Observation of electroweak production of W gamma with two jets in proton-proton collisions at root s=13 TeV

Contents lists available atScienceDirect

Physics

Letters

B

www.elsevier.com/locate/physletb

Observation

of

electroweak

production

of

W

γ

with

two

jets

in

proton-proton

collisions

at

√

s

=

13 TeV

.

The

CMS

Collaboration



CERN,Geneva,Switzerland

a

r

t

i

c

l

e

i

n

f

o

a

b

s

t

r

a

c

t

Articlehistory:

Received24August2020

Receivedinrevisedform6November2020 Accepted26November2020

Availableonline1December2020 Editor: M.Doser

Keywords:

CMS Physics

Vectorbosonscattering

AfirstobservationispresentedfortheelectroweakproductionofaW boson,aphoton,andtwojetsin proton-protoncollisions.TheW bosondecaysareselectedbyrequiringoneidentifiedelectronormuon andanimbalanceintransversemomentum.Thetwojetsarerequiredtohaveahighdijetmassanda largeseparationinpseudorapidity.ThemeasurementisbasedondatacollectedwiththeCMSdetectorat acenter-of-massenergyof13 TeV,correspondingtoanintegratedluminosityof35.9 fb−1.Theobserved (expected)significanceforthisprocessis4.9(4.6)standarddeviations.Aftercombiningwithpreviously reportedCMSresultsat8 TeV,theobserved(expected)significanceis5.3(4.8)standarddeviations.The crosssectionfortheelectroweakWγjj productioninarestrictedfiducialregionismeasuredas20.4± 4.5 fb andthetotalcrosssectionforW_γproductioninassociationwith2jetsinthesamefiducialregion is 108±16 fb. Allresults are in good agreementwith recent theoretical predictions. Constraints are placedonanomalousquarticgaugecouplingsintermsofdimension-8effectivefieldtheoryoperators.

©2020TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

1. Introduction

After thediscoveryoftheHiggsbosonattheCERNLHC [1–3], oneoftheprimary goalsofhigh-energyphysicsistoexaminethe detailsofthemechanismofelectroweak(EW)symmetrybreaking, e.g., throughmeasurements ofthe propertiesofthe Higgsboson. Vectorbosonscattering(VBS)processescomprisean independent andcomplementarymethodtostudyEWsymmetrybreaking.The nonabelian nature of gauge interactions in the standard model (SM)leadstoarichvarietyofVBSprocesseswithuniquefeatures andopportunitiestoprobephysicsbeyondtheSM(BSM).

The highenergy and luminosity of the LHC make it possible to study the rare VBS processesin detail. TheCMS Collaboration reported the EW production of two W bosons of same electric charge produced in association with two jets (W±W±jj), with a significance of 5.5 standard deviations (SD) based on the initial proton-proton(pp) datacollected at13 TeV [4].There havebeen additional VBS results from both the ATLAS and CMS Collabora-tions. Notably, ATLAS observed EW (W±W±jj) productionwith a significanceof6.5 SD [5].CMSrecentlyreportedanobservationof WZ VBSevents ata significanceof6.8 SD [6], alongwithfurther studiesintheW±W±jj channel,basedondatacollectedat13TeV. Moreover,VBS processesinvolvingaphotoninthefinalstate,W

γ

andZ

γ

scattering,werealsoreportedbyATLASandCMS,basedon

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

datacollected at

√

s

=

8 TeV, corresponding to an integrated lu-minosityofapproximately20 fb−1 [7–9].Theobserved(expected) significanceforW

γ

scatteringfromCMSwas2.7(1.5) SD.ForZ

γ

scatteringATLASandCMSobserved(expected)significancesof2.0 (1.8)and3.0(2.1)SD,respectively,basedontheSM prediction.A recentupdateonZ

γ

scatteringfromCMS,basedontheinitialdata collectedat13TeV combinedwith8TeV results [10],reportedan observed(expected)significanceof4.7(5.5)SD.

Thispaperpresentsameasurement ofVBS intheW

γ

channel at

√

s

=

13 TeV. As shown in Fig. 1, the signal process includes both VBS and non-VBS EW diagrams, such as EW contributions throughtriple andquarticgaugecouplings. QCD-induced produc-tionofW

γ

jj canalsotake place,asshowninthediagramonthe right, withbothjetsoriginatingfromQCD vertices.Thediagrams shownarerepresentativeofthemanypossibilitiesintheSM.The effectsofBSMphysics,suchasanomaloustripleandquarticgauge couplings(aTGCandaQGC),arealsopossible [11].WhileaTGCare wellconstrainedbyotherprocessesincludingHiggsbosonand di-bosonproduction,VBSstudiesaremoresensitivetoaQGC.

The data correspond to an integrated luminosity of 35.9

±

0.9 fb−1collected during2016usingtheCMSdetector [12] atthe LHC.FormeasuringtheEWW

γ

jj production,candidateeventsare selectedby requiring one identified lepton (either an electronor muon), oneidentified photon, twojetswitha large rapidity sep-arationandalargedijetinvariantmass(mjj),andamoderate im-balanceintransversemomentum,pmiss_T .Thisselectionreducesthe contributionfromthestrong(QCD)productionofjetsproduced

to-https://doi.org/10.1016/j.physletb.2020.135988

0370-2693/©2020TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).Fundedby SCOAP3_.

Fig. 1. Representativediagramsforνγjj productionattheLHCforEWproduction(left),EWproductionthroughtriple(middleleft)andquartic(middleright)gaugeboson couplings,andQCD-inducedprocesses(right).

getherwiththeW bosonandthephoton,makingtheexperimental signature an ideal topology forVBS W

γ

studies.The interference among the VBS diagrams ensures the unitarity of the VBS cross section in theSM athighenergy, andan interferenceis also ex-pectedbetweenQCDandEWprocesses [13,14].

2. TheCMSdetector

The central feature ofthe CMS [12] apparatus is a supercon-ducting solenoid of6 m internal diameter, providing a magnetic field of 3.8 T. A silicon pixel and strip tracker, a lead tungstate crystalelectromagnetic calorimeter(ECAL), and abrass and scin-tillatorhadroncalorimeter(HCAL),eachcomposedofabarreland twoendcapsectionsresidewithinthevolumeofthesolenoid. For-wardcalorimetersextendthecoverageprovidedbythebarreland endcap detectors up to a pseudorapidity of

|

η

|

=

5. Muons are detected ingas-ionization chambers embedded in the steel flux-returnyokeoutsidethesolenoid.

Events of interest are selected using a two-tiered trigger sys-tem [15]. The first level (L1),composed of specialized hardware processors, usesinformationfromthecalorimetersandmuon de-tectorstoselecteventsatarateofaround100 kHz withalatency of4 μs.Thesecondlevelconsistsofafarmofprocessorsrunninga versionofthefulleventreconstructionsoftwareoptimizedforfast processingthatreducestheeventratetoaround1 kHz beforedata storage.

AmoredetaileddescriptionoftheCMSdetector,togetherwith adefinitionofthecoordinatesystemandkinematicvariables,can befoundinRef. [12].

3. Signalandbackgroundsimulation

The signal andbackground processes are simulated using the Monte Carlo (MC) generator MadGraph5_amc@nlo (MG5) [16]. The EW W

γ

text j j signal is simulated at leading order (LO) us-ing version 2.6.0. The main background from QCD W

γ

is sim-ulated with up to one jet in the matrix element calculation at next-to-leading order (NLO) with version 2.4.2, using the FxFx scheme [17] to merge jets from the matrix element calculation and parton showering. The interference between the EW and QCD processes is predicted to 1–3% in the signal region and is treated as a systematic uncertainty. Other background contribu-tions include diboson VV processes (WW, WZ, ZZ) simulated at LO with pythia 8.212 [18], single top quark processes simulated with powheg 2.0 [19], andtt

γ

productionsimulatedatNLOwith MG5usingtheFxFx jetmergingscheme.Cross sectionsevaluated at NLO inthe QCD couplingstrength (

α

S) are usedto normalize thesesimulatedeventsamples.

The pythia package,withtheCUETP8M1 [20,21] tune,is used forpartonshowering,hadronization,andunderlying-event simula-tion.TheNNPDF 3.0set [22] ofpartondistributionfunctions(PDFs) is used as default. All simulated events are processed through a Geant4 [23] simulation ofthe CMS detector.Factors determined

bya tag-and-probe technique [24] are usedto correctthe differ-encesbetweendataandsimulationinthetriggerefficiency,aswell asthereconstructionandidentification(ID)efficiencies.Additional overlapping pp interactions (pileup) are superimposed over the hardscatteringinteractionwithadistribution ofprimaryvertices matchingthat obtainedfromthe collision data. The MC samples areanalyzedusingthesameproceduresasthedata.

4. Eventreconstruction

The particle-flow (PF) algorithm [25] reconstructs and identi-fies each individual particle in an event, through an optimized combinationofinformationfromthevariouselementsoftheCMS detector.The energy ofphotonsis obtainedfrom theECAL mea-surement.Theenergyofelectronsisdeterminedfroma combina-tionoftheelectron momentumattheprimary interaction vertex asdeterminedinthetracker,theenergyofthecorrespondingECAL cluster,andtheenergysumofallbremsstrahlungphotonsspatially compatiblewithoriginatingfromtheelectrontrack.Theenergyof muonsisobtainedfromthecurvatureofthecorresponding track. The energy of charged hadrons is determined from a combina-tionoftheirmomentummeasuredinthetrackerandthematching ECALandHCALenergydepositions, corrected fortheresponse of thecalorimeters to hadronicshowers. Finally,the energyof neu-tral hadrons is obtained from the corresponding corrected ECAL and HCAL energies. The PF candidates are used for a variety of purposesin thisanalysis, such asevaluating electron, muon, and photonisolation variables,reconstructing jets,andcomputingthe

pmiss_T intheevent,asdescribedbelow.

Thereconstructedvertexwiththelargestvalueofsummedjet

p2

T istakentobe theprimarypp interactionvertex [26].The jets areclusteredusingtheanti-kT jet findingalgorithm [27,28] using thetracksassignedtocandidateverticesasinputs.

Electron candidates used in the selection of events for this analysisare reconstructed within

|

η

|

<

2.5 for pT

>

25 GeV. The electrons are alsorequired to pass additionalidentification crite-ria: selection on the relative amount ofenergy deposited in the HCAL,a match of the trajectory in thetracker with theposition oftheECALcluster [29],thenumberofmissingmeasurementsin thetracker,thecompatibilityoftheelectrontooriginatefromthe primaryvertex,and

σ

ηη ,aparameterthatquantifiesthespreadin

η

oftheshower inthe ECAL,asdiscussed inSection6.Electrons identifiedasarising fromphotonconversions arerejected [29,30]. Ahigh-qualityIDselectionisusedtoidentifyelectronsinthefinal state,andalooseselectionisusedtoidentifyelectronsforvetoing eventscontainingadditionalleptons.

Muons are reconstructed from information in the muon sys-temandthetrackerwithin

|

η

|

<

2.4 and pT

>

20 GeV [31].Muon candidatesmust satisfy IDcriteria basedon thenumberof mea-surements in the muon system and the tracker, the number of matchedmuon-detectorplanes,thequalityofthecombinedfitto thetrack,andthecompatibilityofthemuontooriginatefromthe primaryvertex.Ahigh-qualityID [31] isusedtoidentifymuonsin

the final state, andaloose ID [31] isused to identifymuonsfor vetoingeventswithadditionalleptons.

Another selection on an isolation variable (Iso) is applied for bothelectrons andmuons.Isoisdefinedrelative tothelepton pT by summingthe pT ofthechargedhadronsandneutralparticles ingeometricalconesof



R

=

√

(

η

)

2

+ (φ)

2

=

0.3

(0.4)

around theelectron(muon)trajectory:

I

=





pcharged_T

+

max



0

,



pneutral_T

+



pγ_T

−

pPU_T



p_T

,

where



pcharged_T is the scalar sum of the transverse momenta of charged hadrons originating from the primary vertex, and



pneutral

T and



pγ_T are,respectively,thescalarpTsumsofneutral hadronsandphotons.Tomitigatepileup(PU)effects,onlycharged hadrons originating at the primary vertex are included. For the neutral-hadron and photon components, an estimate of the ex-pectedPUcontribution(pPU

T ) [32] issubtracted.Forelectrons, pPUT is evaluated using the “jet area” method described in Ref. [33], whereas for muons, pPU

T isassumed tobe one halfof the scalar pT sum deposited in the isolation cone by charged particles not associated with the primary vertex. The factor of one half cor-responds to the approximateratio ofneutral to chargedhadrons produced inthe hadronizationof PU interactions.Electrons pass-ing thehigh-quality(loose)ID selectionareconsidered isolatedif Iso

<

0.0695

(0.175)

ifthepseudorapidity(

η

SC) oftheECAL clus-teris

|

η

SC

|

<

1.479,orIso

<

0.0821

(0.159)

if1.479

<

|

η

SC

|

<

2.5. Muons are considered isolated if Iso

<

0.15

(0.25)

for the high-quality(loose)IDselection.

Photonreconstruction [34] issimilartothatofelectrons,andis performedintheregionof

|

η

|

<

2.5 and forpT

>

20 GeV, exclud-ingtheECALtransitionregionof1.444

<

|

η

|

<

1.566.Tominimize photonmisidentification,photoncandidatesmust:passanelectron veto;satisfycriteriabasedonthedistributionofenergydeposited in the ECAL and HCAL; satisfy criteria on the isolation variables constructedfromthekinematicinputsofthechargedandneutral hadrons; andhaveno other photonsnearthephoton of interest. A high-quality ID [34] is used to identify prompt photons (i.e., notoriginatingfromhadrondecays)inthefinal state,andaloose ID [34] toidentifynonpromptphotons,whicharemainlyproducts ofneutralpiondecay.

JetsarereconstructedfromPFobjectsusingtheanti-kTjet clus-teringalgorithm [27] witha distanceparameter of0.4.Toreduce the contamination fromPU,charged PFcandidates inthe tracker acceptanceof

|

η

|

<

2.4 areexcludedfromjetclusteringwhenthey areassociatedwithPUvertices [25].Thecontributionfromneutral PU particlestothejetenergyiscorrectedbasedontheprojected area of thejet on thefront face ofthe calorimeter [33]. Forthis analysis, jetsare required to have

|

η

|

<

4.7 and pT

>

30 GeV. A jet energycorrection,similarto theonedevelopedfor8TeV col-lisions [35], isobtainedfrom dedicatedstudies weperformed on both data and simulated events (typically involving dijet,

γ+

jet, Z

+

jet,andmultijetproduction).Other residualcorrectionsare ap-pliedtothedataasfunctionsof pT and

η

tocorrectforthesmall differencesbetweendataandsimulation.Additionalqualitycriteria are applied tojet candidates to removespurious jet-like features originatingfromisolatednoisepatterns [36] inthecalorimetersor thetracker.

Thevectorp



miss_T iscomputedasthenegativeofthevectorsum ofthepTofallthePFcandidatesinan event [37],andits magni-tudeisdenotedaspmiss_T .Thejetenergycorrectionsarepropagated to the



pmiss_T . The datato simulation efficiencyratios are used as scalefactorstocorrectthesimulatedeventyields.

5. Eventselection

Candidate events are selected by requiring exactly one elec-tron (muon) with pT

>

30 GeV and

|

η



|

<

2.5

(2.4),

with trans-verse mass of the W boson mW

T

>

30 GeV. We define mWT as

2p

TpmissT

[

1

−

cos

(φ

,pmiss

T

)

]

, where p



T is the pT of the lepton and

φ

_,pmiss

T isthe azimuthal anglebetweenthelepton andthe



pmiss_T directions. Events are required to contain a well-identified and isolated photon with pγ_T

>

25 GeV, pmiss_T

>

30 GeV, and at leasttwojetswith

|

η

|

<

4.7 and pT

>

40

(30)

GeV fortheleading (second)jet.Aseparationof



R

>

0.5 isrequiredbetweenanytwo selectedobjects(photon, lepton, jets),asdetailedinSection 9.In theelectron channel we furtherrequirethe invariant mass(mγ) of the selected photon and electron to be inconsistent with the Z boson mass peak,

|

mγ

−

91

|

>

10 GeV, which suppresses the Z

→

e+e− background where one electron is misidentified as a photon. Based on the pseudorapidity ofthe photon, the electron andmuon channelsare eachsubdividedintoa barrelregion with

|

η

_γ

|

<

1.444,andanendcapregionwith1.566

<

|

η

_γ

|

<

2.5. Inthisanalysis,botha controlandasignal regionaredefined. The control region (CR) isconstructed with an aim of validating thesimulatedsamplesandbackgroundestimationmethodsusing data.In addition tothe previous selections, thecontrol region is definedbyarequirementthat200

<

mjj

<

400 GeV.

The signal region (SR) is defined by the previous selections plustheadditionalrequirementsthat mjj

>

500 GeV,

|

η

jj

|

>

2.5, mWγ

>

100 GeV,

|

yWγ

− (

yj1

+

yj2

)/2

|

<

1.2 [38], and

|φ

Wγ

−

φ

j1,j2

|

>

2 radians, wheremWγ and

φ

Wγ are, respectively, the in-variantmassandazimuthal angle ofthe W bosonand

γ

system,

φ

j1,j2 isthe azimuthalangle ofthedijetsystem, and yj1(2) isthe rapidity of the leading (second) jet. The longitudinal component oftheneutrinomomentum isestimatedby solving thequadratic equationthatconstrains themassofthechargedleptonand neu-trinosystemtotheworld-averagevalueoftheW bosonmass [39]. As described in Ref. [40], when there are multiplesolutions, the onewiththesmallestlongitudinalmomentumischosen;ifthere areonlycomplexsolutions,therealpartischosenasthe longitu-dinalmomentum.Therequirementson

|

yWγ

− (

yj1

+

yj2

)/2

|

and on

|φ

Wγ

− φ

j1,j2

|

areintendedtoensurethatthemomentumofthe W

γ

systemisbalancedbythatofthedijetsystem,whichwouldbe thecaseiftherewerenoadditionalQCDradiation.Theseselection requirementswerechosenbyoptimizingtheexpectedsignificance oftheEWsignal.

6. Backgroundestimation

ThebackgroundsareshowninFig.2.Theyieldsofthese back-groundsareobtainedfromasimultaneous fittothe datainboth the SR and CR with the QCD W

γ

jj normalization from the MC simulation.Thetheoreticalandexperimentaluncertainties are as-sumedcorrelatedbetweentheSRandCR.The signalstrengthfor theQCD W

γ

jj background is 1.28+₋0_0..18₁₆. The details are described inSections7–10.Additionalbackgroundsaredescribed inthe fol-lowingparagraphs.”

Reconstructedphotonsandleptonsthatdonotarisefrom out-goingparticlesinthehardinteractionintheeventaredenotedas misidentified(misID) photonsandleptons.Thiscategory includes physical photons and leptons, as well as those of purely instru-mental origins.Because of the variety of sources of these misID particles and the difficulty of modeling instrumental effects, we usedata-basedmethodstoestimatetheircontribution.

ThebackgroundfrommisIDphotonsarisesmainlyfromW

+

jets ortopquark+jetseventswithajet misreconstructedasaphoton. The method used to estimate this background involves measur-ing in CMS data and applying a per-photon extrapolation factor

in whichthe denominator is chosen to be orthogonal to thefull photon selection, but similar enough that the systematic uncer-taintiesduetotheextrapolationare wellunderstood.Thephoton inthedenominatorisrequiredtofailthehigh-qualityIDandpass the loose ID [8,41]. The extrapolation factor is determined from a template fit to the photon

σ

ηη distribution,which is smallfor

promptphotonsandlargefornonpromptphotons.Thenonprompt template usedin thefitis obtainedfroma sidebandofthe pho-tonisolationvariableinW

+

jetsdata.Moredetailscanbefoundin Ref. [10].

Thebackgroundfromjetsmisidentifiedasleptonsisestimated in asimilar fashion.To extrapolatefromthe looseleptons to the high-qualityones,anextrapolationfactorisdefinedas:

f 1

−

f

,

where f isthelepton misidentificationrate,definedastheratio ofthenumberofmisIDleptonswheretheleptonpassesthe high-quality ID tothetotal numberpassing onlythelooseID require-ments. Toreduce additional contamination fromgenuineleptons, theW

+

jetsandZ

+

jetscontributionsaresubtractedfromboththe numeratoranddenominator.Theextrapolationfactorismeasured as a function of the

η

and pT of the lepton in a CR dominated by dijet events. The dijet CR is defined by selecting one lepton, onejetthatiswellseparatedfromthelepton,andlow pmiss_T .This techniqueisalsousedanddescribedinRef. [4].

The background category “double misID” is definedas events containing both a misID photon and a misID lepton. Its yield is estimated froma sample whereboth the photon and thelepton thatare requiredtopassthelooseIDselection,andfailthe high-qualityID.Sucheventsareassignedaweightequaltotheproduct ofthemisIDextrapolationfactorsofthephotonandlepton.Double misID events contaminate the single misID background estimate becausethesecondobjectisassumedtobegenuine.Consequently, each time a weight is added to the double misID estimate, the sameweightissubtractedfromboththesingle-photonand single-leptonestimates.Inaddition,eventsinwhichgenuinephotonsand leptonspassthelooseIDbutfailthehigh-qualityIDselection con-taminate boththesingle anddoublemisID estimates.Thissource ofcontaminationisestimatedandremovedusingsimulatedevents withreconstructedobjectsmatchedtogenerator-levelobjects.

Otherbackgrounds,includingtop quarkanddibosonprocesses, are estimatedfromMC simulation andarenormalized tothe in-tegratedluminosityoftheCMSdatasetusinginclusivecross sec-tions calculated atNLO in QCD. The e

→ γ

background includes eventswithanelectronmisIDasaphoton.Weapply

|

mγ

−

91

|

>

10 GeV to minimize thiscontribution.Theremaining background is estimated from simulated Drell–Yan and tt

γ

events that con-tain a photonmatched toan electronatthegenerator levelwith



R

=

0.3.

Fig.2showsthephotonptdistributioninthemuonbarrel con-trol region fordata andbackground estimates.The data and the estimatesareingoodagreement.

7. Systematicuncertainties

Systematic uncertainties that affect the measurements arise fromexperimentalinputs,suchasdetectoreffectsandthemethods usedtocomputehigher-levelquantities,e.g.,efficiencies,and the-oreticalinputssuch asthechoiceoftherenormalization(

μ

R)and factorization(

μ

F)scales,andthechoiceofPDFsets.Eachsourceof systematicuncertaintyisquantifiedbyevaluatingitseffectonthe yield and distribution of relevant kinematic variables in the sig-nal and background categories. The uncertainties are propagated tothefinaldistributionsandcalculatedbin-by-binasdescribedin Section8.

Fig. 2. ThephotonpTdistributioninthemuonbarrelcontrolregionfordataand backgroundestimations.ThemisIDbackgroundsarederivedfromdata,whereasthe remainingbackgroundsareestimatedfromsimulation.AlleventswithphotonpT> 195 GeV areincludedinthelastbin.Thehatchedbandsrepresentthestatistical uncertaintiesonthepredictedyields.Thebottomgraphshowsthedatadividedby theprediction.

Table 1 summarizes all the systematic uncertainties. The sys-tematicuncertainties intheleptontrigger,reconstruction,and se-lectionefficiencies,measuredusingatag-and-probetechnique,are 2–3%.The uncertainties in jet energyscale (JES)have thelargest impact on the measurement. The JES and jet energy resolution (JER)effectsareestimatedbyshifting/smearingthejetsinthe sim-ulations up and down by one standard deviation, and are then propagated to all relevant variables including VBS jet kinematic properties and pmiss

T , based on which the impact on signal and backgroundyieldsare evaluated.The uncertaintiesduetotheJES andJERcorrespondingtodifferentprocessesanddifferentmjj-mγ binsare in theranges 0.9–78%and0.7–21%,respectively. An un-certainty of2.5% inthe integratedluminosity [42] isused forall processesestimatedfromsimulationandforthespecifiedfiducial crosssection.Thestatisticaluncertaintiesduetothefinitesizeof boththesimulatedanddatasamplesusedinourbackgroundand signal prediction are estimated assuming Poisson statistics. The uncertainties relatedto thefinite numberof simulatedeventsor to thelimited numberof eventsin the datacontrol samples are 7–11% for the EW W

γ

jj signal, 6–36% for the QCD-induced W

γ

background,43–72%forthenonpromptleptoncontamination and 7–36%forthenonpromptphotonbackground.Theseuncertainties areuncorrelatedacrossdifferentprocesses andbins ofanysingle distribution,andgrowwithincreasingmjjandmγ.

An overall systematic uncertainty in the nonprompt photon backgroundestimate is defined asthe quadraticsum ofthe sys-tematicuncertaintiesfromseveraldistinctsources.Anuncertainty becauseofthe choice ofthe isolation variablesidebandis evalu-atedbyestimatingthenonpromptphotonfractionwithalternative choicesofthe isolation sideband [8]. A nonclosureuncertaintyis defined by performing the nonprompt photon fraction fits using simulatedeventsandcomparingtheresultswiththeknown frac-tions. The nonclosure uncertainty in the endcap region is worse thaninthebarrelregionandworsensasthephoton pT increases. Theoverallsystematicuncertaintyinthenonpromptphoton back-groundis inthe range of12–22%, dominatedby thenonclosure.

Table 1

Relativesystematicuncertaintiesintheestimatedsignalandbackgroundyieldsinunitsofpercent.Therangesreflectthedependenceofthespecifieduncertaintyonmjjand

mγ.

Source EW Wγjj QCD Wγjj VV ttγ QCD Zγ Single t MisID photon MisID lepton Double misID e→ γ JES 0.9–6.9 11–28 6.4–38 3.7–16 12–78 3.3–18 — — — 11–28 JER 0.7–2.2 0.7–4.1 6.9–21 1.3–4.9 6.5–15 2.9–7.1 — — — 0.7–4.1 Integrated luminosity 2.5 2.5 2.5 2.5 2.5 2.5 — — — 2.5 MisID photon — — — — — — 12–22 — 12–22 — MisID lepton — — — — — — — 30 30 — μR/μFscales 1.5–11 6.1–20 — — — — — — — — PDF 3.2–5.6 1–2 — — — — — — — — Interference 1.8–2.8 — — — — — — — — —

Cross section for ttγ — — — 10 — — — — — —

Cross section for VV — — 10 — — — — — — —

Modeling of pileup 0–0.6 0.3–1.4 4.8–13 2.6–3.9 6.2–19 1.0–3.9 — — — 0.3–1.4 Statistical uncertainty 7–11 6–36 45–100 13–56 16–100 17–55 7–36 43–72 30–100 54–100 L1 mistiming 1.7–2.4 0.8–1.6 0.5–1.6 1.4–2.5 0.6–3.6 1.0–2.1 — — — 1.1–2.8 Muon ID/Iso 0.3 0.3 0.3 0.3 0.3 0.3 — — — 0.3 Muon trigger 0.3 0.2 0.2 0.2 0.1 0.1 — — — 0.2 Electron reconstruction 0.5 0.6 0.5 0.6 0.6 0.5 — — — 0.5 Electron ID/Iso 1.3 1.3 1.3 1.3 1.3 1.3 — — — 1.3 Electron trigger 2.5 2.5 2.5 2.5 2.5 2.5 — — — 2.5 Photon ID 1.2 1.2 1.1 1.2 1.3 1.2 — — — 1.2

Similarly, the dominant uncertainty inthe nonprompt lepton es-timate is associated with the nonclosure, which is calculated by comparing two yields,one fromthe

γ+

jetsevents andtheother fromthe

γ+

jetseventswherethe misIDlepton ratesare applied to eventswitha lepton that passestheloose,but failsthe high-quality ID. The selection used is the same as in the main event selection,exceptthatthemW_T andpmiss_T requirementsareremoved to increase the statisticalpower. The uncertaintyassociated with thenonpromptleptonbackgroundis30%.

The effectsof thechoice of

μ

R and

μ

F inthe theoretical cal-culation for signal and background processes are estimated by independently changing

μ

R and

μ

F up and down by a factor of two fromtheir nominal value in each event, with the condition that 1/2

<

μ

R

/

μ

F

<

2.Theuncertainties are definedasthe max-imal differences fromthe nominalvalues. The PDF uncertainties areevaluatedaccordingtotheproceduredescribedinRef. [43] us-ingtheNNPDF3.0set.Forthesignalprocess,thescaleuncertainty varieswithintherangeof1.5–11%andthePDFuncertaintyvaries within therange3.2–5.6%, increasingwithmjj andmγ.The scale uncertainty in the QCD-induced W

γ

process, which has a very large impactonthe measurement,variesintherange6.1–20%.It is constrainedby thesimultaneous fitto thedata intheCR. The PDFuncertaintyofQCD-inducedW

γ

productionisintherangeof 1–2%.

TheinterferencetermbetweentheEW- andQCD-induced pro-cesses, i.e.,

O(

α

4

_α

S

)

at tree level, is estimated at particle level using MG5. The contribution of the interference is calculated as thedifferencebetweentheinclusiveW

γ

jj production,which con-tains the interference term, and the sum of the pure EW- and QCD-induced W

γ

jj. The interference is positive, and the ratio of theinterferencetoEWW

γ

jj isintherange2–4%,decreasingwith increasingmjj.Thesevaluesareusedassystematicuncertaintiesin thesignalprocess.

Acorrectionfactorisappliedtothesimulatedeventstoaccount for the L1 trigger occasionally firing at the wrong time because ofthe darkeningofthe ECALcrystals.This mistimingresultsina loss of trigger efficiency in the data and is not modeled by the simulation.The uncertainties duetothesecorrection factors vary by 1–4%, and are treatedascorrelated across different processes andbins.

Allofthesystematicuncertainties discussedaboveareapplied bothtothesignalsignificancemeasurementandinthesearchfor aQGCcontributions.Theyarealsopropagatedtotheuncertaintyin themeasuredfiducialcrosssection,withtheexceptionofthe

theo-reticaluncertaintiesassociatedwiththesignalcrosssection.Allof thesystematicuncertaintiesexceptthosethatarise fromthe trig-ger efficiency and the lepton identification and misidentification are considered to be correlated between the electron and muon channels.

8. TheEWW

γ

productionmeasurement

Table2showsthesimulatedsignalandbackgroundyieldsprior toanyfitting, aswellastheobserveddatayields. Toquantifythe significanceof the observationof EW production ofthe W

γ

sig-nal,we perform a statisticalanalysisof the eventyields through afitto the(mjj

,

mγ)two-dimensional (2D) distribution.Bothmjj andmγarepowerfulvariablesfordistinguishingbetweenthe sig-nalandQCDW

γ

background,andthe2Danalysisprovidesalarger expectedsignificancethaneithervariablealone.Forthis measure-ment,andthemeasurementsinSections9 and10,theSRis fur-therdivided into fourbins inmjj (lowerboundariesof 500, 800, 1200,and1700GeV) andthree binsinmγ (lowerboundariesof 30,80, and130 GeV). The data in the CRare fit simultaneously withthedataintheSR.Fig.3showstheresultant2Dfitted distri-butions.

The signal significance is quantified on the basis of a profile likelihoodtest statistic [44].Thisteststatisticinvolvestheratioof twoPoissonlikelihoodfunctions,oneinwhichthesignalstrength is fixed to zeroand one in which the signal strength is allowed tohaveanypositivevalue.Thesignalstrengthrepresentstheratio ofobservedtoexpectedsignalyields. Systematicuncertaintiesare addedasparameters intothelikelihoodfunction toscalethe rel-evant process usinglog-normal functions. The distribution inthe test statistic is assumed to be in the asymptotic regime where there is a simple relationship betweenits value andthe signifi-cance ofthe result [45]. The observed (expected)signal strength parameter is

μ

ˆ

=

1.20+₋0₀._.26₂₄

(1.00

+₋0₀._.27₂₅), corresponding to an ob-served (expected) statistical significance of 4.9 (4.6) SD for the analyzed13TeV dataset.

Thisresultcan becombined withtheprevious CMS measure-mentat8 TeV described inRef. [9] assuming thesignal strength doesnotchangewiththecenterofmassenergy.Therearetwo un-certaintiesthatarecorrelatedbetweenthe8and13TeV analyses. ThetheoreticaluncertaintiesinthesignalandQCDW

γ

background ofthe8TeV analysisincludemultiplesources,butaredominated by the renormalization and factorization scale uncertainties, and are therefore correlated with the corresponding uncertainties in

Table 2

Signal,background,anddatayieldsafterthefinalselection.Statisticalandsystematicuncertainties (be-forethefitting)areaddedinquadrature.

Electron barrel Electron endcap Muon barrel Muon endcap MisID photon 81.0±5.2 48.1±4.9 134.8±8.2 52.1±4.8 MisID lepton 63.7±12.3 27.8±7.2 46.8±10.6 23.1±6.5 QCD Wγjj 154.2±12.0 41.1±4.4 221.2±15.8 72.1±6.2 ttγ 20.6±1.6 5.1±0.6 28.3±1.8 6.9±0.8 QCD Zγ 18.0±3.1 1.9±0.9 16.2±3.0 4.9±1.3 Single t 4.9±0.8 2.5±0.5 6.8±0.9 2.4±0.5 VV 4.2±1.6 0.6±0.6 7.5±2.1 1.4±0.7 e→ γ 1.5±0.6 2.1±0.8 1.7±0.7 1.1±0.6 Total background 348.3±18.4 129.1±9.9 463.4±21.2 163.8±10.4 EW Wγjj 48.8±2.2 16.1±1.0 74.5±2.8 24.4±1.3 Total predicted 397.1±18.5 145.2±10.0 537.9±21.4 188.2±10.5 Data 393 159 565 201

Fig. 3. The2DdistributionsusedinthefitforthesignalstrengthofEWWγ +2 jetsforeventsintheelectronbarrel(upperleft),electronendcap(upperright),muonbarrel (lowerleft),andmuonendcap(lowerright).Thehatchedbandsrepresentthesystematicuncertaintiesonthepredictedyields.Thepredictedyieldsareshownwiththeir best-fitnormalizations.

the 13 TeV analysis. All other uncertainties are uncorrelated be-tweenthe8and13TeV analyses.Aftercombiningourresultwith that at 8 TeV using this correlation scheme, the observed (ex-pected)significanceis5.3(4.8)SD.

9. FiducialEWW

γ

jj crosssectionmeasurement

A fiducial cross section at 13 TeV is extracted in the same (mjj

,

mγ) binning used in the calculation of significance, and through the same simultaneous fit used in the CR. The fiducial region is defined using the MC generator quantities: one lepton with p

T

>

30 GeV and

|

η



|

<

2.4, pmissT

>

30 GeV, p γ

T

>

25 GeV,

|

η

_γ

|

<

1.444 or 1.566

<

|

η

_γ

|

<

2.5,



Rγ

>

0.5, mWT

>

30 GeV, twojetswith p_Tj1(2)

>

40

(30)

GeV,with

|

η

j

|

<

4.7,mjj

>

500 GeV,



Rjj

>

0.5,



Rj

>

0.5,



Rjγ

>

0.5,and

|

η

jj

|

>

2.5.Theleptons are reconstructed at the particlelevel with fullyrecovered final-state radiation. The acceptance is defined as the fraction of the generatedsignaleventspassingthefiducialregionselection,which isextractedusingMG5.Thetheoreticaluncertaintybecauseofthe extrapolationbetweenthefiducialandSRisnegligible(<1%).We definethecrosssectionas

σ

fid

₍

_{13 TeV}

₎

₌

_σ

g

μ α

ˆ

gf

,

where the cross section for the generated signal events is

σ

g

=

0.776 pb, the signal strength parameter

μ

ˆ

=

1.20₋+₀0._.26₂₄, and the acceptance

α

gf

=

0.02195. The observed fiducial cross section is

σ

fid

EW

(13 TeV)

=

20.4

±

0.4(lumi)

±

2.8(stat)

±

3.5(syst) fb

=

20.4

±

4.5 fb.

10. FiducialEW+QCDW

γ

jj crosssectionmeasurement

InadditiontotheEW W

γ

jj process,wealsodetermineacross sectionforinclusiveEW+QCDW

γ

jj production.Thefiducialregion is the same as that for EW W

γ

jj and the formula for the cross sectionis

σ

fid

=

μ

σ

_gEW

α

_gfEW

+

σ

_gQCD

α

_gfQCD



.

SincetheQCDW

γ +

2 jetsispartofthesignal,theCRisnolonger includedinthecalculatedsignalstrength.

The inputs used for the fit are similar to the ones for EW W

γ

jj, with the difference that EW andQCD W

γ

jj are combined as signal. The crosssection forQCD W

γ

jj is 178.6 pb, and

α

_gfQCD

is calculated to be 0.0004068. The measured signal strength for inclusive W

γ

jj is 1.21₋+₀0._.17₁₆ and the observed fiducial cross sec-tionis

σ

fid

EW+QCD

(13 TeV)

=

108

±

2(lumi)

±

5(stat)

±

15(syst) fb

=

108

±

16 fb.Fig.4showsthepost-fitresults.

11. Limitsonanomalousquarticgaugecouplings

The effects of BSM physics can be modeled in a generic way through a collection of linearly independent higher-dimensional operators in effectivefield theory [11]. As mentioned above,VBS is moresuitable toconstrain aQGC. Thelowest dimension opera-tors that modify quarticgauge couplingsbut do not exhibit two or three weak gauge boson vertices are dimension-eight. Refer-ence [46] proposesnineindependentcharge-conjugateand parity-conserving dimension-eight effective operators by assuming the SU(2)

×

U(1)symmetryoftheEW gaugefield.The modelincludes a Higgs doublet to incorporatethe presence of an SM Higgs bo-son.AcontributionfromaQGCsenhancestheproductionofevents withlargeW

γ

mass.TheoperatorsaffectingtheW

γ

jj channelcan be divided into two categories. The operators

L

M,0–

L

M,7 contain an SU(2)field strength,the U(1)field strength,andthe covariant

derivative oftheHiggsdoublet field.The operators

L

T,0–

L

T,2 and

L

T,5–

L

T,7, contain onlythe two field strengths. Thecoefficient of theoperator

L

X,Yisdenotedby fX,Y

/

4,where

istheunknown scaleofBSMphysics.

A simulation is performed that includes the effects of the aQGCsinadditiontotheSMEWW

γ

jj process,aswellasany inter-ferencebetweenthetwo.WeusethemWγ distributiontoextract limitsontheaQGC parameters.Toobtainacontinuousprediction forthesignalasafunctionoftheanomalouscoupling,aquadratic fitisperformedtothe SM+aQGCyield asa functionofthe aQGC coefficient,separatelyineachmWγ binintheaQGC region,which isdefinedbasedon thecommonselection inSection 5,withthe furtherrequirementsmjj

>

800 GeV,

|

η

jj

|

>

2.5,mWγ

>

150 GeV, andpγ_T

>

100 GeV.AstheaQGCcontributionsarisefrompureVBS diagramsandare moreenhanced inthe VBSphase spaceregion, and the anomalous operators lead to more energetic final state particles,theadditionalrequirementsareoptimizedtoenhancethe aQGCsensitivitybasedonthesimulationstudies.Fig.5showsthe resultingdistributioninmWγ.No statisticallysignificantexcessof eventsrelativetotheSMpredictionisobserved.

ThefollowingprofilelikelihoodteststatisticisusedintheaQGC limitsettingprocedure:

tαtest

= −

2 log

L

(

α

test

, ˆˆθ )

L

(

α

ˆ

, ˆθ )

.

ThelikelihoodfunctionistheproductofPoissondistributionsand a normalconstraining termwith nuisanceparameters represent-ing thesources of systematicuncertainties in each bin.The final likelihood function is the product of the likelihood functions of theelectronandmuonchannels.ThemainconstraintontheaQGC parametersisfromthehighestmWγ bin.Theparameter

α

test rep-resentstheaQGCpointbeingtested,andthesymbol

θ

represents avectorofnuisanceparametersassumedtofollowlog-normal dis-tributions. The parameter

ˆˆθ

corresponds to the maximum ofthe likelihoodfunctionatthepoint

α

test.The

α

ˆ

and

ˆθ

parameters cor-respondtothesingle globalmaximumofthelikelihoodfunction. Thistest statistic is assumedto followa noncentral

χ

2 distribu-tion [44].Itisthereforepossibletoextractthelimitsimmediately fromthe difference in the negative log-likelihood (NLL) function

NLL

=

tαtest

/2 [

47].The95%confidencelevel(CL)limitona

one-dimensionalaQGCparametercorrespondsto2NLL

=

3.84.Fig.6

showsthelikelihoodscan ofparameter fT,0

/

4 inthecalculation oftheobservedlimits.

Theobservedandexpected95%CL limitsonthecoefficientsof theseoperators,showninTable3,areobtainedbyvaryingthe co-efficientofoneoperatoratatime,withallotherssetto0,theSM value. Theyield ofthe EW signalin anybinis a quadratic func-tionofthecoefficient,whoseminimumingeneraldoesnotoccur atacoefficientvalueof0becauseofinterferencewiththeSM op-erators. Wethereforeset upperandlower limitson theoperator coefficientsthroughalimit-settingprocedurethatinvolvesfirst ob-tainingtheglobalmaximumoftheprofilelikelihoodfunction,and thenthemaximumoftheprofilelikelihoodfunctionatfixed coef-ficientvalues,whichcanbecomparedtotheglobalmaximumand convertedto CLs. NLO EW correctionsto VBS W

γ

canbe sizable andincrease asafunctionofmjj,whichmaybiastheaQGC mea-surement. Althoughthere isno NLO EWcalculation available yet forVBSW

γ

,wehaveinsteadtestedwiththenumbersfrom same-signWW scattering [48,49], andthe effect on the aQGC limit is foundtobe negligible.Theunitaritybound (Ubound) isdefinedas thescatteringenergyatwhichtheaQGCcouplingstrength,when setequal to theobserved limit, wouldresultin a scattering am-plitude that violatesunitarity. The value of Ubound is determined usingthe vbfnlo 2.7.1framework [50],takingintoaccountthe

dif-Fig. 4. The2DdistributionsusedinthefitforthesignalstrengthofEW+QCDWγ +2 jetsintheelectronbarrel(upperleft),electronendcap(upperright),muonbarrel (lowerleft)andmuonendcap(lowerright).Thehatchedbandsrepresentthesystematicuncertaintiesonthepredictedyields.Thepredictedyieldsareshownwiththeir best-fitnormalizations.

ference between vbfnlo and MG5. These are the most stringent limitstodateontheaQGCparameters fM,2–5

/

4 and fT,6–7

/

4. 12. Summary

The cross section for the electroweak production of a W bo-son,aphoton,andtwojetsismeasuredinproton-protoncollisions ata center-of-mass energyof13 TeV.The datacorrespond toan integratedluminosity of35.9 fb−1 collected withtheCMS detec-tor.Eventsareselectedbyrequiringoneidentifiedlepton(electron or muon), a moderate missing transverse momentum, one pho-ton,andtwojetswithalargerapidityseparationandalargedijet mass.The observedsignificanceis4.9standard deviations,where asignificanceof4.6standarddeviationsisexpectedbasedonthe standard model.After combinationwithpreviously reportedCMS results based on 8 TeV data, the observed (expected) signal sig-nificance is5.3(4.8)standard deviations.Thisconstitutesthefirst observationofelectroweakW

γ

jj productioninproton-proton col-lisions. The cross section forthe electroweak W

γ

jj production in

Table 3

Theexclusionlimitsat95%CL oneachaQGCcoefficient,parameterizedusingthe distributioninmWγ,andlistedalongwiththeunitaritybound.Allcoupling param-eterlimitsareinTeV−4_,whiletheU

boundvaluesareinTeV.

Parameters Obs. limit Exp. limit Ubound

fM,0/4 [−8.1,8.0] [−7.7,7.6] 1.0 fM,1/4 [−12,12] [−11,11] 1.2 fM,2/4 [−2.8,2.8] [−2.7,2.7] 1.3 fM,3/4 [−4.4,4.4] [−4.0,4.1] 1.5 fM,4/4 [−5.0,5.0] [−4.7,4.7] 1.5 fM,5/4 [−8.3,8.3] [−7.9,7.7] 1.8 fM,6/4 [−16,16] [−15,15] 1.0 fM,7/4 [−21,20] [−19,19] 1.3 fT,0/4 [−0.6,0.6] [−0.6,0.6] 1.4 fT,1/4 [−0.4,0.4] [−0.3,0.4] 1.5 fT,2/4 [−1.0,1.2] [−1.0,1.2] 1.5 fT,5/4 [−0.5,0.5] [−0.4,0.4] 1.8 fT,6/4 [−0.4,0.4] [−0.3,0.4] 1.7 fT,7/4 [−0.9,0.9] [−0.8,0.9] 1.8

Fig. 5. ThemWγdistributionofeventssatisfyingtheaQGCregionselection,which isusedtosetconstraintsontheanomalouscouplingparameters.Theorangeline representsanonzero fT,0/4setting.AlleventswithmWγ>950 GeV areincluded inthelastbin.Thehatchedbandsrepresentthestatisticaluncertaintiesinthe pre-dictedyields.

Fig. 6. Observed 95% CL interval on the aQGC parameter fT,0/4.

a restricted fiducialregion is measured as 20.4

±

4.5 fb and the total cross section for W

γ

production in association with 2 jets in the samefiducial region is 108

±

16 fb,consistent with stan-dard model predictions.Constraints placed on anomalous quartic gaugecouplingsintermsofdimension-8effectivefieldtheory op-eratorsare competitive withprevious results. Fortheparameters

fM,2–5

/

4 and fT,6–7

/

4,theconstraintsarethemoststringentto date.

Declarationofcompetinginterest

Theauthorsdeclarethattheyhavenoknowncompeting finan-cialinterestsorpersonalrelationshipsthatcouldhaveappearedto influencetheworkreportedinthispaper.

Acknowledgements

WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the technical andadministrativestaffsat CERNandat other CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcentersand personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythe computinginfrastructure essentialto ouranalyses. Finally, we acknowledge the enduring support for the construc-tion andoperation oftheLHC andtheCMSdetectorprovided by the followingfundingagencies:BMBWF andFWF(Austria); FNRS

andFWO (Belgium); CNPq, CAPES, FAPERJ,FAPERGS, andFAPESP (Brazil); MES (Bulgaria); CERN; CAS, MOST, and NSFC (China); COLCIENCIAS (Colombia); MSES and CSF (Croatia); RIF (Cyprus); SENESCYT (Ecuador); MoER, ERC IUT, PUT and ERDF (Estonia); AcademyofFinland,MEC,andHIP (Finland);CEA andCNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); NK-FIA (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN(Italy);MSIPandNRF(RepublicofKorea);MES(Latvia);LAS (Lithuania);MOEandUM(Malaysia);BUAP,CINVESTAV,CONACYT, LNS,SEP,andUASLP-FAI(Mexico);MOS(Montenegro);MBIE(New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portu-gal);JINR(Dubna);MON,ROSATOM, RAS,RFBR,andNRCKI (Rus-sia);MESTD(Serbia);SEIDI,CPAN,PCTI,andFEDER(Spain);MoSTR (Sri Lanka); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter,IPST,STAR,andNSTDA(Thailand);TUBITAKandTAEK (Turkey);NASU (Ukraine); STFC (United Kingdom);DOE andNSF (USA).

Individuals have received support from the Marie-Curie pro-gramandtheEuropeanResearchCouncilandHorizon2020Grant, contractNos.675440,752730,and765710(EuropeanUnion);the Leventis Foundation; theAlfred P. Sloan Foundation; the Alexan-dervon HumboldtFoundation;theBelgianFederal SciencePolicy Office; the Fonds pour la Formation à la Recherche dans l’In-dustrieetdansl’Agriculture (FRIA-Belgium); theAgentschapvoor Innovatie door Wetenschap en Technologie (IWT-Belgium); the F.R.S.-FNRS andFWO (Belgium) under the “Excellence of Science – EOS” – be.h project n. 30820817; the Beijing Municipal Sci-ence and Technology Commission, No. Z191100007219010; the Ministry of Education, Youth and Sports (MEYS) of the Czech Republic;theDeutscheForschungsgemeinschaft(DFG)under Ger-many’s Excellence Strategy – EXC 2121 “Quantum Universe” – 390833306; the Lendület (“Momentum”) Program and the János Bolyai Research Scholarship of the Hungarian Academy of Sci-ences, the New National Excellence Program ÚNKP, the NK-FIA research grants 123842, 123959, 124845, 124850, 125105, 128713, 128786, and 129058 (Hungary); the Council of Science andIndustrialResearch,India; theHOMING PLUSprogramofthe Foundation for Polish Science, cofinanced from European Union, Regional 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 2014/13/B/ST2/02543, 2014/15/B/ST2/03998, and 2015/19/B/ST2/ 02861,Sonata-bis2012/07/E/ST2/01406;theNationalPriorities Re-searchProgram byQatar NationalResearchFund;theMinistry of ScienceandHigherEducation,projectno.02.a03.21.0005(Russia); the ProgramaEstatal de Fomento de la Investigación Científica y Técnica de Excelencia María de Maeztu, grant MDM-2015-0509 and the Programa Severo Ochoa del Principado de Asturias; the ThalisandAristeiaprogramscofinancedby EU-ESFandtheGreek NSRF;theRachadapisekSompotFundforPostdoctoralFellowship, Chulalongkorn University and the Chulalongkorn Academic into Its2ndCenturyProject AdvancementProject(Thailand);theKavli Foundation;the NvidiaCorporation; the SuperMicroCorporation; the Welch Foundation, contract C-1845; and the Weston Havens Foundation(USA).

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TheCMSCollaboration

A.M. Sirunyan

†

,

A. Tumasyan

YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam,

F. Ambrogi,

T. Bergauer,

M. Dragicevic,

J. Erö,

A. Escalante Del Valle,

R. Frühwirth

1

,

M. Jeitler

1

,

N. Krammer,

L. Lechner,

D. Liko,

T. Madlener,

I. Mikulec,

F.M. Pitters,

N. Rad,

J. Schieck

1

,

R. Schöfbeck,

M. Spanring,

S. Templ,

W. Waltenberger,

C.-E. Wulz

1

,

M. Zarucki

InstitutfürHochenergiephysik,Wien,Austria

V. Chekhovsky,

A. Litomin,

V. Makarenko,

J. Suarez Gonzalez

InstituteforNuclearProblems,Minsk,Belarus

M.R. Darwish

2

,

E.A. De Wolf,

D. Di Croce,

X. Janssen,

T. Kello

3

,

A. Lelek,

M. Pieters,

H. Rejeb Sfar,

H. Van Haevermaet,

P. Van Mechelen,

S. Van Putte,

N. Van Remortel

UniversiteitAntwerpen,Antwerpen,Belgium

F. Blekman,

E.S. Bols,

S.S. Chhibra,

J. D’Hondt,

J. De Clercq,

D. Lontkovskyi,

S. Lowette,

I. Marchesini,

S. Moortgat,

A. Morton,

Q. Python,

S. Tavernier,

W. Van Doninck,

P. Van Mulders

VrijeUniversiteitBrussel,Brussel,Belgium

D. Beghin,

B. Bilin,

B. Clerbaux,

G. De Lentdecker,

B. Dorney,

L. Favart,

A. Grebenyuk,

A.K. Kalsi,

I. Makarenko,

L. Moureaux,

L. Pétré,

A. Popov,

N. Postiau,

E. Starling,

L. Thomas,

C. Vander Velde,

P. Vanlaer,

D. Vannerom,

L. Wezenbeek

UniversitéLibredeBruxelles,Bruxelles,Belgium

T. Cornelis,

D. Dobur,

M. Gruchala,

I. Khvastunov

4

,

M. Niedziela,

C. Roskas,

K. Skovpen,

M. Tytgat,

W. Verbeke,

B. Vermassen,

M. Vit

GhentUniversity,Ghent,Belgium

G. Bruno,

F. Bury,

C. Caputo,

P. David,

C. Delaere,

M. Delcourt,

I.S. Donertas,

A. Giammanco,

V. Lemaitre,

K. Mondal,

J. Prisciandaro,

A. Taliercio,

M. Teklishyn,

P. Vischia,

S. Wuyckens,

J. Zobec

UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium

G.A. Alves,

G. Correia Silva,

C. Hensel,

A. Moraes

CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

W.L. Aldá Júnior,

E. Belchior Batista Das Chagas,

H. Brandao Malbouisson,

W. Carvalho,

J. Chinellato

5

,

E. Coelho,

E.M. Da Costa,

G.G. Da Silveira

6

,

D. De Jesus Damiao,

S. Fonseca De Souza,

J. Martins

7

,

D. Matos Figueiredo,

M. Medina Jaime

8

,

M. Melo De Almeida,

C. Mora Herrera,

L. Mundim,

H. Nogima,

P. Rebello Teles,

L.J. Sanchez Rosas,

A. Santoro,

S.M. Silva Do Amaral,

A. Sznajder,

M. Thiel,

E.J. Tonelli Manganote

5

,

F. Torres Da Silva De Araujo,

A. Vilela Pereira

UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

C.A. Bernardes

a

,

L. Calligaris

a

,

T.R. Fernandez Perez Tomei

a

,

E.M. Gregores

b

,

D.S. Lemos

a

,

P.G. Mercadante

b

,

S.F. Novaes

a

,

Sandra S. Padula

a

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

A. Aleksandrov,

G. Antchev,

I. Atanasov,

R. Hadjiiska,

P. Iaydjiev,

M. Misheva,

M. Rodozov,

M. Shopova,

G. Sultanov

M. Bonchev,

A. Dimitrov,

T. Ivanov,

L. Litov,

B. Pavlov,

P. Petkov,

A. Petrov

UniversityofSofia,Sofia,Bulgaria

W. Fang

3

,

Q. Guo,

H. Wang,

L. Yuan

BeihangUniversity,Beijing,China

M. Ahmad,

Z. Hu,

Y. Wang

DepartmentofPhysics,TsinghuaUniversity,Beijing,China

E. Chapon,

G.M. Chen

9

,

H.S. Chen

9

,

M. Chen,

A. Kapoor,

D. Leggat,

H. Liao,

Z. Liu,

R. Sharma,

A. Spiezia,

J. Tao,

J. Thomas-wilsker,

J. Wang,

H. Zhang,

S. Zhang

9

,

J. Zhao

InstituteofHighEnergyPhysics,Beijing,China

A. Agapitos,

Y. Ban,

C. Chen,

Q. Huang,

A. Levin,

Q. Li,

M. Lu,

X. Lyu,

Y. Mao,

S.J. Qian,

D. Wang,

Q. Wang,

J. Xiao

StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

Z. You

SunYat-SenUniversity,Guangzhou,China

X. Gao

3

InstituteofModernPhysicsandKeyLaboratoryofNuclearPhysicsandIon-beamApplication(MOE)- FudanUniversity,Shanghai,China

M. Xiao

ZhejiangUniversity,Hangzhou,China

C. Avila,

A. Cabrera,

C. Florez,

J. Fraga,

A. Sarkar,

M.A. Segura Delgado

UniversidaddeLosAndes,Bogota,Colombia

J. Jaramillo,

J. Mejia Guisao,

F. Ramirez,

J.D. Ruiz Alvarez,

C.A. Salazar González,

N. Vanegas Arbelaez

UniversidaddeAntioquia,Medellin,Colombia

D. Giljanovic,

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,

D. Majumder,

M. Roguljic,

A. Starodumov

10

,

T. Susa

InstituteRudjerBoskovic,Zagreb,Croatia

M.W. Ather,

A. Attikis,

E. Erodotou,

A. Ioannou,

G. Kole,

M. Kolosova,

S. Konstantinou,

G. Mavromanolakis,

J. Mousa,

C. Nicolaou,

F. Ptochos,

P.A. Razis,

H. Rykaczewski,

H. Saka,

D. Tsiakkouri

UniversityofCyprus,Nicosia,Cyprus

M. Finger

11

,

M. Finger Jr.

11

,

A. Kveton,

J. Tomsa

CharlesUniversity,Prague,CzechRepublic

E. Ayala

EscuelaPolitecnicaNacional,Quito,Ecuador

UniversidadSanFranciscodeQuito,Quito,Ecuador

A.A. Abdelalim

12

,

13

,

S. Elgammal

14

,

A. Ellithi Kamel

15

AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt

A. Lotfy,

M.A. Mahmoud

CenterforHighEnergyPhysics(CHEP-FU),FayoumUniversity,El-Fayoum,Egypt

S. Bhowmik,

A. Carvalho Antunes De Oliveira,

R.K. Dewanjee,

K. Ehataht,

M. Kadastik,

M. Raidal,

C. Veelken

NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia

P. Eerola,

L. Forthomme,

H. Kirschenmann,

K. Osterberg,

M. Voutilainen

DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland

E. Brücken,

F. Garcia,

J. Havukainen,

V. Karimäki,

M.S. Kim,

R. Kinnunen,

T. Lampén,

K. Lassila-Perini,

S. Laurila,

S. Lehti,

T. Lindén,

H. Siikonen,

E. Tuominen,

J. Tuominiemi

HelsinkiInstituteofPhysics,Helsinki,Finland

P. Luukka,

T. Tuuva

LappeenrantaUniversityofTechnology,Lappeenranta,Finland

C. Amendola,

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,

B. Lenzi,

E. Locci,

J. Malcles,

J. Rander,

A. Rosowsky,

M.Ö. Sahin,

A. Savoy-Navarro

16

,

M. Titov,

G.B. Yu

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

S. Ahuja,

F. Beaudette,

M. Bonanomi,

A. Buchot Perraguin,

P. Busson,

C. Charlot,

O. Davignon,

B. Diab,

G. Falmagne,

R. Granier de Cassagnac,

A. Hakimi,

I. Kucher,

A. Lobanov,

C. Martin Perez,

M. Nguyen,

C. Ochando,

P. Paganini,

J. Rembser,

R. Salerno,

J.B. Sauvan,

Y. Sirois,

A. Zabi,

A. Zghiche

LaboratoireLeprince-Ringuet,CNRS/IN2P3,EcolePolytechnique,InstitutPolytechniquedeParis,Paris,France

J.-L. Agram

17

,

J. Andrea,

D. Bloch,

G. Bourgatte,

J.-M. Brom,

E.C. Chabert,

C. Collard,

J.-C. Fontaine

17

,

D. Gelé,

U. Goerlach,

C. Grimault,

A.-C. Le Bihan,

P. Van Hove

UniversitédeStrasbourg,CNRS,IPHCUMR7178,Strasbourg,France

E. Asilar,

S. Beauceron,

C. Bernet,

G. Boudoul,

C. Camen,

A. Carle,

N. Chanon,

D. Contardo,

P. Depasse,

H. El Mamouni,

J. Fay,

S. Gascon,

M. Gouzevitch,

B. Ille,

Sa. Jain,

I.B. Laktineh,

H. Lattaud,

A. Lesauvage,

M. Lethuillier,

L. Mirabito,

L. Torterotot,

G. Touquet,

M. Vander Donckt,

S. Viret

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

I. Bagaturia

18

,

Z. Tsamalaidze

11

GeorgianTechnicalUniversity,Tbilisi,Georgia

L. Feld,

K. Klein,

M. Lipinski,

D. Meuser,

A. Pauls,

M. Preuten,

M.P. Rauch,

J. Schulz,

M. Teroerde

RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany

D. Eliseev,

M. Erdmann,

P. Fackeldey,

B. Fischer,

S. Ghosh,

T. Hebbeker,

K. Hoepfner,

H. Keller,

L. Mastrolorenzo,

M. Merschmeyer,

A. Meyer,

P. Millet,

G. Mocellin,

S. Mondal,

S. Mukherjee,

D. Noll,

A. Novak,

T. Pook,

A. Pozdnyakov,

T. Quast,

M. Radziej,

Y. Rath,

H. Reithler,

J. Roemer,

A. Schmidt,

S.C. Schuler,

A. Sharma,

S. Wiedenbeck,

S. Zaleski