanceof1.1standarddeviation.

TheagreementofthedatawiththeSM-only hypothesisis es-timatedby calculating pSM(qqobs)for each Mj j binseparately.

Thelargestdifferenceisfound intheMj j range3.0–3.6 TeV with

a probability of 17% to obtain a deviationfrom the SM-only hy-pothesislargerthantheobserved,corresponding toasignificance of1.4standard deviations.Includingthe two highest Mj j binsin

thelikelihoodreducesthissignificanceto0.9standarddeviations, correspondingtoaprobabilityof39%.

Amodified-frequentistapproach[53,54,52]isusedtoset exclu-sionlimitsonthescale .LimitsontheSM+NPmodelsareset basedonthequantityCLs=pSM+NP(qqobs)/(1−pSM(qqobs)), whichis required to be 0.05 for a 95% confidence level (CL) ex-clusion.TheobservedandexpectedexclusionlimitsondifferentCI andADD modelsobtainedinthisanalysisat95% CLare listedin Tables 2 and 3respectively.Note thattheCIpredictions with ex-actNLOQCDcorrectionsshowasmallerenhancementatlow χdijet relativetoQCDthandothecorrespondingLOCIpredictions,as de-scribedindetailinRef.[55],andthereforeresultinlessstringent limits.

Fig. 3. Observed (solidlines)andexpected(dashedlines)95%CLlowerlimitsfor theCIscalesfordifferentcompositenessmodels(NLO),fortheADDmodelscale withGRWparameterizationTandfortheADDmodelscalewithHLZ

parameteri-zationMS.Thegraybandsindicatethecorrespondinguncertaintiesintheexpected

exclusionlimits.

These results are also summarized in Fig. 3. The limits on MS for the differentnED (nED≥2) directly followfrom thelimit forT.Asacrosscheck,thelimitsfortheCIscale+LL/R Rarealso

determined for the casein which the data are not corrected for detectoreffectsandinsteadthesimulation predictionsare convo-lutedwiththedetectorresolutions.Theextractedlimitsarefound to agree with the quoted ones within 1%. We also quantify the effect of the inclusion of EW corrections in the QCD prediction onthe+LL/R R (LO)observedlimit,whichwouldbereducedfrom 10.3 TeVto9.8 TeVifEWcorrectionswereneglected.

6. Summary

Normalized dijet angular distributions have been measured withtheCMSdetectoroverawiderangeofdijetinvariantmasses. Nosignificantdeviationfromthestandardmodelpredictionsis ob-served.Lowerlimitsare setonthecontactinteractionscale fora varietyofquark compositenessmodelsthatincludeNLOQCD cor-rections and on the cutoff scale for the ADD models withextra dimensions. The95% confidencelevellower limitson thecontact interaction scale  are inthe range 8.8–15.2 TeV. The improved description of the data resulting from the inclusion of the elec-troweak corrections yields approximately 5% higher limits. The lower limits on the cutoff scales in the ADD models, T (GRW)

andMS (HLZ),areintherange5.9–8.4 TeV.Theseresultsrepresent

themoststringentsetoflimitsoncontactinteractionscale, mod-elledatNLO,andthebestlimitsonthebenchmarkADDmodelto date.

Acknowledgements

WewouldliketothankS. DittmaierandA. Hussforproviding us with the electroweak correction factors. We congratulate our colleagues in the CERNaccelerator departments forthe excellent performance ofthe LHC andthankthe technicaland administra-tive staffsatCERN andatotherCMSinstitutesfortheir contribu-tions to the successof the CMSeffort. In addition, we gratefully acknowledgethe computingcenters andpersonnelofthe World-wideLHCComputingGridfordeliveringsoeffectivelythe

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comput-Fig. A.4. Electroweak correctionfactorsversusχdijetforeachMj jrange,derivedby

theauthorsofRef.[48]at8 TeVc.m.energywithpT1,2aschoicefortheμRand

μFscalesandtheCT10-NLOPDFset.

ing infrastructure essential to our analyses. Finally, we acknowl-edge theenduring support forthe construction and operation of theLHCandtheCMSdetectorprovidedby thefollowingfunding agencies: BMWFWandFWF (Austria);FNRSandFWO (Belgium); CNPq,CAPES,FAPERJ,andFAPESP (Brazil); MES(Bulgaria); CERN; CAS,MoST,andNSFC(China);COLCIENCIAS(Colombia);MSESand CSF (Croatia); RPF (Cyprus); MoER, ERC IUT andERDF (Estonia); AcademyofFinland,MEC,andHIP(Finland);CEAandCNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA andNIH(Hungary);DAEandDST(India);IPM(Iran);SFI(Ireland); INFN (Italy); MSIP and NRF (Republic of Korea);LAS (Lithuania); MOE and UM(Malaysia); CINVESTAV,CONACYT, SEP, and UASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland);FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS andRFBR(Russia);MESTD(Serbia);SEIDIandCPAN(Spain);Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU andSFFR(Ukraine);STFC(UnitedKingdom);DOEandNSF(USA). Appendix A. EWcorrectionstodijetangulardistributions

Fig. A.4showstheEWcorrectionstothedijetangular distribu-tions.Thecorrectionsarebasedonthesamecalculationsandtools usedtoderivetheEWcorrectionstoinclusivejetanddijet produc-tioncrosssectionspublishedinRef.[48].TheauthorsofRef.[48] haveprovidedtheexactnumberstobeappliedtothedijetangular distributionaspresentedinthispaper.TheEWcorrectionschange thepredictions ofthenormalized χdijet distributionsby up to4% (14%)atlow(high) Mj j.

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CMSCollaboration

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

YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam, T. Bergauer, M. Dragicevic,J. Erö,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, 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, J. Lauwers,

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

N. Van Remortel,A. Van Spilbeeck

UniversiteitAntwerpen,Antwerpen,Belgium

F. Blekman,S. Blyweert, J. D’Hondt,N. Daci, N. Heracleous, J. Keaveney,S. Lowette, M. Maes,A. Olbrechts,

Q. Python, D. Strom, S. Tavernier,W. Van Doninck, P. Van Mulders, G.P. Van Onsem,I. Villella

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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, F. Zenoni

UniversitéLibredeBruxelles,Bruxelles,Belgium

V. Adler,K. Beernaert, L. Benucci, A. Cimmino,S. Costantini, S. Crucy, S. Dildick,A. Fagot, G. Garcia,

J. Mccartin, A.A. Ocampo Rios,D. 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, A. Jafari, 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

aUniversidadeEstadualPaulista,SãoPaulo,Brazil bUniversidadeFederaldoABC,SãoPaulo,Brazil

A. Aleksandrov, V. Genchev2,P. Iaydjiev, A. Marinov, S. Piperov,M. Rodozov, G. Sultanov,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, T. Cheng, R. Du,C.H. Jiang, R. Plestina7,F. Romeo,J. Tao,

Z. Wang

InstituteofHighEnergyPhysics,Beijing,China

C. Asawatangtrakuldee, Y. Ban, Q. Li, S. Liu,Y. Mao, S.J. Qian, 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

UniversidaddeLosAndes,Bogota,Colombia

N. Godinovic, D. Lelas, D. Polic, I. Puljak

UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia

Z. Antunovic, M. Kovac

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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. Radi12,13

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. Agram14,J. Andrea, A. Aubin,D. Bloch, J.-M. Brom,E.C. Chabert, C. Collard,E. Conte14,

J.-C. Fontaine14,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,

R. Chierici,D. Contardo2, P. Depasse,H. El Mamouni, J. Fan, J. Fay, S. Gascon, M. Gouzevitch, B. Ille,

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

Z. Tsamalaidze8

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

A. Ostapchuk, 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, F. Hoehle, B. Kargoll,

T. Kress, Y. Kuessel,A. Künsken, 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. Bergholz15, A. Bethani,K. Borras,

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

S. Dooling,T. Dorland, G. Eckerlin,D. Eckstein, T. Eichhorn, G. Flucke, J. Garay Garcia, A. Geiser,

P. Gunnellini, J. Hauk, M. Hempel15, D. Horton, H. Jung,A. Kalogeropoulos, M. Kasemann,P. Katsas,

J. Kieseler, C. Kleinwort,I. Korol, D. Krücker, W. Lange,J. Leonard, K. Lipka,A. Lobanov, W. Lohmann15,

B. Lutz, R. Mankel, I. Marfin15,I.-A. Melzer-Pellmann, A.B. Meyer, G. Mittag, J. Mnich, A. Mussgiller,

S. Naumann-Emme,A. Nayak, O. Novgorodova, E. Ntomari,H. Perrey, D. Pitzl,R. Placakyte, A. Raspereza,

P.M. Ribeiro Cipriano, B. Roland,E. Ron, M.Ö. Sahin, J. Salfeld-Nebgen,P. Saxena, R. Schmidt15,

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, A. Perieanu,N. Pietsch, J. Poehlsen,T. Poehlsen, D. Rathjens, C. Sander,

H. Schettler, P. Schleper, E. Schlieckau,A. Schmidt, M. Seidel, V. Sola, H. Stadie,G. Steinbrück,

D. Troendle,E. Usai, L. Vanelderen,A. Vanhoefer

UniversityofHamburg,Hamburg,Germany

C. Barth, C. Baus,J. Berger, C. Böser, E. Butz,T. Chwalek, W. De Boer,A. Descroix, A. Dierlamm,M. Feindt,

F. Frensch, M. Giffels,A. Gilbert, 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

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

UniversityofAthens,Athens,Greece

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

J. Strologas

UniversityofIoánnina,Ioánnina,Greece

G. Bencze,C. Hajdu, P. Hidas, D. Horvath16, F. Sikler,V. Veszpremi, G. Vesztergombi17,A.J. Zsigmond

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N. Beni,S. Czellar, J. Karancsi18,J. Molnar, J. Palinkas, Z. Szillasi

InstituteofNuclearResearchATOMKI,Debrecen,Hungary

A. Makovec,P. Raics, Z.L. Trocsanyi, B. Ujvari

UniversityofDebrecen,Debrecen,Hungary

S.K. Swain

NationalInstituteofScienceEducationandResearch,Bhubaneswar,India

S.B. Beri,V. Bhatnagar, R. Gupta, U. Bhawandeep, A.K. Kalsi,M. Kaur, R. Kumar,M. Mittal, N. Nishu,

J.B. Singh

PanjabUniversity,Chandigarh,India

Ashok Kumar,Arun Kumar, S. Ahuja, A. Bhardwaj,B.C. Choudhary, A. Kumar,S. Malhotra, M. Naimuddin,

K. Ranjan,V. Sharma

UniversityofDelhi,Delhi,India

S. Banerjee, S. Bhattacharya, K. Chatterjee,S. Dutta, B. Gomber, Sa. Jain, Sh. Jain,R. Khurana,A. Modak,

S. Mukherjee,D. Roy, S. Sarkar, M. Sharan

SahaInstituteofNuclearPhysics,Kolkata,India

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

BhabhaAtomicResearchCentre,Mumbai,India

T. Aziz,S. Banerjee, S. Bhowmik19, R.M. Chatterjee, R.K. Dewanjee,S. Dugad, S. Ganguly, S. Ghosh,

M. Guchait,A. Gurtu20, G. Kole, S. Kumar, M. Maity19,G. Majumder, K. Mazumdar, G.B. Mohanty,

B. Parida,K. Sudhakar, N. Wickramage21

TataInstituteofFundamentalResearch,Mumbai,India

H. Bakhshiansohi,H. Behnamian,S.M. Etesami22, A. Fahim23, R. Goldouzian, M. Khakzad,

M. Mohammadi Najafabadi,M. Naseri, S. Paktinat Mehdiabadi, F. Rezaei Hosseinabadi, B. Safarzadeh24,

M. Zeinali

InstituteforResearchinFundamentalSciences(IPM),Tehran,Iran

M. Felcini,M. Grunewald

UniversityCollegeDublin,Dublin,Ireland

M. Abbresciaa,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,A. Sharma, L. Silvestrisa,2,R. Vendittia,b

aINFNSezionediBari,Bari,Italy bUniversitàdiBari,Bari,Italy cPolitecnicodiBari,Bari,Italy

G. Abbiendia,A.C. Benvenutia, D. Bonacorsia,b, S. Braibant-Giacomellia,b,L. Brigliadoria,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,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

aINFNSezionediBologna,Bologna,Italy bUniversitàdiBologna,Bologna,Italy

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

aINFNSezionediCatania,Catania,Italy bUniversitàdiCatania,Catania,Italy cCSFNSM,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

aINFNSezionediFirenze,Firenze,Italy bUniversitàdiFirenze,Firenze,Italy

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

INFNLaboratoriNazionalidiFrascati,Frascati,Italy

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

aINFNSezionediGenova,Genova,Italy bUniversitàdiGenova,Genova,Italy

M.E. Dinardoa,b,S. Fiorendia,b, S. Gennaia,2,R. Gerosaa,b,2,A. Ghezzia,b,P. Govonia,b,M.T. Lucchinia,b,2, S. Malvezzia, R.A. Manzonia,b,A. Martellia,b,B. Marzocchia,b, D. Menascea, L. Moronia,M. Paganonia,b, D. Pedrinia,S. Ragazzia,b,N. Redaellia, T. Tabarelli de Fatisa,b

aINFNSezionediMilano-Bicocca,Milano,Italy bUniversitàdiMilano-Bicocca,Milano,Italy

S. Buontempoa, N. Cavalloa,c, S. Di Guidaa,d,2, F. Fabozzia,c,A.O.M. Iorioa,b,L. Listaa, S. Meolaa,d,2,

M. Merolaa, P. Paoluccia,2

aINFNSezionediNapoli,Napoli,Italy bUniversitàdiNapoli‘FedericoII’,Napoli,Italy cUniversitàdellaBasilicata(Potenza),Napoli,Italy dUniversitàG.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

aINFNSezionediPadova,Padova,Italy bUniversitàdiPadova,Padova,Italy cUniversitàdiTrento(Trento),Padova,Italy

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

aINFNSezionediPavia,Pavia,Italy bUniversitàdiPavia,Pavia,Italy

M. Biasinia,b, G.M. Bileia,D. Ciangottinia,b,L. Fanòa,b,P. Laricciaa,b, G. Mantovania,b, M. Menichellia, A. Sahaa, A. Santocchiaa,b,A. Spieziaa,b,2

aINFNSezionediPerugia,Perugia,Italy bUniversitàdiPerugia,Perugia,Italy

K. Androsova,25,P. Azzurria,G. Bagliesia,J. Bernardinia,T. Boccalia,G. Broccoloa,c,R. Castaldia,

M.A. Cioccia,25, R. Dell’Orsoa,S. Donatoa,c,F. Fioria,c,L. Foàa,c,A. Giassia, M.T. Grippoa,25, F. Ligabuea,c, T. Lomtadzea, L. Martinia,b, A. Messineoa,b,C.S. Moona,26, F. Pallaa,2, A. Rizzia,b, A. Savoy-Navarroa,27,

A.T. Serbana,P. Spagnoloa,P. Squillaciotia,25,R. Tenchinia, G. Tonellia,b,A. Venturia, P.G. Verdinia, C. Vernieria,c,2

aINFNSezionediPisa,Pisa,Italy bUniversitàdiPisa,Pisa,Italy

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L. Baronea,b, F. Cavallaria,G. D’imperioa,b,D. Del Rea,b, M. Diemoza,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

aINFNSezionediRoma,Roma,Italy bUniversitàdiRoma,Roma,Italy

N. Amapanea,b,R. Arcidiaconoa,c, S. Argiroa,b, 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

aINFNSezionediTorino,Torino,Italy bUniversitàdiTorino,Torino,Italy

cUniversitàdelPiemonteOrientale(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, A. Schizzia,b, T. Umera,b,A. Zanettia

a

INFNSezionediTrieste,Trieste,Italy bUniversitàdiTrieste,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, 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

NationalCentreforParticlePhysics,UniversitiMalaya,KualaLumpur,Malaysia

E. Casimiro Linares, H. Castilla-Valdez,E. De La Cruz-Burelo, I. Heredia-de La Cruz28,

A. Hernandez-Almada,R. Lopez-Fernandez, A. Sanchez-Hernandez

CentrodeInvestigacionydeEstudiosAvanzadosdelIPN,MexicoCity,Mexico

S. Carrillo Moreno, F. Vazquez Valencia

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I. Pedraza, H.A. Salazar Ibarguen

BenemeritaUniversidadAutonomadePuebla,Puebla,Mexico

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, W.A. Khan, T. Khurshid,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,L. Lloret Iglesias,

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

LaboratóriodeInstrumentaçãoeFísicaExperimentaldePartículas,Lisboa,Portugal

P. Bunin,M. Gavrilenko, I. Golutvin, I. Gorbunov, V. Karjavin, V. Konoplyanikov, A. Lanev, A. Malakhov,

V. Matveev29,P. Moisenz, V. Palichik, V. Perelygin, M. Savina, S. Shmatov, S. Shulha,N. Skatchkov,

V. Smirnov, A. Zarubin

JointInstituteforNuclearResearch,Dubna,Russia

V. Golovtsov, Y. Ivanov,V. Kim30, 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, I. Pozdnyakov, G. Safronov, S. Semenov,

A. Spiridonov, V. Stolin, E. Vlasov, A. Zhokin

InstituteforTheoreticalandExperimentalPhysics,Moscow,Russia

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. Dubinin31, L. Dudko,A. Ershov, V. Klyukhin, O. Kodolova,I. Lokhtin,

S. Obraztsov,M. Perfilov, S. Petrushanko, V. Savrin

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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. Adzic32,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,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

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, P. Bloch, A. Bocci, A. Bonato, O. Bondu,C. Botta, H. Breuker,

T. Camporesi, G. Cerminara, S. Colafranceschi33,M. D’Alfonso, D. d’Enterria, A. Dabrowski,A. David,

F. De Guio,A. De Roeck, S. De Visscher, E. Di Marco,M. Dobson, M. Dordevic, B. Dorney,

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. Rolandi34, M. Rovere, H. Sakulin, C. Schäfer, C. Schwick,A. Sharma,

P. Siegrist,P. Silva, M. Simon, P. Sphicas35, D. Spiga,J. Steggemann,B. Stieger, M. Stoye, Y. Takahashi,

D. Treille, A. Tsirou,G.I. Veres17, 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

PaulScherrerInstitut,Villigen,Switzerland

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

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

P. Martinez Ruiz del Arbol,M. Masciovecchio, D. Meister, N. Mohr,C. Nägeli36, F. Nessi-Tedaldi,

F. Pandolfi,F. Pauss, M. Peruzzi,M. Quittnat, L. Rebane, M. Rossini,A. Starodumov37, M. Takahashi,

K. Theofilatos,R. Wallny, H.A. Weber

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C. Amsler38, 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, G. Singh, N. Srimanobhas,N. Suwonjandee

ChulalongkornUniversity,FacultyofScience,DepartmentofPhysics,Bangkok,Thailand

A. Adiguzel, M.N. Bakirci39, S. Cerci40,C. Dozen, I. Dumanoglu, E. Eskut, S. Girgis, G. Gokbulut,

E. Gurpinar,I. Hos, E.E. Kangal, A. Kayis Topaksu,G. Onengut41,K. Ozdemir, S. Ozturk39, A. Polatoz,

D. Sunar Cerci40,B. Tali40, H. Topakli39,M. Vergili

CukurovaUniversity,Adana,Turkey

I.V. Akin, B. Bilin,S. Bilmis, H. Gamsizkan42,B. Isildak43,G. Karapinar44,K. Ocalan45, S. Sekmen,

U.E. Surat,M. Yalvac, M. Zeyrek

MiddleEastTechnicalUniversity,PhysicsDepartment,Ankara,Turkey

E.A. Albayrak46,E. Gülmez,M. Kaya47, O. Kaya48,T. Yetkin49

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,J. Goldstein, M. Grimes, G.P. Heath, H.F. Heath,J. Jacob,

L. Kreczko, C. Lucas,Z. Meng, D.M. Newbold50, S. Paramesvaran,A. Poll, T. Sakuma,S. Senkin, V.J. Smith,

T. Williams

UniversityofBristol,Bristol,UnitedKingdom

K.W. Bell, A. Belyaev51, 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, G. Hall,G. Iles, M. Jarvis,

G. Karapostoli,M. Kenzie, R. Lane, R. Lucas50,L. Lyons, A.-M. Magnan,S. Malik, B. Mathias, J. Nash,

A. Nikitenko37,J. Pela, M. Pesaresi, K. Petridis, D.M. Raymond, S. Rogerson,A. Rose, C. Seez,P. Sharp†,

A. Tapper,M. Vazquez Acosta, T. Virdee, S.C. Zenz

ImperialCollege,London,UnitedKingdom

J.E. Cole, P.R. Hobson, A. Khan,P. Kyberd, D. Leggat,D. Leslie, W. Martin,I.D. Reid, P. Symonds,

L. Teodorescu,M. Turner

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