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Physics
Letters
B
www.elsevier.com/locate/physletb
Search
for
gauge-mediated
supersymmetry
in
events
with
at
least
one
photon
and
missing
transverse
momentum
in
pp
collisions
at
√
s
=
13
TeV
.TheCMS Collaboration CERN,Switzerland a r t i c l e i n f o a b s t ra c t Articlehistory: Received21November2017Receivedinrevisedform5February2018 Accepted19February2018
Availableonline23February2018 Editor:M.Doser Keywords: CMS Physics Software Computing
A search for gauge-mediated supersymmetry (SUSY) in final states with photons and large missing transversemomentumispresented.Thedatasampleofppcollisionsat√s=13TeV wascollectedwith the CMSdetectoratthe CERNLHCandcorrespondstoanintegratedluminosityof35.9 fb−1.Dataare
comparedwithmodelsinwhichthelightestneutralinohasbino- orwino-likecomponents,resultingin decaystophotonsandgravitinos,wherethegravitinosescapedetection.Theeventselectionisoptimized for both electroweak (EWK) and strong productionSUSY scenarios.The observed data are consistent withstandardmodelpredictions,andlimitsaresetinthecontextofageneralgaugemediationmodelin whichgauginomassesupto980 GeVareexcludedat95%confidencelevel.Gauginomassesbelow780 and950 GeVareexcludedintwosimplifiedmodelswithEWKproductionofmass-degeneratecharginos andneutralinos.Stringentlimitsaresetonsimplifiedmodelsbasedongluinoandsquarkpairproduction, excluding gluino(squark)massesupto 2100(1750) GeVdependingontheassumptions madeforthe decaymodesandintermediateparticlemasses.Thisanalysissetsthehighestmasslimitstodateinthe studiedEWKmodels,andintheconsideredstrongproductionmodelswhenthemassdifferencebetween thegauginosandthesquarksorgluinosissmall.
©2018TheAuthor.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3.
1. Introduction
Thesearchforphysicsbeyondthestandardmodel(SM)isone of the key research topics of the CMS experiment at the CERN LHC.Especiallyafter thediscovery ofa Higgsboson withamass of around 125 GeV in 2012 [1–3], supersymmetry (SUSY) [4–17] isone ofthe theoretically favoredpossible extensionsof theSM. Among several explanations for unsolved problems in particle physics, SUSY provides a mechanism for stabilizing the SM-like Higgs boson mass atthe electroweak (EWK) scale. Since current searches are pushing the limitson strongly produced SUSY par-ticles (sparticles) beyond the one-TeV threshold, the interest in probing gaugino masses via EWK production is growing. While searchesforheavysparticlesespeciallyprofitfromtheincrease in the center-of-mass energy due to the large increase of the pro-ductioncrosssection,searchesforEWKproductionbenefitfroma largerdataset,ascollectedbytheCMSexperimentin2016.
In this Letter, a search for SUSY focusing on gauge-mediated SUSYbreaking(GMSB) [18–24] scenariosispresented.TheR-parity
E-mailaddress:cms-publication-committee-chair@cern.ch.
[25] isassumedtobeconserved,sothatSUSYparticlesarealways produced in pairs. The gravitino (G)is the lightest SUSY particle (LSP) and escapes undetected,leading to missingtransverse mo-mentum(pmiss
T )inthedetector.Thenext-to-LSP(NLSP)isassumed to be thelightest neutralino(χ0
1). Dependingon its composition, theχ0
1 candecayaccordingtoχ10→NG,whereN iseithera pho-ton(γ),anSM-likeHiggsboson(H),oraZ boson.Ifthegauginos arenearlymass-degenerate,thechargino(χ1±)decaysχ1±→W±G are also possible. TheG is assumedto have negligiblemass and theNLSPisassumedtodecaypromptly.
TheanalyzeddatasetwascollectedattheCERNLHCin proton-proton collisions at a center-of-mass energy of 13 TeV and cor-responds to an integrated luminosity of35.9 fb−1. Events are re-quiredtocontainatleastonehigh-energyphotonandlarge pmissT . In order to maintain sensitivity to EWK SUSY production, there is no explicitevent selection criterion requiring hadronicenergy, i.e., thepresence ofjetsinthe event.In GMSBSUSY, pmiss
T arises fromthestableandnoninteractingG,whilephotonsoriginatefrom
χ0
1 →γG decays. The energy of the photon as well as of the gravitino and thus the pmissT is governed by the χ10 mass, and theχ0
1→γG branchingfractionisdeterminedbytheneutralino’s
https://doi.org/10.1016/j.physletb.2018.02.045
0370-2693/©2018TheAuthor.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).Fundedby SCOAP3.
Fig. 1. InthecontextofGGM,severalproductionanddecaychannelsarepossible.Thediagramofthedominantprocessχ0
2–χ1±productionisshown(upperleft),wherethe
gauginodecaysdependonthemassconfigurationunderstudy.IntheTChiWgmodel(upperright),thegauginosaremassdegenerate.TheTChiNgmodelcomprisesχ1±pair
production(lowerleft)andχ1±χ10production(lowerright),wheretheχ1±isonlyslightlyheavierthantheχ10,soonlylow-momentum(soft)particlesappearinthedecay
ofχ1±toχ10.
binoand wino components and its mass. Compared to analyses requiringphotonsandlargehadronicactivity,thisanalysishas su-periorsensitivity to GMSB SUSY in EWK production,andalso in strong productionif the squark, gluino,and the lightest gaugino massesaresimilar(compressed-spectrumscenarios).
Anearlierversionofthisanalysis [26] wascarriedoutbyCMS ona special8 TeV dataset recordedaspartofthe “parked-data” program [27] correspondingtoanintegratedluminosityof7.4 fb−1 usingadedicatedtrigger andalower photontransverse momen-tum(pT) thresholdof30 GeV. The ATLASandCMScollaborations have also searched fordirect EWK production ofgauginos in fi-nalstateswithatleastonephotonandoneelectronormuon [28, 29], and in the two-photon channel [29–31]. Single-photon and HT-based analyses [31], where HT is the scalarsum ofhadronic jet transversemomenta, havegood sensitivityfor strong produc-tioninGMSBmodelsbutlacksensitivityforEWKproductionand compressed-spectrumscenarios.
2. Signalmodels
To interpret the results, a general gauge mediation (GGM) [32–37] scenario dominatedby EWKproductionis used. Further-more,two EWKproductionandfourstrongproductionsimplified modelscenarios (SMS) [38] are considered forinterpretation. For theGGMscenario,thesquarkandgluinomassesaresettoahigh scale rendering them inaccessible andstrong production negligi-ble.Thebinoandwinomassesthereforefullydeterminethemodel pointunderstudyandarevaried intheinterpretation.The χ10 is assumedtobepurelybino-like,whiletheχ1±andχ0
2 areassumed tobepurely wino-like.ThedominantprocessforEWKGGM pro-duction is shown in Fig. 1 (upper left). In the GGM framework, where the gauginos are not mass-degenerate by construction, a largerχ±–χ0
1 massdifferenceincreasesthehadronicenergyinthe finalstateiftheZ,H,orW bosonsdecayhadronically.
The EWK simplified scenario TChiWg probes associated pro-ductionofmass-degeneratecharginosandneutralinos(χ1±χ0
1), as-suming the decay modes χ0
1 →γG and χ1±→W±G, as shown inFig.1(upperright).TheTChiNgscenarioassumesnearly mass-degenerateχ1± andχ0
1,butconsiders χ1±χ1∓ andχ1±χ10 produc-tionasshowninFig.1(lowerleftandright).Inthisscenario,the
χ1±isassumedtohaveaslightlyhighermass thanχ0
1,andit
de-caystoχ0
1 andlow-momentumparticlesoutsidetheacceptanceof thisanalysis. Theneutralinosare assumedtodecayasχ10→γG,
χ0
1→ZG, andχ10→HG with50,25,and25%probability, respec-tively.
The strong production SMS models T5gg, T5Wg, T6gg, and T6WgareshowninFig.2,whereT5ggandT5Wgrepresentgluino pairproduction,andT6ggandT6Wg squarkpairproduction.The neutralino decays as χ0
1 →γG, while the chargino decays as
χ1±→W±G. In the T5Wg and T6Wg scenario,a branching frac-tionof50% isassumedforthechargedandneutraldecaysofthe gluino or squark.The T5gg(T6gg) scenario assumes a branching fractionof100%forg˜→qqχ0
1 (q→qχ10).
3. TheCMSdetector
The central feature of the CMS apparatus is a superconduct-ing solenoid of6 m internal diameter, providing a magneticfield of3.8 T. Withinthe solenoidvolume are asilicon pixelandstrip tracker,aleadtungstatecrystalelectromagneticcalorimeter(ECAL), andabrass andscintillatorhadroncalorimeter(HCAL),each com-posed of a barrel and two endcap sections. Extensive forward calorimetrycomplementsthecoverageprovidedbythebarreland endcapdetectors.Muonsaremeasuredingas-ionizationdetectors embeddedinthesteelflux-returnyokeoutsidethesolenoid.
In the barrel section of the ECAL, an energy resolution of approximately 1% is achieved for unconverted or late-converting photons arising from the H→γ γ decay forphotons with pT> 25GeV.Theremainingbarrelphotonshaveanenergyresolutionof about1.3%uptoapseudorapidityof|η|=1,risingtoabout2.5%at |η|=1.4.Intheendcaps,theenergyresolutionofunconvertedor late-convertingphotonsisabout2.5%,whiletheremainingendcap photonshavearesolutionbetween3and4% [39].
AmoredetaileddescriptionoftheCMSdetector,togetherwith adefinitionofthe coordinatesystemusedandtherelevant kine-maticvariables,canbefoundinRef. [40].
4. Objectreconstructionandsimulation
The particle-flow (PF) event algorithm [41] reconstructs and identifies each individualparticle withan optimized combination
Fig. 2. Forstronggluinopair-productionthesimplifiedscenariosT5gg(upperleft)andT5Wg(upperright)andforsquarkpair-productionthesimplifiedscenariosT6gg (lowerleft)andT6Wg(lowerright)arestudied.IntheT5Wg(T6Wg)scenario,abranchingfractionof50%isassumedforthedecays˜g→qqχ1±andg˜→qqχ
0 1 (q→qχ1±
andq→qχ0
1),resultinginfinalstateswithzero,one,ortwophotons.
ofinformationfromthevariouselementsoftheCMSdetector.The energy of photons is directly obtained from the ECAL measure-ment, corrected for zero-suppression effects. Fully reconstructed photonconversionsareusedbythePFalgorithmandareincluded in the set of photon candidates. The energy of electrons is de-termined from a combination of the electron momentum at the primary interaction vertex asdetermined by thetracker, the en-ergyofthecorresponding ECALcluster,andtheenergysumofall bremsstrahlungphotonsspatiallycompatiblewithoriginatingfrom theelectrontrack.Theenergyofmuonsisobtainedfromthe cur-vatureofthecorrespondingtrack.Theenergyofchargedhadrons isdetermined froma combinationoftheir momentum measured inthetrackerandthe matchingECALandHCALenergydeposits, corrected forzero-suppressioneffects andfor theresponse func-tion of the calorimeters to hadronicshowers. Finally, the energy of neutralhadrons is obtainedfrom the corresponding corrected ECALandHCALenergy.
Photons are reconstructed [39] from clustersin theECAL and arerequiredtobeisolated.TheenergydepositintheHCALtower closest tothe seed ofthe ECALsupercluster [42] assignedtothe photon isrequiredto be lessthan5% ofthe energydepositedin theECAL.Aphoton-liketransverseECALshowershapeisrequired. The photon isolation is determined by computingthe transverse energyina cone centeredaround thephoton momentum vector. The cone has an outer radius of 0.3 in R=(φ)2+ (η)2, where φistheazimuthalangle,andthecontributionofthephoton isremoved. Corrections fortheeffects ofmultipleinteractions in thesameoradjacentbunchcrossing(pileup)areappliedtoall iso-lationenergies,dependingonthe ηofthephoton.Toensurethat nophotonwithanomalouslyhighaposterioricorrectionspopulate thesignal region,arequirementthat atleast30% ofthephoton’s energy be deposited in the seed crystal is imposed for all con-sidered photons. A photon candidatemust exceed a minimal pT of 15 GeV. Photons are efficientlydiscriminated against electrons byrequiringthatphotonshavenomatchingpatternofenergy de-positsinthepixeldetector.
The vector pmissT is defined as the projection onto the plane perpendiculartothebeamsofthenegativevectorsumofthe mo-mentaofallPFcandidatesinanevent.The magnitudeof pmiss
T is referredtoaspmissT .
JetsarereconstructedfromPFcandidateswiththeanti-kT clus-tering algorithm [43] as implemented in the FastJet [44]
pack-age,usingadistanceparameterof0.4. Jetenergycorrections [45, 46] are derived from MonteCarlo (MC) simulation,andare con-firmed within situmeasurements of theenergy balance indijet and γ+jet events.Thesecorrectionsarealsopropagatedto pmiss
T . Jets with pT>30GeV and |η| <3 are required to be geometri-callyisolatedfromidentifiedphotons,electrons,andmuons,where electronsandmuonshavetofulfillstandardidentification require-ments to be considered in this isolation criterion. Filters against anomalouslyhighpmissT frominstrumentaleffectsareapplied [47]. The reconstructed vertex with the largest value of summed physics-object p2T is takento be the primary pp interaction ver-tex.Thephysicsobjectsarethejets,clusteredusingthejetfinding algorithm [43,44] with the tracks assigned to the vertex as in-puts, andtheassociated missingtransversemomentum, takenas thenegativevectorsumofthepTofthosejets.
The SM background processes contributing to the signal and control regions are modeled using MC simulations. The quantum chromodynamics(QCD)multijet, γ +jets,andW andZ processes are generatedwith MadGraph5_amc@nlo 2.3.3 [48,49] atleading order (LO), while thett(+γ) processes are generatedat next-to-leading order(NLO) [48,50].The WW diboson productionis gen-erated with Powheg v2 [51–55], and WZ and ZZ production are generated using pythia8.205 [56]. The Zγ sample is scaled with photon pT dependent next-to-next-to-leading logarithmic (NNLL) K-factors [57], which are ofthe order of1.3. A constant next-to-NLO(NNLO)K-factorof1.34isappliedtotheWγ productioncross section [57], andNLOK-factors oftheorder of1.2areapplied to the W and Z(→νν) productioncross sections.The diboson pro-duction cross sections are available at NLO (ZZ, WZ) and NNLO (WW) precision [58]. The Wγ andZγ processes,collectively de-notedas Vγ, arethe dominantbackgroundsin thesignal region. A datasidebandregionisusedtoobtainadditionalscalefactorsfor the V(γ) and γ+jets samples,whereV(γ)comprisesthe Wand Z bosonproduction,withandwithoutphotonradiation.
The GGM signal scan is generated with pythia8, while the SMSsignalscansaregeneratedwith MadGraph5_amc@nlo at LO. The cross sections are calculated atNLO andNLO+NLL accuracy [59–67] fortheGGMandtheSMSscans,respectively,withallthe unconsidered sparticlesassumedto be heavy anddecoupled. For the EWK models, the cross sections are computed in a limit of mass-degeneratewinoχ0
event-by-eventbasis to matchthe distribution of the numberof interactionverticesobservedindata.
5. Eventselection
The data are recorded using a trigger requiring one photon that passes very loose identification criteria and has a pT of at least165 GeV [73]. The eventsinthe subsequentanalysisare re-quiredtocontain atleastoneidentifiedandisolatedphotonwith pT>180GeV inthecentralbarrelpartofthedetector(|η| <1.44) that has been accepted by the trigger. The photons are required tohaveanangulardistanceinthe η–φplane of R >0.5 tothe nearestjet.TosuppresseventswherethepmissT mainlyarisesfrom asignificantmismeasurement ofajet’senergy,all jetswithpT> 100GeV must fulfill φ (pmissT , jet) >0.3, where φ (pmissT , jet) is thedistancein φbetweenthejetandthepmissT .Atleastone recon-structedvertexpereventisrequired [74].Tomaintainhighsignal acceptanceforallstudiedsignalscenariosnoselectioncriteriaare appliedon the presenceor absenceof jetsorleptons, except for thephoton isolationcriteria.Thephoton triggerefficiencyforthis selectionisfoundtobe γ=94.3±0.4%,independentofthe kine-maticeventvariablesusedintheanalysis.
The preselected events with at least one high-pT photon are separatedinto a signal region and an orthogonal control region. Thesignalregionisdefinedbypmiss
T >300GeV andMT(γ, pmissT ) > 300GeV, where MT(γ, pmissT ) is the transverse mass of the pho-ton with the highest energy and pmiss
T , and roughly represents theNLSPmassintheSUSY scenarioscontaining thedecayχ0
1 →
γG. The requirement MT(γ, pmissT ) >300GeV was chosen to op-timize the statistics in the control region under maximization of the signal acceptances. The region with pmissT >100GeV and MT(γ, pmissT ) >100GeV, but excluding the signal region, defines thesignal-depleteddatacontrolregion.
Multiple exclusive signal bins are defined with respect to SγT ≡pmiss
T +
γipT(γi), the scalar sum of p
miss
T and the pT of all photons in the event. The region with pmiss
T >300GeV and MT(γ, pmissT ) >300GeV, but SγT ≤600GeV has negligible signal contamination and is used to validate the background estima-tion. The four SγT regions 600–800, 800–1000, 1000–1300, and >1300GeV define exclusive bins that are simultaneously inter-pretedina multichannelcountingexperimentforbestsensitivity. Thefullselection requirementstodefine eachregionused inthis analysisaresummarizedinTable1.
Theselectiondiffersinseveralaspects fromtheanalysisusing 8 TeV data [26].Thetriggerusedinthe8 TeV analysisallowedfor verylow photon pT and pmissT selections. The“pmissT significance” that definedthesignal andcontrol regions has beenreplaced by pmissT forsimplicityandtoallowforeasierreinterpretationsofthe results.Theanalysisisoptimizedsuchthatnolossinsensitivityis ensured.
MT(γ,pT ) >100 GeV
pmiss
T <300 GeV or MT(γ,pmissT )<300 GeV
Validation region Preselection pmiss T >300 GeV MT(γ,pmissT ) >300 GeV SγT<600 GeV Signal region Preselection pmiss T >300 GeV MT(γ,pmissT ) >300 GeV SγT>600 GeV 6. Backgroundestimation
TheSMbackgroundinthephotonandpmissT finalstateis dom-inated by vector bosonproduction withinitial-statephoton radi-ation,inparticularby theZγ →ννγ process.Direct photon pro-duction inassociation withjets, γ +jets, also contributesatlow valuesof pmissT andthus low values of SγT. Asubdominant back-ground arises from electrons misidentified as photons (e→γ). Further minorcontributions originate fromttγ and diboson pro-duction. The most relevant backgrounds, V(γ) and γ +jets, are modeledby MCsimulationandarescaledtothedatainthedata controlregionatlowvaluesof pmissT andMT(γ, pmissT ).The contri-butionfromeventswithe→γ misidentificationispredictedfrom data.AllremainingminorcontributionsaremodeledbyMC simu-lation.
ThenormalizationoftheV(γ)and γ+jets backgroundsis de-termined in the control region by a simultaneous χ2-fit in bins of φ (pmissT , nearest jet/γ),which is the angulardistance in the transverse plane of the pmiss
T andthe nearest jet orphoton. The distribution of φ (pmissT , nearest jet/γ) sufficiently separates the shapesofV(γ)and γ+jets backgrounds,sothatscalingone back-groundcannotcompensatefortheother.Contributionsfromother SMprocessesaresmallandarekeptconstantinthefit.Underthe constraintofafixedtotalyield,thescalefactorsfortheV(γ)and
γ+jets simulationsaregivenbytheminimumofthe χ2 distribu-tion.Theresultingscalefactorsare
SFV(γ)=0.87±0.06, (1)
SFγ+jets=1.83±0.06, (2)
where theuncertainties are of statisticaloriginonly. The post-fit distributionof φ (pmissT , nearest jet/γ)isshowninFig.3.Thesize of the measured factors isconsistent with the expectations [57]. The scalefactorforV(γ) issmallerthanunity becauseEWK cor-rections,whicharenotcontainedintheK-factors,aresmallerthan unity forhighphoton pT. The γ+jets scalefactor islarger than unity since no K-factor is applied andQCD corrections for mul-tijet backgrounds are large. The factors are found to be stable withrespecttosystematicvariationsofthemethod.Different con-trolregionselections, avariety oftemplatevariables, andvarious binningsofthetemplate variableshavebeenstudied.Signal con-taminationbecomes relevantifthe gauginosare light because in
Fig. 3. Thepost-fitdistributionsfor theγ+jets (blue)andV(γ)(orange) back-groundinthecontrolregiontogetherwiththefixedbackground(darkmagenta) andthetotalfitdistributionstackedontothefixedbackgrounds(red)areshown. Thestatisticaluncertainty(σstat)ofthepost-fit distributionisshowninthered
hatchedareaandthesystematicuncertaintyofthefixedbackground(σsyst, fixed)is
indicatedwiththedarkmagentahatchedarea.ThevaluesSFV(γ )andSFγ+jets in
thelegendaretheresultingscalefactors.Thepulldistributiononlyconsidersthe statisticaluncertainty.(Forinterpretationofthecolorsinthefigure(s),thereaderis referredtothewebversionofthisarticle.)
termsofitskinematicalvariablestheproductionoflightgauginos issimilartothat ofV(γ)productionandistakenintoaccount in the statisticalanalysis. In theremaining phase space, signal con-taminationisnegligible.
Electrons that are misidentified as photons create a subdom-inant background, which can be predicted from data with good statisticalprecision. The misidentification rate fe→γ is measured indatainZ→e+e−decayswiththe“tag-and-probe”method [75]. The dependence of the misidentificationrate on the electron pT and ηisstudied.Nonresonante+e−backgroundfromnonZ boson eventsisestimatedfromeμevents.Theresultingmisidentification rateindatais
fe→γ =2.7±1.3%. (3) The uncertainty of 50% takes into account the variation of the misidentificationrateasa functionofthe photon pT, η,and sev-eralothervariables.
Thee→γ backgroundismodeledfromadatacontrol sample withthesameeventselectionasthesignalregion,butcontaining anidentifiedelectroninsteadofaphoton.Thesampleisweighted by fe→γ .The uncertaintyofthisestimation isdominatedby the systematic uncertainties in the misidentification rate. The statis-ticaluncertainty is negligible because the electron selection effi-ciencyisabout40timeslargerthan fe→γ .The methodhasbeen validatedusingMCsimulation,asshowninFig.4.
Theminorcontributionsfromtt(γ) anddibosonprocessesare modeled using MC simulation as discussed above. Events where electrons are misidentified as photons are removed at the gen-erator level to avoid overlaps. Based on simulation studies, the backgroundfromQCDmultijeteventsisfoundtobenegligible.
Alluncertaintiesthatwouldaffectthenormalizationare elimi-natedfortheV(γ)and γ+jets backgroundsbytheMC normaliza-tionmethod.Therefore,theonlyremaininguncertaintiesoriginate fromthesimulatedshapeofthesebackgrounds.Theshape uncer-tainty dueto the choice ofthe renormalizationand factorization scales has been determined by varying these scales in different combinationsof factors0.5, 1,and2 andrepeating the fitofthe V(γ) and γ +jets backgrounds. The prediction for each combi-nation is compared in thefour signal region bins for both
back-grounds separately and bin-by-bin. The largest deviation in the respective bin is taken as the systematic uncertainty and varies in the rangeof 3.8–9.0%and 2.8–7.1%for the V(γ) and γ +jets backgrounds,respectively.The LHC4PDFprocedure [76] is usedto determinetheshapeuncertaintyduetothechoiceofthePDFsand isdeterminedbin-by-bininthesignalregionandtakenas system-aticuncertainty,varyingintherangeof1.6–3.8%fortheV(γ)and 1.9–8.2%for γ+jets the background.Althoughthereis nodirect usageofjets,theanalysisisaffectedbythepropagationofthejet energy scale (JES)uncertainty to pmissT . The resulting uncertainty affectingthe finalselection isdeterminedby propagatingthe up-ward anddownward shift of the JES to pmissT and repeating the analysisusing theshifted pmissT . Thelargest deviationinthe pre-diction istakenassystematicuncertaintyandvariesintherange of5.0–5.9%fortheV(γ)and0.9–32%forthe γ+jets background. Thelargedeviationof32%for γ+jets affectsthehighestbininSγT, where onlyapproximatelyone γ+jets eventisexpected, so the absoluteeffectofthislargeuncertaintyissmall.A30%uncertainty isassumedforthett(γ)crosssection,correspondingtoa conser-vative estimateof theuncertaintywithrespect tothe latestCMS measurement [77].Theuncertaintyinthedibosoncrosssectionis assumedtobe30%.Furthersystematicuncertainties,alsoaffecting the signal simulation,arise fromthe triggerefficiency (0.4%),the data to MC photon identification efficiency scale factor (2%) and theintegratedluminosity(2.5%) [78].
We improvethe MadGraph modeling of initial-stateradiation (ISR), which affects thetotal transverse momentum (pISRT ) of the system of SUSY particles, by reweighting the pISRT distribution of MC SUSYevents. Thisreweighting procedureis based on studies of the pT of Z boson events [79]. The reweighting factors range between 1.18at pISRT =125GeV and 0.78for pISRT >600GeV. We takethedeviationfromunityasthesystematicuncertaintyinthe reweightingprocedure.
The systematicuncertainties affecting the background predic-tionandthesignalsaresummarizedinTables2and3,respectively. InFig.5thesignalsensitivevariable SγT isshownforthe con-trol selection, used to derive scale factors for the γ +jets and V(γ) simulated samples, and for the validation selection. Good agreementisobservedbetweentheselecteddataandtheSM back-groundprediction.
7. Resultsandinterpretation
Distributions of SγT in the four search regions are shown in Fig.6.Thecorresponding yieldsare giveninTable4foreachbin, alsoshowingthecontributionsoftheindividualbackground com-ponents. The statistical uncertainty in the e→γ background is causedby thelimitedsizeofthe collecteddatasample. Allother statisticaluncertaintiesareduetothelimitednumberofsimulated events.Thetotalsystematicuncertaintyresultsfromthequadratic sum of the systematic uncertainties of each background compo-nent. Good agreement is observed between the SM background predictionandtherecordeddata,withoutindicationforthe pres-enceofnewphysics.
Limits are calculated in one- and two-dimensional parameter spaces for theEWK and strongproduction models introduced in Section 1. Upperlimitson thesignal cross section are calculated at95% confidencelevel (CL)using amodified frequentist CLs ap-proach [80–82] with aprofile likelihoodtest statisticand asymp-toticformulae [83].The95%CLobserveduppercrosssectionlimit, aswell asthe expectedandobserved exclusioncontours, forthe EWKGGMsignalscanareshowninFig.7.Thelimitsarepresented inthewino-binomassplane.Theanalysisreachesthehighest sen-sitivity fornearly degeneratewinoandbinomasses. Inthis case, the analysis excludes wino and bino masses up to 980 GeV at
Fig. 4. ValidationoftheelectronmisidentificationbackgroundestimationmethodusingMCsimulation.Intheselectionwithatleastonephotonwith pT>100GeV,the
predictionofthee→γ misidentificationestimationmethodiscomparedtodirectsimulationinthephoton pT(left)andthepmissT (right)distributions.Theblackandred
hatchedareasrepresentthestatistical(σstat, pred)andthe50%systematic(σsyst, pred)uncertaintiesoftheprediction,respectively.Eventspopulatingthephasespacebeyond
theshownrangeareincludedinthelastbin.
Fig. 5. Datatosimulationcomparisonsinthecontrolregion(left)andthevalidationregion(right).EventswithSγT beyondtheshownrangeareincludedinthelastbin.The
hatchedlightgraybandintheupperpanel,aswellasthesolidlightgraybandinthelowerpanelrepresentthetotalsystematicuncertainty(σsyst).Thedarkgraybandin
thelowerpanelindicatesthequadraticsumofthestatisticalandsystematicuncertainties(σtot).
Table 2
Systematicuncertaintiesinthebackgroundpredictioninpercent.
V(γ) γ+jets e→γ tt(γ) Diboson Fit uncert. of statistical origin 6.9 3.3 – – – Scale uncertainty in shape 3.8–9.0 2.8–7.1 – – – PDF uncertainty in shape 1.6–3.8 1.9–8.2 – – – JES uncertainty in shape 5.0–5.9 0.9–32 – – –
Tag-and-probe fit – – 50 – –
Cross section, PDF, scales – – – 30 30
Integrated luminosity – – – 2.5 2.5
Photon eff. scale factor – – – 2.0 2.0
Trigger efficiency – – – 0.4 0.4
95% CL,improvingon the formerbest limit of710 GeV [26]. The sensitivitydecreaseswitha largerwino-bino masssplitting since on average the energy of the photons and gravitinos decreases, while more energy is transfered to the other decay products of theχ1±andχ0
2.
The limits for the EWK TChiWg and TChiNg simplified mod-elsare shown asa functionof mNLSP in Fig.8 together withthe theoretical cross section. The analysis excludes NLSP masses be-low780 GeV at95%CLintheTChiWgscenarioandbelow950 GeV intheTChiNgscenario.Duetotheslightexcessobservedwith re-specttotheSMbackgroundpredictionespeciallyinthehighestSγT
bins,the observedlimitsare weaker thanthe expectedexclusion limitsof920 (1070) GeV fortheTChiWg (TChiNg)scenario.
The resultsarealso interpretedinsimplified modelsof strong production scenarios. The two scenarios T5gg and T5Wg repre-sent the gluino pair production withtwo photons andone pho-ton and one W boson in the final state, respectively. The cross section limits and exclusioncontours are shownin Fig. 9 in the g− χ10/χ1± mass plane. This search can exclude gluino masses of up to 2100 (2000) GeV in the T5gg (T5Wg) scenario. The limit gets weaker at low NSLP massesbecause ofthe acceptance loss, which mostly arises from the lower energy of the photons and
Table 3
Systematicuncertaintiesinthesignalpredictionsinpercent.
Source Signal scenario
EWK Strong production Statistical MC precision per signal region 1–28 2–50
Fast simulation uncertainty in pmiss
T <0.1–5 <0.1–25
Scale uncertainty in shape <0.1–1.8 <0.1–1.2 Integrated luminosity 2.5 2.5
Trigger efficiency 0.4 0.4
Photon scale factor 2.0 2.0
Pileup <0.1–0.4 <0.1–2.1
ISR reweighting 0.6–3.0 –
Table 4
Backgroundanddatayields,aswellasthestatisticalandsystematicuncertainties fortheseparatesignalregionbins.Forthetotalbackgrounduncertaintythe uncer-taintiesoftheindividualbackgroundcomponentsaresummedquadratically.
SγT: 600–800 GeV
Yield σstat σsyst
V(γ) 213 4.4 21.3 γ+jets 5 1.1 0.5 tt(γ) 13 5.7 3.9 e→γ 29 0.9 14.2 Diboson 7 2.8 2.1 Total 267 7.9 26.0 Data 281 SγT: 800–1000 GeV
Yield σstat σsyst
V(γ) 76.8 1.9 8.1 γ+jets 4.4 1.2 0.4 tt(γ) 8.0 3.8 2.4 e→γ 9.2 0.5 4.6 Diboson 1.9 1.7 0.6 Total 100.2 4.7 9.7 Data 101 STγ: 1000–1300 GeV
Yield σstat σsyst
V(γ) 35.0 1.3 3.9 γ+jets 4.2 1.3 0.4 tt(γ) 3.5 0.9 1.1 e→γ 4.7 0.4 2.3 Diboson 5.4 3.0 1.6 Total 52.8 3.6 5.0 Data 65 SγT:>1300 GeV
Yield σstat σsyst
V(γ) 12.6 0.7 1.6 γ+jets 1.1 0.5 0.4 tt(γ) 0.7 0.5 0.2 e→γ 1.5 0.2 0.8 Diboson 1.7 1.7 0.5 Total 17.6 2.0 1.9 Data 24
the gravitinos accompanied by larger hadronic activity in the event.
Similar scenarios, T6gg and T6Wg, based on squark produc-tion are also used for interpretation and are shown in Fig. 10. Here, squark masses up to 1750 (1650) GeV are excluded for T6gg (T6Wg).
Themass limitsonsquarks are weaker comparedto thoseon gluinosduetothegenerallylower productioncrosssection. How-ever, for squark production the hadronic activity in the eventis lowercomparedtogluinoproduction,slightlyreducingthe depen-denceon theq− χ0
1/χ1± mass difference. The higher sensitivity intheT5ggandT6ggmodelsis duetotwo photonscontributing toSγT,increasingtheseparationpowerbetweenthesignalandthe SMbackground.
8. Summary
Asearchforelectroweak(EWK)andstrongproductionof gaug-inosintheframeworkofgaugemediatedsupersymmetrybreaking infinalstateswithphotonsandlargemissingtransverse momen-tumhasbeenperformed. Adataset recordedby theCMS exper-imentat a center-of-massenergy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1, was analyzed. The data were found to agree with the expectation from the standard model, withoutanyindicationofnewphysics.
The analysis is sensitive to EWK production of gauginos and to strong production of gluinos and squarks in particular if the massdifferencebetweengauginosandgluinosorsquarksissmall. Atwo-dimensional EWK signalscan in theframework of general
Fig. 6. Comparisonofthemeasurementandpredictioninthesignalregioninfour exclusivebinsofSγT.Forguidance,twoSUSYbenchmarksignalpointsarestacked
ontheSMbackgroundprediction,wheretheTChiWgsignalpointcorrespondsto aNLSPmassof700 GeV andtheT5Wgsignalpointcorrespondstoagluinomass of1750 GeV andaNLSPmassof1700 GeV.EventswithvaluesofSγT beyondthe
shownrangeareincludedinthelastbin.Thehatchedlightgraybandintheupper panel,aswellasthesolidlightgraybandinthelowerpanelrepresentthetotal systematicuncertainty(σsyst).Thedarkgraybandinthelowerpanelindicatesthe
quadraticsumofthestatisticalandsystematicuncertainties(σtot).
Fig. 7. Observeduppercrosssectionlimitat95% CLfortheEWKGGMsignalinthe wino-binomassplane.Thethicklinesrepresenttheobserved(black)andexpected (red)exclusioncontours,wherethephasespaceclosertothediagonalisexcluded bytheanalysis.Thethindottedredcurvesindicatetheregioncontaining68%of thedistributionoflimitsexpectedunderthebackground-onlyhypothesis.Thethin solidblackcurvesshowthechangeintheobservedlimitduetovariationofthe signalcrosssectionswithintheirtheoreticaluncertainties.
gauge mediation is used to interpret the results. In the case of similarwinoandbinomasses,theanalysisexcludesmassesbelow 980 GeV at 95% confidence level, improving on the current best limit by 270 GeV [26]. TwoEWKsimplified models arealso used for the interpretation. The analysis excludesmasses of the next-to-lightestsupersymmetricparticleχ0
1 below780(950) GeV inthe TChiWg (TChiNg) scenario. Additionally, limits are set for strong production simplified models based on gluino (T5gg, T5Wg) and squark (T6gg, T6Wg) pair production, excluding gluino (squark) massesupto2100(1750) GeV.Thisanalysiscomplementssearches inthephoton+jets,diphoton,andphoton+leptonsfinalstates,and setsthemoststringentlimitstodateintheEWKproduction mod-els, andin the strong productionmodels when the gauginos are degenerateinmasswiththegluinoorsquarks.
Fig. 8. Observed(black)andexpected(red)uppercrosssectionlimitsasafunctionoftheNLSPmassfortheTChiWg(left)andTChiNg(right)modeltogetherwiththe correspondingtheoreticalcrosssection(blue).Theinner(green)bandandtheouter(yellow)bandindicatetheregionscontaining68and95%,respectively,ofthedistribution oflimitsexpectedunderthebackground-onlyhypothesis.Thesolidbluelinesrepresentthetheoreticaluncertaintyinthesignalcrosssection.
Fig. 9. The95%CLlimitsfortheT5gg(left)andT5Wg(right)SMSmodelsinthegluino-neutralino/charginomassplane.Thecolorscaleencodestheobserveduppercross sectionlimitforeachpoint.Thethicklinesrepresenttheobserved(black)andexpected(red)exclusioncontours,wherethephasespaceoflowermassesisexcludedby theanalysis.Thethindottedredcurvesindicatetheregioncontaining68%ofthedistributionoflimitsexpectedunderthebackground-onlyhypothesis.Thethinsolidblack curvesshowthechangeintheobservedlimitduetovariationofthesignalcrosssectionswithintheirtheoreticaluncertainties.
Fig. 10. The95%CLlimitsfortheT6gg(left)andT6Wg(right)SMSmodelsinthesquark-neutralino/charginomassplane.Thecolorscaleencodestheobserveduppercross sectionlimitforeachpoint.Thethicklinesrepresenttheobserved(black)andexpected(red)exclusioncontours,wherethephasespaceoflowermassesisexcludedby theanalysis.Thethindottedredcurvesindicatetheregioncontaining68%ofthedistributionoflimitsexpectedunderthebackground-onlyhypothesis.Thethinsolidblack curvesshowthechangeintheobservedlimitduetovariationofthesignalcrosssectionswithintheirtheoreticaluncertainties.Forthesignalproductioncrosssectionfive accessiblemass-degeneratesquarkflavorsforqLandqRwereassumed.
Acknowledgements
WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the technicalandadministrativestaffs atCERN andatother CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcenters and personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythe computinginfrastructureessential to ouranalyses. Finally, we acknowledge the enduring support for the construc-tionandoperation oftheLHCandthe CMSdetectorprovidedby thefollowingfundingagencies:BMWFWandFWF(Austria);FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, 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);MOE andUM (Malaysia); BUAP, CINVESTAV,CONACYT, LNS, SEP, and UASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland);FCT(Portugal);JINR(Dubna);MON,RosAtom,RAS,RFBR andRAEP(Russia);MESTD (Serbia);SEIDI,CPAN,PCTI andFEDER (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 andtheEuropeanResearchCouncilandHorizon2020Grant, contract No. 675440 (European Union); the Leventis Founda-tion; the A. P. Sloan Foundation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation à la Recherche dans l’Industrie et dans l’A-griculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the Ministry of Ed-ucation, Youth and Sports (MEYS) of the Czech Republic; the Council of Science and Industrial Research, India; the HOMING PLUS program of the Foundation for Polish Science, cofinanced from European Union, Regional Development Fund, the Mobil-ity Plus program of the Ministry of Science and Higher Edu-cation, the National Science Center (Poland), contracts Harmo-nia2014/14/M/ST2/00428, Opus2014/13/B/ST2/02543,2014/15/B/ ST2/03998, and 2015/19/B/ST2/02861, Sonata-bis 2012/07/E/ST2/ 01406;theNationalPrioritiesResearchProgrambyQatarNational ResearchFund;theProgramaSeveroOchoadelPrincipado de As-turias; the Thalis and Aristeia programs cofinanced by EU-ESF andtheGreekNSRF;the RachadapisekSompotFund for Postdoc-toralFellowship,ChulalongkornUniversity andtheChulalongkorn AcademicintoIts 2ndCenturyProjectAdvancementProject (Thai-land); the Welch Foundation, contract C-1845; and the Weston HavensFoundation(USA).
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TheCMSCollaboration
A.M. Sirunyan,A. Tumasyan
YerevanPhysicsInstitute,Yerevan,Armenia
W. Adam, F. Ambrogi, E. Asilar,T. Bergauer, J. Brandstetter, E. Brondolin,M. Dragicevic, J. Erö,M. Flechl,
M. Friedl,R. Frühwirth1,V.M. Ghete, J. Grossmann, J. Hrubec, M. Jeitler1, A. König, N. Krammer,
I. Krätschmer,D. Liko, T. Madlener,I. Mikulec, E. Pree, N. Rad, H. Rohringer, J. Schieck1, R. Schöfbeck,
M. Spanring, D. Spitzbart,W. Waltenberger, J. Wittmann, C.-E. Wulz1, M. Zarucki
InstitutfürHochenergiephysik,Wien,Austria
V. Chekhovsky, V. Mossolov,J. Suarez Gonzalez
InstituteforNuclearProblems,Minsk,Belarus
E.A. De Wolf,D. Di Croce, X. Janssen, J. Lauwers,M. Van De Klundert, H. Van Haevermaet,
P. Van Mechelen, N. Van Remortel
UniversiteitAntwerpen,Antwerpen,Belgium
S. Abu Zeid,F. Blekman, J. D’Hondt, I. De Bruyn, J. De Clercq, K. Deroover, G. Flouris, D. Lontkovskyi,
S. Lowette,I. Marchesini, S. Moortgat, L. Moreels,Q. Python, K. Skovpen, S. Tavernier, W. Van Doninck,
P. Van Mulders, I. Van Parijs
VrijeUniversiteitBrussel,Brussel,Belgium
D. Beghin, H. Brun, B. Clerbaux, G. De Lentdecker, H. Delannoy, B. Dorney,G. Fasanella, L. Favart,
R. Goldouzian, A. Grebenyuk,T. Lenzi, J. Luetic, T. Maerschalk, A. Marinov,T. Seva, E. Starling,
C. Vander Velde, P. Vanlaer, D. Vannerom,R. Yonamine, F. Zenoni, F. Zhang2
UniversitéLibredeBruxelles,Bruxelles,Belgium
A. Cimmino, T. Cornelis,D. Dobur, A. Fagot,M. Gul, I. Khvastunov3,D. Poyraz, C. Roskas, S. Salva,
M. Tytgat, W. Verbeke,N. Zaganidis
GhentUniversity,Ghent,Belgium
H. Bakhshiansohi,O. Bondu, S. Brochet,G. Bruno, C. Caputo, A. Caudron, P. David, S. De Visscher,
C. Delaere, M. Delcourt, B. Francois,A. Giammanco, M. Komm, G. Krintiras,V. Lemaitre, A. Magitteri,
A. Mertens, M. Musich, K. Piotrzkowski,L. Quertenmont, A. Saggio, M. Vidal Marono, S. Wertz,J. Zobec
UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium
W.L. Aldá Júnior, F.L. Alves,G.A. Alves, L. Brito,M. Correa Martins Junior,C. Hensel, A. Moraes,M.E. Pol,
P. Rebello Teles
CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil
E. Belchior Batista Das Chagas, W. Carvalho,J. Chinellato4,E. Coelho, E.M. Da Costa, G.G. Da Silveira5,
D. De Jesus Damiao,S. Fonseca De Souza, L.M. Huertas Guativa, H. Malbouisson,M. Melo De Almeida,
C. Mora Herrera,L. Mundim, H. Nogima,L.J. Sanchez Rosas, A. Santoro,A. Sznajder, M. Thiel,
E.J. Tonelli Manganote4,F. Torres Da Silva De Araujo, A. Vilela Pereira
UniversityofSofia,Sofia,Bulgaria
W. Fang6, X. Gao6,L. Yuan
BeihangUniversity,Beijing,China
M. Ahmad, J.G. Bian, G.M. Chen,H.S. Chen, M. Chen, Y. Chen, C.H. Jiang, D. Leggat,H. Liao, Z. Liu,
F. Romeo,S.M. Shaheen, A. Spiezia,J. Tao, C. Wang, Z. Wang, E. Yazgan, H. Zhang,S. Zhang, J. Zhao
InstituteofHighEnergyPhysics,Beijing,China
Y. Ban, G. Chen, J. Li,Q. Li, S. Liu, Y. Mao,S.J. Qian, D. Wang,Z. Xu
StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China
Y. Wang
TsinghuaUniversity,Beijing,China
C. Avila,A. Cabrera, L.F. Chaparro Sierra, C. Florez,C.F. González Hernández, J.D. Ruiz Alvarez,
M.A. Segura Delgado
UniversidaddeLosAndes,Bogota,Colombia
B. Courbon,N. Godinovic, D. Lelas,I. Puljak, P.M. Ribeiro Cipriano, T. Sculac
UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia
Z. Antunovic,M. Kovac
UniversityofSplit,FacultyofScience,Split,Croatia
V. Brigljevic,D. Ferencek, K. Kadija,B. Mesic, A. Starodumov7, T. Susa
InstituteRudjerBoskovic,Zagreb,Croatia
M.W. Ather,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
A. Ellithi Kamel9,S. Khalil10, A. Mohamed10
AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt
R.K. Dewanjee,M. Kadastik, L. Perrini, M. Raidal, A. Tiko,C. Veelken
P. Eerola, H. Kirschenmann,J. Pekkanen,M. Voutilainen
DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland
J. Havukainen, J.K. Heikkilä, T. Järvinen,V. Karimäki, R. Kinnunen, T. Lampén, K. Lassila-Perini,S. Laurila,
S. Lehti, T. Lindén,P. Luukka, H. Siikonen, E. Tuominen, J. Tuominiemi
HelsinkiInstituteofPhysics,Helsinki,Finland
T. Tuuva
LappeenrantaUniversityofTechnology,Lappeenranta,Finland
M. Besancon, F. Couderc,M. Dejardin, D. Denegri, J.L. Faure, F. Ferri, S. Ganjour, S. Ghosh, P. Gras,
G. Hamel de Monchenault, P. Jarry,I. Kucher, C. Leloup,E. Locci, M. Machet, J. Malcles,G. Negro,
J. Rander, A. Rosowsky, M.Ö. Sahin,M. Titov
IRFU,CEA,UniversitéParis-Saclay,Gif-sur-Yvette,France
A. Abdulsalam, C. Amendola, I. Antropov, S. Baffioni, F. Beaudette, P. Busson, L. Cadamuro, C. Charlot,
R. Granier de Cassagnac, M. Jo,S. Lisniak, A. Lobanov, J. Martin Blanco, M. Nguyen,C. Ochando,
G. Ortona,P. Paganini, P. Pigard,R. Salerno, J.B. Sauvan, Y. Sirois, A.G. Stahl Leiton, T. Strebler, Y. Yilmaz,
A. Zabi, A. Zghiche
LaboratoireLeprince-Ringuet,Ecolepolytechnique,CNRS/IN2P3,UniversitéParis-Saclay,Palaiseau,France
J.-L. Agram11, J. Andrea, D. Bloch,J.-M. Brom, M. Buttignol,E.C. Chabert, N. Chanon, C. Collard,
E. Conte11, X. Coubez, J.-C. Fontaine11,D. Gelé, U. Goerlach,M. Jansová, A.-C. Le Bihan, N. Tonon,
P. Van Hove
UniversitédeStrasbourg,CNRS,IPHCUMR7178,F-67000Strasbourg,France
S. Gadrat
CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France
S. Beauceron,C. Bernet, G. Boudoul, R. Chierici,D. Contardo, P. Depasse, H. El Mamouni,J. Fay, L. Finco,
S. Gascon, M. Gouzevitch, G. Grenier, B. Ille, F. Lagarde, I.B. Laktineh,M. Lethuillier, L. Mirabito,
A.L. Pequegnot, S. Perries, A. Popov12,V. Sordini, M. Vander Donckt, S. Viret
UniversitédeLyon,UniversitéClaudeBernardLyon1,CNRS-IN2P3,InstitutdePhysiqueNucléairedeLyon,Villeurbanne,France
A. Khvedelidze8
GeorgianTechnicalUniversity,Tbilisi,Georgia
Z. Tsamalaidze8
TbilisiStateUniversity,Tbilisi,Georgia
C. Autermann, L. Feld, M.K. Kiesel, K. Klein, M. Lipinski, M. Preuten,C. Schomakers, J. Schulz,
M. Teroerde,V. Zhukov12
RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany
A. Albert, E. Dietz-Laursonn, D. Duchardt, M. Endres,M. Erdmann, S. Erdweg, T. Esch,R. Fischer, A. Güth,
M. Hamer,T. Hebbeker,C. Heidemann, K. Hoepfner,S. Knutzen, M. Merschmeyer,A. Meyer, P. Millet,
S. Mukherjee,T. Pook, M. Radziej, H. Reithler,M. Rieger, F. Scheuch,D. Teyssier, S. Thüer
W. Lange,A. Lelek, T. Lenz, J. Leonard,K. Lipka, W. Lohmann16,R. Mankel, I.-A. Melzer-Pellmann,
A.B. Meyer, G. Mittag, J. Mnich, A. Mussgiller, E. Ntomari,D. Pitzl, A. Raspereza,M. Savitskyi,P. Saxena,
R. Shevchenko,S. Spannagel, N. Stefaniuk, G.P. Van Onsem,R. Walsh, Y. Wen, K. Wichmann,C. Wissing,
O. Zenaiev
DeutschesElektronen-Synchrotron,Hamburg,Germany
R. Aggleton,S. Bein, V. Blobel, M. Centis Vignali, T. Dreyer,E. Garutti, D. Gonzalez, J. Haller,
A. Hinzmann, M. Hoffmann,A. Karavdina, R. Klanner, R. Kogler,N. Kovalchuk, S. Kurz, T. Lapsien,
D. Marconi,M. Meyer, M. Niedziela, D. Nowatschin, F. Pantaleo13,T. Peiffer, A. Perieanu, C. Scharf,
P. Schleper, A. Schmidt, S. Schumann,J. Schwandt,J. Sonneveld, H. Stadie,G. Steinbrück, F.M. Stober,
M. Stöver,H. Tholen, D. Troendle, E. Usai, A. Vanhoefer, B. Vormwald
UniversityofHamburg,Hamburg,Germany
M. Akbiyik, C. Barth,M. Baselga,S. Baur, E. Butz, R. Caspart, T. Chwalek, F. Colombo, W. De Boer,
A. Dierlamm,N. Faltermann, B. Freund,R. Friese, M. Giffels,M.A. Harrendorf,F. Hartmann13,
S.M. Heindl,U. Husemann, F. Kassel13, S. Kudella, H. Mildner, M.U. Mozer,Th. Müller, M. Plagge,
G. Quast, K. Rabbertz,M. Schröder, I. Shvetsov,G. Sieber, H.J. Simonis, R. Ulrich, S. Wayand,M. Weber,
T. Weiler, S. Williamson,C. Wöhrmann, R. Wolf
InstitutfürExperimentelleKernphysik,Karlsruhe,Germany
G. Anagnostou,G. Daskalakis, T. Geralis,A. Kyriakis, D. Loukas,I. Topsis-Giotis
InstituteofNuclearandParticlePhysics(INPP),NCSRDemokritos,AghiaParaskevi,Greece
G. Karathanasis,S. Kesisoglou, A. Panagiotou, N. Saoulidou
NationalandKapodistrianUniversityofAthens,Athens,Greece
K. Kousouris
NationalTechnicalUniversityofAthens,Athens,Greece
I. Evangelou,C. Foudas, P. Gianneios, P. Katsoulis, P. Kokkas, S. Mallios,N. Manthos, I. Papadopoulos,
E. Paradas, J. Strologas,F.A. Triantis, D. Tsitsonis
UniversityofIoánnina,Ioánnina,Greece
M. Csanad,N. Filipovic, G. Pasztor,O. Surányi, G.I. Veres17
MTA-ELTELendületCMSParticleandNuclearPhysicsGroup,EötvösLorándUniversity,Budapest,Hungary
G. Bencze,C. Hajdu, D. Horvath18, Á. Hunyadi, F. Sikler,V. Veszpremi
WignerResearchCentreforPhysics,Budapest,Hungary
N. Beni,S. Czellar, J. Karancsi19,A. Makovec,J. Molnar, Z. Szillasi
M. Bartók17,P. Raics, Z.L. Trocsanyi, B. Ujvari
InstituteofPhysics,UniversityofDebrecen,Debrecen,Hungary
S. Choudhury, J.R. Komaragiri
IndianInstituteofScience(IISc),Bangalore,India
S. Bahinipati20, S. Bhowmik, P. Mal, K. Mandal, A. Nayak21, D.K. Sahoo20, N. Sahoo, S.K. Swain
NationalInstituteofScienceEducationandResearch,Bhubaneswar,India
S. Bansal, S.B. Beri,V. Bhatnagar, R. Chawla, N. Dhingra, A.K. Kalsi,A. Kaur, M. Kaur, S. Kaur,R. Kumar,
P. Kumari, A. Mehta,J.B. Singh, G. Walia
PanjabUniversity,Chandigarh,India
Ashok Kumar, Aashaq Shah, A. Bhardwaj,S. Chauhan,B.C. Choudhary, R.B. Garg, S. Keshri,A. Kumar,
S. Malhotra, M. Naimuddin,K. Ranjan, R. Sharma
UniversityofDelhi,Delhi,India
R. Bhardwaj,R. Bhattacharya, S. Bhattacharya, U. Bhawandeep, S. Dey,S. Dutt, S. Dutta, S. Ghosh,
N. Majumdar, A. Modak, K. Mondal, S. Mukhopadhyay, S. Nandan, A. Purohit,A. Roy, S. Roy Chowdhury,
S. Sarkar,M. Sharan, S. Thakur
SahaInstituteofNuclearPhysics,HBNI,Kolkata,India
P.K. Behera
IndianInstituteofTechnologyMadras,Madras,India
R. Chudasama, D. Dutta, V. Jha,V. Kumar, A.K. Mohanty13,P.K. Netrakanti,L.M. Pant, P. Shukla,A. Topkar
BhabhaAtomicResearchCentre,Mumbai,India
T. Aziz, S. Dugad,B. Mahakud, S. Mitra, G.B. Mohanty, N. Sur, B. Sutar
TataInstituteofFundamentalResearch-A,Mumbai,India
S. Banerjee, S. Bhattacharya, S. Chatterjee,P. Das, M. Guchait, Sa. Jain, S. Kumar, M. Maity22,
G. Majumder, K. Mazumdar,T. Sarkar22, N. Wickramage23
TataInstituteofFundamentalResearch-B,Mumbai,India
S. Chauhan,S. Dube, V. Hegde, A. Kapoor, K. Kothekar, S. Pandey, A. Rane, S. Sharma
IndianInstituteofScienceEducationandResearch(IISER),Pune,India
S. Chenarani24, E. Eskandari Tadavani,S.M. Etesami24,M. Khakzad, M. Mohammadi Najafabadi,
M. Naseri, S. Paktinat Mehdiabadi25,F. Rezaei Hosseinabadi, B. Safarzadeh26,M. Zeinali
InstituteforResearchinFundamentalSciences(IPM),Tehran,Iran
M. Felcini,M. Grunewald
UniversityCollegeDublin,Dublin,Ireland
M. Abbresciaa,b, C. Calabriaa,b,A. Colaleoa,D. Creanzaa,c, L. Cristellaa,b,N. De Filippisa,c,
M. De Palmaa,b, F. Erricoa,b, L. Fiorea, G. Iasellia,c, S. Lezkia,b, G. Maggia,c,M. Maggia, G. Minielloa,b,
S. Mya,b, S. Nuzzoa,b,A. Pompilia,b,G. Pugliesea,c, R. Radognaa,A. Ranieria, G. Selvaggia,b, A. Sharmaa,
L. Silvestrisa,13,R. Vendittia,P. Verwilligena
aINFNSezionediBari,Bari,Italy bUniversitàdiBari,Bari,Italy cPolitecnicodiBari,Bari,Italy
aINFNSezionediCatania,Catania,Italy bUniversitàdiCatania,Catania,Italy
G. Barbaglia,K. Chatterjeea,b,V. Ciullia,b,C. Civininia,R. D’Alessandroa,b, E. Focardia,b, P. Lenzia,b,
M. Meschinia, S. Paolettia,L. Russoa,27,G. Sguazzonia,D. Stroma,L. Viliania,b,13
aINFNSezionediFirenze,Firenze,Italy bUniversitàdiFirenze,Firenze,Italy
L. Benussi,S. Bianco, F. Fabbri, D. Piccolo,F. Primavera13
INFNLaboratoriNazionalidiFrascati,Frascati,Italy
V. Calvellia,b, F. Ferroa, F. Raveraa,b, E. Robuttia,S. Tosia,b
aINFNSezionediGenova,Genova,Italy bUniversitàdiGenova,Genova,Italy
A. Benagliaa,A. Beschib,L. Brianzaa,b,F. Brivioa,b,V. Cirioloa,b,13, M.E. Dinardoa,b,S. Fiorendia,b,
S. Gennaia,A. Ghezzia,b,P. Govonia,b,M. Malbertia,b,S. Malvezzia,R.A. Manzonia,b,D. Menascea,
L. Moronia, M. Paganonia,b,K. Pauwelsa,b, D. Pedrinia,S. Pigazzinia,b,28,S. Ragazzia,b,
T. Tabarelli de Fatisa,b
aINFNSezionediMilano-Bicocca,Milano,Italy bUniversitàdiMilano-Bicocca,Milano,Italy
S. Buontempoa, N. Cavalloa,c,S. Di Guidaa,d,13, F. Fabozzia,c,F. Fiengaa,b, A.O.M. Iorioa,b,W.A. Khana,
L. Listaa,S. Meolaa,d,13,P. Paoluccia,13,C. Sciaccaa,b,F. Thyssena
aINFNSezionediNapoli,Napoli,Italy bUniversitàdiNapoli‘FedericoII’,Napoli,Italy cUniversitàdellaBasilicata,Potenza,Italy dUniversitàG.Marconi,Roma,Italy
P. Azzia, 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, F. Gonellaa, A. Gozzelinoa,S. Lacapraraa,P. Lujan,
N. Pozzobona,b, P. Ronchesea,b,R. Rossina,b,F. Simonettoa,b, E. Torassaa,S. Venturaa, P. Zottoa,b,
G. Zumerlea,b
aINFNSezionediPadova,Padova,Italy bUniversitàdiPadova,Padova,Italy cUniversitàdiTrento,Trento,Italy
A. Braghieria, A. Magnania,P. Montagnaa,b, S.P. Rattia,b,V. Rea,M. Ressegottia,b,C. Riccardia,b,
P. Salvinia, I. Vaia,b,P. Vituloa,b
aINFNSezionediPavia,Pavia,Italy bUniversitàdiPavia,Pavia,Italy
L. Alunni Solestizia,b, M. Biasinia,b, G.M. Bileia,C. Cecchia,b,D. Ciangottinia,b, L. Fanòa,b,R. Leonardia,b,
E. Manonia,G. Mantovania,b,V. Mariania,b,M. Menichellia, A. Rossia,b,A. Santocchiaa,b, D. Spigaa
aINFNSezionediPerugia,Perugia,Italy bUniversitàdiPerugia,Perugia,Italy