Measurement of differential cross sections for Z boson pair production in association with jets at sqrt(s) = 8 and 13 TeV

Contents lists available atScienceDirect

Physics

Letters

B

www.elsevier.com/locate/physletb

Measurement

of

differential

cross

sections

for

Z

boson

pair

production

in

association

with

jets

at

√

s

=

8 and

13 TeV

.

The

CMS

Collaboration



CERN,Switzerland

a

r

t

i

c

l

e

i

n

f

o

a

b

s

t

r

a

c

t

Articlehistory:

Received28June2018

Receivedinrevisedform14October2018

Accepted6November2018

Availableonline9November2018

Editor:M.Doser Keywords: CMS Physics SM ZZ ZZjets VBS

ThisLetterreports measurementsofdifferential crosssections forthe productionoftwo Z bosonsin association withjetsinproton–proton collisions at√s=8 and13 TeV.The analysis isbasedondata samples collectedattheLHCwith theCMS detector,corresponding tointegratedluminosities of19.7 and35.9 fb−1_{at8and13 TeV,respectively.Themeasurementsareperformedintheleptonicdecaymodes}

ZZ→ +− + −,where,=e,

μ

.Thedifferentialcrosssectionsasafunctionofthejetmultiplicity, thetransversemomentumpT,andpseudorapidityofthepT-leadingandsubleadingjetsarepresented.In

addition,thedifferentialcrosssectionsasafunctionofvariablessensitivetothevectorbosonscattering, suchastheinvariantmassofthetwopT-leadingjetsandtheirpseudorapidityseparation,arereported.

Theresultsarecomparedtotheoreticalpredictionsandfoundingoodagreementwithinthetheoretical andexperimentaluncertainties.

©2018TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3.

1. Introduction

Theproductionofmassivevector bosonpairs isakey process forthe understandingofboth thenon-Abeliangauge structureof thestandardmodel(SM)andoftheelectroweaksymmetry break-ingmechanism. Thus, relevantinformationcan begathered mea-suring vector boson scattering [1] and triboson production pro-cessesthatoccurthroughtheelectroweak(EW)productionofjets inassociationwithbosons.Becauseoftheverylow crosssections fortheseprocessescompared toothersleading to thesame final state, a detailed understanding of the quantum chromodynamics (QCD) corrections to the associated production of vector boson pairsandjetsisofparamountimportance.Theanalysispresented inthis Letter hasbeen designedto provide such detailed under-standing.

BoththeATLAS andCMSCollaborationshavemeasuredthe in-clusiveproductioncrosssectionofZ bosonpairsandthe differen-tialcrosssectionsasafunctionofZ bosonpairobservables [2–8]. InthisLetter we presentnewmeasurements of differentialcross sections forthe production of two Z bosons in association with jetsinproton–proton(pp)collisionsat

√

s

=

8 and13TeV that

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

tend the analyses of Refs. [6,8] to jet variables. The most recent publicationfromtheATLASCollaboration[4] includesjetvariables as well. The decay modes ofthe Z boson to electron andmuon (



=

e

,

μ

) pairs have been exploited. Reconstructed distributions are corrected for event selection efficiency and detector resolu-tion effects by means of an iterative unfolding technique, which makesuseofaresponsematrixtomapphysicsvariablesat gener-atorlevelontotheirreconstructedvalues.

ThisLetterpresentsthedependenceofthecrosssectiononthe jetmultiplicityandthekinematicpropertiesofthetwopT-leading

jets (where pT is the transverse momentum). Comparison with

theoreticalpredictionsprovidesanimportanttestoftheQCD cor-rectionstoZZ production.Normalizeddifferentialcrosssectionsas a functionofthe pT andpseudorapidity

η

ofthetwo pT-leading

jets,aswellastheirinvariantmass(mjj)andpseudorapidity

sepa-ration(



η

jj),arepresented.Thestudyofmjjestablishesthebasis

for future multiboson final-state searches and for the investiga-tion of phenomena involving interactions with four bosons at a single vertex, while the measurement of the



η

jj distribution is

instrumental in the study of vector boson scattering. The anal-ysis presented inthis paper together with the analyses reported in [5–9] seeksa detailedunderstandingof theSM processesthat generatefourleptons inthefinal statethrough theproductionof twoZbosons.Allmeasurementsarecomparedtopredictionsfrom

https://doi.org/10.1016/j.physletb.2018.11.007

0370-2693/©2018TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).Fundedby SCOAP3_.

recent Monte Carlo (MC) event generators. The data sets corre-spond to integrated luminosities of 19.7and 35.9 fb−1, collected bytheCMSCollaborationat8and13 TeV,respectively.

2. TheCMSdetector

The central feature of the CMS apparatus is a superconduct-ingsolenoidof6 m internaldiameter,providingamagneticfieldof 3.8 T.Withinthesolenoidvolumearesiliconpixelandstrip track-ingdetectors,alead tungstatecrystalelectromagneticcalorimeter (ECAL), and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections. Forward calorimeters extend the

η

coverage provided by the barrel and endcap detectors up to

|

η

|

=

5. Muons are measured in gas-ionization detectors embedded in the steelflux-return yoke out-sidethesolenoid,usingthreedifferenttechnologies:drifttubesfor

|

η

|

<

1

.

2,cathodestrip chambersfor0

.

9

<

|

η

|

<

2

.

4,andresistive platechambersfor

|

η

|

<

1

.

6.Thesilicontrackermeasurescharged particles within the range

|

η

|

<

2

.

5. For nonisolated particles in therange1

<

pT

<

10GeV and

|

η

|

<

1

.

4,thetrackresolutionsare

typically1.5%inpTand25–90(45–150) μm inthetransverse

(lon-gitudinal)impactparameter[10].

ThefirstleveloftheCMStriggersystem [11],composedof cus-tomhardware processors, usesinformationfromthecalorimeters andmuon detectors to select the mostinteresting events within a time interval oflessthan 4 μs. The high-level triggerprocessor farmfurtherdecreasestheeventratefromaround100 kHz toless than1 kHz,beforedatastorage.

AmoredetaileddescriptionoftheCMSdetector,togetherwith adefinitionofthecoordinatesystemused andthe relevant kine-maticvariables,canbefoundinRef. [12].

3. Signalandbackgroundsimulation

Several MC event generators are used to simulate the signal andbackgroundcontributions.TheMCsimulationsamplesare em-ployed to optimize the event selection, evaluate the signal effi-ciency andacceptance, estimate partof the background,and ex-tracttheunfoldingresponsematricesusedtocorrectfordetector effectsinthemeasureddistributions.

For the 8 TeV data analysis, MadGraph5 1.3.3 [13,14] is used to simulatethe production ofthe four-lepton final state at lead-ing order (LO) inQCD with up to 2jets includedin the matrix-elementcalculations. powheg 2.0 [15–18] isusedforthe simula-tionofthesameprocessatnext-to-leading-order(NLO).Asample ofeventsgeneratedwith MadGraph5_amc@nlo 2.3.3(abbreviated as MG5_amc@nlo inthefollowing) [14,19],whichsimulatessignal processes at NLO with zeroand one jet included inthe matrix-elementcalculations,isproducedonlyatgeneratorlevelandused for comparison purposes. For the 13 TeV data analysis, the four-leptonprocessesaresimulatedatNLOinQCD with0or1jet in-cludedinthematrix-elementcalculationswith MG5_amc@nlo and with powheg 2.0atNLO.The latterisscaledbya factorof1.1to reproducethetotalZZ productioncrosssectioncalculatedat next-to-next-to-leading order (NNLO) [20] at 13 TeV. MG5_amc@nlo and powheg 2.0, forboth the 8and 13 TeV analyses,include ZZ, Zγ∗, Z,and

γ

∗

γ

∗ processes, withthe generator level constraint

m+−

>

4GeV applied to all pairs of oppositely charged same-flavorleptons,toavoidinfrareddivergences.

Thegg

→

ZZ processes,whichoccurvialoop-induceddiagrams, are generated at LO with mcfm 6.7 (7.0) [21] for the 8 (13) TeV analysis.The13 TeV samplesarescaledbyafactorof1.7tomatch thecrosssectioncomputedatNLO [22].Electroweakproductionof fourleptons andtwo jetsissimulatedatLOwith Phantom [23]. Thissampleincludestribosonprocesses,wheretheZ bosonpairis

accompaniedbyathirdvectorbosonthatdecaysintojets,aswell asdiagramswithquarticvertices.

Other dibosonandtriboson processes(WZ,Zγ,WWZ) aswell asttZ,tt,andZ+jets samplesaregeneratedatLOwith MadGraph5 for the 8 TeV analysis, and at NLO with MG5_amc@nlo, for the 13 TeV analysis.

For the 8 TeV analysis, the pythia 6.4.24 [24] package, with parameters set by the Z2* tune [25], is used for parton shower-ing,hadronization,andtheunderlyingeventsimulationforallMC samplesexceptfor MG5_amc@nlo,forwhich pythia 8.205 [26] is employed.The defaultsetsofpartondistributionfunctions(PDFs) are CTEQ6L [27] for the LO generators, and CT10 [28], for the NLO ones.Forthe13 TeV analysis, pythia 8.212 [26],with param-eters set by the CUETP8M1 tune [29], is used for parton show-ering, hadronization, and the underlying event simulation. The NNPDF3.0 [30] PDFsetisthedefault.Forallsimulatedevent sam-ples,thePDFsusedareevaluatedatthesameorderinQCDasthe processinthesample.

Thedetectorresponseissimulatedusingadetaileddescription of theCMSdetectorimplementedwiththe Geant4 package [31]. The simulatedeventsare reconstructedwiththesamealgorithms usedforthedata.Thesimulatedsamplesincludeadditional inter-actionsperbunchcrossing,referredtoaspileup.Simulatedevents are weighted so that the pileup distribution reproduces that ob-served inthe data,withan averageofabout21(27)interactions perbunchcrossingforthe8(13) TeV dataset.

4. Particlereconstructionandeventselection

The primary triggers for this analysisrequire the presence of twolooselyisolatedleptonsofthesameorofdifferentflavor. The minimum pT forthefirst leptonis17 GeV,while itis8 (12) GeV

forthesecond leptoninthe8(13) TeV analysis.Triggersrequiring a tripletoflow-pT leptons withno isolationrequirementand,for

the13 TeV analysis,isolatedsingle-electronandsingle-muon trig-gers, withminimal pT-thresholds of27 and22 GeV, respectively,

help to increase the efficiency. The overall trigger efficiency for eventsthatpasstheZZ selectionisgreaterthan98%.

The offline event selection procedure issimilar to that of the inclusiveZZ analyses [6–8] andisbasedonaglobalevent descrip-tion [32] thatclassifiesparticlesintomutuallyexclusivecategories: chargedhadrons, neutralhadrons,photons, muons, andelectrons. Events arerequiredtohaveatleastonevertex [10] within24 cm ofthe geometriccenterofthedetectoralong thebeamdirection, andwithin2 cm inthetransverseplane.Becauseofpileupthe se-lectedeventcanhaveseveralreconstructedvertices.

For the analysis at 8 TeV the vertex with the largest sum of the p2_T of the tracks associated to it is chosen as the primary pp interaction vertex, while at 13 TeV the reconstructed vertex with the largest value of summed physics-object p2_T is taken to be the primary vertex. The physics objects are the objects re-turned by a jet finding algorithm [33,34] applied to all charged tracks associated withthevertex, andthe associatedmissing pT,

taken asthe negative vector sum ofthe pT of thosejets. Events

withleptonsareselectedbyrequiringeachleptontracktohavea transverse impact parameter, withrespect to theprimary vertex, smaller than 0.5 cm anda longitudinal impactparameter smaller than 1.0 cm.

Electrons are measured in the range

|

η

|

<

2

.

5 by using both thetrackingsystemandtheECAL.Theyareidentifiedbymeansof a multivariate discriminant that includes observables sensitive to bremsstrahlungalong theelectron trajectory,the geometricaland momentum-energyagreementbetweentheelectrontrackandthe associated energy cluster in the ECAL, the shape of the electro-magneticshower,andvariablesthatdiscriminateagainstelectrons

originatingfromphotonconversions [35].Themomentum resolu-tionforelectronswithpT

≈

45GeV fromZ

→

e+e− decaysranges

from1.7%fornonshoweringelectronsinthebarrelregionto4.5% forshoweringelectronsintheendcaps [35].

Muonsare reconstructed inthe range

|

η

|

<

2

.

4 by combining information from the silicon tracker and the muon system [36]. Thematchingbetweentheinnerandouter tracksproceedseither outside-in,startingfromatrackinthemuonsystem,orinside-out, startingfromatrackinthesilicontracker.Themuonsareselected amongthereconstructedmuontrackcandidatesbyapplying min-imalrequirementsonthetrackinboth themuonsystemandthe inner tracker system, and taking into account the compatibility withminimum-ionizing particleenergydeposits inthe calorime-ters. In the intermediate range of 20

<

pT

<

100GeV, matching

muonsto tracks measured inthe silicon trackerresults in a rel-ativepTresolutionof1.3–2.0%inthebarrel,andbetterthan6%in

theendcaps.ThepT resolutioninthebarrelisbetterthan10%for

muonswithpTupto1 TeV [36].

Electrons (muons) are considered candidates for inclusion in thefour-leptonfinal statesifthey have p_T

>

7

(

5

)

GeV and

|

η



|

<

2

.

5

(

2

.

4

)

. Inorder to suppresselectrons fromphoton conversions andmuonsoriginatingfromin-flightdecaysofhadrons, weplace arequirementontheimpactparametercomputedinthree dimen-sions.We require that the ratioof the impact parameter forthe trackanditsuncertaintytobelessthan4.Todiscriminatebetween promptleptons fromZ boson decay andthosearising from elec-troweakdecaysofhadronswithinjets,anisolationrequirementfor leptonsisimposed.Therelativeisolationisdefinedas

Riso

=

 

charged hadrons pT

+

max



0

,



neutral hadrons pT

+



photons pT

−

pPUT



p_T

,

(1)

where the sums run over the chargedand neutral hadrons, and photons,ina conedefinedby



R

≡

√

(

η

)

2

_{+ (φ)}

2 _aroundthe

leptontrajectory. Theradius



R isset tobe0.4and0.3inthe8 and13 TeV dataanalyses,respectively. Tominimize the contribu-tionof chargedparticles from pileupto the isolation calculation, chargedhadronsare includedonlyifthey originatefromthe pri-maryvertex.Thecontributionsofneutralparticlesfrompileupto theactivityinside theconearoundaleptonisreferred toas pPU

T ,

andisobtainedwithdifferent methodsfor electronsand muons. Forelectrons,pPU_T isevaluatedwiththejetareamethoddescribed inRef. [37]. Formuons, it is takento be halfthe sumof the pT

of all charged particles in the cone originating from pileup ver-tices.The factorofone-half accountsfortheexpectedfractionof neutralto chargedparticles in hadronicinteractions. A lepton is consideredisolatedifRiso

<

0

.

4

(

0

.

35

)

inthe8(13) TeV data

anal-ysis.

Thelepton momentumscales are calibratedinbins of p

T and

η

usingthedecayproductsofknownresonancesdecayingto lep-tonpairs.Themeasuredleptonmomentumscaleiscorrectedwith a Z

→ 

+



− sample, by matching the peak of the reconstructed dilepton mass spectrum to the nominal value of mZ [38]. Muon

momentaarecalibratedbyusing J

/ψ

decaysaswell.We account for final-state radiation of leptons by correcting their momenta withphotonsofpT

>

2GeV andwithinaconeof



R

=

0

.

5 around

thelepton momentumdirection [39,40]. Thephotonsselected by this algorithm are excluded from the lepton isolation computa-tion. The efficiency of the lepton reconstruction and selection is measured with the tag-and-probe technique [41] in bins of p_T

and

η

. Thismeasurement isused to correctthe simulation effi-ciency.

Jets are reconstructed from particle candidates by means of the anti-kT clustering algorithm [33], as implemented in the

FastJet package [34], with a distance parameter of 0.5 (0.4) in the 8 (13) TeV data analysis. The jet energy resolution amounts typicallyto15%at10 GeV,8%at100 GeV,and4%at1 TeV.

Jet energy corrections are extracted from the data and the simulatedevents by combiningseveralmeasurements and meth-ods that account for the effects of pileup, non-uniform de-tector response, and residual data-simulation jet energy scale (JES) differences. The JES calibration [42,43] relies on corrections parametrizedintermsoftheuncorrected pTand

η

ofthejet,and

areappliedasmultiplicativefactorstothefour-momentumvector ofeachjet.

Inordertomaximizethereconstructionefficiencywhile reduc-ing the instrumental background andcontamination from pileup jets, looseidentification quality criteria [44] are imposed onjets, based on the energy fraction carried by charged and neutral hadrons, as well as charged leptons and photons. A minimum threshold of 30 GeV onthe pT of jets isrequired to ensure that

they are well measured and to reduce thepileup contamination. Jets are required to have

|

η

|

<

4

.

7 and to be separated from all selected lepton candidates by at least



R

=

0

.

5

(

0

.

4

)

in the 8 (13) TeV analysis.

AsignaleventmustcontainatleasttwoZ

/

γ

∗ candidates,each reconstructed from a pair of isolated electrons or muons of op-posite charges. The highest-pT lepton must have pT

>

20GeV,

and the second-highest lepton pe

T

>

10

(

12

)

GeV if it is an

elec-tron, or pμ_T

>

10GeV in case of a muon for the analysis at

√

s

=

8

(

13

)

TeV. All leptons are required to be separated by



R



, 





>

0

.

02,andelectronsare requiredtobeseparatedfrom muonsby



R

(

e

,

μ

) >

0

.

05.

Withineachevent,allpermutationsofoppositelycharged lep-tons givinga validpair of Z

/

γ

∗ candidatesare considered sepa-rately. For each 4



candidate, the lepton pair with the invariant mass closest tothe nominalZ boson massis denotedby Z1 and

the other dilepton candidate is denoted by Z2. Both Z1 and Z2

are required to have a mass between 60 and120 GeV. All pairs ofoppositely chargedleptons inthe4



candidatearerequired to have m

>

4GeV regardless of their flavor to remove contribu-tionsfromthedecayoflow-masshadronresonances.

If multiple 4



candidates within an event pass thisselection, the candidate with mZ1 closest to the nominal Z boson mass is

chosen. In therare cases (0.3%)of furtherambiguity, which may arise in events with more than 4 leptons, the Z2 candidate that

maximizesthescalarpTsumofthefourleptonsischosen.Theset

ofselectioncriteriajustdescribedisreferredtoastheZZ selection, andgivesatotalof288 (927)observedeventsat

√

s

=

8

(

13

)

TeV. ThecorrespondingnumberofexpectedsignaleventsfromMC pre-dictionisabout271 (850).

5. Backgroundestimation

Thelargestsourceofbackgroundarisesfromprocessesinwhich heavy-flavor jets produce secondary leptons, and from processes inwhich jetsare misidentified asleptons. Themain contributing processesareZ+jets,tt,andWZ+jets.

However, the lepton identification and isolation requirements reduce this background to a very small level compared to the signal. The residual contribution is estimated fromdata samples consisting of Z +



events that are required to pass the ZZ se-lection described in Section 4, except that either one or both leptons belonging to the Z2 candidate fail the isolation or

iden-tification requirements. Two control samples are selected, with one and two misidentified leptons, respectively. The background yieldinthesignalregionisestimatedbyweightingthenumberof

Table 1

ThecontributionstotheuncertaintyintheabsoluteandnormalizeddifferentialcrosssectionmeasurementsinFig.2and3, upperpanels.Uncertaintiesthatdependonjetmultiplicityarelistedasarange.

Systematic source 8 TeV data 13 TeV data

Absolute (%) Normalized (%) Absolute (%) Normalized (%)

Trigger 1.5 – 2.0 –

Lepton reconstruction and selection 0.9–4.4 ≤0.1 3.7–4.5 0.1–0.8

Jet energy scale 1.5–9.2 1.5–9.1 4.6–17.5 4.6–17.5

Jet energy resolution 0.2–1.7 0.2–1.7 2.1–8.4 2.1–8.4

Background yields 0.7–7.2 0.7–5.4 0.5–2.8 0.4–2.0

Pileup 1.8 1.8 0.3–1.9 0.6–1.8

Luminosity 2.6 – 2.5 –

Choice of Monte Carlo generators 0.2–3.7 0.2–3.7 0.5–5.0 0.8–4.7

qq/gg cross section 0.1–0.8 0.1–0.8 <0.1–0.3 0.1–0.2

PDF 1.0 – <0.1–0.2 <0.1–0.2

αS <0.1 <0.1 ≤0.1 ≤0.1

eventsinthecontrolsamplesby theleptonmisidentificationrate measured indataina dedicatedcontrol region.The procedureis identicalto that of Refs. [7,8] and isdescribed in more detail in Ref. [39].

Anothersource ofbackground arisesfromprocesses that pro-duce four genuine high-pT isolated leptons, pp

→

ttZ and pp

→

WWZ.Thiscontributionissmallandisestimatedbyusingthe cor-respondingsimulatedsamples.

Thetotalestimatedbackgroundyieldsare8

±

4 (37

±

11)events inthe8(13) TeV signalregion.

6. Systematicuncertainties

Thesystematicuncertaintiesareestimatedbyvaryingthe quan-tities that may affect the cross section and by propagating the changes to the analysis procedure. The systematic uncertainties fromsourcesthat mayaffectthedifferential crosssection shapes havebeen estimatedthrough theunfolding procedure by recom-putingtheresponsematrix,aftervaryingeachsourceofsystematic uncertainty independently and in both directions, up anddown. The systematicuncertainties inthe differentialcross section asa functionof thejet multiplicity are summarizedinTable 1.Those that depend on the number of jets in the event are listed as a range.

Thesystematicuncertaintyinthetriggerefficiencyisevaluated bytakingthedifferencebetweenthevalueobtainedfromthedata andthat fromthe simulatedevents, and it leads to a 1.5(2.0)% uncertainty in the differential cross sections measured with the 8(13) TeV data. Theuncertainties arising fromlepton reconstruc-tionandselection (identification,isolation, andimpactparameter determination)dependonthejetmultiplicity,aresensitiveto sta-tisticalfluctuations,andrangebetween0.9and4.4%,inthe8 TeV analysis(3.7and4.5%,inthe13 TeV analysis).Thelargest contribu-tiontothesystematicuncertaintyinthedifferentialcrosssection measurementscomesfromtheJESdetermination,whichincreases withthejetmultiplicityandreaches9.2(17.5)%whenthenumber ofjetsexceedstwointhe8(13) TeV analysis.Likewise,the uncer-taintyduetothejetenergyresolution(JER)increasesfrom0.2to 1.7% (2.1 to 8.4%) for the 8 (13) TeV samples. The larger JES and JERuncertaintiesforthe13 TeVsamplereflecttheincrease inthe numberof softjets(with pT close tothe 30 GeV threshold) asa

functionofthecenter-of-massenergy.

The uncertainties in the Z+jets, WZ+jets, and tt background have two components, which are added in quadrature. The first relates to the different relative fraction of these background processes in the control sample where we measure the lepton misidentificationrateandthesampletowhichthisrateisapplied.

Thesecondisthestatisticaluncertaintyinthecontrolsample.The effectoftheseuncertaintiesincreaseswiththejetmultiplicityand amounts to 0.7–6.9% (0.5–2.4%) in the 8 (13) TeV measurement. The contribution to the uncertainty from the modeling of gen-uine four lepton background is smaller and varies between 0.1 and2.0% (

<

0

.

1 and 1.2%)forthe 8(13) TeV data. Thepileup un-certainty isevaluated by varying thepileup modeling in theMC samples within its uncertainty. The uncertainty inthe integrated luminosity is 2.6 [45] and 2.5% [46] for the 8 and 13 TeV data, respectively.

The contributionoftheMCgenerator choicetothesystematic uncertainty isobtainedby comparingthe resultsfoundwithtwo different sets of MC samples: MadGraph5

+

mcfm

+

Phantom (MG5_amc@nlo

+

mcfm

+

Phantom) and powheg

+

mcfm

+

Phantom_{forthe8(13) TeV measurement,andrangesfrom0.2to} 3.7% (0.5 to 5.0%) at 8 (13) TeV. The impact of the relative con-tribution ofthe qq

→

ZZ and gg

→

ZZ processes inthe response matrix definitionis lessthan 1%and isevaluated by varying the corresponding crosssection within theirrenormalizationand fac-torizationscaleuncertainties.For8 TeV,wherenoLOtoNLOfactor isappliedtothe mcfm cross section,thegg

→

ZZ cross sectionis variedby100%ofitsvalue.ThestatisticaluncertaintiesoftheMC samples resultin negligible contributionsto the response matrix uncertainty.The systematicuncertaintyarisingfromthechoiceof the PDF andthestrong couplingstrength

α

S hasbeenevaluated

using the PDF4LHC recommendations [47–49], using the CT10, MSTW08,andNNPDF2.3 [50] PDF sets,in the8 TeV analysis,and theNNPDF3.0setinthe13 TeV analysis.

Thetotalsystematicuncertaintyisobtainedbysummingallthe sources inquadrature,takingintoaccountthecorrelationsamong thedifferentchannels.

For the normalizeddifferential cross sections,only systematic uncertainties affectingtheshape ofthedistributions arerelevant. The uncertainties in the luminosity and trigger efficiency cancel out completely,as well asother contributions to the uncertainty inthetotalyield.

7. TheZZ+jets differentialcrosssectionmeasurements

The distributionsofthe jetmultiplicity combiningthe4μ, 4e, and 2μ2e channels are shown in Fig. 1, together with the SM expectations, the estimated backgrounds,and the systematic un-certaintyintheprediction.

The differential pp

→

ZZ

→ 





 cross section is measured asa functionof thejet multiplicity,the pT-leading jet transverse

momentum (pj1_T)andpseudorapidity (ηj1) withthe8 and13 TeV

Fig. 1. Distributionofthereconstructedjetmultiplicityinthe8 TeV (left)and13 TeV (right)data.Thepointsrepresentthedataandtheverticalbarscorrespondtothe

statis-ticaluncertainty.TheshadedhistogramsrepresentMCpredictionsandthebackgroundestimates,whilethehatchedbandontheirsumindicatesthesystematicuncertainty

oftheprediction.TheZ+jets andtt backgroundisobtainedfromthedata.

Table 2

Phasespacedefinitionsforcrosssectionmeasurements

at8 TeV [6] and13 TeV [8].Thecommondefinitions

ap-plytobothmeasurements.

8 TeV 13 TeV pe T>7 GeV,|ηe| <2.5 peT>5 GeV,|ηe| <2.5 pμT>5 GeV,|ημ| <2.4 p μ T>5 GeV,|ημ| <2.5 Common definitions p1 T >20 GeV, p 2 T >10 GeV

m+−>4 GeV (any opposite-sign same-flavor pair)

60< (mZ1,mZ2) <120 GeV

one jet at 8 TeV, the differential cross section as a function of the pT-subleadingjet transverse momentum (pj2_T) and

pseudora-pidity (ηj2), aswell asthe invariant mass of thetwo pT-leading

jets (mjj) and their pseudorapidity separation (



η

jj) are

stud-ied at 13 TeV only. For all measurements we consider jets with

pj_T

>

30GeV and

|

η

j

|

<

4

.

7.Forthejetmultiplicitydistributionwe

alsopresentthemeasurementsmadewithcentraljets(

|

η

j

|

<

2

.

4)

only. The measurements are performed for the two slightly dif-ferent phase space regions adopted for the 8 [6] and 13 [8] TeV data,which are givenin Table 2.The generator-level lepton mo-menta are corrected by adding the momenta of generator-level photons within



R

(,

γ

) <

0

.

1. The Z bosons are then selected withthesamemethodadoptedtoextractthesignalatthe recon-structionlevel. Inorder to define the jetsat generator level,the generatedparticlesareclusteredusingtheanti-kT algorithm,with

adistanceparameteridenticaltothecorrespondingone at recon-structionlevel.

Eachdistribution iscorrectedfortheeventselectionefficiency andthe detectorresolution effects by means of a response ma-trix that translates the physics variables at generator level into their reconstructed values. The correction procedure is based on theiterativeD’Agostiniunfoldingmethodtechnique [51],as imple-mentedinthe RooUnfold toolkit [52],andregularizedbystopping afterfouriterations. Therobustness oftheresultistestedagainst thesingular valuedecomposition(SVD) [53] alternativeunfolding method.Foreachmeasureddistribution,aresponsematrixis eval-uatedusingtwodifferentsetsofgenerators:thefirstoneincludes MadGraph_{5 (qq}

→

_{ZZ), mcfm (gg}

→

_{ZZ) and Phantom (qq}

→

ZZ

+

2jets)forthe8 TeV datasetand MG5_amc@nlo (qq

→

ZZ),

mcfm(gg

→

ZZ) and Phantom (qq

→

ZZ

+

2 jets)forthe 13 TeV dataset.Inthesecondone,the powheg sampleisinsteadusedfor theqq

→

ZZ process inboththe 8and13 TeV data analyses.The formerset,wheretheleading-orderMCgeneratorcansimulateup totwojetsatmatrix-elementlevel,istakenasthereference,while the latteris used forcomparison andto estimate the systematic uncertainty dueto the MC generator choice. Afterthe unfolding, thecrosssectionsforpp

→

ZZ

+

N jets

→ 







+

N jets,forN

=

0, 1,2,and

≥

3,areextracted.

Thedifferentialcrosssectionsasafunctionofthejet multiplic-ity are shown in Fig. 2 for

|

η

j

|

<

4

.

7 (upper) and for

|

η

j

|

<

2

.

4

(lower). The ratios between the measured and expected distri-butions from the MadGraph5, MG5_amc@nlo, and powheg set of samples for

√

s

=

8TeV, and powheg and MG5_amc@nlo for

√

s

=

13TeV are also shown in the figures. Uncertainties in the MCpredictionsatthematrix-elementlevelareevaluatedby vary-ingtherenormalizationandfactorizationscalesindependently,up and down,by a factorof two with respect to thedefault values of

μ

R

=

μ

F

=

m4for powheg and

μ

R

=

μ

F

=

1₂



pj_T

+



p_T for

MG_{5_amc@nlo.Inthe mcfm predictions,theuncertaintyintheLO} to NLO cross section scaling factor includes the renormalization and factorizationscales uncertainty. The theoretical uncertainties also include the uncertainties in the PDF and

α

S. The measured

and expectedcross section valuesfor

|

η

j

|

<

4

.

7 are given in

Ta-bles3and4.

Thedifferential distributions,normalizedto thecrosssections, are presented in Figs. 3–6 together with the theoretical predic-tions. Forthe theoretical predictions, only theuncertainty in the shapeisincluded,whichyieldsasmalleruncertaintycomparedto the unnormalized case. Fig.3 (toppanels) showsthe normalized differentialcrosssectionasafunction ofthejetmultiplicity,with

|

η

j

|

<

4

.

7. The observed fraction of events in the first bin with

zero jets is larger than the predicted value, while for 1, 2, and

≥

3 jets, the fraction is lower.Better agreement is observed for

|

η

j

|

<

2

.

4 (Fig.3,bottompanels).Themeasurementsofthe

differ-ential crosssection asa function ofthe jetmultiplicity are fairly wellreproducedbythepredictionsbothat8and13 TeV whenNLO matrix-elementcalculationsareusedinconjunctionwith pythia 8 forpartonshowering,hadronization,andunderlyingevent simula-tion. Inthe data,jets tendto havea lower pT value than in the

simulations andtherefore,onaverage,they arelesslikelyto pass the 30 GeV threshold,thus increasing thenumberof eventswith no jets. The observation of fewer events than expected with at leastonejet canbe ascribedtoa softerdistribution ofthe

trans-Fig. 2. Differentialcrosssectionsofpp→ZZ→4asafunctionofthemultiplicityofjetswith|ηj|<4.7 (toppanels)and|ηj|<2.4 (bottompanels),forthe8(left)and13

(right) TeV data.Themeasurementsarecomparedtothepredictionsof MG5_amc@nlo, powheg,and MadGraph5(8 TeV only)setsofsamples.EachMCset,alongwiththe

mainMCgenerator,includesthe mcfm and Phantom generators. pythia 6and pythia 8areusedforpartonshowering,hadronization,andunderlyingeventsimulation,for

the8and13 TeV analysis,respectively,withthesoleexceptionof MG5_amc@nlo,whichisalwaysinterfacedto pythia 8.Thetotalexperimentaluncertaintiesareshownas hatchedregions,whilethecoloredbandsdisplaythetheoreticaluncertaintiesinthematrix-elementcalculations.

Table 3

Thepp→ZZ→ _ _{crosssectionat}√_{s=8TeV asafunctionofthejetmultiplicity.Theintegratedluminosity}

uncer-taintyfornumberofjets=2and≥3isnegligibleandnotquoted.Thecrosssectionsarecomparedtothetheoretical

predictions(lastcolumn)from MG5_amc@nlo+mcfm+Phantom.

Number of jets (|ηj| <4.7) Cross section [fb] Theoretical cross section [fb]

0 16.3±1.2 (stat)+1.0

−0.9(syst)±0.4 (lumi) 13.2+

0.9

−0.7

1 3.2±0.6 (stat)₋+00..33(syst)±0.1 (lumi) 4.0+

0.5 −0.3 2 0.7±0.3 (stat)+0.1 −0.1(syst) 1.2+ 0.2 −0.1 ≥3 0.14±0.1 (stat)+₋00..0101(syst) 0.3+ 0.1 −0.1

verse momentum of the hadronic particles recoiling against the dibosonsystem.Thisexplanationissupportedbythemeasurement of a softer-than-expected pT distribution of the ZZ system [6,8].

The observeddiscrepancymaybe duetohigher-ordercorrections toZZ production,notincludedinMCsamplesusedinthisanalysis, ortothepartonshowermodeling.

Table 4

Thepp→ZZ→ __{crosssectionat}√_{s=13TeV asafunctionofthejetmultiplicity.Theintegratedluminosity}

uncer-taintyforthenumberofjets≥3issmallerthan0.1 fb andisnotquoted.Thecrosssectionsarecomparedtothetheoretical

predictions(lastcolumn)from MG5_amc@nlo+mcfm+Phantom.

Number of jets (|ηj| <4.7) Cross section [fb] Theoretical cross section [fb]

0 28.3±1.3 (stat)₋+11..75(syst)±0.7 (lumi) 23.6+

0.8 −0.9 1 8.0±0.8 (stat)+0.7 −0.8(syst)±0.2 (lumi) 9.7+ 0.5 −0.5

2 3.0±0.5 (stat)₋+00..34(syst)±0.1 (lumi) 4.0+

0.3 −0.3 ≥3 1.3±0.4 (stat)+0.2 −0.2(syst) 1.7+ 0.1 −0.1

Fig. 3. Differentialcrosssectionsnormalizedtothecrosssectionofpp→ZZ→4asafunctionofthemultiplicityofjetswith|ηj|<4.7 (toppanels)and|ηj|<2.4 (bottom panels),forthe8(left)and13(right) TeV data.OtherdetailsareasdescribedinthecaptionofFig.2.

Fig. 4 shows the differential cross sections at 8 and 13 TeV asfunctions ofthe transverse momentum and pseudorapidity of the pT-leading jet, normalized to the cross section for Njets

≥

1.

Figs. 5 and 6 show the cross section at 13 TeV as a function of

severalvariablesforeventswith Njets

≥

2, normalizedtothe

cor-respondingcrosssection.Morespecifically,Fig.5presentsthe nor-malized differential cross sections asfunctions of the transverse momentum and pseudorapidity of the pT-subleading jet, while

Fig. 4. DifferentialcrosssectionsnormalizedtothecrosssectionforNjets≥1 ofpp→ZZ→4asafunctionofthepT-leadingjettransversemomentum(toppanels)and theabsolutevalueofthepseudorapidity(bottompanels),forthe8(left)and13(right) TeV data.OtherdetailsareasdescribedinthecaptionofFig.2.

Fig. 6 displays the differential cross section as a function of mjj

and



η

jj.

Overall agreement is observed between data and theoretical predictions for all measurements related to the pT-leading and

subleadingjets.The



η

jjdistribution(Fig.6,right)measuredwith

13 TeV data tendstobe steeper thanthe MCpredictions, butthe differencesarenotstatisticallysignificant.

8. Summary

Thedifferential crosssectionsforthe productionofZ pairs in thefour-leptonfinalstateinassociationwithjetsinproton–proton collisions at

√

s

=

8 and 13 TeV have been measured. The data correspond to an integrated luminosity of 19.7 (35.9) fb−1 for a center-of-massenergyof 8 (13) TeV.Cross sections are presented

fortheproductionofapairofZ bosonsasafunctionofthe num-ber ofjets, the transverse momentum pT, andpseudorapidity of

the pT-leading and subleadingjets. Distributions of theinvariant

mass of the two pT-leading jets andtheir separationin

pseudo-rapidity arealsopresented.Good agreementisobservedbetween the measurements and the theoretical predictions when next-to-leading order matrix-elementcalculationsare usedtogether with the pythia partonshowersimulation.CrosssectionsforZZ produc-tion inassociationwithjet havebeenmeasured withaprecision ranging from 10 to 72% (8 to 38%) at 8 (13) TeV, for jet multi-plicities ranging from 0to

≥

3.The systematic uncertaintyis of the samesize,or smaller,than thestatisticalone.Analyses using future, largerdata sets,withsmaller statisticaluncertainties, will allow thetheoreticalpredictionofZZ+jets toundergomore strin-genttests.

Fig. 5. DifferentialcrosssectionsnormalizedtothecrosssectionforNjets≥2 ofpp→ZZ→4at√s=13TeV asafunctionofthepT-subleadingjettransversemomentum (left)andtheabsolutevalueofthepseudorapidity(right).OtherdetailsareasdescribedinthecaptionofFig.2.

Fig. 6. DifferentialcrosssectionsnormalizedtothecrosssectionforNjets≥2 ofpp→ZZ→4at√s=13TeV asafunctionoftheinvariantmassofthetwopT-leadingjets (left)andtheirpseudorapidityseparation(right).OtherdetailsareasdescribedinthecaptionofFig.2.

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 effectivelythecomputinginfrastructure essential toour analyses. Finally, we acknowledge the enduring support for the construc-tionandoperationofthe LHCandtheCMSdetectorprovided by 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);NKFIA (Hungary);DAE

andDST (India); IPM(Iran);SFI (Ireland); INFN (Italy);MSIP and NRF(RepublicofKorea);LAS(Lithuania);MOEandUM(Malaysia); BUAP, CINVESTAV, CONACYT, LNS, SEP, and UASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT(Portugal);JINR(Dubna);MON,ROSATOM,RASandRFBR (Rus-sia);MESTD (Serbia);SEIDI,CPAN,PCTI andFEDER(Spain); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR, andNSTDA (Thailand); TÜBITAK and TAEK (Turkey); NASU andSFFR(Ukraine);STFC(UnitedKingdom);DOEandNSF(USA).

Individuals have received support from the Marie-Curie pro-gramandtheEuropeanResearchCouncilandHorizon2020Grant, contract No. 675440 (European Union); the Leventis Foundation; the Alfred P. Sloan Foundation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation à la Recherche dans l’Industrie et dans l’A-griculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the F.R.S.-FNRS and FWO (Belgium) under the “Excellence of Science – EOS” – be.h

projectNo. 30820817;theMinistryofEducation,YouthandSports (MEYS) of the Czech Republic; the Lendület (“Momentum”) Pro-gram and the János Bolyai Research Scholarship of the Hungar-ian Academy of Sciences, the New National Excellence Program ÚNKP,theNKFIAresearchgrants123842,123959,124845,124850 and125105 (Hungary);the Council ofScience andIndustrial Re-search, India; the HOMING PLUS program of the Foundation for Polish Science, cofinanced fromEuropean Union, Regional Devel-opment Fund, the MobilityPlus program of the Ministry of Sci-enceandHigher Education,the NationalScienceCentre (Poland), contracts Harmonia 2014/14/M/ST2/00428, Opus 2014/13/B/ST2/ 02543,2014/15/B/ST2/03998,and2015/19/B/ST2/02861,Sonata-bis 2012/07/E/ST2/01406;theNationalPrioritiesResearchProgramby Qatar National Research Fund; the Programa Estatal de Fomento de la Investigación Científica y Técnica de Excelencia María de Maeztu, grant MDM-2015-0509 and the Programa Severo Ochoa delPrincipadode Asturias;the ThalisandAristeia programs cofi-nancedbyEU-ESFandtheGreekNSRF;theRachadapisekSompot FundforPostdoctoralFellowship,ChulalongkornUniversityandthe ChulalongkornAcademicintoIts2ndCenturyProjectAdvancement Project(Thailand);theWelchFoundation,contractC-1845;andthe WestonHavensFoundation(USA).

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A.M. Sirunyan,

A. Tumasyan

YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam,

F. Ambrogi,

E. Asilar,

T. Bergauer,

J. Brandstetter,

M. Dragicevic,

J. Erö,

A. Escalante Del Valle,

M. Flechl,

R. Frühwirth

1

,

V.M. Ghete,

J. Hrubec,

M. Jeitler

1

,

N. Krammer,

I. Krätschmer,

D. Liko,

T. Madlener,

I. Mikulec,

N. Rad,

H. Rohringer,

J. Schieck

1

,

R. Schöfbeck,

M. Spanring,

D. Spitzbart,

A. Taurok,

W. Waltenberger,

J. Wittmann,

C.-E. Wulz

1

,

M. Zarucki

InstitutfürHochenergiephysik,Wien,Austria

V. Chekhovsky,

V. Mossolov,

J. Suarez Gonzalez

InstituteforNuclearProblems,Minsk,Belarus

E.A. De Wolf,

D. Di Croce,

X. Janssen,

J. Lauwers,

M. Pieters,

M. Van De Klundert,

H. Van Haevermaet,

P. Van Mechelen,

N. Van Remortel

UniversiteitAntwerpen,Antwerpen,Belgium

S. Abu Zeid,

F. Blekman,

J. D’Hondt,

I. De Bruyn,

J. De Clercq,

K. Deroover,

G. Flouris,

D. Lontkovskyi,

S. Lowette,

I. Marchesini,

S. Moortgat,

L. Moreels,

Q. Python,

K. Skovpen,

S. Tavernier,

W. Van Doninck,

P. Van Mulders,

I. Van Parijs

VrijeUniversiteitBrussel,Brussel,Belgium

D. Beghin,

B. Bilin,

H. Brun,

B. Clerbaux,

G. De Lentdecker,

H. Delannoy,

B. Dorney,

G. Fasanella,

L. Favart,

R. Goldouzian,

A. Grebenyuk,

A.K. Kalsi,

T. Lenzi,

J. Luetic,

N. Postiau,

E. Starling,

L. Thomas,

C. Vander Velde,

P. Vanlaer,

D. Vannerom,

Q. Wang

UniversitéLibredeBruxelles,Bruxelles,Belgium

T. Cornelis,

D. Dobur,

A. Fagot,

M. Gul,

I. Khvastunov

2

,

D. Poyraz,

C. Roskas,

D. Trocino,

M. Tytgat,

W. Verbeke,

B. Vermassen,

M. Vit,

N. Zaganidis

H. Bakhshiansohi,

O. Bondu,

S. Brochet,

G. Bruno,

C. Caputo,

P. David,

C. Delaere,

M. Delcourt,

B. Francois,

A. Giammanco,

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V. Lemaitre,

A. Magitteri,

A. Mertens,

M. Musich,

K. Piotrzkowski,

A. Saggio,

M. Vidal Marono,

S. Wertz,

J. Zobec

UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium

F.L. Alves,

G.A. Alves,

M. Correa Martins Junior,

G. Correia Silva,

C. Hensel,

A. Moraes,

M.E. Pol,

P. Rebello Teles

CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

E. Belchior Batista Das Chagas,

W. Carvalho,

J. Chinellato

3

,

E. Coelho,

E.M. Da Costa,

G.G. Da Silveira

4

,

D. De Jesus Damiao,

C. De Oliveira Martins,

S. Fonseca De Souza,

H. Malbouisson,

D. Matos Figueiredo,

M. Melo De Almeida,

C. Mora Herrera,

L. Mundim,

H. Nogima,

W.L. Prado Da Silva,

L.J. Sanchez Rosas,

A. Santoro,

A. Sznajder,

M. Thiel,

E.J. Tonelli Manganote

3

,

F. Torres Da Silva De Araujo,

A. Vilela Pereira

UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

S. Ahuja

a

,

C.A. Bernardes

a

,

L. Calligaris

a

,

T.R. Fernandez Perez Tomei

a

,

E.M. Gregores

b

,

P.G. Mercadante

b

,

S.F. Novaes

a

,

Sandra S. Padula

a

,

D. Romero Abad

b

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

A. Aleksandrov,

R. Hadjiiska,

P. Iaydjiev,

A. Marinov,

M. Misheva,

M. Rodozov,

M. Shopova,

G. Sultanov

InstituteforNuclearResearchandNuclearEnergy,BulgarianAcademyofSciences,Sofia,Bulgaria

A. Dimitrov,

L. Litov,

B. Pavlov,

P. Petkov

UniversityofSofia,Sofia,Bulgaria

W. Fang

5

,

X. Gao

5

,

L. Yuan

BeihangUniversity,Beijing,China

M. Ahmad,

J.G. Bian,

G.M. Chen,

H.S. Chen,

M. Chen,

Y. Chen,

C.H. Jiang,

D. Leggat,

H. Liao,

Z. Liu,

F. Romeo,

S.M. Shaheen

6

,

A. Spiezia,

J. Tao,

C. Wang,

Z. Wang,

E. Yazgan,

H. Zhang,

J. Zhao

InstituteofHighEnergyPhysics,Beijing,China

Y. Ban,

G. Chen,

A. Levin,

J. Li,

L. Li,

Q. Li,

Y. Mao,

S.J. Qian,

D. Wang,

Z. Xu

StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

Y. Wang

TsinghuaUniversity,Beijing,China

C. Avila,

A. Cabrera,

C.A. Carrillo Montoya,

L.F. Chaparro Sierra,

C. Florez,

C.F. González Hernández,

M.A. Segura Delgado

UniversidaddeLosAndes,Bogota,Colombia

B. Courbon,

N. Godinovic,

D. Lelas,

I. Puljak,

T. Sculac

UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia

Z. Antunovic,

M. Kovac

UniversityofSplit,FacultyofScience,Split,Croatia

V. Brigljevic,

D. Ferencek,

K. Kadija,

B. Mesic,

A. Starodumov

7

,

T. Susa

M.W. Ather,

A. Attikis,

M. Kolosova,

G. Mavromanolakis,

J. Mousa,

C. Nicolaou,

F. Ptochos,

P.A. Razis,

H. Rykaczewski

UniversityofCyprus,Nicosia,Cyprus

M. Finger

8

,

M. Finger Jr.

8

CharlesUniversity,Prague,CzechRepublic

E. Ayala

EscuelaPolitecnicaNacional,Quito,Ecuador

E. Carrera Jarrin

UniversidadSanFranciscodeQuito,Quito,Ecuador

A. Ellithi Kamel

9

,

M.A. Mahmoud

10

,

11

,

E. Salama

11

,

12

AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt

S. Bhowmik,

A. Carvalho Antunes De Oliveira,

R.K. Dewanjee,

K. Ehataht,

M. Kadastik,

M. Raidal,

C. Veelken

NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia

P. Eerola,

H. Kirschenmann,

J. Pekkanen,

M. Voutilainen

DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland

J. Havukainen,

J.K. Heikkilä,

T. Järvinen,

V. Karimäki,

R. Kinnunen,

T. Lampén,

K. Lassila-Perini,

S. Laurila,

S. Lehti,

T. Lindén,

P. Luukka,

T. Mäenpää,

H. Siikonen,

E. Tuominen,

J. Tuominiemi

HelsinkiInstituteofPhysics,Helsinki,Finland

T. Tuuva

LappeenrantaUniversityofTechnology,Lappeenranta,Finland

M. Besancon,

F. Couderc,

M. Dejardin,

D. Denegri,

J.L. Faure,

F. Ferri,

S. Ganjour,

A. Givernaud,

P. Gras,

G. Hamel de Monchenault,

P. Jarry,

C. Leloup,

E. Locci,

J. Malcles,

G. Negro,

J. Rander,

A. Rosowsky,

M.Ö. Sahin,

M. Titov

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

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,

C. Amendola,

I. Antropov,

F. Beaudette,

P. Busson,

C. Charlot,

R. Granier de Cassagnac,

I. Kucher,

A. Lobanov,

J. Martin Blanco,

M. Nguyen,

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J.B. Sauvan,

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A. Zabi,

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

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D. Bloch,

J.-M. Brom,

E.C. Chabert,

V. Cherepanov,

C. Collard,

E. Conte

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14

,

D. Gelé,

U. Goerlach,

M. Jansová,

A.-C. Le Bihan,

N. Tonon,

P. Van Hove

UniversitédeStrasbourg,CNRS,IPHCUMR7178,Strasbourg,France

S. Gadrat

CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France

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C. Bernet,

G. Boudoul,

N. Chanon,

R. Chierici,

D. Contardo,

P. Depasse,

H. El Mamouni,

J. Fay,

L. Finco,

S. Gascon,

M. Gouzevitch,

G. Grenier,

B. Ille,

F. Lagarde,

I.B. Laktineh,

H. Lattaud,

M. Lethuillier,

L. Mirabito,

A.L. Pequegnot,

S. Perries,

A. Popov

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M. Vander Donckt,

S. Viret,

S. Zhang

T. Toriashvili

16

GeorgianTechnicalUniversity,Tbilisi,Georgia

I. Bagaturia

17

TbilisiStateUniversity,Tbilisi,Georgia

C. Autermann,

L. Feld,

M.K. Kiesel,

K. Klein,

M. Lipinski,

M. Preuten,

M.P. Rauch,

C. Schomakers,

J. Schulz,

M. Teroerde,

B. Wittmer,

V. Zhukov

15

RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany

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D. Duchardt,

M. Endres,

M. Erdmann,

T. Esch,

R. Fischer,

S. Ghosh,

A. Güth,

T. Hebbeker,

C. Heidemann,

K. Hoepfner,

H. Keller,

S. Knutzen,

L. Mastrolorenzo,

M. Merschmeyer,

A. Meyer,

P. Millet,

S. Mukherjee,

T. Pook,

M. Radziej,

H. Reithler,

M. Rieger,

F. Scheuch,

A. Schmidt,

D. Teyssier

RWTHAachenUniversity,III.PhysikalischesInstitutA,Aachen,Germany

G. Flügge,

O. Hlushchenko,

T. Kress,

A. Künsken,

T. Müller,

A. Nehrkorn,

A. Nowack,

C. Pistone,

O. Pooth,

D. Roy,

H. Sert,

A. Stahl

18

RWTHAachenUniversity,III.PhysikalischesInstitutB,Aachen,Germany

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T. Arndt,

C. Asawatangtrakuldee,

I. Babounikau,

K. Beernaert,

O. Behnke,

U. Behrens,

A. Bermúdez Martínez,

D. Bertsche,

A.A. Bin Anuar,

K. Borras

19

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A. Campbell,

P. Connor,

C. Contreras-Campana,

F. Costanza,

V. Danilov,

A. De Wit,

M.M. Defranchis,

C. Diez Pardos,

D. Domínguez Damiani,

G. Eckerlin,

T. Eichhorn,

A. Elwood,

E. Eren,

E. Gallo

20

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A. Geiser,

J.M. Grados Luyando,

A. Grohsjean,

P. Gunnellini,

M. Guthoff,

M. Haranko,

A. Harb,

J. Hauk,

H. Jung,

M. Kasemann,

J. Keaveney,

C. Kleinwort,

J. Knolle,

D. Krücker,

W. Lange,

A. Lelek,

T. Lenz,

K. Lipka,

W. Lohmann

21

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R. Mankel,

I.-A. Melzer-Pellmann,

A.B. Meyer,

M. Meyer,

M. Missiroli,

G. Mittag,

J. Mnich,

V. Myronenko,

S.K. Pflitsch,

D. Pitzl,

A. Raspereza,

M. Savitskyi,

P. Saxena,

P. Schütze,

C. Schwanenberger,

R. Shevchenko,

A. Singh,

H. Tholen,

O. Turkot,

A. Vagnerini,

G.P. Van Onsem,

R. Walsh,

Y. Wen,

K. Wichmann,

C. Wissing,

O. Zenaiev

DeutschesElektronen-Synchrotron,Hamburg,Germany

R. Aggleton,

S. Bein,

L. Benato,

A. Benecke,

V. Blobel,

M. Centis Vignali,

T. Dreyer,

E. Garutti,

D. Gonzalez,

J. Haller,

A. Hinzmann,

A. Karavdina,

G. Kasieczka,

R. Klanner,

R. Kogler,

N. Kovalchuk,

S. Kurz,

V. Kutzner,

J. Lange,

D. Marconi,

J. Multhaup,

M. Niedziela,

D. Nowatschin,

A. Perieanu,

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O. Rieger,

C. Scharf,

P. Schleper,

S. Schumann,

J. Schwandt,

J. Sonneveld,

H. Stadie,

G. Steinbrück,

F.M. Stober,

M. Stöver,

D. Troendle,

A. Vanhoefer,

B. Vormwald

UniversityofHamburg,Hamburg,Germany

M. Akbiyik,

C. Barth,

M. Baselga,

S. Baur,

E. Butz,

R. Caspart,

T. Chwalek,

F. Colombo,

W. De Boer,

A. Dierlamm,

K. El Morabit,

N. Faltermann,

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M. Giffels,

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U. Husemann,

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18

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S. Kudella,

H. Mildner,

S. Mitra,

M.U. Mozer,

Th. Müller,

M. Plagge,

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K. Rabbertz,

M. Schröder,

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H.J. Simonis,

R. Ulrich,

S. Wayand,

M. Weber,

T. Weiler,

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C. Wöhrmann,

R. Wolf

KarlsruherInstitutfuerTechnology,Germany

G. Anagnostou,

G. Daskalakis,

T. Geralis,

A. Kyriakis,

D. Loukas,

G. Paspalaki,

I. Topsis-Giotis

InstituteofNuclearandParticlePhysics(INPP),NCSRDemokritos,AghiaParaskevi,Greece

G. Karathanasis,

S. Kesisoglou,

P. Kontaxakis,

A. Panagiotou,

I. Papavergou,

N. Saoulidou,

E. Tziaferi,

K. Vellidis

K. Kousouris,

I. Papakrivopoulos,

G. Tsipolitis

NationalTechnicalUniversityofAthens,Athens,Greece

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C. Foudas,

P. Gianneios,

P. Katsoulis,

P. Kokkas,

S. Mallios,

N. Manthos,

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E. Paradas,

J. Strologas,

F.A. Triantis,

D. Tsitsonis

UniversityofIoánnina,Ioánnina,Greece

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22

,

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P. Major,

M.I. Nagy,

G. Pasztor,

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MTA-ELTELendületCMSParticleandNuclearPhysicsGroup,EötvösLorándUniversity,Budapest,Hungary

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C. Hajdu,

D. Horvath

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F. Sikler,

T.Á. Vámi,

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WignerResearchCentreforPhysics,Budapest,Hungary

N. Beni,

S. Czellar,

J. Karancsi

24

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J. Molnar,

Z. Szillasi

InstituteofNuclearResearchATOMKI,Debrecen,Hungary

P. Raics,

Z.L. Trocsanyi,

B. Ujvari

InstituteofPhysics,UniversityofDebrecen,Debrecen,Hungary

S. Choudhury,

J.R. Komaragiri,

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IndianInstituteofScience(IISc),Bangalore,India

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25

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26

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NationalInstituteofScienceEducationandResearch,HBNI,Bhubaneswar,India

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UniversityofDelhi,Delhi,India

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27

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IndianInstituteofTechnologyMadras,Madras,India

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D. Dutta,

V. Jha,

V. Kumar,

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M.A. Bhat,

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TataInstituteofFundamentalResearch-A,Mumbai,India

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