Search for dijet resonances in proton-proton collisions at root s=13 TeV and constraints on dark matter and other models

Contents lists available atScienceDirect

Physics

Letters

B

www.elsevier.com/locate/physletb

Search

for

dijet

resonances

in

proton–proton

collisions

at

√

s

=

13

TeV

and

constraints

on

dark

matter

and

other

models

.TheCMS Collaboration CERN,Switzerland

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

Articlehistory:

Received11November2016

Receivedinrevisedform21January2017 Accepted6February2017

Availableonline14February2017 Editor:M.Doser Keywords: CMS Physics Search Exotica Dijet Resonance

A search is presented for narrow resonances decaying to dijet final states in proton–proton collisions at

√

s=13 TeV using data corresponding to an integrated luminosity of 12.9 fb−1_{. The dijet mass spectrum}

is well described by a smooth parameterization and no significant evidence for the production of new particles is observed. Upper limits at 95% confidence level are reported on the production cross section for narrow resonances with masses above 0.6 TeV. In the context of specific models, the limits exclude string resonances with masses below 7.4 TeV, scalar diquarks below 6.9 TeV, axigluons and colorons below 5.5 TeV, excited quarks below 5.4 TeV, color-octet scalars below 3.0 TeV, W_{bosons below}

2.7 TeV, Z _{bosons below 2.1 TeV and between 2.3 and 2.6 TeV, and RS gravitons below 1.9 TeV. These}

extend previous limits in the dijet channel. Vector and axial-vector mediators in a simplified model of interactions between quarks and dark matter are excluded below 2.0 TeV. The first limits in the dijet channel on dark matter mediators are presented as functions of dark matter mass and are compared to the exclusions of dark matter in direct detection experiments.

©2017 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3_.

1. Introduction

Thedijetmass(mjj) spectruminproton–proton(pp) collisions

arisingfromtheproductionofpartonsathightransverse momen-tum(pT) ispredictedby quantumchromodynamics (QCD) tofall

smoothly withincreasing dijetmass.Manymodelsofphysics be-yondthestandardmodel(SM)requirenewparticlesthatcoupleto quarks(q)andgluons(g)andcanbeobservedasresonancesinthe dijetmassspectrum.Oneexampleisamodelinwhichdarkmatter (DM)particlescoupletoquarksthroughaDMmediator.This me-diatorcandecayto eitherapairofDMparticlesora pairofjets andthereforecan be observedasa dijetresonance [1]. Here,we reportasearch fornarrowdijetresonances,whicharethosewith naturalwidthsthatare smallcomparedtotheexperimentalmass resolution.

Thisletter presentsthe results oftwo searches fordijet reso-nances,usingdatacollected in2016withtheCMSdetectoratthe CERNLHCinpp collisionsat√s=13TeV,correspondingtoan in-tegratedluminosityof12.9 fb−1.Thefirstisa high-mass search for resonanceswithmassabove1.6 TeVusingdijeteventsthatare re-constructedoffline.Similarhigh-masssearcheswere publishedby

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

CMSandATLASat√s=13TeV[2,3],8 TeV[4–6],and7 TeV[7–13] usingstrategiesreviewedinRef.[14].Themostrecentlypublished high-mass searches useddatacollected in 2015corresponding to anintegratedluminosityof2.4 fb−1_{byCMS[2]and3.6 fb}−1_by

AT-LAS[3].Thesecondisa low-mass search forresonanceswithmass between0.6and1.6 TeVusingdijeteventsthat arereconstructed, selected,andrecordedinacompactformbythehigh-leveltrigger (HLT) ina technique calleddata scouting [15]. Data scoutingwas previouslyusedforasimilarlow-masssearchpublishedbyCMSat √

s=8TeV[16].

We present model-independent results and, in addition, con-sider the following benchmark models of s-channel dijet reso-nances: string resonances [17,18], scalar diquarks [19], axiglu-ons [20,21], colorons [21,22], excited quarks (q∗) [23,24], color-octet scalars [25], new gauge bosons (W and Z) with SM-like orleptophobiccouplings[26],DMmediators[27,28],andRandall– Sundrum (RS) gravitons (G) [29]. In the color-octet scalar model the squaredanomalous couplingusedis k2

s =1/2 [30],yielding a

width andacross section that ishalf thevalue used inthe pre-vious CMSsearch[2].FollowingtherecommendationsofRef.[27] the DM mediator in a simplified model [28] is assumedto be a spin-1particleandtodecayonlytoqq andpairsofDMparticles, with unknown mass mDM, and with a universal quark coupling

http://dx.doi.org/10.1016/j.physletb.2017.02.012

0370-2693/©2017TheAuthor.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).Fundedby SCOAP3_.

gq=0.25 and a DM coupling gDM=1.0.Otherwise, the specific

choicesofparameters forthe benchmarkmodelsarethe sameas thosethat wereusedinpreviousCMSsearches,andcanbefound inRef.[7].

2. Jetreconstructionandeventselection

TheCMSdetectoranditscoordinatesystem, includingthe az-imuthalangleφandthepseudorapidity η,aredescribedindetail inRef.[31].The centralfeature oftheCMSapparatusis a super-conductingsolenoid of6 m internal diameterproviding an axial fieldof3.8T.Withinthefield volumearelocatedthesiliconpixel andstriptracker(|η|<2.4) andthebarrelandendcap calorime-ters(|η|<3),whichconsistofaleadtungstatecrystal electromag-neticcalorimeter,anda brass andscintillator hadroncalorimeter. Anironandquartz-fiberhadron calorimeterislocatedinthe for-wardregion(3<|η|<5),outsidethefieldvolume.Fortriggering purposesandto facilitatejet reconstruction,the calorimetercells aregroupedintotowersprojectingradiallyoutwardfromthe cen-terofthedetector.

Aparticle-flow(PF)eventalgorithmreconstructsandidentifies each individual particle with an optimized combination of infor-mation from the various elements of the CMS detector [32,33]. Particles are classified as muons, electrons, photons, and either chargedorneutralhadrons.Jetsarereconstructedeitherusing par-ticleflow, givingPF-jets, orfromenergydepositsinthe calorime-ters,givingCalo-jets. PF-jets reconstructed offlineare used inthe high-masssearch,andCalo-jetsreconstructedbytheHLTareused inthelow-masssearch. Toreconstructbothtypesofjets, weuse the anti-kT algorithm [34,35] with a distance parameter of 0.4,

as implemented in the FastJet package [36]. For the high-mass search,atleastone reconstructedvertexisrequired.The primary vertexisdefinedasthevertexwiththehighestsumof p2

T ofthe

associatedtracks.ForPF-jets, chargedPFcandidates not originat-ingfromtheprimary vertexareremoved priorto thejetfinding. Forboth typesof jets, an event-by-event correction basedon jet area[37,38] isappliedto thejetenergyto removetheestimated contribution from additional collisions in the same or adjacent bunchcrossings(pileup).

Eventsareselectedusingatwo-tiertriggersystem.Events sat-isfyingloosejetrequirementsatthe firstlevel(L1)are examined bytheHLT.TheHLTuses HT,thescalarsumofthejet pT fromall

jetsintheeventwith|η|<3 thatsatisfy ajet pT requirement,to

selectevents.Forthehigh-mass search,PF-jets with pT>30GeV

are used to compute HT, andevents are accepted by the HLT if

theysatisfytherequirement HT>800GeV.Wethenselectevents

withmjj>1.06TeV for which the combined L1 trigger and HLT

arefound tobe fullyefficient.Forthelow-mass search,when an eventpasses the HLT, the Calo-jets reconstructed at the HLT are saved,alongwiththeeventenergydensityandmissingtransverse momentumreconstructed fromthe calorimeter.The shorter time foreventreconstructionofcalorimeterquantitiesandthereduced eventsize recordedfor theseevents allow areduced HT

thresh-old compared to thehigh-mass search. Forthe low-mass search, Calo-jets with pT>40GeV are used to compute HT, the

thresh-oldis HT>250GeV,andweselecteventswith mjj>0.45TeV for

whichthetriggerisfullyefficient.

Thejet momentaand energies are corrected usingcalibration constantsobtainedfromsimulation,testbeamresults,andpp col-lision data at √s=13TeV. The methods described in Ref. [38] are used and all in-situ calibrations are obtained from the cur-rentdata.AlljetsarerequiredtohavepT>30GeV and |η|<2.5.

The two jets with largest pT are defined as the leading jets. Jet

identification(ID)criteriaareapplied toremove spurious jets as-sociatedwithcalorimeternoise.ThejetIDforPF-jetsisdescribed

in Ref. [39]. The jet ID for Calo-jets requires that the jet be de-tectedbyboththeelectromagneticandhadroniccalorimeterswith the fraction of jet energy deposited within the electromagnetic calorimeterbetween 5and95% of the totaljet energy. An event isrejectedifeitherofthetwoleadingjetsfailsthejetIDcriteria.

Spatially closejetsare combinedinto “wide jets”andusedto determine the dijet mass, asin the previous CMS searches [4,6, 7,10]. The wide-jet algorithm,designed fordijetresonance event reconstruction, reduces the analysis sensitivity to gluon radia-tion from the final-state partons. The two leading jets are used as seeds and the four-vectors of all other jets, if within R = 

(η)2_{+ (φ)}2_{<1.1, are added to the nearest leading jet to}

obtaintwowidejets,whichthenformthedijetsystem.The back-groundfrom t-channel dijeteventspeaksatlargevaluesof|ηjj|

and is suppressed by requiring the pseudorapidity separation of thetwo wide jetstosatisfy |ηjj|<1.3. Theabove requirements

maximize thesearch sensitivityforisotropicdecaysof dijet reso-nancesinthepresenceofQCDdijetbackground.Forthelow-mass search,afterwidejetreconstructionandeventselection,weusea correctionderivedfromasmallersample ofdijetdatatocalibrate the wide jetsreconstructed fromCalo-jets atHLT. With this cor-rection,basedona dijetbalancetag-and-probemethodsimilarto that discussed inRef. [38], thewide jetsfrom Calo-jetshave the sameresponseasthosereconstructedfromPF-jets.

3. Dijetmassspectrumandfit

Fig. 1 showsthe dijet mass spectra, defined as the observed numberofeventsineachbindividedbytheintegratedluminosity and thebin width, withpredefined bins of widthcorresponding to the dijet mass resolution [12]. The highest mass event has a dijetmassof7.7 TeV.Thedijetmassspectraforboththehigh- and low-masssearchesarefitwiththefollowingparameterization:

dσ

dmjj =

P0(1−x)P1

xP2+P3ln(x) , (1)

where x =mjj/√s and P0, P1, P2, and P3 are four free

param-eters. The functional form in Eq. (1) was also used in previous searches [2–13,16,40] to describe the data. In Fig. 1 we show the result of binned maximum likelihood fits, performed inde-pendently, whichyields the followingchi-squared pernumber of degreesoffreedom: χ2_{/NDF=33.3/42 for thehigh-mass search}

and χ2_{/NDF=17.3/22 for the low-mass search. The dijet mass}

spectraarewellmodeledbythebackgroundfits.Inthelower pan-els ofFig. 1,in theregion ofdijetmassbetween1.1and2.0 TeV, the bin-by-bin differences betweenthe dataand the background fitarenotidenticalinthetwosearchesbecausefluctuationsin re-constructeddijetmassforCalo-jetsandPF-jetsarenotcompletely correlated.

We search for narrowresonances in the dijetmass spectrum. Fig. 1showsexamplesofdijetmassdistributionsforsignalevents generatedwiththe pythia 8.205[41]programwiththeCUETP8M1 tune [42,43] and including a Geant4-based [44] simulation of the CMS detector. The predicted mass distributions have Gaus-siancoresfromjetenergyresolution,andtailstowardslowermass valuesprimarily fromQCD radiation.Thecontribution ofthelow mass tailto the lineshapedependson the partoncontent ofthe resonance (qq, qg, or gg). Resonances containing gluons, which emitmoreQCDradiationthanquarks,arewiderandhaveamore pronounced tail. The signal distributions shown in Fig. 1 are for qq,qg,andgg resonanceswithsignalcrosssectionscorresponding tothelimitsat95%confidencelevel(CL)obtainedbythisanalysis, asdescribed below.There is noevidencefor anarrow resonance inthedata.Themostsignificant excessofthedatarelativetothe

Fig. 1. Dijetmass spectra(points)comparedto afittedparameterizationofthe background(solidcurve)forthelow-masssearch(top)andthehigh-masssearch (bottom).Thelowerpanelineachplotshowsthedifferencebetweenthedataand thefittedparametrization,dividedbythestatisticaluncertaintyofthedata. Pre-dictedsignalsfromnarrowgluon–gluon,quark–gluon,andquark–quarkresonances areshownwithcrosssectionsequaltotheobservedupperlimitsat95%CL.

backgroundfitcomesfromthefiveconsecutivebinsbetween0.74 and1.00 TeVinthelowmasssearchshowninFig. 1.Fittingthese datato qq,qg, andgg resonanceswithamass of0.85 TeVyields localsignificancesof2.2,2.5and2.6standarddeviationsincluding systematicuncertainties,respectively.

4. Limitsondijetresonances

Weusethedijetmassspectrumfromwidejets,thebackground parameterization,andthe dijetresonanceshapesto setlimitson theproductionofnewparticlesdecayingtothepartonpairsqq (or qq),qg,andgg.Aseparatelimitisdeterminedforeachfinalstate

(qq,qg,andgg)becauseofthedependenceofthedijetresonance shapeonthetypesofthetwofinal-statepartons.

Thedominantsourcesofsystematicuncertaintyarethejet en-ergyscaleandresolution,integratedluminosity,andtheestimation ofbackground.Theuncertaintyinthejetenergyscaleinboththe low-massandthehigh-mass searchis2%andisdeterminedfrom √

s=13TeV data using the methods described inRef. [38]. This uncertainty ispropagated to thelimitsby shiftingthe dijetmass shape for signal by ±2%. The uncertainty in the jet energy res-olution translatesintoan uncertaintyof10% in theresolution of the dijetmass[38],andis propagated tothe limitsby observing the effect ofincreasing anddecreasing by 10% the reconstructed widthofthedijetmassshapeforsignal.Theuncertaintyinthe in-tegratedluminosityis6.2%,andispropagatedtothenormalization of thesignal. Changesinthe valuesofthe parametersdescribing thebackgroundintroduceachangeinthesignalstrength,whichis accountedforasasystematicuncertaintyasdiscussedinthenext paragraph.

The modified frequentist method[45,46] isutilized toset up-per limitson signal crosssections,following theprescription de-scribed inRefs. [47,48].We usea multi-bincountingexperiment likelihood,whichisaproductofPoissondistributions correspond-ing todifferentbins.Weevaluate thelikelihoodindependentlyat each value ofresonancepolemass from0.6to1.6 TeVin 50-GeV steps inthelow-masssearch, andfrom1.6to 7.5 TeVin100-GeV stepsinthehigh-masssearch.Thesystematicuncertaintiesare im-plemented asnuisance parameters in the likelihood model,with Gaussian constraintsfor the jet energy scale andresolution, and log-normal constraints fortheintegratedluminosity. The system-atic uncertaintyin the backgroundis automatically evaluated via profiling, effectively refitting for the optimal values of the back-groundparametersforeachvalueofresonancecrosssection.This procedure givesthe same limits asthe Bayesian procedure used previously for dijetresonance searches at CMS [4]. For both the Bayesian and modified frequentist statistical procedures we find that the backgroundsystematicuncertainty hasthe largesteffect on thelimit.The extentto whichthebackgrounduncertainty af-fects thelimit dependssignificantly on thesignal shapeand the resonance mass,with the largesteffect occurringfor the gg res-onances because they are wider, and the smallest effect for qq resonances.The effectdecreasesastheresonancemassincreases. Forexample,consideringtwosignalsshowninFig. 1:foragg res-onanceatamassof0.75 TeVsystematicuncertaintiesincreasethe limit by afactor of3,andfora qq resonance atamass of6 TeV systematicuncertaintiesincreasethelimitbyonly10%.

Signal injectiontestswereperformedtoinvestigatethe poten-tialbiasintroducedthroughthechoiceofbackground parameteri-zation.Pseudo-datageneratedassuminganalternative parameteri-zation,dσ/dmjj=exp(ln(P0)+P1xP2+P1(1−x)P3),werefitwith

thenominalparameterizationgiveninEq.(1).Thebiasinthe ex-tractedsignalwasfoundtobenegligible.Wetriedotherfunctions butdidnot findanywithfourorfewerparameters thatcould fit ourdata.

Fig. 2 shows themodel-independent observedupper limitsat 95%CLontheproductofthecrosssection(σ),thebranching frac-tion (B),andthe acceptance( A) fornarrow resonances,withthe kinematicrequirements|ηjj|<1.3 and |η|<2.5.Theacceptance

of theminimumdijetmass requirementineach search hasbeen evaluated separately forqq,qg, andgg resonances, andhasbeen takenintoaccountbycorrectingthelimits,andthereforedoesnot appear in the acceptance A. The corrections are independent of thespinandcouplingofthenarrowresonanceattheonepercent level. Fig. 2 also shows the expected limitson the cross section andtheirbandsofuncertainty.Thedifferenceinthelimitsforqq,

Fig. 2. Theobserved95%CLupperlimitsontheproductofthecrosssection,branchingfraction,andacceptanceforquark–quark(topleft),quark–gluon(topright),and gluon–gluon(bottomleft)typedijetresonances.Thecorrespondingexpectedlimits(dashed)andtheirvariationsatthe1and2standarddeviationlevels(shadedbands) arealsoshown.Allobservedlimits(solid)arecompared(bottomright).Limitsarecomparedtopredictedcrosssectionsforstringresonances[17,18],excitedquarks[23,24], axigluons[20],colorons[22],scalardiquarks[19],color-octetscalars[25],newgaugebosonsWandZwithSM-likecouplings[26],darkmattermediatorsformDM=1 GeV

[27,28],andRSgravitons[29].

qg,andgg resonancesatthesameresonancemassoriginatesfrom thedifferenceintheirlineshapes.

Allupperlimitspresentedcanbecomparedtotheparton-level predictions of σB A, without detector simulation, to determine mass limits on new particles. The model predictions shown in Fig. 2arecalculatedinthenarrow-widthapproximation[14]using theCTEQ6L1[49] PDFatleadingorder,withanext-to-leading or-dercorrectionfactorofapproximately1.3includedfortheW and Z models, and approximately 1.2 for the axigluon/coloron mod-els[21].The branching fractionincludes the directdecays ofthe resonanceintothefivelightquarksandgluonsonly,excludingtop quarksfromthedecay,althoughtopquarksareincludedinthe cal-culationoftheresonancewidth.Theacceptanceisevaluatedatthe partonlevelfortheresonancedecaytotwopartons.Inthecaseof isotropicdecays,theacceptanceis A ≈0.6 andisindependentof theresonancemass.Foragivenmodel,newparticlesareexcluded at95%CLinmassregionswherethetheoreticalpredictionliesat orabove the observedupper limit fortheappropriate final state ofFig. 2.Forthe RSgraviton model,the decayfractionis60% to quarksand40% togluons,andwe obtainmasslimitsby

compar-Table 1

Observedandexpectedmasslimitsat95%CL.Thelistedmodelsareexcluded be-tween0.6 TeVandtheindicatedmass.Inadditiontotheobservedmasslimitslisted below,thisanalysisalsoexcludesaZinthemassintervalbetween2.3and2.6 TeV.

Model Final state Limit [TeV] Obs. Exp. String qg 7.4 7.4 Scalar diquark qq 6.9 6.8 Axigluon/coloron qq 5.5 5.6 Excited quark qg 5.4 5.4 Color-octet scalar (k2 s=1/2) gg 3.0 3.3 W qq 2.7 3.1 Z qq 2.1 2.3 DM mediator (mDM=1 GeV) qq 2.0 2.0 RS graviton qq, gg 1.9 1.8

ing themodelcrosssection curvetothe weightedaverage ofthe limitsinthe qq andgg finalstates.Masslimitsonallbenchmark modelsaresummarizedinTable 1andaremorestringentthanthe masslimitsin thedijetchannel previously published by CMS[2] andATLAS[3].

Fig. 3. The95%CLupperlimitsontheuniversalquarkcoupling gqasafunction

ofresonancemassforaleptophobicZresonancethatonlycouplestoquarks.The observedlimits(solid),expectedlimits(dashed)andtheirvariationatthe1and2 standarddeviationlevels(shadedbands)areshown.Dottedhorizontallinesshow thecouplingstrengthforwhichthecrosssectionfordijetproductioninthismodel isthesameasforaDMmediator(seetext).

Masslimitsonnewparticlesaresensitivetoassumptionsabout theircoupling.Conversely,atafixedresonancemass,modelswith smallercouplings are excluded by searcheswithincreased sensi-tivity.Fig. 3showsourupperlimitsonthecouplingasafunction ofmassfora modelofaleptophobicZ resonancewitha univer-salquark coupling, g_q [27], relatedtotheZ couplingconvention ofRef.[50]by gq=gB/6.

5. Limitsondarkmatter

Weuse ourlimitsto constrainsimplified models ofDM,with leptophobicvector andaxial-vector mediatorsthatcoupleonlyto quarks and DM particles [27,28]. Fig. 4 shows the excluded val-ues of mediator mass as a function of mDM for both types of

mediators. For mDM=1GeV,indistinguishable fromzero,the

ex-cludedrangeofmediatormass(MMed)isbetween0.6and2.0 TeV,

as also shown in Fig. 2 and listed in Table 1. An additional ex-cludedrangeof0.5<MMed<0.6TeV,notshown,comesfromthe

low-mass search at √s=8TeV [16]. In Fig. 4 the expected up-per value of excluded MMed increases with mDM to as high as

2.65 TeVbecausethebranchingfractiontoqq increaseswith mDM.

If mDM>MMed/2,themediatorcannotdecaytoDMparticles,and

thedijetcrosssectionfromthemediatormodelsbecomesidentical tothatintheleptophobicZmodelusedinFig. 3withacoupling

g_q =gq=0.25. Therefore for thesevalues of mDM the limitson

the mediator mass inFig. 4 are identicalto the limitson the Z massat gq=0.25 inFig. 3.Similarly,if mDM=0,thelimitsonthe

mediatormassinFig. 4areidenticaltothelimitsontheZmass at g_q =gq/



1+16/(3Nf)≈0.182 inFig. 3,where Nf isthe ef-fective number ofquark flavorscontributingto the width ofthe resonance.

AsoutlinedindetailinRef.[27]theseresultscanalsobe com-pared withresults from direct detection experiments.The limits inFig. 4arefirstre-calculatedat90%CL,andthentranslatedinto theplaneoftheDMmassversustheDM-nucleoninteractioncross section fromthepredictedrelationbetweenthe interactioncross sectionandthemediator mass.Anaxial-vector mediator leadsto aspin-dependent crosssection, σSD_{,anda vectormediator leads}

toaspin-independentcrosssection, σSI_{.Fig. 5showsthe}

compar-ison of these results with darkmatter searches by direct

detec-Fig. 4. The95%CLobserved(solid)andexpected(dashed)excludedregionsinthe plane ofdarkmattermassvs.mediatormass,for anaxial-vectormediator (top) andavectormediator(bottom),arecomparedtoconstraintsfromthecosmological relicdensityofDM(lightgray)determinedfromastrophysicalmeasurements[51, 52]and MadDM version2.0.6[53,54]asdescribedinRef.[55].Followingthe rec-ommendationoftheLHCDMworkinggroup[27,28],theexclusionsarecomputed forDiracDMandforauniversalquarkcouplinggq=0.25 andforaDMcoupling

ofgDM=1.0.Itshouldalsobenotedthattheexcludedregionstronglydependson

thechosencouplingandmodelscenario.Therefore,theexcludedregionsandrelic densitycontoursshowninthisplotarenotapplicabletootherchoicesofcoupling valuesormodels.

tion[56–63].ThegapintheCMSexcluded regioninFig. 5 corre-spondstoastructurewithastatisticalsignificanceofonestandard deviation seen at a mass of 2.2 TeVin Figs. 1–4. For our bench-mark model the present search excludes a significantly smaller σSD _{thanthedirect detectionexperiments,andacompetitive}

re-gion of σSI_{. We note that the absolute exclusion of this search,}

aswellasitsrelativeimportance withrespecttoother dark mat-tersearches,stronglydependsonthechosencouplingandmodel scenario.Nevertheless,thisbenchmarkmodel,avectororan axial-vector mediator withauniversal quark coupling gq=0.25 and a

DMcouplingof gDM=1.0,illustratesthatdijetsearchescanplace

significantboundsonrelevantDMmodelsandthusareimportant ingredientsinthesearchforDM.

6. Summary

Two searches for narrow resonances decaying into a pair of jetshavebeen performedusingproton–protoncollisions at√s=

Fig. 5. Excludedregionsat90%CLintheplaneofdarkmatternucleoninteraction crosssection vs.darkmattermass. (top)TheCMSexclusionofaspin-dependent crosssection (shaded) fromanaxial-vector mediatordecaying todijetsis com-paredwith limits from the PICOexperiments [56,57], IceCube[58],and Super-Kamiokande[59].(bottom)TheCMSexclusionofaspin-independentcrosssection (shaded) from avector mediatordecaying to dijetsis compared with the LUX 2016[60],PandaX-II2016[61],CDMSLite2015[62],andCRESST-II2015[63]limits, whichhavedocumentedthemostconstrainingresultsinthe shownmassrange. TheCMSexclusionsareforDiracDMand couplings gq=0.25 and gDM=1,for

leptophobicaxial-vectorandvectormediators,andtheystronglydependonthese choicesandarenotapplicabletootherchoicesofcouplingvaluesormodels.The CMSlimitsdonotincludeaconstraintontherelicdensity.

a low-masssearchbasedoncalorimeterjets,reconstructedbythe highlevel trigger andrecorded incompact form (data scouting), andahigh-masssearchbasedonparticle-flowjets.Thedijetmass spectraareobservedtobesmoothlyfallingdistributions.Inthe an-alyzeddatasamples,thereisnoevidenceforresonantparticle pro-duction.Generic upperlimitsarepresentedontheproductofthe crosssection, thebranching fraction, andthe acceptancefor nar-rowquark–quark, quark–gluon, andgluon–gluon resonances that areapplicabletoanymodelofnarrowdijetresonanceproduction. Stringresonanceswithmassesbelow7.4 TeVareexcluded at95% confidence level, as are scalar diquarks below 6.9 TeV, axigluons andcolorons below 5.5 TeV,excited quarks below 5.4 TeV, color-octet scalars below 3.0 TeV, W bosons below 2.7 TeV, Z bosons

withSM-likecouplingsbelow2.1 TeVandbetween2.3and2.6 TeV, and Randall–Sundrum gravitons below 1.9 TeV. Thisextends pre-viously published limits inthe dijet channel. The first limitsare seton asimplifiedmodel ofdarkmatter mediatorsbasedonthe dijet channel, excluding vector andaxial-vector mediators below 2.0 TeV,andusingauniversalquarkcoupling gq=0.25 andadark

matter coupling gDM=1.0.Limits on the massof a darkmatter

mediatorarepresentedasafunctionofdarkmattermass,andare translatedinto upper limitson the crosssection for darkmatter particlesscatteringonnucleonsthataremoresensitivethanthose ofdirectdetectionexperimentsforspin-dependentcrosssections.

Acknowledgements

WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the technicalandadministrative staffsatCERN andatother CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcentersand personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythe computinginfrastructureessential to ouranalyses. Finally, we acknowledge the enduring support for the construc-tionandoperation oftheLHC andtheCMSdetectorprovidedby thefollowingfundingagencies:BMWFWandFWF(Austria);FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MOST, and NSFC (China); COLCIEN-CIAS(Colombia);MSESandCSF(Croatia);RPF(Cyprus);SENESCYT (Ecuador); MoER, ERC IUT, and ERDF (Estonia); Academy of Fin-land,MEC,andHIP(Finland);CEAandCNRS/IN2P3(France);BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hun-gary);DAEandDST(India);IPM(Iran);SFI(Ireland);INFN(Italy); MSIPandNRF(RepublicofKorea);LAS (Lithuania);MOEandUM (Malaysia); BUAP, CINVESTAV,CONACYT, LNS, SEP, andUASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland);FCT (Portugal); JINR(Dubna); MON, RosAtom, RAS, and RFBR (Russia); MESTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR, andNSTDA (Thailand); TUBITAK andTAEK (Turkey);NASU andSFFR(Ukraine);STFC(UnitedKingdom);DOEandNSF(USA).

Individuals have received support from the Marie-Curie pro-gram and the European Research Council and EPLANET (Euro-pean Union); the Leventis Foundation; the A.P. Sloan Founda-tion; the Alexander von Humboldt Foundation; the Belgian Fed-eral 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 Technolo-gie (IWT-Belgium); the Ministry of Education, Youth and Sports (MEYS) ofthe Czech Republic;the Council ofScience and Indus-trial Research, India; the HOMING PLUS program of the Foun-dation for Polish Science, cofinanced from European Union, Re-gional Development Fund, the Mobility Plus program of the Ministry of Science and Higher Education, the National Science Center (Poland), contracts Harmonia 2014/14/M/ST2/00428, Opus 2013/11/B/ST2/04202, 2014/13/B/ST2/02543 and 2014/15/B/ST2/ 03998, Sonata-bis 2012/07/E/ST2/01406; the Thalis and Aristeia programs cofinanced by EU-ESF and the Greek NSRF; the Na-tional Priorities Research Program by Qatar National Research Fund; the Programa Clarín-COFUND del Principado de Asturias; theRachadapisekSompotFundforPostdoctoralFellowship, Chula-longkornUniversityandtheChulalongkornAcademic intoIts2nd Century Project Advancement Project (Thailand); and the Welch Foundation,contractC-1845.

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TheCMSCollaboration

A.M. Sirunyan,A. Tumasyan YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam, E. Asilar,T. Bergauer, J. Brandstetter, E. Brondolin, M. Dragicevic, J. Erö,M. Flechl, M. Friedl, R. Frühwirth1, V.M. Ghete, C. Hartl, N. Hörmann, J. Hrubec,M. Jeitler1,A. König, I. Krätschmer, D. Liko, T. Matsushita,I. Mikulec, D. Rabady, N. Rad, B. Rahbaran,H. Rohringer, J. Schieck1,J. Strauss,

W. Waltenberger, C.-E. Wulz1 InstitutfürHochenergiephysik,Wien,Austria

O. Dvornikov,V. Makarenko, V. Mossolov,J. Suarez Gonzalez, V. Zykunov InstituteforNuclearProblems,Minsk,Belarus

N. Shumeiko

NationalCentreforParticleandHighEnergyPhysics,Minsk,Belarus

S. Alderweireldt, E.A. De Wolf,X. Janssen,J. Lauwers, M. Van De Klundert, H. Van Haevermaet, P. Van Mechelen,N. Van Remortel, A. Van Spilbeeck

UniversiteitAntwerpen,Antwerpen,Belgium

S. Abu Zeid,F. Blekman, J. D’Hondt, N. Daci,I. De Bruyn, K. Deroover, S. Lowette,S. Moortgat, L. Moreels, A. Olbrechts,Q. Python, K. Skovpen, S. Tavernier,W. Van Doninck, P. Van Mulders, I. Van Parijs

VrijeUniversiteitBrussel,Brussel,Belgium

H. Brun, B. Clerbaux, G. De Lentdecker, H. Delannoy, G. Fasanella,L. Favart, R. Goldouzian, A. Grebenyuk, G. Karapostoli,T. Lenzi,A. Léonard, J. Luetic, T. Maerschalk,A. Marinov, A. Randle-conde,T. Seva,

C. Vander Velde, P. Vanlaer,D. Vannerom, R. Yonamine,F. Zenoni, F. Zhang2 UniversitéLibredeBruxelles,Bruxelles,Belgium

A. Cimmino,T. Cornelis, D. Dobur,A. Fagot, M. Gul, I. Khvastunov,D. Poyraz, S. Salva, R. Schöfbeck, M. Tytgat,W. Van Driessche, E. Yazgan, N. Zaganidis

GhentUniversity,Ghent,Belgium

H. Bakhshiansohi,C. Beluffi3,O. Bondu, S. Brochet,G. Bruno, A. Caudron, S. De Visscher, C. Delaere, M. Delcourt,B. Francois, A. Giammanco, A. Jafari,M. Komm, G. Krintiras,V. Lemaitre, A. Magitteri, A. Mertens, M. Musich, K. Piotrzkowski,L. Quertenmont,M. Selvaggi, M. Vidal Marono, S. Wertz UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium

N. Beliy

UniversitédeMons,Mons,Belgium

W.L. Aldá Júnior, F.L. Alves,G.A. Alves, L. Brito,C. Hensel,A. Moraes, M.E. Pol, P. Rebello Teles CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

E. Belchior Batista Das Chagas, W. Carvalho,J. Chinellato4,A. Custódio, E.M. Da Costa, G.G. Da Silveira5, D. De Jesus Damiao,C. De Oliveira Martins, S. Fonseca De Souza, L.M. Huertas Guativa, H. Malbouisson, D. Matos Figueiredo, C. Mora Herrera,L. Mundim, H. Nogima,W.L. Prado Da Silva, A. Santoro,

A. Sznajder,E.J. Tonelli Manganote4, A. Vilela Pereira UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

S. Ahujaa, C.A. Bernardesa, S. Dograa,T.R. Fernandez Perez Tomeia,E.M. Gregoresb,P.G. Mercadanteb, C.S. Moona, S.F. Novaesa, Sandra S. Padulaa, D. Romero Abadb,J.C. Ruiz Vargasa

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

A. Aleksandrov, R. Hadjiiska, P. Iaydjiev,M. Rodozov, S. Stoykova, G. Sultanov, M. Vutova InstituteforNuclearResearchandNuclearEnergy,Sofia,Bulgaria

A. Dimitrov, I. Glushkov,L. Litov, B. Pavlov,P. Petkov UniversityofSofia,Sofia,Bulgaria

W. Fang6

BeihangUniversity,Beijing,China

M. Ahmad, J.G. Bian, G.M. Chen, H.S. Chen,M. Chen, Y. Chen7,T. Cheng, C.H. Jiang, D. Leggat, Z. Liu, F. Romeo,M. Ruan, S.M. Shaheen, A. Spiezia,J. Tao, C. Wang, Z. Wang, H. Zhang,J. Zhao

InstituteofHighEnergyPhysics,Beijing,China

Y. Ban, G. Chen, Q. Li, S. Liu,Y. Mao, S.J. Qian, D. Wang,Z. Xu StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

C. Avila,A. Cabrera, L.F. Chaparro Sierra, C. Florez, J.P. Gomez, C.F. González Hernández,J.D. Ruiz Alvarez, J.C. Sanabria

UniversidaddeLosAndes,Bogota,Colombia

N. Godinovic, D. Lelas, I. Puljak,P.M. Ribeiro Cipriano, T. Sculac UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia Z. Antunovic, M. Kovac

UniversityofSplit,FacultyofScience,Split,Croatia

V. Brigljevic,D. Ferencek, K. Kadija,B. Mesic, T. Susa InstituteRudjerBoskovic,Zagreb,Croatia

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

M. Finger8, M. Finger Jr.8 CharlesUniversity,Prague,Czechia

E. Carrera Jarrin

UniversidadSanFranciscodeQuito,Quito,Ecuador

A. Ellithi Kamel9,M.A. Mahmoud10,11, A. Radi11,12

AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt M. Kadastik, L. Perrini, M. Raidal, A. Tiko, C. Veelken

NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia P. Eerola,J. Pekkanen, M. Voutilainen DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland

J. Härkönen,T. Järvinen, V. Karimäki,R. Kinnunen, T. Lampén, K. Lassila-Perini, S. Lehti,T. Lindén, P. Luukka, 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, S. Ghosh,A. Givernaud, P. Gras, G. Hamel de Monchenault, P. Jarry, I. Kucher, E. Locci,M. Machet, J. Malcles,J. Rander, A. Rosowsky, M. Titov

IRFU,CEA,UniversitéParis-Saclay,Gif-sur-Yvette,France

A. Abdulsalam,I. Antropov, S. Baffioni, F. Beaudette, P. Busson, L. Cadamuro, E. Chapon,C. Charlot, O. Davignon,R. Granier de Cassagnac, M. Jo, S. Lisniak,P. Miné, M. Nguyen, C. Ochando, G. Ortona, P. Paganini,P. Pigard, S. Regnard, R. Salerno,Y. Sirois, T. Strebler, Y. Yilmaz, A. Zabi, A. Zghiche LaboratoireLeprince-Ringuet,EcolePolytechnique,IN2P3-CNRS,Palaiseau,France

J.-L. Agram13,J. Andrea, A. Aubin,D. Bloch, J.-M. Brom,M. Buttignol, E.C. Chabert,N. Chanon, C. Collard, E. Conte13,X. Coubez, J.-C. Fontaine13, D. Gelé, U. Goerlach,A.-C. Le Bihan, P. Van Hove

InstitutPluridisciplinaireHubertCurien,UniversitédeStrasbourg,UniversitédeHauteAlsaceMulhouse,CNRS/IN2P3,Strasbourg,France S. Gadrat

CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France

S. Beauceron,C. Bernet, G. Boudoul,C.A. Carrillo Montoya, R. Chierici,D. Contardo, B. Courbon, P. Depasse,H. El Mamouni, J. Fan, J. Fay, S. Gascon, M. Gouzevitch,G. Grenier, B. Ille, F. Lagarde, I.B. Laktineh,M. Lethuillier, L. Mirabito,A.L. Pequegnot, S. Perries, A. Popov14,D. Sabes, V. Sordini, M. Vander Donckt, P. Verdier,S. Viret

UniversitédeLyon,UniversitéClaudeBernardLyon1,CNRS-IN2P3,InstitutdePhysiqueNucléairedeLyon,Villeurbanne,France T. Toriashvili15

GeorgianTechnicalUniversity,Tbilisi,Georgia Z. Tsamalaidze8

TbilisiStateUniversity,Tbilisi,Georgia

C. Autermann,S. Beranek, L. Feld, M.K. Kiesel, K. Klein, M. Lipinski, M. Preuten,C. Schomakers, J. Schulz, T. Verlage

A. Albert, M. Brodski,E. Dietz-Laursonn, D. Duchardt, M. Endres, M. Erdmann,S. Erdweg, T. Esch, R. Fischer,A. Güth, M. Hamer, T. Hebbeker,C. Heidemann, K. Hoepfner, S. Knutzen,M. Merschmeyer, A. Meyer, P. Millet,S. Mukherjee, M. Olschewski, K. Padeken,T. Pook,M. Radziej, H. Reithler, M. Rieger, F. Scheuch,L. Sonnenschein, D. Teyssier, S. Thüer

RWTHAachenUniversity,III.PhysikalischesInstitutA,Aachen,Germany

V. Cherepanov, G. Flügge, B. Kargoll, T. Kress, A. Künsken, J. Lingemann, T. Müller,A. Nehrkorn, A. Nowack,C. Pistone, O. Pooth,A. Stahl16

RWTHAachenUniversity,III.PhysikalischesInstitutB,Aachen,Germany

M. Aldaya Martin,T. Arndt, C. Asawatangtrakuldee, K. Beernaert,O. Behnke, U. Behrens,A.A. Bin Anuar, K. Borras17,A. Campbell, P. Connor, C. Contreras-Campana, F. Costanza, C. Diez Pardos,G. Dolinska, G. Eckerlin, D. Eckstein, T. Eichhorn, E. Eren, E. Gallo18,J. Garay Garcia, A. Geiser, A. Gizhko,

J.M. Grados Luyando, A. Grohsjean, P. Gunnellini, A. Harb,J. Hauk, M. Hempel19,H. Jung,

A. Kalogeropoulos, O. Karacheban19, M. Kasemann,J. Keaveney, C. Kleinwort, I. Korol,D. Krücker, W. Lange, A. Lelek, T. Lenz,J. Leonard, K. Lipka,A. Lobanov, W. Lohmann19, R. Mankel,

I.-A. Melzer-Pellmann,A.B. Meyer, G. Mittag, J. Mnich, A. Mussgiller, E. Ntomari,D. Pitzl,R. Placakyte, A. Raspereza,B. Roland, M.Ö. Sahin,P. Saxena, T. Schoerner-Sadenius,C. Seitz, S. Spannagel, N. Stefaniuk, G.P. Van Onsem,R. Walsh, C. Wissing

DeutschesElektronen-Synchrotron,Hamburg,Germany

V. Blobel, M. Centis Vignali, A.R. Draeger,T. Dreyer, E. Garutti, D. Gonzalez, J. Haller, M. Hoffmann, A. Junkes, R. Klanner, R. Kogler,N. Kovalchuk, T. Lapsien, I. Marchesini, D. Marconi,M. Meyer, M. Niedziela, D. Nowatschin, F. Pantaleo16,T. Peiffer, A. Perieanu, J. Poehlsen, C. Sander,C. Scharf, P. Schleper, A. Schmidt, S. Schumann,J. Schwandt, H. Stadie,G. Steinbrück, F.M. Stober,M. Stöver, H. Tholen, D. Troendle,E. Usai, L. Vanelderen, A. Vanhoefer, B. Vormwald

UniversityofHamburg,Hamburg,Germany

M. Akbiyik, C. Barth,S. Baur, C. Baus, J. Berger,E. Butz, R. Caspart, T. Chwalek, F. Colombo, W. De Boer, A. Dierlamm, S. Fink,B. Freund,R. Friese, M. Giffels,A. Gilbert, P. Goldenzweig,D. Haitz, F. Hartmann16, S.M. Heindl,U. Husemann, I. Katkov14, S. Kudella, H. Mildner,M.U. Mozer, Th. Müller, M. Plagge,

G. Quast, K. Rabbertz,S. Röcker, F. Roscher, M. Schröder,I. Shvetsov, G. Sieber, H.J. Simonis,R. Ulrich, S. Wayand,M. Weber, T. Weiler, S. Williamson, C. Wöhrmann, R. Wolf

InstitutfürExperimentelleKernphysik,Karlsruhe,Germany

G. Anagnostou, G. Daskalakis,T. Geralis,V.A. Giakoumopoulou, A. Kyriakis, D. Loukas, I. Topsis-Giotis InstituteofNuclearandParticlePhysics(INPP),NCSRDemokritos,AghiaParaskevi,Greece

S. Kesisoglou, A. Panagiotou, N. Saoulidou, E. Tziaferi NationalandKapodistrianUniversityofAthens,Athens,Greece

I. Evangelou, G. Flouris,C. Foudas, P. Kokkas, N. Loukas, N. Manthos, I. Papadopoulos,E. Paradas UniversityofIoánnina,Ioánnina,Greece

N. Filipovic, G. Pasztor

MTA-ELTELendületCMSParticleandNuclearPhysicsGroup,EötvösLorándUniversity,Budapest,Hungary

G. Bencze,C. Hajdu, D. Horvath20,F. Sikler, V. Veszpremi,G. Vesztergombi21,A.J. Zsigmond WignerResearchCentreforPhysics,Budapest,Hungary

N. Beni,S. Czellar, J. Karancsi22,A. Makovec,J. Molnar, Z. Szillasi InstituteofNuclearResearchATOMKI,Debrecen,Hungary

M. Bartók21,P. Raics, Z.L. Trocsanyi, B. Ujvari InstituteofPhysics,UniversityofDebrecen,Hungary

S. Bahinipati23,S. Bhowmik24, S. Choudhury25,P. Mal, K. Mandal, A. Nayak26, D.K. Sahoo23, N. Sahoo, S.K. Swain

NationalInstituteofScienceEducationandResearch,Bhubaneswar,India

S. Bansal,S.B. Beri, V. Bhatnagar, R. Chawla, U. Bhawandeep, A.K. Kalsi,A. Kaur, M. Kaur, R. Kumar, P. Kumari,A. Mehta, M. Mittal, J.B. Singh, G. Walia

PanjabUniversity,Chandigarh,India

Ashok Kumar,A. Bhardwaj, B.C. Choudhary, R.B. Garg,S. Keshri, S. Malhotra,M. Naimuddin, N. Nishu, K. Ranjan,R. Sharma, V. Sharma

UniversityofDelhi,Delhi,India

R. Bhattacharya,S. Bhattacharya, K. Chatterjee, S. Dey,S. Dutt, S. Dutta, S. Ghosh, N. Majumdar, A. Modak, K. Mondal,S. Mukhopadhyay, S. Nandan,A. Purohit, A. Roy, D. Roy, S. Roy Chowdhury, S. Sarkar,M. Sharan, S. Thakur

SahaInstituteofNuclearPhysics,Kolkata,India P.K. Behera

IndianInstituteofTechnologyMadras,Madras,India

R. Chudasama,D. Dutta, V. Jha, V. Kumar, A.K. Mohanty16, P.K. Netrakanti,L.M. Pant, P. Shukla,A. Topkar BhabhaAtomicResearchCentre,Mumbai,India

T. Aziz,S. Dugad, G. Kole, B. Mahakud, S. Mitra, G.B. Mohanty, B. Parida,N. Sur, B. Sutar TataInstituteofFundamentalResearch-A,Mumbai,India

S. Banerjee, R.K. Dewanjee,S. Ganguly, M. Guchait,Sa. Jain, S. Kumar, M. Maity24, G. Majumder, K. Mazumdar,T. Sarkar24, N. Wickramage27

TataInstituteofFundamentalResearch-B,Mumbai,India

S. Chauhan,S. Dube, V. Hegde, A. Kapoor, K. Kothekar, S. Pandey, A. Rane, S. Sharma IndianInstituteofScienceEducationandResearch(IISER),Pune,India

S. Chenarani28, E. Eskandari Tadavani,S.M. Etesami28, M. Khakzad, M. Mohammadi Najafabadi, M. Naseri, S. Paktinat Mehdiabadi29,F. Rezaei Hosseinabadi, B. Safarzadeh30,M. Zeinali

InstituteforResearchinFundamentalSciences(IPM),Tehran,Iran M. Felcini,M. Grunewald

UniversityCollegeDublin,Dublin,Ireland

M. Abbresciaa,b, C. Calabriaa,b, C. Caputoa,b, A. Colaleoa,D. Creanzaa,c, L. Cristellaa,b,N. De Filippisa,c, M. De Palmaa,b, L. Fiorea, G. Iasellia,c, G. Maggia,c, M. Maggia,G. Minielloa,b,S. Mya,b,S. Nuzzoa,b, A. Pompilia,b, G. Pugliesea,c,R. Radognaa,b,A. Ranieria, G. Selvaggia,b, A. Sharmaa, L. Silvestrisa,16, R. Vendittia,b, P. Verwilligena

a

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

G. Abbiendia,C. Battilana, D. Bonacorsia,b, S. Braibant-Giacomellia,b, L. Brigliadoria,b, R. Campaninia,b, P. Capiluppia,b,A. Castroa,b,F.R. Cavalloa,S.S. Chhibraa,b, 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. Tosia,b,16

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

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

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

G. Barbaglia, V. Ciullia,b_{,C. Civinini}a_{, R. D’Alessandro}a,b_{,E. Focardi}a,b_{,P. Lenzi}a,b_{, M. Meschini}a_,

S. Paolettia,L. Russoa,31, G. Sguazzonia, D. Stroma, L. Viliania,b,16

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

L. Benussi, S. Bianco, F. Fabbri,D. Piccolo, F. Primavera16 INFNLaboratoriNazionalidiFrascati,Frascati,Italy

V. Calvellia,b, F. Ferroa, M.R. Mongea,b,E. Robuttia, S. Tosia,b

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

L. Brianzaa,b,16,F. Brivioa,b,V. Ciriolo, M.E. Dinardoa,b,S. Fiorendia,b,16,S. Gennaia,A. Ghezzia,b, P. Govonia,b,M. Malbertia,b, S. Malvezzia, R.A. Manzonia,b,D. Menascea,L. Moronia,M. Paganonia,b, D. Pedrinia,S. Pigazzinia,b,S. Ragazzia,b,T. Tabarelli de Fatisa,b

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

S. Buontempoa, N. Cavalloa,c, G. De Nardo, S. Di Guidaa,d,16, M. Espositoa,b, F. Fabozzia,c,F. Fiengaa,b, A.O.M. Iorioa,b_{, G. Lanza}a_{,L. Lista}a_{, S. Meola}a,d,16_{,P. Paolucci}a,16_{, C. Sciacca}a,b_{, F. Thyssen}a

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

P. Azzia,16, N. Bacchettaa, L. Benatoa,b,D. Biselloa,b, A. Bolettia,b,M. Dall’Ossoa,b,

P. De Castro Manzanoa, T. Dorigoa,U. Dossellia, F. Gasparinia,b, U. Gasparinia,b,A. Gozzelinoa, S. Lacapraraa,M. Margonia,b,A.T. Meneguzzoa,b,M. Passaseoa,J. Pazzinia,b,N. Pozzobona,b, P. Ronchesea,b,M. Sgaravattoa,F. Simonettoa,b, E. Torassaa, S. Venturaa,M. Zanettia,b,P. Zottoa,b, G. Zumerlea,b

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

A. Braghieria,F. Fallavollitaa,b, A. Magnania,b, P. Montagnaa,b,S.P. Rattia,b, V. Rea, C. Riccardia,b, P. Salvinia, I. Vaia,b, P. Vituloa,b

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

L. Alunni Solestizia,b_{,G.M. Bilei}a_{, D. Ciangottini}a,b_{,L. Fanò}a,b_{, P. Lariccia}a,b_{,R. Leonardi}a,b_,

G. Mantovania,b,M. Menichellia, A. Sahaa, A. Santocchiaa,b

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

K. Androsova,31,P. Azzurria,16,G. Bagliesia,J. Bernardinia,T. Boccalia,R. Castaldia, M.A. Cioccia,31, R. Dell’Orsoa,S. Donatoa,c,G. Fedi, A. Giassia,M.T. Grippoa,31,F. Ligabuea,c, T. Lomtadzea, L. Martinia,b, A. Messineoa,b, F. Pallaa,A. Rizzia,b,A. Savoy-Navarroa,32, P. Spagnoloa,R. Tenchinia, G. Tonellia,b, A. Venturia,P.G. Verdinia

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

c_{ScuolaNormaleSuperiorediPisa,Pisa,Italy}

L. Baronea,b, F. Cavallaria,M. Cipriania,b, D. Del Rea,b,16, M. Diemoza, G. D’Imperiob, S. Gellia,b, E. Longoa,b, F. Margarolia,b, B. Marzocchia,b,P. Meridiania, G. Organtinia,b,R. Paramattia, F. Preiatoa,b, S. Rahatloua,b,C. Rovellia, F. Santanastasioa,b

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

N. Amapanea,b,R. Arcidiaconoa,c,16,S. Argiroa,b,M. Arneodoa,c,N. Bartosika,R. Bellana,b, C. Biinoa, N. Cartigliaa,F. Cennaa,b, M. Costaa,b,R. Covarellia,b,A. Deganoa,b,N. Demariaa, L. Fincoa,b, B. Kiania,b, C. Mariottia, S. Masellia,E. Migliorea,b, V. Monacoa,b, E. Monteila,b, M. Montenoa,M.M. Obertinoa,b, L. Pachera,b,N. Pastronea, M. Pelliccionia, G.L. Pinna Angionia,b,F. Raveraa,b,A. Romeroa,b, M. Ruspaa,c, R. Sacchia,b, K. Shchelinaa,b, V. Solaa,A. Solanoa,b,A. Staianoa,P. Traczyka,b

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

c_{UniversitàdelPiemonteOrientale,Novara,Italy}

S. Belfortea,M. Casarsaa, F. Cossuttia,G. Della Riccaa,b, A. Zanettia

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

D.H. Kim,G.N. Kim, M.S. Kim, S. Lee, S.W. Lee, Y.D. Oh,S. Sekmen, D.C. Son,Y.C. Yang KyungpookNationalUniversity,Daegu,RepublicofKorea

A. Lee

ChonbukNationalUniversity,Jeonju,RepublicofKorea H. Kim

ChonnamNationalUniversity,InstituteforUniverseandElementaryParticles,Kwangju,RepublicofKorea J.A. Brochero Cifuentes,T.J. Kim

HanyangUniversity,Seoul,RepublicofKorea

S. Cho,S. Choi, Y. Go,D. Gyun, S. Ha,B. Hong, Y. Jo, Y. Kim, K. Lee,K.S. Lee,S. Lee,J. Lim, S.K. Park, Y. Roh KoreaUniversity,Seoul,RepublicofKorea

J. Almond,J. Kim, H. Lee,S.B. Oh, B.C. Radburn-Smith, S.h. Seo, U.K. Yang,H.D. Yoo, G.B. Yu SeoulNationalUniversity,Seoul,RepublicofKorea

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

Y. Choi,J. Goh, C. Hwang, J. Lee,I. Yu SungkyunkwanUniversity,Suwon,RepublicofKorea

V. Dudenas, A. Juodagalvis,J. Vaitkus VilniusUniversity,Vilnius,Lithuania

I. Ahmed,Z.A. Ibrahim, J.R. Komaragiri, M.A.B. Md Ali33,F. Mohamad Idris34,W.A.T. Wan Abdullah, M.N. Yusli,Z. Zolkapli

NationalCentreforParticlePhysics,UniversitiMalaya,KualaLumpur,Malaysia

H. Castilla-Valdez, E. De La Cruz-Burelo,I. Heredia-De La Cruz35,A. Hernandez-Almada, R. Lopez-Fernandez, R. Magaña Villalba, J. Mejia Guisao,A. Sanchez-Hernandez

CentrodeInvestigacionydeEstudiosAvanzadosdelIPN,MexicoCity,Mexico

S. Carrillo Moreno, C. Oropeza Barrera, F. Vazquez Valencia UniversidadIberoamericana,MexicoCity,Mexico

S. Carpinteyro, I. Pedraza, H.A. Salazar Ibarguen, C. Uribe Estrada BenemeritaUniversidadAutonomadePuebla,Puebla,Mexico

A. Morelos Pineda

UniversidadAutónomadeSanLuisPotosí,SanLuisPotosí,Mexico D. Krofcheck

UniversityofAuckland,Auckland,NewZealand P.H. Butler

UniversityofCanterbury,Christchurch,NewZealand

A. Ahmad, M. Ahmad, Q. Hassan,H.R. Hoorani, W.A. Khan, A. Saddique,M.A. Shah, M. Shoaib, M. Waqas 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

K. Bunkowski,A. Byszuk36, K. Doroba,A. Kalinowski, M. Konecki,J. Krolikowski, M. Misiura, M. Olszewski, M. Walczak

InstituteofExperimentalPhysics,FacultyofPhysics,UniversityofWarsaw,Warsaw,Poland

P. Bargassa,C. Beirão Da Cruz E Silva, B. Calpas, A. Di Francesco, P. Faccioli,P.G. Ferreira Parracho, M. Gallinaro,J. Hollar, N. Leonardo,L. Lloret Iglesias, M.V. Nemallapudi,J. Rodrigues Antunes, J. Seixas, O. Toldaiev, D. Vadruccio,J. Varela, P. Vischia

LaboratóriodeInstrumentaçãoeFísicaExperimentaldePartículas,Lisboa,Portugal

V. Alexakhin,P. Bunin, I. Golutvin, I. Gorbunov, A. Kamenev,V. Karjavin, A. Lanev, A. Malakhov, V. Matveev37,38, V. Palichik,V. Perelygin, M. Savina, S. Shmatov, S. Shulha, N. Skatchkov,V. Smirnov, N. Voytishin,A. Zarubin

JointInstituteforNuclearResearch,Dubna,Russia

L. Chtchipounov,V. Golovtsov, Y. Ivanov, V. Kim39, E. Kuznetsova40,V. Murzin, V. Oreshkin, V. Sulimov, A. Vorobyev

PetersburgNuclearPhysicsInstitute,Gatchina(St.Petersburg),Russia

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

V. Epshteyn,V. Gavrilov, N. Lychkovskaya,V. Popov, I. Pozdnyakov,G. Safronov, A. Spiridonov, M. Toms, E. Vlasov,A. Zhokin

InstituteforTheoreticalandExperimentalPhysics,Moscow,Russia A. Bylinkin38

MoscowInstituteofPhysicsandTechnology,Russia

M. Chadeeva41, M. Danilov41,V. Rusinov

NationalResearchNuclearUniversity‘MoscowEngineeringPhysicsInstitute’(MEPhI),Moscow,Russia

V. Andreev,M. Azarkin38,I. Dremin38, M. Kirakosyan, A. Leonidov38,A. Terkulov P.N.LebedevPhysicalInstitute,Moscow,Russia

A. Baskakov,A. Belyaev, E. Boos,V. Bunichev, M. Dubinin42, L. Dudko, A. Ershov, A. Gribushin, V. Klyukhin, O. Kodolova,I. Lokhtin, I. Miagkov, S. Obraztsov,V. Savrin, A. Snigirev

SkobeltsynInstituteofNuclearPhysics,LomonosovMoscowStateUniversity,Moscow,Russia V. Blinov43, Y. Skovpen43,D. Shtol43

NovosibirskStateUniversity(NSU),Novosibirsk,Russia

I. Azhgirey,I. Bayshev,S. Bitioukov, D. Elumakhov, V. Kachanov, A. Kalinin, D. Konstantinov, V. Krychkine, V. Petrov, R. Ryutin, A. Sobol,S. Troshin, N. Tyurin,A. Uzunian, A. Volkov StateResearchCenterofRussianFederation,InstituteforHighEnergyPhysics,Protvino,Russia

P. Adzic44,P. Cirkovic, D. Devetak,M. Dordevic, J. Milosevic,V. Rekovic UniversityofBelgrade,FacultyofPhysicsandVincaInstituteofNuclearSciences,Belgrade,Serbia

J. Alcaraz Maestre,M. Barrio Luna, E. Calvo,M. Cerrada,M. Chamizo Llatas, N. Colino, B. De La Cruz, A. Delgado Peris,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

J.F. de Trocóniz,M. Missiroli, D. Moran UniversidadAutónomadeMadrid,Madrid,Spain

J. Cuevas,J. Fernandez Menendez, I. Gonzalez Caballero, J.R. González Fernández,E. Palencia Cortezon, S. Sanchez Cruz,I. Suárez Andrés, J.M. Vizan Garcia

UniversidaddeOviedo,Oviedo,Spain

I.J. Cabrillo, A. Calderon, E. Curras, M. Fernandez,J. Garcia-Ferrero,G. Gomez, A. Lopez Virto, J. Marco, C. Martinez Rivero,F. Matorras, J. Piedra Gomez, T. Rodrigo,A. Ruiz-Jimeno, L. Scodellaro,N. Trevisani, 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, P. Bloch,A. Bocci, C. Botta, T. Camporesi, R. Castello,M. Cepeda, G. Cerminara, Y. Chen,D. d’Enterria, A. Dabrowski,V. Daponte, A. David,M. De Gruttola, A. De Roeck, E. Di Marco45,M. Dobson, B. Dorney, T. du Pree,D. Duggan, M. Dünser, N. Dupont, A. Elliott-Peisert,P. Everaerts, S. Fartoukh, G. Franzoni, J. Fulcher,W. Funk, D. Gigi, K. Gill,M. Girone, F. Glege, D. Gulhan, S. Gundacker, M. Guthoff, P. Harris,J. Hegeman, V. Innocente, P. Janot,J. Kieseler, H. Kirschenmann,V. Knünz,A. Kornmayer16,M.J. Kortelainen, K. Kousouris,

M. Krammer1,C. Lange, P. Lecoq, C. Lourenço,M.T. Lucchini,L. Malgeri, M. Mannelli,A. Martelli, F. Meijers, J.A. Merlin, S. Mersi, E. Meschi,P. Milenovic46,F. Moortgat, S. Morovic, M. Mulders,

H. Neugebauer,S. Orfanelli, L. Orsini, L. Pape,E. Perez, M. Peruzzi,A. Petrilli, G. Petrucciani, A. Pfeiffer, M. Pierini,A. Racz, T. Reis,G. Rolandi47, M. Rovere,H. Sakulin, J.B. Sauvan, C. Schäfer, C. Schwick, M. Seidel,A. Sharma, P. Silva,P. Sphicas48,J. Steggemann, M. Stoye,Y. Takahashi, M. Tosi, D. Treille, A. Triossi,A. Tsirou, V. Veckalns49,G.I. Veres21,M. Verweij, N. Wardle, H.K. Wöhri, A. Zagozdzinska36, W.D. Zeuner

CERN,EuropeanOrganizationforNuclearResearch,Geneva,Switzerland

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

PaulScherrerInstitut,Villigen,Switzerland

F. Bachmair, L. Bäni, L. Bianchini, B. Casal, G. Dissertori, M. Dittmar, M. Donegà, C. Grab, C. Heidegger, D. Hits, J. Hoss,G. Kasieczka, W. Lustermann,B. Mangano,M. Marionneau, P. Martinez Ruiz del Arbol, M. Masciovecchio, M.T. Meinhard,D. Meister, F. Micheli,P. Musella, F. Nessi-Tedaldi, F. Pandolfi, J. Pata, F. Pauss,G. Perrin, L. Perrozzi,M. Quittnat, M. Rossini, M. Schönenberger, A. Starodumov50,

V.R. Tavolaro, K. Theofilatos, R. Wallny InstituteforParticlePhysics,ETHZurich,Zurich,Switzerland

T.K. Aarrestad, C. Amsler51, L. Caminada,M.F. Canelli, A. De Cosa, C. Galloni,A. Hinzmann, T. Hreus, B. Kilminster, J. Ngadiuba,D. Pinna,G. Rauco, P. Robmann, D. Salerno, Y. Yang,A. Zucchetta

UniversitätZürich,Zurich,Switzerland

V. Candelise,T.H. Doan, Sh. Jain,R. Khurana, M. Konyushikhin, C.M. Kuo, W. Lin, A. Pozdnyakov,S.S. Yu NationalCentralUniversity,Chung-Li,Taiwan

Arun Kumar, P. Chang, Y.H. Chang,Y. Chao, K.F. Chen, P.H. Chen, F. Fiori, W.-S. Hou, Y. Hsiung, Y.F. Liu, R.-S. Lu, M. Miñano Moya,E. Paganis, A. Psallidas, J.f. Tsai

NationalTaiwanUniversity(NTU),Taipei,Taiwan

B. Asavapibhop, G. Singh, N. Srimanobhas,N. Suwonjandee ChulalongkornUniversity,FacultyofScience,DepartmentofPhysics,Bangkok,Thailand

A. Adiguzel, S. Cerci52,S. Damarseckin, Z.S. Demiroglu, C. Dozen,I. Dumanoglu, S. Girgis, G. Gokbulut, Y. Guler, I. Hos53,E.E. Kangal54, O. Kara, A. Kayis Topaksu,U. Kiminsu,M. Oglakci, G. Onengut55, K. Ozdemir56, D. Sunar Cerci52, H. Topakli57,S. Turkcapar, I.S. Zorbakir,C. Zorbilmez

CukurovaUniversity–PhysicsDepartment,ScienceandArtFaculty,Turkey

B. Bilin, S. Bilmis, B. Isildak58, G. Karapinar59, M. Yalvac, M. Zeyrek MiddleEastTechnicalUniversity,PhysicsDepartment,Ankara,Turkey

E. Gülmez,M. Kaya60,O. Kaya61, E.A. Yetkin62, T. Yetkin63 BogaziciUniversity,Istanbul,Turkey

A. Cakir,K. Cankocak, S. Sen64 IstanbulTechnicalUniversity,Istanbul,Turkey B. Grynyov