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Physics
Letters
B
www.elsevier.com/locate/physletb
Measurement
of
the
cross
section
for
electroweak
production
of
Zγ
in
association
with
two
jets
and
constraints
on
anomalous
quartic
gauge
couplings
in
proton–proton
collisions
at
√
s
=
8 TeV
.TheCMS Collaboration CERN,Switzerland
a r t i c l e i n f o a b s t ra c t
Articlehistory:
Received10February2017 Receivedinrevisedform9April2017 Accepted27April2017
Availableonline2May2017 Editor:M.Doser Keywords: CMS Physics aQGC Electroweakproduction
A measurement is presented of the cross section for the electroweak production of a Z boson and a photon in association with two jets in proton–proton collisions at √s=8 TeV. The Z bosons are identified through their decays to electron or muon pairs. The measurement is based on data collected with the CMS detector corresponding to an integrated luminosity of 19.7 fb−1. The electroweak contribution has a significance of 3.0 standard deviations, and the measured fiducial cross section is 1.86+−00..9075(stat)−+00..3426(syst)±0.05 (lumi) fb, while the summed electroweak and quantum chromodynamic total cross section in the same region is observed to be 5.94+−11..5335(stat)−+00..4337(syst)±0.13 (lumi) fb. Both
measurements are consistent with the leading-order standard model predictions. Limits on anomalous quartic gauge couplings are set based on the Zγ mass distribution.
©2017 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3.
1. Introduction
With the discovery of the Higgs boson at the CERN LHC [1, 2], the standard model (SM) became a great success. The high energy and luminosity of the LHC provides the opportunity to observe many processes that are predicted by the SM, includ-ing electroweak production of multiple gauge bosons (WVγ [3], Vγ γ [4–6]), vector boson scattering (VBS) (same charge W±W± scattering [7–9], γ γ →W+W− [10], EW Wγjj [11], W±Z [12]), andvector bosonfusion(VBF) (EWW(Z)jj [13–16]). Samecharge W±W± scattering has been observed by ATLAS, and the exclu-sive γ γ→W+W− processbyCMS,bothwithsignificanceslarger than3standarddeviations.Thetribosonfinal stateZγ γ hasbeen observedbyATLASandCMSwithasignificancelargerthan5 stan-dard deviations. The EW productionof a Z boson (decaying into two oppositely-charged leptons), a photon, and two jets (hence-forth denoted Zγjj) has never been studied before, and is the subjectof thispaper. While the crosssection forquantum chro-modynamic(QCD)inducedZγjj productionisordersofmagnitude largerthan theone forEW production,thelattercan be usedto perform important tests of the SM, and to search for
contribu- E-mailaddress:cms-publication-committee-chair@cern.ch.
tions fromphysicsbeyondtheSM thatcouldmanifestthemselves asanomaloustrilinearorquarticgauge bosoncouplings(aTGCor aQGC[3–7,9–12]).
This letterpresentsameasurement oftheassociated EW pro-duction of Zγjj, using the 8 TeV proton–proton collision data recorded by the CMS detector. The major processes contributing to EWZγjj production arerepresentedby theFeynmandiagrams inFig. 1.Theyare(a) bremsstrahlung,(b) multiperipheral(or non-resonant)production,(c, d) VBFwitheithertwotrilineargauge bo-soncouplings(TGC),or(e) VBSwithquarticgaugebosoncouplings (QGC).TheVBSprocessesareparticularlyinterestingbecausethey involve QGCs(e.g.WWZγ). Itis not possible,however,to isolate theQGCprocessesfromtheothercontributions,such asthe dou-ble TGC processes that are topologically similar. The interference oftheVBS diagramsensuresunitarity ofthe VBScrosssection in theSMathighenergy.Wepresentmeasurementsofthecombined cross sections for all EW processes that result in the Zγjj final state. The main background sourceis Zγjj productionwhere the associatedjetsareproducedthroughQCD-inducedprocesses(such astheFeynman diagramgiveninFig. 1(f)).Otherbackgrounds in-cludejetsorleptonsmisidentifiedasphotons,dibosonprocessesin which aW orZbosondecaysintotwo jetsandthe photon orig-inates frominitialorfinal-state radiation,andcontributionsfrom topquarkpairsandsingletopquarkproduction.
http://dx.doi.org/10.1016/j.physletb.2017.04.071
0370-2693/©2017TheAuthor.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).Fundedby SCOAP3.
Fig. 1. RepresentativediagramsforEWZγjj productionattheLHC:(a)bremsstrahlung,(b)multiperipheral,(c,d)VBFwithTGC,(e)VBSincludingQGC,and(f)Example diagramfortheQCDZγjj production.
2. TheCMSdetector
The central feature of the CMS apparatus is a superconduct-ingsolenoidof 6 minternal diameter,providing amagnetic field of3.8 T.Withinthesolenoidvolumeare asilicon pixelandstrip tracker,aleadtungstatecrystalelectromagneticcalorimeter(ECAL), andabrassandscintillatorhadroncalorimeter(HCAL),each com-posedofa barreland twoendcap sections.Forwardcalorimeters extendthepseudorapidity, η,coverage providedbythebarreland endcapdetectors.Muonsaremeasuredingas-ionizationdetectors embeddedinthesteelflux-returnyokeoutsidethesolenoid.
Theparticle-flow(PF)eventalgorithm[17,18]reconstructsand identifieseach individual particlewithan optimizedcombination of information from the various elements of the CMS detector. The energy of photons is directly obtainedfrom the ECAL mea-surement, corrected for zero-suppression effects. The energy of electrons is determined from a combinationof the electron mo-mentum at the primary interaction vertex as determined by the tracker,theenergyofthecorrespondingECALcluster,andthe en-ergysumofallbremsstrahlungphotonsspatially compatiblewith originatingfrom the electron track.The energy of muonsis ob-tainedfromthecurvatureofthecorresponding track.Theenergy ofchargedhadronsisdeterminedfromacombinationoftheir mo-mentummeasuredinthetrackerandthematchingECALandHCAL energydeposits,correctedforzero-suppressioneffectsandforthe responsefunctionofthecalorimeterstohadronicshowers.Finally, theenergyofneutralhadronsisobtainedfromthecorresponding correctedECALandHCALenergy.
InthebarrelsectionoftheECAL,anenergyresolutionofabout 1% isachievedfor unconverted orlate-converting photonsinthe tensofGeVenergyrange.Theresolutionforother photonsinthe barrel section is about 1.3% up to |η|=1, rising to about 2.5% at |η|=1.4. In the endcaps, the resolution for unconverted or late-converting photonsis about2.5%, andthe resolution forthe remainingphotonsintheendcapisbetween3%and4%[19].When combininginformationfromtheentiredetector,thejetenergy res-olutionistypically15%at10 GeV,8%at100 GeV,and4%at1 TeV. Muons are measured in the range of |η|<2.4, with detec-tionplanesutilizingthree technologies:drift tubes,cathode strip chambers,andresistive-platechambers.Matchingmuonstotracks
measuredinthesilicontrackerresultsinapTresolutionformuons
with20<pT<100 GeV of1.3–2.0%inthebarrelandbetterthan
6%intheendcaps.
Theelectronmomentumisestimatedbycombiningtheenergy measurement in the ECAL withthe momentum measurement in the tracker. The momentum resolution for electrons with trans-verse momentum pT≈45 GeV from Z→ee decays ranges from
1.7% for nonshowering electrons in the barrelregion to 4.5% for showering electrons in the endcaps. The dielectron mass resolu-tionforZ→ee decaysis1.9%whenbothelectronsareintheECAL barrel,and2.9%whenbothelectronsareintheendcaps.
AmoredetaileddescriptionoftheCMSdetector,togetherwith adefinitionofthe coordinatesystemusedandtherelevant kine-maticvariables,canbefoundinRef.[20].
3. Eventreconstructionandselection
Candidateeventsare selectedonlinewithtriggers thatrequire two muons or electrons, where the leading andsubleading lep-tonshavepT>17 and8 GeV respectively,with|η|<2.4 (muons)
or|η|<2.5 (electrons).Theoverall triggerefficiencyisabout94% and 90% formuons and electrons, respectively, witha small de-pendenceonpTand η.
Muonsarereconstructedwithaglobalfitusingboththeinner trackingsystemandthemuonspectrometer. Anisolation require-mentisappliedinordertosuppressthebackgroundfrommultijet events[21,22].Electroncandidatesarereconstructedby matching energydepositsintheECALwithreconstructedtracks;they must pass stringent quality criteriaand an isolation requirement [23]. Chargedleptons mustoriginate fromtheprimary vertex,whichis defined asthe vertex whose tracks havethe highest sum of p2T. We require that each event has exactly two oppositely charged muons(electrons) with pT>20 GeV and |η|<2.4(2.5) andthat
theinvariantmassofthedileptonsystemmustsatisfy70<M<
110 GeV.Theselectionefficienciesforleptonsaremeasuredusing thetag-and-probemethod[24]andareapproximately96%forthe muons[25]and80%fortheelectrons[21].
Photon candidates are reconstructed from energy deposits in the ECALwith no associatedtrack. Quality selection criteria[19]
Table 1
Summaryofthethreedifferenteventcriteria:(1)selectionfortheEWsignalmeasurement;(2)thecrosssection measurement;and(3)theselectionfortheaQGCsearch.“j1”and“j2”representthejetsthathavethelargestand second-largestpT,“1”and“2”denotetheleptonandantileptonfromthedecayoftheZboson,y istherapidity, φZγ ,jjistheabsolutedifferencebetween φZγ and φj1j2,andtheangularseparation R=
(η)2+ (φ)2. Common selection pj1T,j2>30 GeV,|ηj1,j2| <4.7 pT1,2>20 GeV,|η1,2| <2 .4 |ηγ| <1.4442 Mjj>150 GeV 70<M<110 GeV
EW signal measurement Fiducial cross section aQGC search
pγT>25 GeV p γ T>20 GeV p γ T>60 GeV |ηjj| >1.6 |ηjj| >2.5 |ηjj| >2.5 Rj>0.3,Rjj,γj,γ >0.5 Rjj,γj,γ ,j>0.4 Rj>0.3,Rjj,γj,γ >0.5 |yZγ− (yj1+yj2)/2| <1.2 Mjj>400 GeV Mjj>400 GeV φZγ ,jj>2.0 radians
Mjj>400 GeV with two divided regions
400<Mjj<800 GeV and Mjj>800 GeV
are applied to the reconstructed photons to suppress the back-ground from hadrons misidentified as photons. The observables usedin thephoton selection are: (1) PF-basedisolation variables that are corrected for the contribution from additional proton– protoncollisionsinthe samebunchcrossing(pileup);(2) a small ratio of hadronic energy in the HCAL to electromagnetic energy in the ECAL matched in (η,φ) (where φ is azimuthal angle in radians); (3) thetransverse widthof theelectromagnetic shower along the η direction [19]; and (4) an electron track veto. We consideronlyphotonsintheECALbarrelregion(|η|<1.44) with pT>25 GeV.Eventswiththephotoncandidateinoneofthe
end-caps (|η|>1.57) are excluded from the selection because their signalpurityislowerandsystematicuncertaintiesarelarge.
Hadronic jets are formed from the particles reconstructed by thePFalgorithm,usingthe FastJet softwarepackage[26]andthe anti-kT jetclustering algorithm[27] withadistanceparameter of
0.5. To reduce the contamination from pileup,charged PF candi-datesinthetrackeracceptanceregion|η|<2.4,areexcludedfrom thejetclusteringprocedureifassociatedwithpileupvertices.The contributionofneutralparticles frompileupeventstothe jet en-ergyistakenintoaccountby meansofacorrectionbasedonthe projected area ofthe jet onthe front faceof thecalorimeter. Jet energycorrectionsarederivedfromameasurementofthepT
bal-anceindijetandphoton+jeteventsindata[28].Furtherresidual corrections as functionsof pT and η are applied to the data to
correctforthesmalldifferencesbetweendataandsimulation. Ad-ditionalquality criteriaare appliedtothejetsinordertoremove spurious jet-like features originatingfrom isolated noisepatterns in thecalorimeters or inthe tracker[29]. The two jetswiththe highest pT are taggedasthe signaljetsandare requiredtohave
pT>30 GeV and |η|<4.7. Since we are primarily interested in
theVBStopologies,werequirethat theinvariantmassofthetwo jets,Mjj>150 GeV.
Table 1presentsa summary ofthethree differentsection cri-teria that are used for(1) the SM EW signal search, (2) the SM fiducial cross section measurement, and (3) the aQGC searches. The criteria isolate events consistent with the VBS topology of two high-energy scatteredjetsseparated by a large rapidity gap. Thecrosssectionmeasurementaddstwovariablessensitivetothe VBSprocess:|yZγ− (yj1+yj2)/2|,whichensurestheZγ systems
is located between the scattered jets in eta; and φZγ,jj, which
requiresthe Zγ system transversemomentum is consistent with recoilingagainst the transversemomentum ofthe twocombined jets.The fiducialcrosssection criteriaconstraintheVBS topology withonly basickinematic cutsthat define the acceptance ofthe
CMS detectorand a simple two dimensionalrequirement on the rapidityseparationandinvariantmassofthejets.AtightpγT selec-tionisappliedtoreachahigherexpectedsignificanceinasearch forapossibleaQGCsignalintheEWZγjj process.
4. Dataandsimulation
WeusedatacollectedwiththeCMSdetector,correspondingto an integratedluminosityof19.7 fb−1,atproton–proton center-of-massenergyof8 TeV.
TheEWsignal, Zγjj,atleading-order(LO),andthemain back-ground, QCD Zγ with 0–3additionaljets, forwhich the next-to-leading-order(NLO)QCDpredictionhasbeentakenfromRef.[30], matched withparton shower based on the so-called “MLM pre-scription” [31,32], are simulated using MadGraph v5.1.3.30 [33] interfaced with pythia v6.424 [34] for hadronization and show-ering,usingaCTEQ6L1partondistributionfunction(PDF)set[35]. The second significant background contribution comes from pro-cesseswhereajetismisidentifiedasaphoton(fakephoton),and thiscontributionisestimatedfromdata.Otherbackground contri-butions come fromdibosonprocesses (WW/WZ/ZZ)simulatedby pythia,singletop processessimulatedby powheg,andttγ simu-latedusing MadGraph interfacedwith pythia.The next-to-leading-order QCD cross sections are used to normalizethese simulated samples,exceptforttγ whereanLOpredictionistaken.
All thesimulatedeventsare processedthrough a Geant4[36] simulation of the CMS detector. The tag-and-probe technique is usedtocorrectfordata-MonteCarlo(MC)differencesinthetrigger efficiency, aswell asthe reconstructionandselection efficiencies. Additional proton–protoninteractions are superimposed over the hard scattering interaction with the distribution of primary ver-ticesmatchingthatobtainedfromthecollisiondata.
5. Backgroundmodeling
The dominant source of backgroundto the EW signal isQCD Zγ +jets production.The shapeofthisbackgroundistakenfrom MC simulationandthenormalizationis evaluatedfromdataina control region,definedas150<Mjj<400 GeV,wherethe signal
contribution is below 1%. The simulated MC events correctly re-produce theyieldoftheseeventswithacorrectionfactorof1.00 ±0.22forthecombinedZ→μ+μ−andZ→e+e− channels.The value is comparable with the NLO QCD K factor from Ref. [30], whichisaround1.1forMjj<400 GeV.
Fig. 2. TheMjjdistributionsmeasuredin(top)muonand(bottom)electron
chan-nels.The data(solidsymbols witherror barsrepresentingthe statistical uncer-tainties)arecomparedtoadata-drivenbackgroundestimate,combinedwith MC predictionsforthesignalcontribution.Thehashedbandsrepresentthefull uncer-taintyinthepredictions,asdescribedinSection6.Thelastbinincludesoverflow events.
The background from fake photons arises mainly from Z+jets eventswhereone jetsatisfiesthe photonID criteria. The estima-tionisbasedoneventssimilartotheonesselectedwiththe base-lineselectiondescribedinTable 1,exceptthatthephotonmustfail thetightphoton IDandsatisfy alooserID requirementbasedon thechargedisolationvariable.Thisselectionensuresthatthe pho-tonarisesfromajet,butstillhaskinematicpropertiessimilartoa genuinephoton satisfyingthetight photonID.We selectgenuine photonsusing σηη , a photon identification variable that exploits thesmalllateralextension oftheelectromagneticshower[25,19]. Based on the difference between the σηη distributions for fake photonsandgenuinephotons,afitismadetonormalizethe num-ber of events with fake photons to the number of events with genuine photons andobtain the probability to have a fake pho-ton. The fake photon probability is calculated based on different pγT regionsinamannersimilartothatdescribedinRef.[37].
Other backgrounds, including top quark and diboson produc-tionprocessesareestimatedfromMCsimulationsandnormalized totheintegratedluminosity ofthedatasample. Thecontribution fromthesebackgroundsislessthan 10% afterapplyingthe kine-maticselection(Section3)andisnegligibleoncethefinalEWand aQGCselectioncriteria(Sections7and8)areapplied.
The Mjj distributions for the Z→μ+μ− and e+e− channels
aftertheselectionrequirementsdescribed inSection 3are shown inFig. 2.Theobserveddistributionsarecomparedtothecombined predictionofthebackgroundsandoftheEWZγjj signal.
Table 2
Summaryofthemajoruncertainties.
Source Uncertainty
QCDZγ+jetsnormalization 22%(400<Mjj<800 GeV)
24%(Mjj>800 GeV)
Fakephotonfromjet (pγT dependent)
15%(20–30 GeV) 22%(30–50 GeV) 49%(>50 GeV)
Triggerefficiency 1.2%(Z→μ+μ−),1.7%(Z →e+e−) Leptonselectionefficiency 1.9%(Z→μ+μ−),1.0%(Z →e+e−) Jetenergyscaleandresolution 14%(Mjj>400 GeV)
ttγ crosssection 20%[3] Pileupmodeling 1.0% Renormalization/factorization scale(signal) 9.0%(400<Mjj<800 GeV) 12% (Mjj>800 GeV)(SM) 14%(aQGC) PDF(signal) 4.2%(400<Mjj<800 GeV) 2.4% (Mjj>800 GeV)(SM) 4.3%(aQGC)
Interference(signal) 18%(400<Mjj<800 GeV)
11% (Mjj>800 GeV)(SM)
Luminosity 2.6%
6. Systematicuncertainties
The systematicuncertainty inthe QCD Zγ + jetsbackground estimationis22% forbothZ→μ+μ− andZ→e+e−;it is dom-inated by the large statistical uncertainty in the control region usedfornormalization.Theshapeuncertaintiesthatarerelatedto the extrapolationofthe normalizationfactorto thesignal region (Mjj>400 GeV) are determined by varying the renormalization
andfactorizationscalesaswellastheMLMmatchingscale[31,32] upanddownbyafactoroftwo.Finally,wecombineboththe nor-malizationfactoruncertaintyandtheshapeuncertaintytoobtain thetotaluncertainty.
Thesystematicuncertaintyinthe backgroundestimationfrom fakephotonsarisesfromthevariationinthechoiceofthecharged isolationsidebandandthe σηη distributionusedforestimatingthe fakephotonprobability.Thetotaluncertaintiesinthefakephoton background estimation can be found in Table 2. The theoretical uncertaintyinthetopquarkbackgroundis20%[3].
The systematic uncertainties in the estimation of the trigger efficiency, measured using the tag-and-probe technique, are 1.2% and 1.7% for the Z→μ+μ− and Z→e+e− channels, respec-tively.Using similar methods, the systematicuncertainties inthe efficienciesforleptonreconstructionandidentificationinthetwo channelsare1.9%and1.0%,respectively.Thesystematicuncertainty inthejetenergyscaleandresolutionisestimatedbyvarying the jet energy scale and resolution up and down within their pT
-and η-dependent uncertainties [28]. The uncertainty is 14% for Mjj>400 GeV. Anothersource ofuncertainty isthe modeling of
thepileup.Theinelasticcrosssectionisvariedby±5%inorderto evaluatethiscontribution.Theuncertaintyintheintegrated lumi-nosityis2.6%[38].
Therearealsothreesourcesoftheoreticaluncertaintiesapplied tothesignalonly.ThePDF uncertaintyforthesignalisestimated with the CT10 [39] PDF set, following the asymmetric Hessian methodintroduced inRefs. [40,41].The scaleuncertaintyis eval-uated by varying the renormalizationandfactorization scales in-dependentlybyafactoroftwo.Themagnitudeoftheinterference betweenQCDandEWZγjj processesisassignedassystematic un-certaintiesinthetwo Mjjranges.
All the systematicuncertainties described are appliedto both the signal significance measurement and the aQGC search. They are also propagated to the uncertainty in the measured fiducial
Table 3
SignalandbackgroundyieldsafterthefinalselectionfortheSMmeasurement,for thetwobinsof400 <Mjj<800 GeV (upper)andMjj>800 GeV (lower).Only
sta-tisticaluncertaintiesarereported.
400<Mjj<800 GeV Muon Electron
Fake photon from jet 3.4±0.8 1.7±0.5 Other background 0.1±0.1 0.1±0.1 QCD Zγjj 4.8±0.9 5.0±1.0 EW Zγjj 1.7±0.1 1.8±0.1 Total background 8.3±1.2 6.8±1.1
Data 13 8
Mjj>800 GeV Muon Electron
Fake photon from jet 0.4±0.3 0.1±0.1 Other background 0±0 0±0 QCD Zγjj 0.4±0.1 1.1±0.2 EW Zγjj 1.8±0.1 1.8±0.1 Total background 0.8±0.3 1.2±0.2
Data 5 2
crosssection,withtheexceptionofthetheoreticaluncertainty as-sociatedwiththesignalcrosssection.
AlltheuncertaintiesinouranalysisaresummarizedinTable 2.
7. Measurementofthesignalsignificanceandfiducialcross section
As shown in Table 1, in addition to the common selection, we apply three further requirements to isolate the EW signal: |yZγ− (yj1+yj2)/2|<1.2,|ηjj|>1.6,andφZγ,jj>2.0 radians.
Theselectionrequirementsarechosenbyoptimizingtheexpected significance. We apply the CLs criterion described in Refs. [42,
43] to assess the signal significance, based on the binned Mjj
distribution, usingonly the two rightmost bins corresponding to 400<Mjj<800 GeV and Mjj>800 GeV. We consider QCD Zγjj
production and events without Zγ as background and EW Zγjj productionassignal.
Table 3 summarizes the numberof events predictedfor each processwiththenumberofeventsobserved.ForEWZγjj produc-tion, the observations are found to be compatiblewith expecta-tions in the differentchannels. By combining both channels, we find evidencefor EW Zγjj production withan observed and ex-pectedsignificanceof3.0and2.1standarddeviations,respectively. We determine the ratio of the observed signal to that expected from the SM for LO EW Zγjj production as μˆ =1.5+−00..96 using a binned likelihood fit over the two ranges of the Mjj
distribu-tion.
Applying the same criteria, we can also measure the signifi-cance of the combined EW and QCD Zγjj process. As shown in Table 3,withthetwo decaychannelscombinedinthe search re-gion,ofthesignal events7.0(38.4%)areestimatedtocome from EWproductionandtheremaining11.3fromQCDproduction.Asa result, theobserved(expected)significance forthecombinedEW andQCDZγjj processis5.7(5.5)standarddeviations.
TodeterminethecrosssectionforEWZγjj productionwe use a fiducial kinematic region based on the acceptance of the CMS detectorwithaminimalselectionontheMjjandηjjvariablesto
selecttheVBStopology.Thefiducialregionisdefinedasdescribed in Table 1. We define the cross section in the fiducial region as σf =σgμ αˆ g f where σg is the cross section for generated sig-nal events, μˆ is the signal strength, and αg f is the acceptance forthegeneratedeventsinthefiducial region,evaluatedthrough simulation. The fiducial cross section for EW Zγjj production is 1.86−+00..9075(stat)+−00..3426(syst)±0.05(lumi) fb,consistentwiththe the-oreticalpredictionatLOof1.27±0.11(scale)±0.05(PDF)fb cal-culatedusing MadGraph.
The cross section for all processes that produce the Zγjj fi-nal state can be compared to theoretical predictions. The fidu-cial region studied here lies in a particularly interesting region of phase space because of the substantial contribution to Zγjj from EW production. By restrictingthe phase space to the fidu-cial region for the EW process as defined before, the expected fractionofEWeventsinthecombinedsampleofEWandQCD sig-nal eventsis26%, andthecross sectionof thecombinedprocess is 5.94−+11..5335(stat)+−00..4337(syst)±0.13(lumi) fb, which is consistent withthetheoreticalpredictionatLOcalculatedusing MadGraph: 5.05±1.22(scale)±0.31(PDF)fb.
8. Searchforanomalousquarticgaugecouplings
TheeffectsofanynewphysicsbetweentheTeVandthePlanck scalemightbesignificantinthehighenergytailsofmeasurements attheLHCandcanbeparameterizedviaeffectiveanomalous cou-plings.WiththediscoveryoftheHiggsboson,higher-dimensional operatorscanbeintroducedinalinearway[44]:
LaQGC= fM0 4 Tr WμνWμν× (Dβ )†Dβ + fM1 4 Tr WμνWνβ× (Dβ )†Dμ + fM2 4 BμνBμν× (Dβ )†Dβ + fM3 4 BμνBνβ ×(Dβ )†Dμ + fT0 4T r[ ˆWμνWˆ μν] ×T r[ ˆW αβWˆαβ] + fT2 4 T r[ ˆWαμWˆ μβ] ×T r[ ˆW βνWˆνα] + fT8 4BμνB μνB αβBαβ+ fT9 4BαμB μβB βνBνα, (1)
where fM0,1,2,3 and fT0,2,8,9 are coefficients ofrelevant effective
operators, andrepresents thescale ofnewphysics responsible for anomalous couplings. The Lagrangian of the aQGCsis imple-mentedwithinthe MadGraph package.
Westudythedistributionofthemassofthedileptonand pho-ton system, MZγ ,tosearch forcontributionsfromaQGCs.The ef-fectsof newphysicswouldbe seen athigherenergyandmodify the interference of VBS diagrams. To select the region sensitive to new physics, we require pγT >60 GeV. The selection for the aQGC analysisis described in Table 1. The Zγ mass distribution is shown in Fig. 3, where the last bin includes all events with MZγ>420 GeV.Becausenosignificantexcessisseen intheMZγ distribution, we usetheshape ofthe MZγ distributionto extract limitsonaQGCcontributions.
Withtheparameterizationofsignalsandrelatedsystematic un-certainties, foreach aQGC parameter, we reweight theSM signal shapetotheaQGCshape.Thefollowingteststatisticisused:
tαtest= −2 ln
L(αtest, ˆˆθ )
L(αˆ, ˆθ ) , (2)
where the likelihood function (L) is constructed for both lepton channelsandcombined,usingabin-wisePoissondistributionwith profiled nuisanceparameters (θ). αtest represents theaQGC point
being tested. The symbol ˆˆθ represents the values corresponding tothemaximumofthelikelihoodatthepoint αtest,whileαˆ and
ˆθ correspond to the globalmaximum ofthe likelihood. This test statistic isassumed tofollow a χ2 distribution [45], fromwhich
Fig. 3. TheinvariantmassdistributionoftheZγ systemforeventsthatpassthe aQGCselection.Thehighestmassbinincludeseventswith MZγ>420 GeV.Error
barsrepresentthestatisticaluncertaintyinthedata,whilethesystematic uncer-taintiesintheaQGCsignalandbackgroundestimateareshownashatchedbands.
Table 4
Observedandexpectedshape-basedexclusionlimitsforeachaQGC param-eterat95%CL,withoutaformfactorapplied.
Observed limits (TeV−4) Expected limits (TeV−4) −71<fM0/4<75 −109<fM0/4<111 −190<fM1/4<182 −281<fM1/4<280 −32<fM2/4<31 −47<fM2/4<47 −58<fM3/4<59 −87<fM3/4<87 −3.8<fT0/4<3.4 −5.1<fT0/4<5.1 −4.4<fT1/4<4.4 −6.5<fT1/4<6.5 −9.9<fT2/4<9.0 −14.0<fT2/4<14.5 −1.8<fT8/4<1.8 −2.7<fT8/4<2.7 −4.0<fT9/4<4.0 −6.0<fT9/4<6.0
couplingparameterisvaried overasetofdiscretevalues,keeping theotherparametersfixedtozero.
An effective theory is only valid at energies lower than the scaleofnewphysics,andhigh-dimensionaloperatorswithnonzero aQGCvaluescanleadtounitarityviolationatsufficientlyhigh en-ergies.ForeachaQGClistedinTable 4,wecheckedthestated up-perlimitagainsttheunitarybound[46]obtainedwith vbfnlo[47]. Ingeneral,wefindthelimitsonallaQGCparametersaresetinthe unitaryunsaferegion,exceptfor fT9 wheretheunitarityboundis
upto6 TeV.Formfactorscan beintroducedtounitarizethehigh energycontribution,howeveritisdifficulttocompareresultsfrom differentexperimentsanditisnottheoreticallywellmotivated.In thisstudyall ofthe aQGC limitsshown are evaluated without a formfactor, and can be directly compared to limits set in refer-ences[3–7,9–12].
9. Conclusions
Themeasurementofthecrosssectionfortheelectroweak pro-duction ofa Z boson anda photon in association withtwo jets, wherethe Z boson decaysinto electronor muonpairs, was pre-sented.The measurement isbasedon asample ofproton–proton collisions collected with the CMS detector at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb−1.Wefindevidence forEWZγjj productionwithan
ob-served(expected)significanceof3.0(2.1)standarddeviations.The fiducial cross section forEW Zγjj production is measured to be 1.86−+00..9075(stat)+−00..3426(syst)±0.05(lumi) fb,consistentwiththe the-oreticalprediction.ThefiducialcrosssectionforcombinedEWand QCD Zγjj production is5.94+−11..3553(stat)+−00..4337(syst)±0.13(lumi) fb, whichisalsoconsistentwiththeleading-ordertheoretical predic-tion.
Intheframework ofdimension-eight effectivefieldtheory op-erators,limitsontheaQGCparameters fM0,1,2,3 and fT0,1,2,8,9are
setat95%confidencelevel.Thisisthefirstconstraintsonthe neu-tralaQGCparameters fT8.
Acknowledgements
WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the technicalandadministrative staffsatCERN andatother CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcentersand personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythe computinginfrastructureessential to ouranalyses. Finally, we acknowledge the enduring support for the construc-tionandoperation oftheLHC andtheCMSdetectorprovidedby thefollowingfundingagencies:BMWFWandFWF(Austria);FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIEN-CIAS(Colombia);MSESandCSF(Croatia);RPF(Cyprus);SENESCYT (Ecuador); MoER, ERC IUT, and ERDF (Estonia); Academy of Fin-land,MEC,andHIP(Finland);CEAandCNRS/IN2P3(France);BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hun-gary);DAEandDST(India);IPM(Iran);SFI(Ireland);INFN(Italy); MSIPandNRF(RepublicofKorea);LAS (Lithuania);MOEandUM (Malaysia); BUAP, CINVESTAV,CONACYT, LNS, SEP, andUASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland);FCT(Portugal);JINR(Dubna);MON, RosAtom,RAS,RFBR andRAEP(Russia);MESTD (Serbia);SEIDI,CPAN, PCTIandFEDER (Spain);SwissFundingAgencies(Switzerland);MST(Taipei); ThEP-Center, IPST, STAR, and NSTDA (Thailand); TUBITAK and TAEK (Turkey);NASUandSFFR(Ukraine); STFC(United Kingdom);DOE andNSF(USA).
Individuals have received support from the Marie-Curie pro-gram and the European Research Council and EPLANET (Euro-pean Union); the Leventis Foundation; the A.P. Sloan Founda-tion; the Alexander von Humboldt Foundation; the Belgian Fed-eral Science Policy Office; the Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technolo-gie (IWT-Belgium); the Ministry of Education, Youth and Sports (MEYS) ofthe Czech Republic;the Council ofScience and Indus-trial Research, India; the HOMING PLUS program of the Foun-dation for Polish Science, cofinanced from European Union, Re-gional Development Fund, the Mobility Plus program of the Ministry of Science and Higher Education, the National Science Center (Poland), contracts Harmonia 2014/14/M/ST2/00428, Opus 2014/13/B/ST2/02543, 2014/15/B/ST2/03998, and 2015/19/B/ST2/ 02861,Sonata-bis2012/07/E/ST2/01406;theNationalPriorities Re-search Program by Qatar National Research Fund; the Programa Clarín-COFUND del Principado de Asturias; the Thalis and Aris-teia programs cofinanced by EU-ESF and the Greek NSRF; the Rachadapisek Sompot Fund for Postdoctoral Fellowship, Chula-longkornUniversityandtheChulalongkornAcademic intoIts2nd Century Project Advancement Project (Thailand); and the Welch Foundation,contractC-1845.
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TheCMSCollaboration
V. Khachatryan,A.M. Sirunyan, A. Tumasyan
YerevanPhysicsInstitute,Yerevan,Armenia
W. Adam, E. Asilar,T. Bergauer, J. Brandstetter, E. Brondolin, M. Dragicevic, J. Erö,M. Flechl, M. Friedl,
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W. Treberer-Treberspurg,W. Waltenberger, C.-E. Wulz1
InstitutfürHochenergiephysik,Wien,Austria
V. Mossolov,N. Shumeiko,J. Suarez Gonzalez
NationalCentreforParticleandHighEnergyPhysics,Minsk,Belarus
S. Alderweireldt, E.A. De Wolf,X. Janssen,J. Lauwers, M. Van De Klundert, H. Van Haevermaet,
P. Van Mechelen,N. Van Remortel, A. Van Spilbeeck
UniversiteitAntwerpen,Antwerpen,Belgium
S. Abu Zeid,F. Blekman, J. D’Hondt, N. Daci,I. De Bruyn, K. Deroover, N. Heracleous,S. Lowette,
S. Moortgat, L. Moreels,A. Olbrechts,Q. Python, S. Tavernier, W. Van Doninck, P. Van Mulders,
I. Van Parijs
VrijeUniversiteitBrussel,Brussel,Belgium
H. Brun, C. Caillol, B. Clerbaux, G. De Lentdecker, H. Delannoy, G. Fasanella,L. Favart, R. Goldouzian,
A. Grebenyuk,G. Karapostoli,T. Lenzi, A. Léonard,J. Luetic, T. Maerschalk,A. Marinov, A. Randle-conde,
T. Seva,C. Vander Velde, P. Vanlaer,R. Yonamine, F. Zenoni, F. Zhang2
UniversitéLibredeBruxelles,Bruxelles,Belgium
A. Cimmino,T. Cornelis, D. Dobur, A. Fagot, G. Garcia, M. Gul, D. Poyraz,S. Salva, R. Schöfbeck, M. Tytgat,
W. Van Driessche, E. Yazgan,N. Zaganidis
GhentUniversity,Ghent,Belgium
C. Beluffi3, O. Bondu,S. Brochet,G. Bruno, A. Caudron, L. Ceard,S. De Visscher, C. Delaere, M. Delcourt,
L. Forthomme,B. Francois, A. Giammanco,A. Jafari, P. Jez,M. Komm, V. Lemaitre, A. Magitteri,
A. Mertens, M. Musich, C. Nuttens, K. Piotrzkowski,L. Quertenmont,M. Selvaggi, M. Vidal Marono,
S. Wertz
UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium
N. Beliy
UniversitédeMons,Mons,Belgium
W.L. Aldá Júnior, F.L. Alves,G.A. Alves,L. Brito, C. Hensel,A. Moraes, M.E. Pol,P. Rebello Teles
CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil
E. Belchior Batista Das Chagas, W. Carvalho,J. Chinellato4, A. Custódio, E.M. Da Costa, G.G. Da Silveira,
D. De Jesus Damiao,C. De Oliveira Martins, S. Fonseca De Souza, L.M. Huertas Guativa, H. Malbouisson,
D. Matos Figueiredo,C. Mora Herrera, L. Mundim,H. Nogima, W.L. Prado Da Silva, A. Santoro,
A. Sznajder,E.J. Tonelli Manganote4,A. Vilela Pereira
S. Ahujaa, C.A. Bernardesb, S. Dograa,T.R. Fernandez Perez Tomeia, E.M. Gregoresb, P.G. Mercadanteb,
C.S. Moona,5,S.F. Novaesa,Sandra S. Padulaa, D. Romero Abadb, J.C. Ruiz Vargas
aUniversidadeEstadualPaulista,SãoPaulo,Brazil bUniversidadeFederaldoABC,SãoPaulo,Brazil
A. Aleksandrov, R. Hadjiiska, P. Iaydjiev,M. Rodozov, S. Stoykova, G. Sultanov, M. Vutova
InstituteforNuclearResearchandNuclearEnergy,Sofia,Bulgaria
A. Dimitrov, I. Glushkov,L. Litov, B. Pavlov,P. Petkov
UniversityofSofia,Sofia,Bulgaria
W. Fang6
BeihangUniversity,Beijing,China
M. Ahmad, J.G. Bian, G.M. Chen, H.S. Chen,M. Chen, Y. Chen7,T. Cheng, C.H. Jiang, D. Leggat, Z. Liu,
F. Romeo,S.M. Shaheen, A. Spiezia, J. Tao, C. Wang,Z. Wang, H. Zhang, J. Zhao
InstituteofHighEnergyPhysics,Beijing,China
Y. Ban, Q. Li, S. Liu,Y. Mao, S.J. Qian, D. Wang,Z. Xu, D. Yang,Z. Zhang
StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China
C. Avila,A. Cabrera, L.F. Chaparro Sierra, C. Florez, J.P. Gomez, C.F. González Hernández,J.D. Ruiz Alvarez,
J.C. Sanabria
UniversidaddeLosAndes,Bogota,Colombia
N. Godinovic, D. Lelas, I. Puljak,P.M. Ribeiro Cipriano
UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia
Z. Antunovic, M. Kovac
UniversityofSplit,FacultyofScience,Split,Croatia
V. Brigljevic,D. Ferencek, K. Kadija,S. Micanovic, L. Sudic
InstituteRudjerBoskovic,Zagreb,Croatia
A. Attikis, G. Mavromanolakis, J. Mousa,C. Nicolaou, F. Ptochos, P.A. Razis,H. Rykaczewski
UniversityofCyprus,Nicosia,Cyprus
M. Finger8, M. Finger Jr.8
CharlesUniversity,Prague,CzechRepublic
E. Carrera Jarrin
UniversidadSanFranciscodeQuito,Quito,Ecuador
S. Elgammal9,A. Mohamed10, Y. Mohammed11,E. Salama9,12
AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt
B. Calpas, M. Kadastik, M. Murumaa, L. Perrini, M. Raidal, A. Tiko, C. Veelken
NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia
P. Eerola, J. Pekkanen,M. Voutilainen
J. Härkönen,V. Karimäki, R. Kinnunen, T. Lampén, K. Lassila-Perini,S. Lehti, T. Lindén,P. Luukka,
T. Peltola,J. Tuominiemi,E. Tuovinen, L. Wendland
HelsinkiInstituteofPhysics,Helsinki,Finland
J. Talvitie,T. Tuuva
LappeenrantaUniversityofTechnology,Lappeenranta,Finland
M. Besancon,F. Couderc, M. Dejardin, D. Denegri,B. Fabbro, J.L. Faure, C. Favaro, F. Ferri, S. Ganjour,
S. Ghosh,A. Givernaud, P. Gras, G. Hamel de Monchenault, P. Jarry, I. Kucher, E. Locci,M. Machet,
J. Malcles,J. Rander, A. Rosowsky, M. Titov, A. Zghiche
IRFU,CEA,UniversitéParis-Saclay,Gif-sur-Yvette,France
A. Abdulsalam,I. Antropov, S. Baffioni, F. Beaudette, P. Busson, L. Cadamuro, E. Chapon,C. Charlot,
O. Davignon,R. Granier de Cassagnac, M. Jo, S. Lisniak,P. Miné, I.N. Naranjo, M. Nguyen,C. Ochando,
G. Ortona,P. Paganini, P. Pigard,S. Regnard, R. Salerno, Y. Sirois, T. Strebler, Y. Yilmaz,A. Zabi
LaboratoireLeprince-Ringuet,EcolePolytechnique,IN2P3-CNRS,Palaiseau,France
J.-L. Agram13,J. Andrea, A. Aubin,D. Bloch, J.-M. Brom,M. Buttignol, E.C. Chabert,N. Chanon, C. Collard,
E. Conte13,X. Coubez, J.-C. Fontaine13, D. Gelé, U. Goerlach,A.-C. Le Bihan, J.A. Merlin14, K. Skovpen,
P. Van Hove
InstitutPluridisciplinaireHubertCurien(IPHC),UniversitédeStrasbourg,CNRS-IN2P3,France
S. Gadrat
CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France
S. Beauceron,C. Bernet, G. Boudoul,E. Bouvier, C.A. Carrillo Montoya, R. Chierici,D. Contardo,
B. Courbon,P. Depasse, H. El Mamouni,J. Fan, J. Fay, S. Gascon,M. Gouzevitch, G. Grenier, B. Ille,
F. Lagarde,I.B. Laktineh, M. Lethuillier,L. Mirabito, A.L. Pequegnot, S. Perries,A. Popov15,D. Sabes,
V. Sordini,M. Vander Donckt, P. Verdier, S. Viret
UniversitédeLyon,UniversitéClaudeBernardLyon1,CNRS-IN2P3,InstitutdePhysiqueNucléairedeLyon,Villeurbanne,France
A. Khvedelidze8
GeorgianTechnicalUniversity,Tbilisi,Georgia
I. Bagaturia16
TbilisiStateUniversity,Tbilisi,Georgia
C. Autermann,S. Beranek, L. Feld, A. Heister, M.K. Kiesel, K. Klein, M. Lipinski, A. Ostapchuk, M. Preuten,
F. Raupach, S. Schael, C. Schomakers,J.F. Schulte,J. Schulz, T. Verlage,H. Weber, V. Zhukov15
RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany
M. Brodski,E. Dietz-Laursonn, D. Duchardt, M. Endres,M. Erdmann, S. Erdweg, T. Esch, R. Fischer,
A. Güth, T. Hebbeker,C. Heidemann, K. Hoepfner, S. Knutzen,M. Merschmeyer, A. Meyer,P. Millet,
S. Mukherjee,M. Olschewski, K. Padeken,P. Papacz, T. Pook,M. Radziej, H. Reithler, M. Rieger,
F. Scheuch,L. Sonnenschein, D. Teyssier,S. Thüer
RWTHAachenUniversity,III.PhysikalischesInstitutA,Aachen,Germany
V. Cherepanov, Y. Erdogan,G. Flügge, F. Hoehle, B. Kargoll, T. Kress, A. Künsken, J. Lingemann,
A. Nehrkorn, A. Nowack,I.M. Nugent, C. Pistone,O. Pooth, A. Stahl14
M. Aldaya Martin,C. Asawatangtrakuldee, I. Asin, K. Beernaert, O. Behnke,U. Behrens,A.A. Bin Anuar,
K. Borras17,A. Campbell, P. Connor, C. Contreras-Campana, F. Costanza, C. Diez Pardos,G. Dolinska,
G. Eckerlin, D. Eckstein, E. Gallo18, J. Garay Garcia, A. Geiser, A. Gizhko, J.M. Grados Luyando,
P. Gunnellini, A. Harb, J. Hauk, M. Hempel19,H. Jung,A. Kalogeropoulos,O. Karacheban19,M. Kasemann,
J. Keaveney, J. Kieseler, C. Kleinwort,I. Korol, W. Lange, A. Lelek, J. Leonard,K. Lipka, A. Lobanov,
W. Lohmann19, R. Mankel, I.-A. Melzer-Pellmann,A.B. Meyer, G. Mittag, J. Mnich, A. Mussgiller,
E. Ntomari,D. Pitzl, R. Placakyte, A. Raspereza,B. Roland, M.Ö. Sahin,P. Saxena, T. Schoerner-Sadenius,
C. Seitz, S. Spannagel, N. Stefaniuk,K.D. Trippkewitz, G.P. Van Onsem, R. Walsh, C. Wissing
DeutschesElektronen-Synchrotron,Hamburg,Germany
V. Blobel, M. Centis Vignali, A.R. Draeger,T. Dreyer, E. Garutti, K. Goebel, D. Gonzalez, J. Haller,
M. Hoffmann, A. Junkes,R. Klanner,R. Kogler, N. Kovalchuk,T. Lapsien,T. Lenz,I. Marchesini, D. Marconi,
M. Meyer, M. Niedziela,D. Nowatschin, J. Ott, F. Pantaleo14,T. Peiffer, A. Perieanu, J. Poehlsen, C. Sander,
C. Scharf, P. Schleper, A. Schmidt, S. Schumann,J. Schwandt,H. Stadie, G. Steinbrück, F.M. Stober,
M. Stöver, H. Tholen, D. Troendle,E. Usai, L. Vanelderen,A. Vanhoefer, B. Vormwald
UniversityofHamburg,Hamburg,Germany
C. Barth,C. Baus, J. Berger,E. Butz, T. Chwalek, F. Colombo, W. De Boer, A. Dierlamm,S. Fink, R. Friese,
M. Giffels,A. Gilbert, D. Haitz, F. Hartmann14, S.M. Heindl,U. Husemann, I. Katkov15, P. Lobelle Pardo,
B. Maier, H. Mildner, M.U. Mozer, T. Müller,Th. Müller, M. Plagge, G. Quast, K. Rabbertz, S. Röcker,
F. Roscher,M. Schröder, G. Sieber, H.J. Simonis,R. Ulrich, J. Wagner-Kuhr, S. Wayand, M. Weber,
T. Weiler, S. Williamson,C. Wöhrmann, R. Wolf
InstitutfürExperimentelleKernphysik,Karlsruhe,Germany
G. Anagnostou, G. Daskalakis,T. Geralis,V.A. Giakoumopoulou, A. Kyriakis, D. Loukas, I. Topsis-Giotis
InstituteofNuclearandParticlePhysics(INPP),NCSRDemokritos,AghiaParaskevi,Greece
A. Agapitos, S. Kesisoglou, A. Panagiotou, N. Saoulidou, E. Tziaferi
NationalandKapodistrianUniversityofAthens,Athens,Greece
I. Evangelou, G. Flouris,C. Foudas, P. Kokkas, N. Loukas, N. Manthos, I. Papadopoulos,E. Paradas
UniversityofIoánnina,Ioánnina,Greece
N. Filipovic
MTA-ELTELendületCMSParticleandNuclearPhysicsGroup,EötvösLorándUniversity,Budapest,Hungary
G. Bencze,C. Hajdu, P. Hidas, D. Horvath20, F. Sikler,V. Veszpremi, G. Vesztergombi21,A.J. Zsigmond
WignerResearchCentreforPhysics,Budapest,Hungary
N. Beni, S. Czellar, J. Karancsi22,A. Makovec, J. Molnar,Z. Szillasi
InstituteofNuclearResearchATOMKI,Debrecen,Hungary
M. Bartók21,P. Raics, Z.L. Trocsanyi, B. Ujvari
InstituteofPhysics,UniversityofDebrecen,Hungary
S. Bahinipati, S. Choudhury23,P. Mal, K. Mandal, A. Nayak24, D.K. Sahoo,N. Sahoo, S.K. Swain
NationalInstituteofScienceEducationandResearch,Bhubaneswar,India
S. Bansal, S.B. Beri,V. Bhatnagar, R. Chawla, R. Gupta,U. Bhawandeep, A.K. Kalsi,A. Kaur, M. Kaur,
R. Kumar,A. Mehta, M. Mittal, J.B. Singh, G. Walia
Ashok Kumar,A. Bhardwaj, B.C. Choudhary, R.B. Garg,S. Keshri, A. Kumar,S. Malhotra, M. Naimuddin,
N. Nishu, K. Ranjan,R. Sharma, V. Sharma
UniversityofDelhi,Delhi,India
R. Bhattacharya,S. Bhattacharya, K. Chatterjee, S. Dey,S. Dutt, S. Dutta, S. Ghosh, N. Majumdar,
A. Modak, K. Mondal,S. Mukhopadhyay, S. Nandan,A. Purohit, A. Roy, D. Roy, S. Roy Chowdhury,
S. Sarkar,M. Sharan, S. Thakur
SahaInstituteofNuclearPhysics,Kolkata,India
P.K. Behera
IndianInstituteofTechnologyMadras,Madras,India
R. Chudasama,D. Dutta, V. Jha, V. Kumar, A.K. Mohanty14, P.K. Netrakanti,L.M. Pant, P. Shukla,A. Topkar
BhabhaAtomicResearchCentre,Mumbai,India
T. Aziz,S. Dugad, G. Kole, B. Mahakud, S. Mitra, G.B. Mohanty, N. Sur, B. Sutar
TataInstituteofFundamentalResearch-A,Mumbai,India
S. Banerjee, S. Bhowmik25,R.K. Dewanjee, S. Ganguly,M. Guchait, Sa. Jain, S. Kumar, M. Maity25,
G. Majumder,K. Mazumdar, B. Parida,T. Sarkar25, N. Wickramage26
TataInstituteofFundamentalResearch-B,Mumbai,India
S. Chauhan,S. Dube, A. Kapoor, K. Kothekar, A. Rane, S. Sharma
IndianInstituteofScienceEducationandResearch(IISER),Pune,India
H. Bakhshiansohi,H. Behnamian,S. Chenarani27,E. Eskandari Tadavani, S.M. Etesami27, A. Fahim28,
M. Khakzad, M. Mohammadi Najafabadi, M. Naseri, S. Paktinat Mehdiabadi,F. Rezaei Hosseinabadi,
B. Safarzadeh29, M. Zeinali
InstituteforResearchinFundamentalSciences(IPM),Tehran,Iran
M. Felcini,M. Grunewald
UniversityCollegeDublin,Dublin,Ireland
M. Abbresciaa,b, C. Calabriaa,b, C. Caputoa,b, A. Colaleoa,D. Creanzaa,c, L. Cristellaa,b,N. De Filippisa,c, M. De Palmaa,b, L. Fiorea, G. Iasellia,c, G. Maggia,c, M. Maggia,G. Minielloa,b,S. Mya,b,S. Nuzzoa,b, A. Pompilia,b, G. Pugliesea,c,R. Radognaa,b,A. Ranieria, G. Selvaggia,b, L. Silvestrisa,14,R. Vendittia,b,
P. Verwilligena
aINFNSezionediBari,Bari,Italy bUniversitàdiBari,Bari,Italy cPolitecnicodiBari,Bari,Italy
G. Abbiendia,C. Battilana, D. Bonacorsia,b, S. Braibant-Giacomellia,b,L. Brigliadoria,b,R. Campaninia,b, P. Capiluppia,b,A. Castroa,b,F.R. Cavalloa, S.S. Chhibraa,b, G. Codispotia,b, M. Cuffiania,b,
G.M. Dallavallea,F. Fabbria,A. Fanfania,b,D. Fasanellaa,b, P. Giacomellia, C. Grandia, L. Guiduccia,b, S. Marcellinia, G. Masettia,A. Montanaria,F.L. Navarriaa,b,A. Perrottaa,A.M. Rossia,b,T. Rovellia,b, G.P. Sirolia,b,N. Tosia,b,14
aINFNSezionediBologna,Bologna,Italy bUniversitàdiBologna,Bologna,Italy
S. Albergoa,b, M. Chiorbolia,b, S. Costaa,b, A. Di Mattiaa,F. Giordanoa,b, R. Potenzaa,b,A. Tricomia,b, C. Tuvea,b
aINFNSezionediCatania,Catania,Italy bUniversitàdiCatania,Catania,Italy
G. Barbaglia, V. Ciullia,b,C. Civininia, R. D’Alessandroa,b,E. Focardia,b,V. Goria,b, P. Lenzia,b, M. Meschinia, S. Paolettia,G. Sguazzonia,L. Viliania,b,14
aINFNSezionediFirenze,Firenze,Italy bUniversitàdiFirenze,Firenze,Italy
L. Benussi, S. Bianco, F. Fabbri,D. Piccolo, F. Primavera14
INFNLaboratoriNazionalidiFrascati,Frascati,Italy
V. Calvellia,b, F. Ferroa, M. Lo Veterea,b, M.R. Mongea,b,E. Robuttia,S. Tosia,b
aINFNSezionediGenova,Genova,Italy bUniversitàdiGenova,Genova,Italy
L. Brianza,M.E. Dinardoa,b, S. Fiorendia,b,S. Gennaia,A. Ghezzia,b, P. Govonia,b,S. Malvezzia,
R.A. Manzonia,b,14, B. Marzocchia,b,D. Menascea,L. Moronia, M. Paganonia,b,D. Pedrinia, S. Pigazzini,
S. Ragazzia,b, T. Tabarelli de Fatisa,b
aINFNSezionediMilano-Bicocca,Milano,Italy bUniversitàdiMilano-Bicocca,Milano,Italy
S. Buontempoa, N. Cavalloa,c, G. De Nardo, S. Di Guidaa,d,14, M. Espositoa,b, F. Fabozzia,c,
A.O.M. Iorioa,b, G. Lanzaa,L. Listaa, S. Meolaa,d,14,M. Merolaa,P. Paoluccia,14, C. Sciaccaa,b, F. Thyssen
aINFNSezionediNapoli,Napoli,Italy bUniversitàdiNapoli‘FedericoII’,Napoli,Italy cUniversitàdellaBasilicata,Potenza,Italy dUniversitàG.Marconi,Roma,Italy
P. Azzia,14, N. Bacchettaa, L. Benatoa,b,D. Biselloa,b, A. Bolettia,b,R. Carlina,b,
A. Carvalho Antunes De Oliveiraa,b, P. Checchiaa,M. Dall’Ossoa,b,P. De Castro Manzanoa,T. Dorigoa,
U. Dossellia,F. Gasparinia,b,U. Gasparinia,b,A. Gozzelinoa,S. Lacapraraa, M. Margonia,b, A.T. Meneguzzoa,b,J. Pazzinia,b,14, N. Pozzobona,b,P. Ronchesea,b, F. Simonettoa,b,E. Torassaa, M. Zanetti,P. Zottoa,b,A. Zucchettaa,b,G. Zumerlea,b
aINFNSezionediPadova,Padova,Italy bUniversitàdiPadova,Padova,Italy cUniversitàdiTrento,Trento,Italy
A. Braghieria,A. Magnania,b, P. Montagnaa,b,S.P. Rattia,b, V. Rea, C. Riccardia,b,P. Salvinia,I. Vaia,b, P. Vituloa,b
aINFNSezionediPavia,Pavia,Italy bUniversitàdiPavia,Pavia,Italy
L. Alunni Solestizia,b,G.M. Bileia, D. Ciangottinia,b,L. Fanòa,b, P. Laricciaa,b,R. Leonardia,b,
G. Mantovania,b,M. Menichellia, A. Sahaa, A. Santocchiaa,b
aINFNSezionediPerugia,Perugia,Italy bUniversitàdiPerugia,Perugia,Italy
K. Androsova,30,P. Azzurria,14, G. Bagliesia, J. Bernardinia, T. Boccalia, R. Castaldia,M.A. Cioccia,30, R. Dell’Orsoa,S. Donatoa,c,G. Fedi, A. Giassia, M.T. Grippoa,30, F. Ligabuea,c,T. Lomtadzea,L. Martinia,b, A. Messineoa,b, F. Pallaa,A. Rizzia,b, A. Savoy-Navarroa,31,P. Spagnoloa,R. Tenchinia,G. Tonellia,b,
A. Venturia, P.G. Verdinia
aINFNSezionediPisa,Pisa,Italy b
UniversitàdiPisa,Pisa,Italy
cScuolaNormaleSuperiorediPisa,Pisa,Italy
L. Baronea,b,F. Cavallaria, M. Cipriania,b,G. D’imperioa,b,14,D. Del Rea,b,14,M. Diemoza,S. Gellia,b, C. Jordaa,E. Longoa,b,F. Margarolia,b,P. Meridiania, G. Organtinia,b,R. Paramattia, F. Preiatoa,b, S. Rahatloua,b,C. Rovellia,F. Santanastasioa,b
aINFNSezionediRoma,Roma,Italy bUniversitàdiRoma,Roma,Italy
N. Amapanea,b,R. Arcidiaconoa,c,14,S. Argiroa,b,M. Arneodoa,c,N. Bartosika,R. Bellana,b, C. Biinoa, N. Cartigliaa,F. Cennaa,b, M. Costaa,b,R. Covarellia,b,A. Deganoa,b,N. Demariaa, L. Fincoa,b, B. Kiania,b, C. Mariottia, S. Masellia,E. Migliorea,b, V. Monacoa,b, E. Monteila,b, M.M. Obertinoa,b,L. Pachera,b, N. Pastronea,M. Pelliccionia,G.L. Pinna Angionia,b, F. Raveraa,b,A. Romeroa,b, M. Ruspaa,c,R. Sacchia,b, K. Shchelinaa,b, V. Solaa,A. Solanoa,b,A. Staianoa,P. Traczyka,b
aINFNSezionediTorino,Torino,Italy bUniversitàdiTorino,Torino,Italy
cUniversitàdelPiemonteOrientale,Novara,Italy
S. Belfortea,M. Casarsaa, F. Cossuttia,G. Della Riccaa,b, C. La Licataa,b, A. Schizzia,b, A. Zanettia
aINFNSezionediTrieste,Trieste,Italy bUniversitàdiTrieste,Trieste,Italy
D.H. Kim,G.N. Kim, M.S. Kim, S. Lee, S.W. Lee, Y.D. Oh,S. Sekmen, D.C. Son,Y.C. Yang
KyungpookNationalUniversity,Daegu,RepublicofKorea
H. Kim,A. Lee
ChonbukNationalUniversity,Jeonju,RepublicofKorea
J.A. Brochero Cifuentes,T.J. Kim
HanyangUniversity,Seoul,RepublicofKorea
S. Cho,S. Choi, Y. Go, D. Gyun,S. Ha,B. Hong, Y. Jo,Y. Kim, B. Lee, K. Lee,K.S. Lee, S. Lee, J. Lim,
S.K. Park,Y. Roh
KoreaUniversity,Seoul,RepublicofKorea
J. Almond,J. Kim, S.B. Oh,S.h. Seo, U.K. Yang,H.D. Yoo, G.B. Yu
SeoulNationalUniversity,Seoul,RepublicofKorea
M. Choi,H. Kim, H. Kim,J.H. Kim, J.S.H. Lee, I.C. Park, G. Ryu, M.S. Ryu
UniversityofSeoul,Seoul,RepublicofKorea
Y. Choi,J. Goh, C. Hwang, D. Kim,J. Lee, I. Yu
SungkyunkwanUniversity,Suwon,RepublicofKorea
V. Dudenas, A. Juodagalvis,J. Vaitkus
VilniusUniversity,Vilnius,Lithuania
I. Ahmed,Z.A. Ibrahim, J.R. Komaragiri, M.A.B. Md Ali32,F. Mohamad Idris33,W.A.T. Wan Abdullah,
M.N. Yusli,Z. Zolkapli
NationalCentreforParticlePhysics,UniversitiMalaya,KualaLumpur,Malaysia
H. Castilla-Valdez,E. De La Cruz-Burelo, I. Heredia-De La Cruz34,A. Hernandez-Almada,
R. Lopez-Fernandez,J. Mejia Guisao, A. Sanchez-Hernandez
CentrodeInvestigacionydeEstudiosAvanzadosdelIPN,MexicoCity,Mexico
S. Carrillo Moreno, C. Oropeza Barrera, F. Vazquez Valencia
UniversidadIberoamericana,MexicoCity,Mexico
S. Carpinteyro, I. Pedraza, H.A. Salazar Ibarguen, C. Uribe Estrada
A. Morelos Pineda
UniversidadAutónomadeSanLuisPotosí,SanLuisPotosí,Mexico
D. Krofcheck
UniversityofAuckland,Auckland,NewZealand
P.H. Butler
UniversityofCanterbury,Christchurch,NewZealand
A. Ahmad, M. Ahmad, Q. Hassan,H.R. Hoorani, W.A. Khan, M.A. Shah, M. Shoaib, M. Waqas
NationalCentreforPhysics,Quaid-I-AzamUniversity,Islamabad,Pakistan
H. Bialkowska, M. Bluj,B. Boimska, T. Frueboes,M. Górski, M. Kazana, K. Nawrocki,
K. Romanowska-Rybinska, M. Szleper,P. Zalewski
NationalCentreforNuclearResearch,Swierk,Poland
K. Bunkowski,A. Byszuk35, K. Doroba,A. Kalinowski, M. Konecki,J. Krolikowski, M. Misiura,
M. Olszewski, M. Walczak
InstituteofExperimentalPhysics,FacultyofPhysics,UniversityofWarsaw,Warsaw,Poland
P. Bargassa,C. Beirão Da Cruz E Silva, A. Di Francesco, P. Faccioli, P.G. Ferreira Parracho,M. Gallinaro,
J. Hollar, N. Leonardo,L. Lloret Iglesias, M.V. Nemallapudi, J. Rodrigues Antunes, J. Seixas,O. Toldaiev,
D. Vadruccio,J. Varela, P. Vischia
LaboratóriodeInstrumentaçãoeFísicaExperimentaldePartículas,Lisboa,Portugal
P. Bunin,I. Golutvin, I. Gorbunov, A. Kamenev, V. Karjavin, V. Korenkov,A. Lanev, A. Malakhov,
V. Matveev36,37, V.V. Mitsyn,P. Moisenz, V. Palichik,V. Perelygin, S. Shmatov, S. Shulha,N. Skatchkov,
V. Smirnov, E. Tikhonenko,A. Zarubin
JointInstituteforNuclearResearch,Dubna,Russia
L. Chtchipounov,V. Golovtsov, Y. Ivanov, V. Kim38, E. Kuznetsova39,V. Murzin, V. Oreshkin, V. Sulimov,
A. Vorobyev
PetersburgNuclearPhysicsInstitute,Gatchina(St.Petersburg),Russia
Yu. Andreev,A. Dermenev, S. Gninenko, N. Golubev, A. Karneyeu,M. Kirsanov, N. Krasnikov,
A. Pashenkov,D. Tlisov, A. Toropin
InstituteforNuclearResearch,Moscow,Russia
V. Epshteyn, V. Gavrilov, N. Lychkovskaya,V. Popov, I. Pozdnyakov, G. Safronov, A. Spiridonov,M. Toms,
E. Vlasov, A. Zhokin
InstituteforTheoreticalandExperimentalPhysics,Moscow,Russia
M. Chadeeva40, M. Danilov40,O. Markin
NationalResearchNuclearUniversity‘MoscowEngineeringPhysicsInstitute’(MEPhI),Moscow,Russia
V. Andreev,M. Azarkin37, I. Dremin37,M. Kirakosyan, A. Leonidov37, S.V. Rusakov,A. Terkulov
P.N.LebedevPhysicalInstitute,Moscow,Russia
A. Baskakov,A. Belyaev, E. Boos,M. Dubinin41,L. Dudko, A. Ershov, A. Gribushin, V. Klyukhin,
O. Kodolova,I. Lokhtin, I. Miagkov, S. Obraztsov,S. Petrushanko,V. Savrin, A. Snigirev