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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
.CMSCollaboration CERN,Switzerland a r t i c l e i n f o a b s t ra c t Articlehistory: Received10November2014 Receivedinrevisedform19April2015 Accepted21April2015Availableonline24April2015 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) / (E−pz)]/2 with E beingthejetenergy and pz the projection ofthejet momentum onto thebeamaxis. Forthescatteringofmassless partons, χdijet is relatedtothe
po-larscatteringangle θ∗ 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.
(ηLL,ηR R,ηR L) ±LL (±1, 0, 0) ±R R ( 0,±1, 0) ±V V (±1,±1,±1) ±A A (±1,±1,∓1) ±(V−A) ( 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 ±(V−A),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
within |y| <2.5.The highest value of Mj j observed in thisdata sampleis5.2 TeV.
3. Crosssectionunfoldinganduncertainties
Themeasured χdijet distributions, definedas (1/σdijet)(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
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+CIwith LL+ (NLO) =10 TeV isshown(redsolidline), andsoisthepredictionforSM+ADDwith T(GRW) =7 TeV (bluedashedline). (Forinterpretationofthereferencestocolorinthisfigurelegend,thereaderis re-ferredtothewebversionofthisarticle.)
SM+CIwith +LL (NLO) =10 TeV andpredictionsforSM+ADD with T (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. NormalizedχdijetdistributionsinthetwohighestMj jranges.Thecorrected data distributions arecomparedto NLOpredictionswith EW corrections(black dottedline).Theoreticaluncertaintiesareindicatedasgraybands.Theerrorbars representstatisticalandexperimentalsystematicuncertaintiescombinedin quadra-ture. Theticksontheerrorbarsrepresentexperimentalsystematicuncertainties only.Thehorizontalbarsindicatethebinwidths.ThepredictionsforthevariousCI andADDmodelsareoverlaid.
crosssection difference σNLOQCD+EW corr−σLOQCD 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.
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 +(V−A)(NLO) 8.8 8.5±1.1 −(V−A)(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(q≥qobs)andpSM(q≤qobs),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(q≤qobs)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(q≥qobs)/(1−pSM(q≤qobs)),
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 theCIscales fordifferentcompositenessmodels(NLO),fortheADDmodelscale withGRWparameterization TandfortheADDmodelscalewithHLZ 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
comput-Fig. A.4. ElectroweakcorrectionfactorsversusχdijetforeachMj 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
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
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,
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M. Vander Donckt, P. Verdier,S. Viret, H. Xiao
UniversitédeLyon,UniversitéClaudeBernardLyon1,CNRS-IN2P3,InstitutdePhysiqueNucléairedeLyon,Villeurbanne,France
Z. Tsamalaidze8
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,
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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
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
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
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
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
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
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
