Search for pair-produced resonances decaying to jet pairs in proton-proton collisions at root s=8 TeV

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Physics

Letters

B

www.elsevier.com/locate/physletb

Search

for

pair-produced

resonances

decaying

to

jet

pairs

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:

Received24December2014 Receivedinrevisedform16April2015 Accepted21April2015

Availableonline24April2015 Editor: M.Doser

Keywords: CMS Physics Dijets

Results are reportedofageneralsearchfor pairproductionofheavyresonances decayingtopairs of hadronic jets inevents with at least fourjets. The study is basedon upto 19.4 fb−1 _{of integrated}

luminosity fromproton–proton collisionsatacenter-of-massenergyof8 TeV,recordedwiththe CMS detector atthe LHC. Limits are determined on the production ofscalar top quarks (top squarks) in theframeworkofR-parityviolatingsupersymmetryandontheproductionofcolor-octetvectorbosons (colorons).FirstlimitsattheLHCareplacedontopsquarkproductionfortwoscenarios.Thefirstassumes decaytoabottomquarkandalight-flavorquarkandisexcludedformassesbetween200and385 GeV, and thesecondassumesdecaytoapairoflight-flavorquarksandisexcludedformassesbetween200 and 350 GeVat95% confidencelevel. Previous limits oncolorons decayingto light-flavor quarks are extendedtoexcludemassesfrom200to835 GeV.

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

1. Introduction

Wepresenttheresultsofasearchforpairproductionofheavy resonances decayingto pairs oflight- and heavy-flavor quarks in multijetevents.Theanalysisisbasedondatasamples correspond-ingtoasmuchas19.4±0.5 fb−1_{[1]ofintegratedluminosityfrom} proton–proton collisions at √s=8 TeV, collected with the CMS detector[2] at the CERN LHC in 2012. Events that have at least fourjetswithhightransversemomentum(pT)withrespecttothe beamdirectionareselectedandinvestigatedforevidenceof pair-produceddijetresonances.

Many models of particle physics beyond the standard model (SM) incorporate particles that decay into fully hadronic final states. Supersymmetric (SUSY) models are SM extensions,which simultaneouslysolvethehierarchyproblemandunifyparticle in-teractions[3,4].In natural SUSY models, wherethere is minimal fine-tuning, thetop quark superpartner(top squark) andthe su-perpartners of the Higgs boson (higgsinos) are required to be light[5–9].NaturalSUSYisunderconstrainedincertainR-parity vi-olating(RPV)scenarios[10].R-parityisaquantumnumberdefined as R= (−1)3B+L+2S, where B and L are the baryon and lepton numbers,respectively, and S is thespin. The RPVsuperpotential, W ,isdefinedas

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

W =1 2λi jkLiLjE c k+ λi jkLiQjD c k+ 1 2λ  i jkU c iDcjDck, (1) where λare thecouplings, i, j,k are thegeneration indices,c is the charge conjugation, L and Q are the doublet superfields of the lepton andquark, respectively, and E, D, and U arethe sin-gletsuperfieldsofthe lepton,down-typeandup-typequarks, re-spectively.ModelsthatincorporateRPVmayallowbaryonnumber violation through a non-zero λ_UDD coupling, and one such un-constrainedscenario [11] isthatofthe hadronicallydecaying top squark,t→qq.If thetop squarks arepair-produced inhadronic collisions andthendecayvia suchan RPVprocess,the finalstate would consist of four jetswith no momentum imbalance in the transverseplane.

In additionto top squarkproduction,hadron collidersearches forpairproductionof resonancesdecayinginto jetpairs are sen-sitive to a number of models that predict new particles carry-ing color quantum numbers. Some models predict pair produc-tionthroughgginteractionsofcolor-octetvectors, alsocalled col-orons (C) [12], which then decay to quark pairs. The associated final state of the signal is characterized by the presence of four high-pTjets.

CDF Collaboration has placed 95%confidence level (CL) exclu-sionlimits[13]ontopsquarkproductionfollowedbyRPVdecays in the mass range 50–90 GeV and on coloronproduction in the mass range50–125 GeV.At theLHC, ATLAS hasplaced limitson scalargluonmassesbetween100and185 GeV[14],andseparately

http://dx.doi.org/10.1016/j.physletb.2015.04.045

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

formasses between 150 and287 GeV [15]. The CMS search for paired dijet resonances resulted in limitson coloron masses be-tween250and740 GeV[16].However,noneofthesesearcheshas beensensitiveenoughtosetlimitsonhadronicRPVdecaysof di-rectlyproducedtopsquarks.

Inthispaper,we concentrateon searchesfortop squarks and colorons.The benchmark signalsare those wherethe top squark isthelightestsupersymmetricparticle,andinonescenariodecays into two light quarks, and in the second scenario it decays into ab quark anda light quark [17–22].We separately consider the possibilityofdecayswithinthecoloronmodel(gg→CC→qqqq).

The analysis employs a well-established search strategy with optimized event selections. The distribution of a variable repre-sentative of the top squark mass is investigated for evidence of a signal consistent with localized deviations from the estimated large,steeply falling SM background todata. The estimate ofthe backgroundisperformedwithafittothefallingpartofthemass spectrumin data,anda SM MC analysis isused to optimizethe signalselectionandtoderivesystematicuncertainties.

2. CMSexperiment

ThecentralfeatureoftheCMSapparatus[2]isa superconduct-ingsolenoidof 6 minternal diameter,providing amagnetic field of3.8 T.Withinthesuperconductingsolenoidvolumeareasilicon pixelandstriptracker,aleadtungstateelectromagnetic calorime-ter (ECAL), and a hadron calorimeter (HCAL), which is made of interleaved layers of scintillator and brass absorber. Muons are measuredingasionizationdetectorsembeddedinthesteelreturn yokeoutsidethesolenoid. Extendedforwardcalorimetry comple-mentsthe coverage providedby thebarrelandendcapdetectors. Energydeposits fromhadronicjetsare measured using theECAL andHCAL. A more detailed description of the CMS detector, to-gether with a definition of the coordinate system used and the relevantkinematicvariables,canbefoundinRef.[2].

3. Triggeringandobjectreconstruction

One data set, representing 19.4 fb−1_{, was recorded over the} entire2012 data taking period with a multilevel trigger system, whichselectedeventswithatleastfourjetswith pT>80 GeV to be reconstructed from only calorimeter information. In addition, asecond data setwas recordedusing thesame triggerlogic, but witha lower jet pT threshold.Thisthresholdwas decreased pro-gressivelyfrom50to45 GeVduringthe2012datatakingperiod. Thelatterdatarepresentonlyasubsetoftheentire2012dataset, correspondingtoanintegratedluminosityof12.4 fb−1.The analy-sisisseparatedintotwoparts:adedicated“low-mass”searchwith afocusonthemassregionfrom200to300 GeV,whichtakes ad-vantageof thislower jet pT threshold,anda “high-mass” search focusingontopsquarkmassesabove300 GeV,whichusesthe en-tire19.4 fb−1 _{datasetandextendstheexpectedtopsquarkmass} searchsensitivityby40 GeV.

TheanalysisisbaseduponobjectsreconstructedusingtheCMS Particle Flow algorithm [23]. This method combines calorimeter information with reconstructed charged particle tracks to iden-tifyindividual particlessuch asphotons,leptons, andneutraland chargedhadrons. Theenergyofphotonsisdirectlyobtainedfrom the calibrated ECAL measurement. The energy of the electron is determined from a combination of its track momentum at the main interaction vertex, the corresponding ECAL cluster energy, andthe energy sumof all bremsstrahlungphotons associated to the track.The energy of a muon is obtained from its associated trackmomentum.Thechargedhadronenergyiscalculatedfroma combinationofthetrackmomentumandthecorrespondingECAL

andHCALenergies,correctedforzero-suppressioneffects,and cal-ibrated for the combined response function of the calorimeters. Finally,theenergyofneutralhadronsisobtainedfromthe corre-spondingcorrectedECALandHCALenergies.Jetsarereconstructed from the particleflow “objects” using theanti-kT algorithm [24] withadistanceparameterof0.5in y–φspace,where y isthe ra-pidity.

Jetenergyscalecorrections[25] areappliedtoaccountforthe combined response function of the calorimeters to hadrons. The correctionsarederivedfromMonteCarlo(MC)simulationandare confirmedwithinsitumeasurementsoftheenergybalanceof di-jet and photon+jet events. In data, a small residual correction factor is included to account for differences in jet response be-tweendataandsimulation.Thetotalsizeoftheappliedcorrections isapproximately5–10%,andthecorrespondinguncertainties vary from 3 to 5%, depending on the measured jet pseudorapidity η

and pT. Toremove misidentified jets, which arise primarily from calorimeternoise, jet quality criteria[26] are applied. More than 99.8% ofall selected jets, in both dataandsignal eventsamples, satisfythesecriteria.

Toidentifyjetsproducedby bquark hadronization,the analy-sis uses themedium selection ofthe combinedsecondary vertex b-tagging algorithm [27]. The algorithm employs a multivariate technique, which takes as input information fromthe transverse impactparameterwithrespecttotheprimaryvertexofthe associ-atedtracksandfromcharacteristicsofthereconstructedsecondary vertices. The output of the algorithm is used to discriminate b quark jets from light-flavor and gluon jets, with typical values of b-tagging efficiency and misidentification probabilities of 72% and 1.1%,respectively.

4. Generationofsimulatedevents

Both top squarkproduction andcoloronproduction are simu-latedusing the MadGraph 5.1.5.12 [28] eventgenerator withthe CTEQ6L1 parton distribution functions[29], andtheir decaysare simulated using the pythia 6.426 [30] MC program. Top squark signaleventsaregeneratedwithuptotwoadditionalinitial-state partons, and each top squark decays into two jets through the

λ_UDD quark RPV coupling. Two scenarios are considered for this coupling.First,thecoupling λ₃₁₂,wherethethreenumerical sub-scriptsrefertothequarkgenerationsofthecorrespondingquarks, issettoanon-zerovaluesuchthatthedecayofthetopsquarkto twolight-flavorjetsisallowed.Thesecondcaseinsteadsetsa non-zerovaluefor λ323,resultingintopsquarkdecayintoonebjetand onelight-flavorjet.Inbothoftheabovecases,thebranching frac-tion of the top squark decay to two jets is set to 100%. For the generationofthissignal,all superpartnersexceptthetopsquarks are takento be decoupled [17–21] andnointermediate particles are produced inthetop squarkdecay. Topsquarks are generated with masses from 100 GeV to 1 TeV in 50 GeV steps for both coupling scenarios. The cross section estimates [31] are made at next-to-leading order(NLO) withnext-to-leading-logarithm (NLL) corrections [32–36], and assigned appropriate theoretical uncer-tainties[31].Forthecoloronsignalscenario,weconsiderthecase whereeachcolorondecaysintotwolight-flavorjetswitha branch-ing fraction of 100%. For this signal, masses are generated from 100 GeVto 2 TeV,andNLO crosssection estimatesare used.For boththetopsquarkandcoloronmodels,thenaturalwidthofthe signal resonanceistakentobe much smallerthantheresolution ofthedetector.BackgroundsfromSMmultijetprocessesare simu-latedthroughmatchedtree-levelmatrixelementsfortwo- to four-jet production using MadGraph, and these events are showered through pythia.Inall samples,theMLMmatchingprocedure[37] is used, and simulation of the CMS detector is performed with Geant4[38].

Fig. 1. ProbabilitydensitydistributionsofthefourthhighestjetpT(top)andRmin (bottom)foreventsfromdata,thesimulatedSMmultijetsample,anda400 GeV topsquarksignal.Statisticaluncertaintiesareshownforthetopsquarksignalas verticalbarsandfor dataasarrows.Eventscontainatleastfourjets,eachwith pT>120 GeV and|η|<2.5,andalldistributionshaveanareanormalizedtounity.

5. Eventselection

Eventsrecordedwiththefour-jettriggersare requiredto have a well-reconstructed primary eventvertex[39].Events must also contain at least four jets, each with |η| <2.5 and reconstructed pT greater than 80 GeV forthe low-pT trigger and120 GeV for thehigher-pTtrigger.Withtheaboverequirements,theoffline ef-ficiencyisabove99%forallselectedevents.

The leading four jets, ordered in pT, are used to createthree unique combinationsof dijetpairs per event. A distancevariable isimplemented to selectthejet pairing that bestcorresponds to thetworesonancedecays, R=(η)2_{+ (φ)}2_{,where ηand}

φ are the differences in η andφ ofbetween two the jets, re-spectively.Thisvariable[40] exploitsthesmallerrelative distance between daughter jets from the same top squark parent decays compared to that between uncorrelated jets. For each dijet pair configurationthevalueof Rdijetiscalculated:

Rdijet=



i=1,2

|Ri−1|, (2)

where Ri _{represents the separation between two jets in dijet} pair i. An offset of 1 has been chosen since this maintains a maximal signal efficiency while minimizing the selection of di-jetsystemscomposedofresolvedjetsfromradiatedgluonspaired withtheir parent jet.The configurationthat minimizesthe value

Rdijetisselected,with Rminrepresentingtheminimum Rdijet fortheevent.Fig. 1showstheprobability densitydistributions of thefourthhighestjet pT andthe Rmin variablefordataevents,

Fig. 2. Probabilitydensitydistributionsofm/mav (top)andηdijet (bottom)for eventsfromdata,the simulatedSMmultijetsample,and a400 GeVtopsquark signal.Statisticaluncertaintiesareshownforthetopsquarksignalasverticalbars andfordataasarrows.Eventscontainatleastfourjets,eachwith pT>120 GeV and|η|<2.5,andalldistributionshaveanareanormalizedtounity.

thoseofa simulatedSMmultijetsample,andthoseof400 GeVtop squarksignalsample.

Onceadijetpairconfigurationischosen,two additional quan-titiesare usedtorejectthe backgroundsfromSMmultijetevents and incorrect signal pairings: the pseudorapidity difference be-tween the two dijet systems ηdijet, and the absolute value of the fractional mass difference m/mav, where m is the differ-encebetweenthetwodijetmassesandmav istheiraveragevalue. Insignal eventswherethecorrectpairingischosen,the m/mav quantityispeakedatzerowithamuchnarrowerdistributionthan thatforSMmultijetbackgroundorincorrectlypairedsignalevents. Thus, thesensitivityofthesearchbenefits fromimposing a max-imum value on m/mav. Similarly, it is advantageous to require that ηdijetbesmall.Fig. 2showstheprobabilitydensity distribu-tionsofthe m/mav and ηdijetvariablesfordataevents,thoseof asimulatedSMmultijetsample,andthoseof400 GeVtopsquark signalsample.Anadditionalkinematicvariable iscalculatedfor eachdijetsystem:

= ⎛ ⎝ i=1,2 |pi_T| ⎞ ⎠ −mav, (3)

where the pT sum is over the two jets in the dijet configura-tion. Thistype ofvariable hasbeen usedextensively inhadronic resonance searchesatboth theTevatronandthe LHC[16,41–44]. Requiringaminimumvalueof resultsinaloweringofthepeak positionvalueofthemav distributionfrombackgroundSMmultijet events.Withthisselectionthemodelingofthebackgroundshape

Fig. 3. DistributionsofthefittosimulatedbackgroundSMmultijetevents(solid redline)anda500 GeVtopsquark(dashedblueline),normalizedtoafactorof tentimesitscrosssection,areshownforthehigh-massoptimizationscenario.The dottedverticallinesrepresentthe integrationwindowusedbythe optimization procedure.

canbeextendedtolower valuesofmav,makingawider rangeof topsquarkandcoloronmassesaccessibletothesearch.

Finally,asthepresenceofheavy-flavorfinal statejetsisa nat-uralextension oftheRPV topsquarkscenarios, theuse ofb tag-gingis exploitedtofurther increase signal sensitivityby increas-ing backgroundrejection.We consider two scenarios:the heavy-flavorsearch, whichuses btagging toincrease thesensitivityfor topsquarkdecaysintoheavy-flavor jets,andtheinclusivesearch, whichfocusesinsteadondecaysintolight-flavorjets.

Theoptimizationforthesignalselectionisperformedasa func-tion of the three kinematic variables described above: m/mav,

ηdijet, , aswell as the fourth jet pT. Because the number of expectedbackgroundeventsislarge,we use S/√B asthemetric forsignal optimization, where S and B are thenumberof signal andbackgroundevents, respectively,and B isdetermined by us-ing the mav ofsimulated SM events.The valuesof S and B are settothenumberofeventswithinawindowofwidth±10% cen-teredatthegeneratedtopsquarkmass,wherethevalueof10%is roughlytwicetheexpectedresolutionforsignalmasses.Westudy thismetricbyevaluating S andB basedoneventspassinga num-ber of thresholds of each kinematic variable and obtain several four-dimensional tables, in which a value of S/√B is found for everycombinationofthefourvariables.Thesetablesareproduced in the low- and high-mass search regions, and for the inclusive andheavy-flavor analyses separately.An exampleof thisisgiven inFig. 3,wherethedistributionfora500 GeVtopsquarkandfor afitto thesimulatedSM multijetdistributionare shownforone operatingpoint.Thesignalshapeisbimodalowingtoasmall frac-tionofeventswithincorrectsignalpairings,andtheGaussianpeak centeredatthegeneratedmassisthepartofthedistributionused in the optimization. The threshold values of the four kinematic variables,correspondingtomaximumvaluesofS/√B inthese ta-bles,aretakenasaworkingpoint.Becauseofsimilarresultsinthis optimization,theinclusiveandheavy-flavorsearchesusecommon workingpoints,withtheexceptionoftheheavy-flavoranalysis re-quirementofb tagging.Asummary ofthe requirementsis listed inTable 1forboth thelow- andhigh-masssearches.Anexample ofthe ηdijet variableisshowninFig. 4.Thecorrelation between thepseudorapidityvaluesforthe twodijetsystemsis plottedfor both400 GeVtopsquarkandsimulatedSMsamples,withthe re-gion of allowed values of the ηdijet variable indicated. For the heavy-flavorsearch, we repeatthe optimizationprocedureby us-ingselections basedon fivedifferentb-tagged jet configurations: atleastoneb-taggedjetintheevent,atleastoneb-taggedjetin

Fig. 4. Theηvalueforthehigher-pTreconstructeddijetsystemversusthatofthe lower-pTdijetsystemintheselectedpair.Thisdistributionisshownfor400 GeV topsquark(top)andsimulatedSMmultijetsamples(bottom),withtherighthand scaleindicatingtheexpectednumberofeventsperbin.Thediagonallines indi-catetheoptimizedregionofallowedηdijetvalues,andeventswithvaluesfalling betweenthetwolinespassthisrequirement.

Table 1

Summaryofthelow- andhigh-massselectioncriteriaforboththeinclusiveand heavy-flavoranalyses.Fortheheavy-flavoranalysis,inadditiontotherequirements below,atleasttwoofthefourhighestpTjetsmustbeb-tagged.

Low-mass search High-mass search

Mass range 200–300 GeV >300 GeV

Integrated luminosity 12.4 fb−1 _{19.4 fb}−1

m/mav <0.15 <0.15

ηdijet <1.0 <1.0

 >70 GeV >100 GeV

Fourth jet pT >80 GeV >120 GeV

the four highest pT jets, at leasttwo b-taggedjets inthe event, atleasttwo b-taggedjetsinthefourhighest pT jets, andatleast oneb-taggedjetineachofthetwochosendijetsystems.Wefind that theoptimal selectionis therequirementthat eventscontain atleasttwob-taggedjetsamongthefourhighestpTjets.

Fig. 5. ThemavdistributionswiththesuperimposedfitfromEq.(4).Theeventsshownsatisfyrequirementsfortheinclusivesearches(left)andtheheavy-flavorsearches (right)inthelow-mass(top)andhigh-mass(bottom)scenarios.Theexpectationfor thetopsquarksignalisindicatedbythebluedashedlineforthelow-masssearch (Mt=250 GeV)andforthehigh-masssearch(Mt=400 GeV).Thebottompartofeachfigureshowsthedifferenceineachbinbetweenthe dataandthebackground estimatedividedbythestatisticaluncertaintyassociatedwiththedata,withtheshadedregionindicatingtheexpecteddistributioninthecaseofthetopsquarksignal appearingindata.Thelastbinineachmavdistributionalsoincludesalloverflowmavevents.

Afterallselectionrequirementsareapplied,thefractionof sig-naleventsremaining intheheavy-flavor search rangesfrom0.4% to 1.2% for the low-mass search and from 0.4% to 1.6% for the high-mass search. Forthe inclusive search, the fraction of signal eventsremainingrangesfrom1.4%to7.4%forthelow-masssearch andfrom1.4% to 6.5% forthe high-mass search. In all scenarios, the leading efficiency loss is due to the required jet pT thresh-olds.Inthedata,approximately20%oftheselectedeventspassing the high-mass search criteria are incommon withthe low-mass search.

6. Backgroundestimationandsystematicuncertainties

ThedominantbackgroundforthissearchcomesfromSM mul-tijetevents.Followinga methodusedpreviously forsimilar reso-nancesearches [42–45],the steeply falling SM backgroundshape ismodeledwiththeuseofafour-parameterfunction:

dN dmav= p0 1−m_√av s p1 m_√av s p2+p3logmav√_s , (4)

whereN isthenumberofeventsand p0 through p3 are parame-tersofthefunction.Localizeddeviationsofthedatafromthe back-groundhypothesis are indicationsofa signal, andthefitteddata distributionsforthefoursearchscenariosareshowninFig. 5.The searchitselfisrestrictedtotheregionmodeledbythebackground

parameterization,whichbeginsat200 GeVforthelow-mass sce-narioandat300 GeV forthehigh-mass scenario.The agreement ofeachbackgroundfittoitsrespectivemassdistributionis quan-tifiedbycomputingineachbinthedifferenceofthedataandthe fit,dividedby thestatisticaluncertaintyassociatedwiththedata. These distributionsindicate that nosignificant deviationisfound inanyofthefoursearchscenarios.

The dominant systematic uncertainties that affect the yield originate from six sources: the imperfect knowledge of the in-tegrated luminosity (2.6%) [1]; the simulation of initial-state ra-diation (5%) [28]; the precision of the jet energy corrections (1–6.2%) [25]; thejet energyresolution (10%) [25]; theefficiency of btagging(2%) [27];the modeling oftheeffect ofmultiplepp interactions (<1.5%)[46].Weuselog-normal priorstomodel sys-tematicuncertaintiesonthesignal,whicharetreatedasnuisance parameters.Toensurethatthechoiceofbackground parameteriza-tiondoesnotintroduceanybiastotheestimateofthebackground obtainedfromthe fit,studiesare performedtoderive the appro-priate associated uncertainties. For the choice of function used to model the background shape, we consider several families of functionsasabasisofcomparison:exponentials,power-law func-tions,andLaurentseries.Usingamethodpreviouslyemployedby CMS [47],we study thedifference inexpected yieldin the pres-ence of a signal by using each of thesefunctions instead of the defaultone,usingsimulatedSM eventsasthedefaultbackground shapeasinputtothepseudo-experiments.

For each pseudo-experiment, each of the parameterizations is fittothefluctuatedbackgroundshape,andthelargestvalueofthe

fractional difference between the alternate fit resultand the de-faultoneiscalculatedforeverymav bin.Themeanoftheresulting distributionis takenasthebin-by-bin uncertainty foreach alter-nateparameterization,andtheaverageofthealternate parameter-izationuncertainties determines theoverall assigned uncertainty. Thisuncertaintyincreaseswithmav from0.3%to0.6%inthe low-masssearch range,andfrom0.5%to30% inthehigh-mass search range.

7.Results

We set upper limits on the production cross section using a Bayesianformalismwithauniformpriorforthecrosssection.The binnedlikelihoodL canbewrittenas

L= i μni i e−μi ni! , (5)

where μi is definedas μi=αNi(S) +Ni(B) andni is the mea-surednumberofevents inthe ithbinofmav.Here, Ni(S) isthe numberofexpectedeventsfromthesignalintheithmav bin, αis aconstanttoscalethesignalamplitude,andNi(B)isthenumber ofexpectedeventsfrombackgroundin theithmav bin.The like-lihoodis combined withthe prior andnuisance parameters,and thenmarginalizedtogivetheposteriordensityforthesignalcross section.Integratingtheposteriordensityto0.95ofthetotalgives the95% CLlimit forthe signal crosssection. Theexpected limits onthecrosssectionareestimatedwithpseudo-experiments gener-atedusingbackgroundshapes,obtainedbysignal-plus-background fitstothedata.Closuretestsareperformedwhereafixedsignalis injected,andtheseconfirmthat thepresenceofsignal wouldnot behiddenintheestimatedbackground.

Fig. 6 shows the observed and expected 95% CL upper lim-its on σ, the cross section, anda dotted red line indicating the NLO+NLL predictions fortop squark production[32–36],where thetopsquarkmassisequaltomav.Theverticaldashedblueline atatopsquarkmassof300 GeVindicatesthetransitionfromthe low- tothehigh-masslimits,andatthismasspointthelimitsare shownforboth analyses.Theproductionoftop squarks undergo-ingRPVdecaysintolight-flavorjetsisexcludedat95%CLfortop squarkmassesfrom200to350 GeV.Topsquarkswhosedecay in-cludesaheavy-flavorjetareexcludedformassesbetween200and 385 GeV.Weexcludetheproductionofcoloronsdecayingintofour jetsat95% CL formasses between200and 835 GeV,asseen in Fig. 7.

8. Summary

Asearch hasbeenperformedforpairproductionofheavy res-onancesdecaying topairs ofjets infour-jet eventsfromproton– protoncollisions at √s=8 TeV with the CMS detector. The dis-tributioninthe averagemass ofselecteddijetpairs hasbeen in-vestigated forlocalized disagreements between the data andthe backgroundestimate.Thismethodtakesadvantageofanumberof additionaloptimizedkinematicrequirementsimposedonthedijet pair.Nosignificantdeviationisfoundbetweentheselectedevents andthe expectedstandardmodelmultijet background.Limits are placedontheproductionofcoloronsdecayingintofourjetswitha 100%branchingfraction,excludingat95%confidencelevel,masses between200 and835 GeV. Forthis model,these resultsinclude firstlimitsinthemassrangesof200–250 GeVand740–835 GeV, extending previous limits [16] to lower masses by 50 GeV, and to higher masses by 95 GeV. Limits are set on top squark pair productionthrough the λ_UDD couplingto final states witheither only light-flavor jets or both light- and heavy-flavor jets with a 100%branchingfraction.Weexcludeata95%confidenceleveltop

Fig. 6. Observedandexpected95%CLcrosssectionlimitsasafunctionoftopsquark mass forthe inclusive(top)and heavy-flavor(bottom) RPVtopsquarksearches basedonresults fromthelow-mass(a)andhigh-mass(b)scenarios.Thedotted redlineshowstheNLO+NLLpredictionsfortopsquarkproduction,andthe ver-ticaldashedbluelineindicatestheboundaryofthelimitsbetweenthelow- and high-massscenarios.

Fig. 7. Observedandexpected95%CLcrosssectionlimitsasafunctionofcoloron massforthepair-producedcoloronsearchbasedonresultsfromthelow-mass (a) andhigh-mass(b)scenarios.ThedottedredlineshowstheNLO+NLLpredictions forcoloronpairproduction,andtheverticaldashedbluelineindicatestheboundary ofthelimitsbetweenthelow- andhigh-massscenarios.

squark productionfollowed by R-parity violating decaysto light-flavorjetsfortopsquarkmassesfrom200to350 GeVanddecays to heavy-flavor jets for massesbetween 200 and385 GeV. Both sets oflimitsare the moststringentsuch limitsto date,and the firstfromtheLHC forthismodelofR-parityviolatingtop squark decay.

Acknowledgements

WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the

technicalandadministrativestaffs atCERN andatother CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcentersand personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythe computinginfrastructureessential to ouranalyses. Finally, we acknowledge the enduring support for the construc-tionandoperation oftheLHCandthe CMSdetectorprovidedby thefollowingfundingagencies:BMWFWandFWF(Austria);FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES(Bulgaria);CERN;CAS,MOST,andNSFC(China);COLCIENCIAS (Colombia);MSESandCSF(Croatia);RPF(Cyprus);MoER,ERCIUT andERDF(Estonia);Academy ofFinland,MEC,andHIP(Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); LAS (Lithuania); MOE and UM(Malaysia); CINVESTAV, CONACYT,SEP,andUASLP-FAI(Mexico);MBIE(NewZealand);PAEC (Pakistan);MSHEandNSC(Poland);FCT(Portugal);JINR(Dubna); MON,RosAtom,RASandRFBR(Russia);MESTD(Serbia);SEIDIand CPAN(Spain);SwissFundingAgencies(Switzerland);MST(Taipei); ThEPCenter,IPST, STARandNSTDA(Thailand);TÜBITAK and TAEK (Turkey);NASUandSFFR(Ukraine); STFC(United Kingdom);DOE andNSF(USA).

Individuals have received support from the Marie-Curie pro-gramandtheEuropeanResearchCouncilandEPLANET(European Union); the Leventis Foundation; the A.P. Sloan Foundation; the Alexandervon HumboldtFoundation;theBelgianFederal Science Policy Office; the Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); theMinistry ofEducation,Youth andSports (MEYS)of theCzech Republic; theCouncil ofScientific and Industrial Research,India; theHOMING PLUSprogram ofFoundation ForPolish Science, co-financed from European Union, Regional Development Fund; the CompagniadiSanPaolo(Torino); theConsorzioper laFisica (Tri-este); MIUR project 20108T4XTM (Italy); the Thalis and Aristeia programs cofinanced by EU-ESF and the Greek NSRF; and the National Priorities Research Program by Qatar National Research Fund.

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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, S. Bansal,T. Cornelis,E.A. De Wolf, X. Janssen,A. Knutsson, J. Lauwers, S. Luyckx, S. Ochesanu,R. Rougny, M. Van De Klundert, H. Van Haevermaet,P. Van Mechelen,N. Van Remortel, A. Van Spilbeeck

UniversiteitAntwerpen,Antwerpen,Belgium

F. Blekman,S. Blyweert, J. D’Hondt,N. Daci, N. Heracleous, J. Keaveney,S. Lowette, M. Maes,A. Olbrechts, Q. Python, D. Strom, S. Tavernier,W. Van Doninck, P. Van Mulders, G.P. Van Onsem,I. Villella

VrijeUniversiteitBrussel,Brussel,Belgium

C. Caillol, B. Clerbaux, G. De Lentdecker, D. Dobur, L. Favart, A.P.R. Gay, A. Grebenyuk,A. Léonard, A. Mohammadi, L. Perniè2,A. Randle-conde, T. Reis,T. Seva, L. Thomas, C. Vander Velde, P. Vanlaer, J. Wang, F. Zenoni

UniversitéLibredeBruxelles,Bruxelles,Belgium

V. Adler,K. Beernaert, L. Benucci, A. Cimmino,S. Costantini, S. Crucy, S. Dildick,A. Fagot, G. Garcia, J. Mccartin,A.A. Ocampo Rios, D. Poyraz, D. Ryckbosch, S. Salva Diblen,M. Sigamani, N. Strobbe, F. Thyssen,M. Tytgat, E. Yazgan, N. Zaganidis

GhentUniversity,Ghent,Belgium

S. Basegmez, C. 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, L. Perrini, A. Pin, K. Piotrzkowski,A. Popov5, L. Quertenmont,M. Selvaggi, M. Vidal Marono, J.M. Vizan Garcia

N. Beliy, T. Caebergs,E. Daubie, G.H. Hammad UniversitédeMons,Mons,Belgium

W.L. Aldá Júnior, G.A. Alves,L. Brito, M. Correa Martins Junior,T. Dos Reis Martins, J. Molina, C. Mora Herrera,M.E. Pol, P. Rebello Teles

CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

W. Carvalho,J. Chinellato6,A. Custódio, E.M. Da Costa, D. De Jesus Damiao, C. De Oliveira Martins, S. Fonseca De Souza, H. Malbouisson, D. Matos Figueiredo,L. Mundim, H. Nogima,W.L. Prado Da Silva, J. Santaolalla, A. Santoro,A. Sznajder, E.J. Tonelli Manganote6,A. Vilela Pereira

UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

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

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

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

InstituteforNuclearResearchandNuclearEnergy,Sofia,Bulgaria

A. Dimitrov, I. Glushkov,L. Litov, B. Pavlov,P. Petkov 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,Z. Xu, W. Zou StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

C. Avila,A. Cabrera, L.F. Chaparro Sierra, C. Florez, J.P. Gomez, B. Gomez Moreno,J.C. Sanabria UniversidaddeLosAndes,Bogota,Colombia

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

UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia Z. Antunovic, M. Kovac

UniversityofSplit,FacultyofScience,Split,Croatia

V. Brigljevic,K. Kadija, J. Luetic, D. Mekterovic, L. Sudic InstituteRudjerBoskovic,Zagreb,Croatia

A. Attikis, G. Mavromanolakis, J. Mousa,C. Nicolaou, F. Ptochos, P.A. Razis UniversityofCyprus,Nicosia,Cyprus

M. Bodlak,M. Finger, M. Finger Jr.8 CharlesUniversity,Prague,CzechRepublic

Y. Assran9, S. Elgammal10,A. Ellithi Kamel11,A. Radi12,13

M. Kadastik, M. Murumaa, M. Raidal, A. Tiko NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia P. Eerola,M. Voutilainen

DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland

J. Härkönen,V. Karimäki, R. Kinnunen, M.J. Kortelainen, T. Lampén, K. Lassila-Perini,S. Lehti, T. Lindén, P. Luukka, T. Mäenpää,T. Peltola, E. Tuominen, J. Tuominiemi, E. Tuovinen,L. Wendland

HelsinkiInstituteofPhysics,Helsinki,Finland J. Talvitie,T. Tuuva

LappeenrantaUniversityofTechnology,Lappeenranta,Finland

M. Besancon,F. Couderc, M. Dejardin, D. Denegri,B. Fabbro, J.L. Faure, C. Favaro, F. Ferri, S. Ganjour, A. Givernaud, P. Gras, G. Hamel de Monchenault,P. Jarry, E. Locci, J. Malcles,J. Rander, A. Rosowsky, M. Titov

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

S. Baffioni,F. Beaudette, P. Busson, E. Chapon,C. Charlot, T. Dahms, M. Dalchenko,L. Dobrzynski, N. Filipovic,A. Florent, R. Granier de Cassagnac, L. Mastrolorenzo, P. Miné, I.N. Naranjo,M. Nguyen, C. Ochando, G. Ortona,P. Paganini, S. Regnard, R. Salerno,J.B. Sauvan, Y. Sirois,C. Veelken, Y. Yilmaz, A. Zabi

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, K. Skovpen, P. Van Hove InstitutPluridisciplinaireHubertCurien,UniversitédeStrasbourg,UniversitédeHauteAlsaceMulhouse,CNRS/IN2P3,Strasbourg,France

S. Gadrat

CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France

S. Beauceron,N. Beaupere, C. Bernet7, 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

InstituteofHighEnergyPhysicsandInformatization,TbilisiStateUniversity,Tbilisi,Georgia

C. Autermann,S. Beranek, M. Bontenackels, M. Edelhoff,L. Feld, A. Heister, K. Klein, M. Lipinski, A. Ostapchuk,M. Preuten, F. Raupach, J. Sammet, S. Schael, J.F. Schulte,H. Weber, B. Wittmer, V. 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

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,O. Pooth, A. Stahl

RWTHAachenUniversity,III.PhysikalischesInstitutB,Aachen,Germany

M. Aldaya Martin,I. Asin, N. Bartosik, J. Behr, U. Behrens,A.J. Bell, A. Bethani, K. Borras, A. Burgmeier, A. Cakir,L. Calligaris, A. Campbell, S. Choudhury, F. Costanza, C. Diez Pardos,G. Dolinska, S. Dooling, T. Dorland,G. Eckerlin, D. Eckstein, T. Eichhorn, G. Flucke, J. Garay Garcia, A. Geiser, A. Gizhko, P. Gunnellini, J. Hauk, M. Hempel15, 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, E. Ntomari,H. Perrey, D. Pitzl,R. Placakyte, A. Raspereza,

P.M. Ribeiro Cipriano, B. Roland,E. Ron, M.Ö. Sahin, J. Salfeld-Nebgen,P. Saxena, T. Schoerner-Sadenius, M. Schröder, C. Seitz,S. Spannagel, A.D.R. Vargas Trevino,R. Walsh, C. Wissing

DeutschesElektronen-Synchrotron,Hamburg,Germany

V. Blobel, M. Centis Vignali, A.R. Draeger,J. Erfle, E. Garutti, K. Goebel, M. Görner, J. Haller,

M. Hoffmann,R.S. Höing, A. Junkes, H. Kirschenmann,R. Klanner, R. Kogler, 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. Hauth,U. Husemann, I. Katkov5,

A. Kornmayer2, P. Lobelle Pardo, M.U. Mozer, T. Müller,Th. Müller, A. Nürnberg, G. Quast, K. Rabbertz, S. Röcker, H.J. Simonis,F.M. Stober, R. Ulrich, J. Wagner-Kuhr, S. Wayand,T. Weiler, R. Wolf

InstitutfürExperimentelleKernphysik,Karlsruhe,Germany

G. Anagnostou, G. Daskalakis,T. Geralis,V.A. Giakoumopoulou, A. Kyriakis, D. Loukas, A. Markou, C. Markou, A. Psallidas, I. Topsis-Giotis

InstituteofNuclearandParticlePhysics(INPP),NCSRDemokritos,AghiaParaskevi,Greece

A. Agapitos, S. Kesisoglou, A. Panagiotou, N. Saoulidou, E. Stiliaris UniversityofAthens,Athens,Greece

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

UniversityofIoánnina,Ioánnina,Greece

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

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

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

PanjabUniversity,Chandigarh,India

Ashok Kumar,Arun Kumar, S. Ahuja, A. Bhardwaj,B.C. Choudhary, A. Kumar,S. Malhotra, M. Naimuddin, K. Ranjan,V. Sharma

UniversityofDelhi,Delhi,India

S. Banerjee, S. Bhattacharya, K. Chatterjee,S. Dutta, B. Gomber, Sa. Jain, Sh. Jain,R. Khurana,A. Modak, S. Mukherjee,D. Roy, S. Sarkar, M. Sharan

SahaInstituteofNuclearPhysics,Kolkata,India

A. Abdulsalam,D. Dutta, V. Kumar, A.K. 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. Sharmaa, L. Silvestrisa,2,R. Vendittia,b,P. Verwilligena

a_{INFNSezionediBari,Bari,Italy} b_{UniversitàdiBari,Bari,Italy} c_{PolitecnicodiBari,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,A.M. Rossia,b,T. Rovellia,b, G.P. Sirolia,b_{,N. Tosi}a,b_{, R. Travaglini}a,b

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

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

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

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

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

L. Benussi, S. Bianco, F. Fabbri,D. Piccolo INFNLaboratoriNazionalidiFrascati,Frascati,Italy

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

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

M.E. Dinardoa,b,S. Fiorendia,b, 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,2,D. Menascea,L. Moronia,

M. Paganonia,b_{,D. Pedrini}a_{,S. Ragazzi}a,b_{, N. Redaelli}a_{,T. Tabarelli de Fatis}a,b a_{INFNSezionediMilano–Bicocca,Milano,Italy}

b_{UniversitàdiMilano–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

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

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

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

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

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

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

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

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

K. Androsova,25,P. Azzurria,G. Bagliesia,J. Bernardinia,T. Boccalia,G. Broccoloa,c,R. Castaldia, M.A. Cioccia,25_{, R. Dell’Orso}a_{,S. Donato}a,c,2_{, G. Fedi,F. Fiori}a,c_{,L. Foà}a,c_{,A. Giassi}a_{, M.T. Grippo}a,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

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

c_{ScuolaNormaleSuperiorediPisa,Pisa,Italy}

L. Baronea,b,F. Cavallaria, G. D’imperioa,b,D. Del Rea,b,M. Diemoza, C. Jordaa,E. Longoa,b,

F. Margarolia,b,P. Meridiania,F. Michelia,b,2, G. Organtinia,b, R. Paramattia,S. Rahatloua,b,C. Rovellia, F. Santanastasioa,b, L. Soffia,b,P. Traczyka,b,2

a_{INFNSezionediRoma,Roma,Italy} b_{UniversitàdiRoma,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. Costa}a,b_{, R. Covarelli,A. Degano}a,b_{, N. Demaria}a_{,L. Finco}a,b,2_{, C. Mariotti}a_,

M. Pelliccionia, G.L. Pinna Angionia,b,A. Potenzaa,b, A. Romeroa,b,M. Ruspaa,c,R. Sacchia,b, A. Solanoa,b,A. Staianoa, U. Tamponia

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

c_{UniversitàdelPiemonteOrientale(Novara),Torino,Italy}

S. Belfortea,V. Candelisea,b,2,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} b_{UniversitàdiTrieste,Trieste,Italy}

S. Chang,A. Kropivnitskaya, S.K. Nam KangwonNationalUniversity,Chunchon,RepublicofKorea

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

T.J. Kim, M.S. Ryu

ChonbukNationalUniversity,Jeonju,RepublicofKorea J.Y. Kim,D.H. Moon, 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

H.D. Yoo

SeoulNationalUniversity,Seoul,RepublicofKorea M. Choi,J.H. Kim, I.C. Park, G. Ryu UniversityofSeoul,Seoul,RepublicofKorea

Y. Choi,Y.K. Choi,J. Goh, D. Kim, E. Kwon, J. Lee, 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 Cruz, A. Hernandez-Almada,R. Lopez-Fernandez, A. Sanchez-Hernandez

CentrodeInvestigacionydeEstudiosAvanzadosdelIPN,MexicoCity,Mexico S. Carrillo Moreno, F. Vazquez Valencia UniversidadIberoamericana,MexicoCity,Mexico

I. Pedraza, H.A. Salazar Ibarguen BenemeritaUniversidadAutonomadePuebla,Puebla,Mexico 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

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

S. Afanasiev,P. Bunin,M. Gavrilenko, I. Golutvin,I. Gorbunov, A. Kamenev, V. Karjavin,V. Konoplyanikov, A. Lanev,A. Malakhov,V. Matveev28, P. Moisenz, V. Palichik,V. Perelygin, S. Shmatov, N. Skatchkov, V. Smirnov, A. Zarubin

JointInstituteforNuclearResearch,Dubna,Russia

V. Golovtsov, Y. Ivanov, V. Kim29,E. Kuznetsova, 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. Azarkin30, I. Dremin30,M. Kirakosyan, A. Leonidov30, G. Mesyats,S.V. Rusakov, A. Vinogradov

P.N.LebedevPhysicalInstitute,Moscow,Russia

A. Belyaev,E. Boos, M. Dubinin31, L. Dudko, A. Ershov, A. Gribushin, V. Klyukhin, O. Kodolova,I. Lokhtin, S. Obraztsov,S. Petrushanko, V. Savrin,A. Snigirev

SkobeltsynInstituteofNuclearPhysics,LomonosovMoscowStateUniversity,Moscow,Russia

I. Azhgirey,I. Bayshev,S. Bitioukov, V. Kachanov, A. Kalinin, D. Konstantinov, V. Krychkine, V. Petrov, R. Ryutin, A. Sobol, L. Tourtchanovitch,S. Troshin, N. Tyurin, A. Uzunian,A. Volkov

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, 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,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, L. Orsini, L. Pape,E. Perez, A. Petrilli, G. Petrucciani,A. Pfeiffer,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, M. Marionneau, P. Martinez Ruiz del Arbol,M. Masciovecchio, D. Meister, N. Mohr,P. Musella, C. Nägeli36, F. Nessi-Tedaldi, F. Pandolfi, F. Pauss,L. Perrozzi,M. Peruzzi, M. Quittnat, L. Rebane, M. Rossini,A. Starodumov37, M. Takahashi, K. Theofilatos,R. Wallny, H.A. Weber

InstituteforParticlePhysics,ETHZurich,Zurich,Switzerland

C. Amsler38,M.F. Canelli, V. Chiochia,A. De Cosa, A. Hinzmann, T. Hreus, B. Kilminster, C. Lange, B. Millan Mejias, J. Ngadiuba,D. Pinna,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. Chao, K.F. Chen, P.H. Chen, C. Dietz, U. Grundler,W.-S. Hou, Y.F. Liu,R.-S. Lu, 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, Y. Guler, 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, C. Zorbilmez

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. Seif El Nasr-storey, S. Senkin, V.J. Smith

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, T. Williams, W.J. Womersley, S.D. Worm

RutherfordAppletonLaboratory,Didcot,UnitedKingdom

M. Baber, R. Bainbridge,O. Buchmuller, D. Burton,D. Colling, N. Cripps, P. Dauncey,G. Davies, M. Della Negra, P. Dunne,A. Elwood, 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, I.D. Reid, P. Symonds, L. Teodorescu, M. Turner

BrunelUniversity,Uxbridge,UnitedKingdom

J. Dittmann, K. Hatakeyama,A. Kasmi, H. Liu, T. Scarborough,Z. Wu BaylorUniversity,Waco,USA

O. Charaf,S.I. Cooper, C. Henderson, P. Rumerio TheUniversityofAlabama,Tuscaloosa,USA

A. Avetisyan, T. Bose,C. Fantasia, P. Lawson, C. Richardson, J. Rohlf, J. St. John,L. Sulak BostonUniversity,Boston,USA

J. Alimena,E. Berry, S. Bhattacharya, G. Christopher, D. Cutts, Z. Demiragli, N. Dhingra, A. Ferapontov, A. Garabedian,U. Heintz, G. Kukartsev, E. Laird,G. Landsberg, M. Luk, M. Narain, M. Segala,

T. Sinthuprasith,T. Speer, J. Swanson BrownUniversity,Providence,USA

R. Breedon,G. Breto, M. Calderon De La Barca Sanchez, S. Chauhan,M. Chertok, J. Conway, R. Conway, P.T. Cox,R. Erbacher, M. Gardner, W. Ko, R. Lander, M. Mulhearn, D. Pellett, J. Pilot, F. Ricci-Tam, S. Shalhout, J. Smith, M. Squires, D. Stolp, M. Tripathi,S. Wilbur, R. Yohay

UniversityofCalifornia,Davis,Davis,USA

R. Cousins,P. Everaerts,C. Farrell, J. Hauser, M. Ignatenko,G. Rakness, E. Takasugi, V. Valuev, M. Weber UniversityofCalifornia,LosAngeles,USA

K. Burt,R. Clare, J. Ellison, J.W. Gary, G. Hanson,J. Heilman, M. Ivova Rikova, P. Jandir, E. Kennedy, F. Lacroix,O.R. Long, A. Luthra, M. Malberti,M. Olmedo Negrete, A. Shrinivas,S. Sumowidagdo, S. Wimpenny

UniversityofCalifornia,Riverside,Riverside,USA

J.G. Branson, G.B. Cerati,S. Cittolin, R.T. D’Agnolo, A. Holzner, R. Kelley, D. Klein, J. Letts,I. Macneill, D. Olivito,S. Padhi, C. Palmer, M. Pieri, M. Sani,V. Sharma, S. Simon, M. Tadel,Y. Tu,A. Vartak, C. Welke, F. Würthwein,A. Yagil,G. Zevi Della Porta

UniversityofCalifornia,SanDiego,LaJolla,USA

D. Barge, J. Bradmiller-Feld, C. Campagnari, T. Danielson,A. Dishaw, V. Dutta,K. Flowers,

M. Franco Sevilla,P. Geffert,C. George, F. Golf, L. Gouskos, J. Incandela,C. Justus, N. Mccoll, S.D. Mullin, J. Richman, D. Stuart,W. To,C. West, J. Yoo

UniversityofCalifornia,SantaBarbara,SantaBarbara,USA

A. Apresyan,A. Bornheim, J. Bunn, Y. Chen, J. Duarte,A. Mott, H.B. Newman, C. Pena,M. Pierini, M. Spiropulu,J.R. Vlimant, R. Wilkinson, S. Xie, R.Y. Zhu

CaliforniaInstituteofTechnology,Pasadena,USA

V. Azzolini,A. Calamba, B. Carlson, T. Ferguson, Y. Iiyama,M. Paulini, J. Russ, H. Vogel, I. Vorobiev CarnegieMellonUniversity,Pittsburgh,USA

J.P. Cumalat,W.T. Ford, A. Gaz, M. Krohn, E. Luiggi Lopez,U. Nauenberg, J.G. Smith, K. Stenson, S.R. Wagner

UniversityofColoradoatBoulder,Boulder,USA

J. Alexander, A. Chatterjee, J. Chaves,J. Chu, S. Dittmer,N. Eggert, N. Mirman, G. Nicolas Kaufman, J.R. Patterson,A. Ryd, E. Salvati, L. Skinnari,W. Sun, W.D. Teo, J. Thom, J. Thompson, J. Tucker,Y. Weng, L. Winstrom,P. Wittich

CornellUniversity,Ithaca,USA D. Winn