Observation of a peaking structure in the J/ψφ mass spectrum from B±→J/ψφK± decays

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Physics

Letters

B

www.elsevier.com/locate/physletb

Observation

of

a

peaking

structure

in

the

J

/ψφ

mass

spectrum

from

B

±

→

J

/ψφ

K

±

decays

Availableonline22May2014 Editor:M.Doser

A peakingstructure intheJ/ψφ massspectrum nearthreshold isobserved inB±_→J/ψφK± decays, produced in pp collisions at √s=7 TeV collected with the CMS detector at the LHC. The data sample, selectedon the basis ofthe dimuon decay mode of the J/ψ,corresponds to an integrated luminosity of 5.2 fb−1_{. Fitting the structure to an S-wave relativistic Breit–Wigner lineshape above}

athree-body phase-spacenonresonantcomponent givesasignal statistical significance exceedingfive standarddeviations.Thefittedmassandwidthvaluesare m =4148.0±2.4(stat.)±6.3(syst.)MeV and

Γ =28+₋15₁₁ (stat.)±19(syst.)MeV,respectively.Evidenceforanadditionalpeaking structureathigher J/ψφmassisalsoreported.

©2014TheAuthors.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/3.0/).FundedbySCOAP3.

1. Introduction

The discovery of new charmonium-like states [1–6] over the last decade poses a challenge to the conventional quark model. Many explanations, such as charmed hybrids, tetraquarks, and molecular states,havebeen proposed forthesenew entities, but their nature remains a puzzle [7,8]. In 2009, the CDF Collabora-tionreported evidence fora narrow structure, whichthey called Y(4140), near the J/ψφ threshold in B±→J/ψφK± decays [9]. Thisstructure,ifconfirmedasanewresonance,wouldbea candi-dateforanexoticmeson[10–18].TheBelleCollaborationsearched forthe Y(4140)through the sameB± decaychannel [19] andin thetwo-photon process γ γ →J/ψφ [20],butdidnot confirmit. UsingthesameB±decaychannel,theLHCbCollaborationrecently reportedfindingnoevidenceforsuchastate,indisagreementwith theCDFresult[21].

InthisLetter,a studyofthe J/ψφ massspectrum fromB+→ J/ψφK+ decaysisreported,wherecharge conjugatedecaymodes areimpliedthroughout.Thedatawerecollectedin2011withthe CompactMuonSolenoid(CMS)detectorfromproton–proton colli-sionsattheLargeHadronCollider(LHC)operatingata center-of-massenergyof7 TeVandcorrespondingtoanintegrated luminos-ityof5.2±0.1 fb−1[22].

A detailed description of CMS can be found elsewhere [23]. The central feature of the CMS apparatus is a superconducting solenoid,13 mlongwitha6 minternaldiameter,whichprovides an axial magnetic field of 3.8 T. Within the field volume is the

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

silicontracker,whichconsistsofapixel-baseddetectorinthe in-ner region andlayers ofmicrostrip detectorsinthe outer region. Charged-particletrajectoriesaremeasuredwiththesilicontracker, covering0< φ≤2π inazimuthand|η|<2.5,wherethe pseudo-rapidity η isdefinedas−ln(tan[θ/2])andθ isthepolarangleof thetrajectoryoftheparticlewithrespecttothe counterclockwise-beam direction. Muons are detected in the pseudorapidity range |η|<2.4 by threetypes ofgas-ionization detectors embedded in thesteelflux-returnyokeofthemagnet:drifttubesinthebarrel, cathodestrip chambersinthe endcaps,andresistive-plate cham-bersinboththebarrelandendcaps.Thestrongmagneticfieldand excellentpositionresolutionofthesilicontrackerenablethe trans-versemomentum(pT)ofamuonmatchedtoareconstructedtrack tobemeasured witharesolutionofapproximately0.7%for pT of 1 GeV.Thepixeldetector,withitsexcellentspatialresolutionand low occupancy, enables theseparation ofB+-decay verticesfrom theprimaryinteractionvertex.

Monte Carlo(MC) simulated data were createdusing pythia6 [24] for the particle production, evtgen [25] for theparticle de-cays, and Geant4[26]fortracing theparticlesthrough adetailed model ofthe detector. Thesesamples were created withthe ap-propriateconditionsforthedataanalyzed,includingtheeffectsof alignment,efficiency,andnumberofsimultaneousppcollisions.

2. Eventselection

Events are chosen using a two-level trigger system. The first level,composed ofcustomhardware processors,uses information fromthe muon detectors toselect dimuon candidates.The high-level trigger (HLT) runs a special version of the offline software

http://dx.doi.org/10.1016/j.physletb.2014.05.055

0370-2693/©2014TheAuthors.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/3.0/).Fundedby SCOAP3_.

Fig. 1. TheJ/ψφK+massdistributionwiththestandardeventselection(left)andthetighterrequirements(right).Thesolidcurvesshowtheresultoffittingthesedistributions toaGaussiansignalandasecond-degreepolynomialbackgroundwhilethedashedcurvesshowthebackgroundcontribution.

code on a processor farm to select events with nonprompt J/ψ

candidatescomingfromthedecaysofB mesons.

Events containing J/ψ candidates are selected by the HLT dimuontrigger.BecauseoftheincreasingLHCinstantaneous lumi-nosity, thereare two configurations of theHLT, corresponding to tworunningperiodsandtwodistinctdatasets.Forbothdatasets, thefollowingrequirementsare alreadyappliedwiththeHLT.The dimuonpTisrequiredtobegreaterthan6.9 GeV,thetwomuons must be oppositely charged and form a three-dimensional (3D) vertexwitha χ2 _{probability greater than0.5–10%,depending on} the running period. The resulting J/ψ vertex must be displaced from the average interaction point (beamspot) in the transverse planeby atleastthreetimesitsuncertainty,which isthesumin quadratureofthesecondary-vertexuncertaintyandthebeamspot sizeinthetransverse plane.Thecosine ofthe anglebetweenthe transverseprojectionsofthelinejoiningthebeamspotanddimuon vertexandthedimuonmomentumdirectionmustexceed0.9.For thelaterdataset,thereisanadditionalrequirementthatthepT of eachmuonbegreaterthan4 GeV.InthefinalselectionofJ/ψ can-didates,thedimuon pT isrequiredto begreater than7 GeV,the

χ2 _{probability of the dimuon vertex is demanded to be greater} than 10%,and thereconstructed dimuon invariant massmust be within150 MeVoftheJ/ψ mass[27].

TheB+→J/ψφK+ candidatesare reconstructedby combining three additional charged-particle tracks that are consistent with originatingfromthedisplacedJ/ψ vertexandhaveatotalcharge of ±1. These tracks are assigned the kaon mass and this mass isusedin accountingfortheeffectsofenergyloss and multiple-scattering.Wedonotapply amassconstraintontheφ candidate becauseourexperimental K+K− massresolution(1.3 MeV)isless than the φ meson natural width (4.3 MeV). The pT of all kaon tracks are required to be greater than 1 GeV. Only tracks that pass the standard CMS quality requirements [28] are used. The fivetracks,withthe μ+μ− invariantmassconstrainedtotheJ/ψ

mass,arerequiredtoforma good3Dvertexwitha χ2 probabil-itygreater than 1%. There are two K+K− combinations fromthe three chargedkaon tracks, andwe use the lower invariant mass astheφ candidate; MCsimulations ofthe B+ decaypredict that the φ signal from the other combination is negligible, which is verifiedinthedata.ThereconstructedK+K−invariant massmust satisfy 1.008 GeV<m(K+K−)<1.035 GeV to be considered asa

φcandidate.Theseselectionrequirementsweredesignedto main-tainhighefficiencyforB+ decaysandwerefixedbeforetheJ/ψφ

massspectrumindatawasexamined.

3. Results

The invariant-mass spectrum of the selected J/ψφK+ candi-dates is shown in the left plot of Fig. 1 for a mass difference

m≡m(μ+μ−K+K−)−m(μ+μ−)<1.568 GeV. We only inves-tigate candidateswithm<1.568 GeV becauseofpossible back-groundfromB0_s→ ψ(2S)φ→J/ψπ+π−φathighervalues,as dis-cussed below.Theinvariant-mass spectrumisfitwithaGaussian signal functionandasecond-degreepolynomialbackground func-tion. The fit returns a B+ mass of 5.2796±0.0006 (stat.)GeV, which agreeswiththe nominalvalue [27],andaGaussian width of 9.6±0.7 (stat.)MeV, which is consistent with the prediction fromtheMCsimulation.TheB+yieldis2480±160(stat.)events, whichistheworld’slargestB+→J/ψφK+ sample.Thecombined B+yieldis2340±120(stat.)eventswheneachdatasetisfitwith two Gaussian signal functions andthe width ofeach function is fixed to theprediction fromMC simulation.Approximately 5% of the selected eventshavemore thanone B+ candidatewithin 1.5 timesourmassresolution(σ)ofthe B+ mass;allcandidates are kept.

Therightplotin Fig. 1displaystheJ/ψK+K−K+invariant-mass distribution after making the following tighter requirements: the

pT of the kaons must be greater than 1.5 GeV, the B+ vertex probability mustbegreaterthan 10%, theB+ vertexmustbe dis-placedfromtheprimaryvertexinthetransverseplanebyatleast seven timesitsuncertainty,andm(K+K−)mustbe within7 MeV of the φ meson mass [27]. With theserequirements, 40% of the B+ candidates are retained, while the background is reducedby more than a factor of ten. This sample of cleaner signal candi-datesisusedasacross-checkoftheresultsobtainedbyemploying the background-corrected J/ψφ mass spectrum, asdescribed be-low.Withtheexceptionofthiscross-check,allresultsareobtained withtheless-restrictivecriteria.

Fig. 2 shows the K+K− invariant-mass distribution for J/ψK+K−K+ candidatesthat have an invariant mass within ±3σ

of the B+ mass. We define events in the range [−12,−6]σ and [6,12]σ oftheB+ massassidebands.Theφ massrestrictionhas beenremoved andasidebandsubtractionhasbeenperformedin Fig. 2.WefitthisdistributiontoaP -waverelativisticBreit–Wigner (BW) functionconvolvedwithaGaussian resolutionfunction.The widthoftheGaussianisfixedto1.3 MeV,obtainedfromMC sim-ulation. The fit has a χ2 _{probability of 23% andreturns a mass} of 1019.4±0.1 MeV and a width of 4.7±0.4 MeV, consistent with the φ meson [27]. The good fit to only a φ component in Fig. 2 indicates that after the J/ψ and φ mass requirements are made and the combinatorial background is subtracted, the

Fig. 2. The B+ sideband-subtracted K+K− invariant-mass distribution for J/ψK+K−K+candidateswithin±3σ ofthenominalB+ mass.Thesolidcurveis theresultofthefitdescribedinthetext.Thedashedlineshowsthezero-candidate baseline.

B+→μ+μ−K+K−K+ candidates are consistentwithbeingsolely J/ψφK+,withnegligiblecontribution fromJ/ψf0(980)K+ or non-resonantJ/ψK+K−K+.

As seen in Fig. 1, there are two main components to the J/ψφK+ invariant-mass spectrum: the B+ signal and a smooth background.PossiblecontributionsfromotherB-hadrondecaysare examinedusingMCsimulationsofinclusiveB+,B0,andB0_s decays. Basedonthisstudy,themass-differenceregion(m>1.568 GeV) isexcluded fromtheanalysistoavoidpotential backgroundfrom B0_s→ ψ(2S)φ→J/ψπ+π−φ decays, whereone pion isassumed tobeakaonandtheotherisnotreconstructed.

ToinvestigatetheJ/ψφinvariant-massdistribution,ratherthan fitting the distribution itself with its large combinatorial back-ground, the J/ψφK+ candidates are divided into 20 MeV-wide

m intervals,and theJ/ψφK+ massdistributions for each inter-valare fit toextract the B+ signal yieldin that interval. Weuse asecond-degreepolynomialforthecombinatorialbackgroundand twoGaussiansfortheB+signal.Thefitisperformedseparatelyfor eachdataset.The meanvaluesofthe twoGaussiansarefixed to theB+mass[27],andthewidthvaluesoftheGaussians,aswellas theirrelativeratio,arefixed tothevaluesobtainedfromMC sim-ulationforeach specificm intervalineachdataset.Theresults ofallthefits aregooddescriptions ofthedatadistributions with anaverage χ2 _{perdegreeoffreedom(dof)closeto1.Theresulting}

m distributionforthecombineddatasetsisshownin Fig. 3.Two peakingstructuresare observedabove thesimulatedphase-space (PS)continuumdistributionshownbythedottedline.

Results obtainedfrom both data sets are consistent. We have checkedthateventswithmultipleB+candidatesdonotartificially enhancethetwo structures.ThetotalnumberofB+ signalevents inthem intervalsbelow1.568 GeVis2320±110(stat.),whichis consistentwiththetotalnumberofB+ candidatesestimatedfrom themassspectrumin Fig. 1.

A full study of the J/ψφ resonant pattern in the B+ →

μ+μ−K+K−K+ decay via an amplitude analysisof the five-body decaywouldrequireadatasampleatleastanorderofmagnitude largerthaniscurrentlyavailable,aswellasmoreprecise informa-tiononpossibleφK+orJ/ψK+resonancesthatmaycontributeto thisdecay.Instead, them distributionis studied,since it is re-latedtotheprojectionofthetwo-dimensional(2D)J/ψφK+Dalitz plotontothem2(J/ψφ)axis.

Beforefittingthem distribution,itmustbecorrectedforthe relativedetection andreconstruction efficienciesof thecandidate events. Since no branching fractions are being determined, only the relative efficiency over the Dalitz plot is required. If a

pos-Fig. 3. The number of B+ →J/ψφK+ candidates as a function of m= m(μ+μ−K+K−) −m(μ+μ−).Thesolidcurve istheglobalunbinned maximum-likelihood fit ofthe data, and the dottedcurve is the backgroundcontribution assumingthree-bodyPS.Thebandisthe±1σuncertaintyrangeforthebackground obtainedfromtheglobalfit.Thedashedanddash-dottedcurvesarebackground curvesobtainedfromtwodifferentevent-mixingprocedures,asdescribedinthe text,andnormalizedtothenumberofthree-bodyPSbackgroundevents.Theshort dashedcurveisthe1Dfittothedata.

sible φK+ or J/ψK+ resonance did exist, the density of events woulddependonthequantumnumbersoftheresonanceandon theinterferenceofthetwostructureswiththepossibleresonance. Ignoring thesepossible interference effects,the MC simulation is used todetermine theefficiencyover them2(φK+) vs.m2(J/ψφ)

Dalitz plot,assuming a PS distribution for the three-body decay B+→J/ψφK+.TheJ/ψandφvectormesondecaysaresimulated usingtheir knownangulardistributions accordingto theVLLand VSS model in evtgen, while we assume there is no polarization forthetwovectors.ThePSMCsimulationisreweightedassuming either transverse orlongitudinal J/ψ and φ polarization. The ef-fectofeitherpolarizationisfoundtobenegligible.Themeasured efficiencyisfairly uniform,varying bylessthan25% overthe en-tire allowed three-body PS. Assuming a uniform PS distribution, the efficiencyforeach m binis takento be the averageof the efficiencies over the fullkinematically allowed m(φK+) range.To estimatethesystematicuncertaintyintheefficiencycausedbyits dependenceontheunknownquantumnumbersofthestructures, andhence ontheir unknown decay angulardistributions, the ef-ficiency is evaluated under the assumption of both a cos2θ and sin2θ dependence,where θ is the helicity angle, defined as the anglein the J/ψφ rest framebetween thedirectionof theboost from the laboratory frame and the J/ψ direction. Since the effi-ciencytends tobe lower towardstheedge oftheDalitz plot,the cos2_{θ dependence gives a lower average efficiency than the} de-faultefficiency,whilethesin2θdependencegivesaslightlyhigher average efficiency.Thisvariation (10%) istakenas thesystematic uncertainty in the efficiency from our lack of knowledge of the quantumnumbersofthestructuresandtheeffectsofinterference withpossibletwo-bodyresonances.

We investigate the possibility that the two structures in the

m distribution arecausedby reflectionsfromresonancesin the other two-body systems, J/ψK+ and φK+. Such reflections are well known in the two-bodysystems from other three-body de-cays because ofkinematic constraints.There are candidate states that decay to φK+ [27], although they are not well established. These could potentially produce reflected structures inthe J/ψφ

spectrum. In particular, a D-wave contribution to K−p scatter-ing in the mass region around 1.7–1.8 GeV has been reported byseveralfixed-targetexperiments[29–31].This isinterpretedas two interferingbroad JP₌₂− _{resonances, labeled K2(1770) and}

Fig. 4. TheyieldofB+→J/ψK+K−K+candidatesinthedataasafunctionofthe K+K−K+ invariantmass.Theerrorbarsrepresentthestatisticaluncertainties.The solidcurveisthepredictionfromthePSsimulation.

K2(1820), with widths in the range 200–300 MeV. These reso-nancesatrelatively lowφK+masscannotaffecttheJ/ψφstructure near threshold, but could contribute to the second J/ψφ struc-ture near m=1.2 GeV. To study possible reflections from the

φK+ spectrum,we considerφK+resonances withvariousmasses, widths,andhelicityangledistributions,butarenotableto repro-ducethe patternofstructuresseeninthe J/ψφ spectrum. More-over, we separately analyze the J/ψφ spectrum forvalues ofthe

φK+ masseslargerthan1.9 GeV, aregionoftheDalitzplot unaf-fectedby postulatedφK+ resonances,andstillobserve the struc-turenearm=1.2 GeV.

There are nocandidate J/ψK+ resonancesreported inthe lit-erature. Still, we have considered such resonances with various masses, widths, and helicity angle distributions. No combination produces a reflected spectrum that matches the observed J/ψφ

spectrum.

Wehavealsocheckedtheeventswithm largerthan1.568 GeV that had been eliminated from the analysis to ensure that they could not cause similar reflections in the low-m region. After subtraction of the B0_s background the m distribution of events withm larger than 1.568 GeVisconsistent withthe prediction based on the three-body phase-space hypothesis for the non-resonantbackground.(Pleaseseethesupplementalmaterialinthe online version at http://dx.doi.org/10.1016/j.physletb.2014.05.055 forplots.)

The results ofthese studies make it improbable that the two structuresseen inthe J/ψφ spectrumaresolelycausedby

reflec-tionsfromresonancesintheothertwo-bodysystems.However,we cannot entirelyexcludethepossibilityofsuchresonances.For in-stance, theK+K−K+ spectrumshownin Fig. 4displays an excess of events above the predictedPS distribution in the 1.7–1.8 GeV region,an excessthatcannotbe attributedtothepresenceofthe J/ψφ structure nearthreshold. Fig. 4is obtainedby dividing the J/ψφK+candidatesinto40 MeV-wideK+K−K+massintervalsand fittingtheJ/ψφK+invariant-massdistributionsforeachintervalto extracttheB+signalyieldinthatinterval.Them distribution af-terexcludingtheregion(1.68<m(K+K−K+)<1.88 GeV)withthe excessofeventsisshownintheleft plotof Fig. 5andthe corre-spondingdistributionfortheexcludedm regionintherightplot. The presence of thelower-mass structure is still apparent in the leftplot,whilethatofthehigher-massstructureisreducedthough still visible.PossibleinterferenceeffectsovertheDalitzplotcould thereforedistorttheshapeoftheobservedJ/ψφ structuresand af-fecttheextractionoftheresonanceparameters.Theeventsample isnotlargeenoughtoinvestigatetheseeffectsfurther.Weassume thatanyinterferenceeffectscanbeneglected.Thestructuresinthe J/ψφ massspectrum are described intermsof zero,one,ortwo noninterfering resonances anda nonresonant continuum compo-nent.

We fit the two structures with S-wave relativistic BW func-tions convolved witha Gaussian mass resolution function whose widthvarieslinearlyfrom1 MeVatthresholdtoabout4 MeVat

m=1.25 GeV,asdeterminedfromsimulation.Eachstructureis described by a mass, width, and yield, all determined from the fit.Thecontinuumisassumedtofollowathree-bodyPSshape.As analternative,tocheckthesensitivityoftheresulttothis assump-tion,theshapeofthecontinuumisobtainedfromanevent-mixing technique wherethe J/ψ,φ,andK+candidatesareselectedfrom differentevents.Weusetwo versionsofthe eventmixing, which differbytheφandK+candidatesbeingselectedinthesameevent or not; they lead to almost identicalshapes. The differences be-tween the two event-mixing shapes and the three-body PS are used to evaluate the systematic uncertainties in the continuum modeling.TofurtherinvestigatetheeffectofapossibleφK+ reso-nancearound1.7 GeVasshownin Fig. 4,wereweightour phase-spaceMCeventswithaφK+massdistributioncorrespondingtoa BW witha massof1.773 GeV andawidthof200–300 MeV[27]. The helicity angle in the φK+ system is then weighted to cor-respond to several different assumptions about the decay of the possibleresonance.WeestimatetheyieldofthepossibleφK+ res-onance in Fig. 4tobe10%ofthetotalnumberofevents.Wefind thattheshapeofthePSm distributionisalwaysabove the var-ious distributions obtained from the above mixing in the range

m<1.12 GeV.Thus, weconcludethatusingthe PSdistribution

Fig. 5. ThenumberofB+→J/ψφK+candidatesasafunctionof m requiringeitherm(φK+) <1.68 GeV orm(φK+) >1.88 GeV (left),or1.68<m(φK+) <1.88 GeV (right). ThesolidcurveisthepredictionfromthePSsimulation.

asthedefaultbackgroundcurveismoreconservativewithrespect tothesignificanceofthelow-masspeakifthereisapossibleeffect fromaφK+resonance.

Themassesandwidthsofthetwo structuresare extractedby dividing the J/ψφK+ candidates into 20 MeV-wide intervals of

m from 1.008 to 1.568 GeV and performing a globalunbinned maximum-likelihood(UML)fittotheJ/ψφK+ invariant-mass dis-tribution in each m interval. The two data sets are fitted sep-arately, witha total of 56 mass spectra fitted simultaneously. In eachfit, theB+ massis fixed toits nominalvalue and themass resolutionδiscalculatedusing:

δ=a0+a1m +a2m2,

wheremisthevalue ofm atthe centerofthebin,anda0,

a1,anda2 aredeterminedfromsimulation,separatelyforthetwo datasets.Thecombinatorialbackgroundineachbinismodeledas asecond-degreepolynomial. Inthe globalfit, theB+ yieldis ex-pressedastheproductoftherelativeefficiencytimesthenumber ofsignal eventsfrom the two BWsand the nonresonant contin-uum events. We fit the J/ψφK+ invariant-mass distribution for each m bin fromthe two data sets simultaneously by project-ing the above product into each bin. The UML fit returns signal eventyieldsof310±70(stat.)and418±170(stat.)forthe lower-andhigher-massstructures, respectively. The corresponding mass differenceandwidthvaluesare: m1=1051.3±2.4(stat.)MeV,

Γ1=28+₋15₁₁ (stat.)MeV; m2=1217.1±5.3 (stat.)MeV, Γ2 = 38+₋30₁₅ (stat.)MeV. The projection of the UML fit assuming two structuresontotheJ/ψφ massspectrumisrepresentedasthesolid linein Fig. 3.

Asacheckonthefittingprocedure,we performanalternative one-dimensional(1D)binned χ2 _{fittothem spectrumshownin} Fig. 3.Thesamesignal andbackgroundfunctionsare usedinthe 1Dfit asintheglobalfit.The resultofthe 1D fit,assuming two structures,isshownasthedashedlinein Fig. 3.Themeasurements ofthemasses, widths, andyields ofthe two structuresfromthe globaland1Dfitsareingoodagreement.

Toevaluatethesignificanceofeachofthetwostructures,three UML and three 1D (binned χ2_{) fits are performed on the data} shownin Fig. 3:(1) abackground-onlyfit(null-hypothesis);(2) a background plus a single S-wave relativistic BW signal function convolvedwitha Gaussian resolution function havinga widthof 2 MeVfor the lower-mass structure; and(3) a background plus two S-wave relativistic BW functions convolved witha Gaussian resolutionfunctiontomodelbothstructures.Thelog-likelihood ra-tio−2lnLinthecaseoftheUMLfitsorthe χ2_changeχ2 _for the1Dfitsbetween(1)and(2)isthenameasureofthestatistical significanceofthe lower-massstructure, whilethe corresponding values betweenfits (2)and (3) give a measure of the statistical significanceofthehigher-massstructure. Theresultingvalues for a decreasein dofof 3 are −2lnL=58 and χ2_{=53 for the} lower-mass structure, and 36 and 37 for the higher-mass struc-ture.

Simulated samples are used to estimate the probability that background fluctuationsalone could give rise to a signal as sig-nificant as that seen in the data for the lower-mass structure. Over 50 million m spectra were generated between 1.008 and 1.568 GeVwith2300eventsforeachspectrum basedona three-bodyPS shape.Themostsignificant fluctuationineach spectrum isfound whose J/ψφ invariant mass iswithin ±3 timesthe un-certaintyintheCDFmassvalue of4.140 GeVandhavingawidth between 10 MeV (half the m bin width) to 80 MeV (half the separationbetweenthetwo structures).We thenobtaintheχ2 distributionsinthesimulatedpurebackgroundsamplesand com-parethemwiththecorresponding valueofthesignal inthedata.

Table 1

Systematicuncertaintiesinthemeasuredmassesandwidthsofthetwopeaking structuresfromthesourceslistedandthetotaluncertainties.

m1(MeV) Γ1(MeV) m2(MeV) Γ2(MeV)

B+background PDF 0.8 7.4 2.6 9.9 B+signal PDF 0.2 3.6 2.7 0.2 Relative efficiency 4.8 6.0 0.9 10.0 m binning 3.7 1.5 2.7 0.2 m structure PDF 0.8 9.3 0.6 4.9 m mass resolution 0.8 6.4 0.6 4.6 m background shape 0.2 7.0 0.3 0.2 Selection requirements 0.8 7.8 5.5 1.8 Total 6.3 19 7.3 16

No generatedspectrumisfoundwithafluctuationhavinga χ2 greater thanorequal tothevalue obtainedin thedata(53).The resulting p-value, takenasthe fractionof thesimulated samples with a χ2 _{value greater than or equal to the value obtained} in the data, is less than 2×10−8, which corresponds to a sig-nificance of more than 5 standard deviations. Because the sec-ond structure could be affected by possible φK+ resonances, it is difficult to model the background shape in that mass range, andwe do not quote a numeric significancefor the higher-mass structure.However, there isclearevidencefora second structure around m=1.2 GeV even afterexcluding the region with pos-sibleK2 resonances.There isalsoasmallexcessofeventsaround

m=1.4 GeV,butwithalocalsignificanceoflessthan3standard deviations.

Variouschecksaremadetoexaminetherobustnessofthetwo structures. Each selection criterion is individually varied, and in no case is there an indication of a bias in the selection proce-dure.Therelative efficienciesforthefirstfivem binsarevaried by ±20% and the fit repeated, confirming the robustness of the significance of the first structure. The m distribution from an sPlot [32] projection is compared to the m distribution shown in Fig. 3.No indication ofbias isfound. The sPlotalgorithm isa background-subtraction technique that weights each event based onthe observedsignal-to-background ratio,inthiscasefromthe fittotheJ/ψφK+massdistributionshownin Fig. 1.Werepeatthe analysiswiththetighterrequirementsdiscussedearlierthatlower the combinatorial backgroundlevel by a factor often andretain 40%oftheB+events,asshownintherightplotin Fig. 1.Them

plot for these events looks similar to Fig. 3, showing two peak-ing structureswhosefittedmassandwidth valuesareconsistent withtheresultsfromthenominaldatasample.No indicationofa possiblebiasisfound.

The estimations of the contributions to the systematic uncer-taintiesinthemassandwidthmeasurementsofthetwostructures shownin Table 1,aredeterminedfromseveralstudies.The uncer-tainties owing tothe probability densityfunctions(PDFs)forthe combinatorialbackgroundshapeinthem(J/ψφK+)spectrumand the B+ signal are studied by using different PDFs such as first-andthird-degree polynomials, exponential functions, anda num-ber of Gaussian functions. The uncertainties in the shape of the relativeefficiencyvs. m areevaluatedbyvaryingtherelative ef-ficiencyinvariousbinsandcomparingwiththe2Defficienciesfor correctionofm(J/ψφ)vs.m(φK+).Theuncertaintiescausedbythe binningofthem spectrumarestudiedbyusing10 MeVbins in-steadof20 MeVbins.Toestimate theuncertaintyfromthesignal fittingfunction,werepeatthefittothem distributionusing ei-theranonrelativisticBWora P -waverelativisticBW functionfor eachstructure.Theuncertaintiesfromthem massresolutionare studiedbyvaryingthemassresolutionvaluesobtainedfrom sim-ulation withintheir statistical uncertainties.Toevaluate potential distortions inthe m background shapecausedby possible φK+

resonances,weobtainthem backgroundshapefromdatausing an event-mixing technique by applyingthe same kinematic con-straintsandtakingtheφandK+candidatesfromthesameevent, buttheJ/ψcandidatefromadifferentevent.Theuncertaintiesdue toselectionrequirementsarestudiedintheMCsample.The over-allsystematicuncertaintiesinthemeasurementofthemassesand widths of the two structures are found by adding in quadrature theindividualcombinationssummarizedin Table 1.

4. Summary

In summary, a peaking structure in the J/ψφ mass spectrum fromB+→J/ψφK+ decays hasbeenobservedinpp collisions at √

s=7 TeV by the CMS Collaboration at the LHC. Assuming an

S-waverelativisticBW lineshapeforthisstructure abovea three-bodyPSshapeforthenonresonantbackground,astatistical signif-icanceofgreater than5standard deviationsisfound. Addingthe J/ψ mass [27] to the extracted m values, the mass and width aremeasuredtobem1=4148.0±2.4(stat.)±6.3(syst.)MeV and

Γ1=28+₋1511(stat.)±19(syst.)MeV.Themeasuredmassandwidth are consistent with the Y(4140) values reported by CDF experi-ment.Therelativebranchingfractionofthispeakingstructurewith respecttothetotal numberofB+→J/ψφK+ eventsisestimated tobe about0.10,withastatisticaluncertaintyofabout 30%. This is consistent with both the value measured by CDF of 15%±5% andtheupperlimitreportedbyLHCb(0.07).Inaddition,evidence fora second peaking structure is found in the same mass spec-trum, with measured mass and width values of m2=4313.8± 5.3(stat.)±7.3(syst.)MeV andΓ2=38+₋3015(stat.)±16(syst.)MeV. Becauseofpossiblereflectionsfromtwo-bodydecays,the statisti-cal significance of the second structure cannot be reliably deter-mined. The two structures are well above thethreshold of open charm (DD) decays and have relatively narrow widths. Conven-tionalcharmoniummesonswiththesemasseswouldbeexpected tohavelargerwidthsandtodecaypredominantlyintoopencharm pairswithsmallbranchingfractionsintoJ/ψφ.Angularanalysesof theB+→J/ψφK+decayswouldhelpelucidatethenatureofthese structures.

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,wegratefullyacknowledgethecomputingcentresand personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythe computinginfrastructureessential to ouranalyses. Finally, we acknowledge the enduring support for the construc-tionandoperation oftheLHCandthe CMSdetectorprovidedby the following funding agencies: BMWF andFWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES(Bulgaria);CERN;CAS,MoST,andNSFC(China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); MoER, SF0690030s09 andERDF(Estonia);Academy ofFinland,MEC,andHIP(Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT(Greece);OTKAandNKTH(Hungary);DAEandDST(India); IPM(Iran);SFI (Ireland);INFN (Italy);NRF andWCU(Republic of Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland);FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS andRFBR(Russia);MESTD(Serbia);SEIDIandCPAN(Spain);Swiss Funding Agencies (Switzerland); NSC (Taipei); ThEPCenter, IPST, STAR and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine);STFC(UnitedKingdom);DOEandNSF(USA).

Individuals have received support from the Marie-Curie pro-gramme and the European Research Council and EPLANET (Eu-ropean 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 Recherchedansl’Industrieetdansl’Agriculture(FRIA-Belgium);the AgentschapvoorInnovatiedoorWetenschapenTechnologie (IWT-Belgium); the MinistryofEducation, Youth andSports(MEYS) of Czech Republic; the Council of Science and Industrial Research, India; the Compagnia di San Paolo (Torino); the HOMING PLUS programmeofFoundationForPolishScience,cofinancedbyEU, Re-gionalDevelopmentFund;andtheThalisandAristeiaprogrammes cofinancedbyEU-ESFandtheGreekNSRF.

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CMSCollaboration

S. Chatrchyan,V. Khachatryan,A.M. Sirunyan, A. Tumasyan

YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam, T. Bergauer, M. Dragicevic,J. Erö,C. Fabjan1,M. Friedl,R. Frühwirth1, V.M. Ghete,

N. Hörmann, J. Hrubec, M. Jeitler1,W. Kiesenhofer, V. Knünz,M. Krammer1, I. Krätschmer,D. Liko,

I. Mikulec,D. Rabady2, B. Rahbaran,C. Rohringer, H. Rohringer, R. Schöfbeck, J. Strauss, A. Taurok,

W. Treberer-Treberspurg,W. Waltenberger, C.-E. Wulz1

InstitutfürHochenergiephysikderOeAW,Wien,Austria

V. Mossolov,N. Shumeiko,J. Suarez Gonzalez

NationalCentreforParticleandHighEnergyPhysics,Minsk,Belarus

S. Alderweireldt, M. Bansal, S. Bansal,T. Cornelis, E.A. De Wolf,X. Janssen,A. Knutsson, S. Luyckx,

L. Mucibello,S. Ochesanu, B. Roland,R. Rougny, Z. Staykova, H. Van Haevermaet,P. Van Mechelen,

N. Van Remortel,A. Van Spilbeeck

UniversiteitAntwerpen,Antwerpen,Belgium

F. Blekman, S. Blyweert,J. D’Hondt, A. Kalogeropoulos,J. Keaveney, M. Maes, A. Olbrechts, S. Tavernier,

W. Van Doninck, P. Van Mulders,G.P. Van Onsem, I. Villella

VrijeUniversiteitBrussel,Brussel,Belgium

B. Clerbaux, G. De Lentdecker, L. Favart, A.P.R. Gay, T. Hreus, A. Léonard,P.E. Marage, A. Mohammadi,

L. Perniè, T. Reis,T. Seva, L. Thomas, C. Vander Velde, P. Vanlaer, J. Wang

UniversitéLibredeBruxelles,Bruxelles,Belgium

V. Adler,K. Beernaert, L. Benucci, A. Cimmino,S. Costantini, S. Dildick,G. Garcia,B. Klein, J. Lellouch,

A. Marinov,J. Mccartin, A.A. Ocampo Rios, D. Ryckbosch, M. Sigamani,N. Strobbe, F. Thyssen, M. Tytgat,

S. Walsh,E. Yazgan, N. Zaganidis

GhentUniversity,Ghent,Belgium

S. Basegmez, C. Beluffi3, G. Bruno,R. Castello, A. Caudron, L. Ceard, C. Delaere, T. du Pree,D. Favart,

L. Forthomme,A. Giammanco4,J. Hollar, P. Jez, V. Lemaitre, J. Liao,O. Militaru, C. Nuttens, D. Pagano,

A. Pin, K. Piotrzkowski,A. Popov5, M. Selvaggi,J.M. Vizan Garcia

N. Beliy, T. Caebergs,E. Daubie, G.H. Hammad

UniversitédeMons,Mons,Belgium

G.A. Alves,M. Correa Martins Junior, T. Martins,M.E. Pol, M.H.G. Souza

CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

W.L. Aldá Júnior, W. Carvalho, J. Chinellato6,A. Custódio, E.M. Da Costa, D. De Jesus Damiao,

C. De Oliveira Martins, S. Fonseca De Souza, H. Malbouisson, M. Malek,D. Matos Figueiredo, L. Mundim,

H. Nogima,W.L. Prado Da Silva, A. Santoro, A. Sznajder,E.J. Tonelli Manganote6,A. Vilela Pereira

UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

C.A. Bernardesb, F.A. Diasa,7,T.R. Fernandez Perez Tomeia, E.M. Gregoresb, C. Laganaa,F. Marinhoa,

P.G. Mercadanteb,S.F. Novaesa,Sandra S. Padulaa

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

V. Genchev2, P. Iaydjiev2,S. Piperov, M. Rodozov,G. Sultanov, M. Vutova

InstituteforNuclearResearchandNuclearEnergy,Sofia,Bulgaria

A. Dimitrov, R. Hadjiiska,V. Kozhuharov, L. Litov,B. Pavlov, P. Petkov

UniversityofSofia,Sofia,Bulgaria

J.G. Bian, G.M. Chen,H.S. Chen, C.H. Jiang, D. Liang, S. Liang,X. Meng, J. Tao, J. Wang, X. Wang,Z. Wang,

H. Xiao,M. Xu

InstituteofHighEnergyPhysics,Beijing,China

C. Asawatangtrakuldee, Y. Ban, Y. Guo, W. Li, S. Liu, Y. Mao,S.J. Qian, H. Teng, D. Wang,L. Zhang, W. Zou

StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

C. Avila,C.A. Carrillo Montoya, L.F. Chaparro Sierra,J.P. Gomez, B. Gomez Moreno, J.C. Sanabria

UniversidaddeLosAndes,Bogota,Colombia

N. Godinovic, D. Lelas, R. Plestina8,D. Polic, I. Puljak

TechnicalUniversityofSplit,Split,Croatia

Z. Antunovic, M. Kovac

UniversityofSplit,Split,Croatia

V. Brigljevic,S. Duric, K. Kadija, J. Luetic, D. Mekterovic, S. Morovic, L. Tikvica

InstituteRudjerBoskovic,Zagreb,Croatia

A. Attikis, G. Mavromanolakis, J. Mousa,C. Nicolaou, F. Ptochos, P.A. Razis

UniversityofCyprus,Nicosia,Cyprus

M. Finger,M. Finger Jr.

CharlesUniversity,Prague,CzechRepublic

A.A. Abdelalim9,Y. Assran10,S. Elgammal9, A. Ellithi Kamel11,M.A. Mahmoud12,A. Radi13,14

AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt

NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia

P. Eerola,G. Fedi, M. Voutilainen

DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland

J. Härkönen,V. Karimäki, R. Kinnunen, M.J. Kortelainen, T. Lampén, K. Lassila-Perini,S. Lehti, T. Lindén,

P. Luukka, T. Mäenpää,T. Peltola, E. Tuominen, J. Tuominiemi, E. Tuovinen,L. Wendland

HelsinkiInstituteofPhysics,Helsinki,Finland

A. Korpela,T. Tuuva

LappeenrantaUniversityofTechnology,Lappeenranta,Finland

M. Besancon,S. Choudhury, F. Couderc, M. Dejardin,D. Denegri, B. Fabbro, J.L. Faure, F. Ferri, S. Ganjour,

A. Givernaud, P. Gras, G. Hamel de Monchenault∗,P. Jarry, E. Locci,J. Malcles,L. Millischer, A. Nayak,

J. Rander,A. Rosowsky, M. Titov

DSM/IRFU,CEA/Saclay,Gif-sur-Yvette,France

S. Baffioni,F. Beaudette, L. Benhabib, L. Bianchini, M. Bluj15,P. Busson, C. Charlot,N. Daci,T. Dahms,

M. Dalchenko,L. Dobrzynski, A. Florent, R. Granier de Cassagnac,M. Haguenauer, P. Miné,C. Mironov,

I.N. Naranjo,M. Nguyen, C. Ochando, P. Paganini, D. Sabes,R. Salerno, Y. Sirois, C. Veelken, A. Zabi

LaboratoireLeprince-Ringuet,EcolePolytechnique,IN2P3-CNRS,Palaiseau,France

J.-L. Agram16,J. Andrea, D. Bloch,D. Bodin, J.-M. Brom,E.C. Chabert, C. Collard,E. Conte16, F. Drouhin16,

J.-C. Fontaine16,D. Gelé, U. Goerlach,C. Goetzmann, P. Juillot, A.-C. Le Bihan, P. Van Hove

InstitutPluridisciplinaireHubertCurien,UniversitédeStrasbourg,UniversitédeHauteAlsaceMulhouse,CNRS/IN2P3,Strasbourg,France

S. Gadrat

CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France

S. Beauceron,N. Beaupere, G. Boudoul,S. Brochet, J. Chasserat, R. Chierici,D. Contardo, P. Depasse,

H. El Mamouni,J. Fay, S. Gascon, M. Gouzevitch, B. Ille, T. Kurca, M. Lethuillier, L. Mirabito,S. Perries,

L. Sgandurra,V. Sordini, Y. Tschudi,M. Vander Donckt, P. Verdier, S. Viret

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

Z. Tsamalaidze17

InstituteofHighEnergyPhysicsandInformatization,TbilisiStateUniversity,Tbilisi,Georgia

C. Autermann,S. Beranek, B. Calpas,M. Edelhoff, L. Feld, N. Heracleous,O. Hindrichs, K. Klein,

A. Ostapchuk,A. Perieanu, F. Raupach, J. Sammet, S. Schael, D. Sprenger, H. Weber, B. Wittmer,

V. Zhukov5

RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany

M. Ata, J. Caudron,E. Dietz-Laursonn, D. Duchardt, M. Erdmann,R. Fischer,A. Güth, T. Hebbeker,

C. Heidemann,K. Hoepfner,D. Klingebiel, P. Kreuzer,M. Merschmeyer, A. Meyer,M. Olschewski,

K. Padeken,P. Papacz, H. Pieta,H. Reithler, S.A. Schmitz,L. Sonnenschein, J. Steggemann, D. Teyssier,

S. Thüer, M. Weber

RWTHAachenUniversity,III.PhysikalischesInstitutA,Aachen,Germany

V. Cherepanov, Y. Erdogan,G. Flügge, H. Geenen, M. Geisler, W. Haj Ahmad, F. Hoehle,B. Kargoll,

T. Kress,Y. Kuessel, J. Lingemann2,A. Nowack, I.M. Nugent,L. Perchalla, O. Pooth, A. Stahl

M. Aldaya Martin,I. Asin, N. Bartosik, J. Behr, W. Behrenhoff, U. Behrens,M. Bergholz18,A. Bethani,

K. Borras, A. Burgmeier,A. Cakir, L. Calligaris,A. Campbell, F. Costanza,C. Diez Pardos, S. Dooling,

T. Dorland,G. Eckerlin, D. Eckstein, G. Flucke, A. Geiser, I. Glushkov,P. Gunnellini, S. Habib,J. Hauk,

G. Hellwig,H. Jung, M. Kasemann, P. Katsas, C. Kleinwort,H. Kluge, M. Krämer,D. Krücker,

E. Kuznetsova, W. Lange, J. Leonard,K. Lipka, W. Lohmann18,B. Lutz, R. Mankel, I. Marfin,

I.-A. Melzer-Pellmann,A.B. Meyer, J. Mnich, A. Mussgiller,S. Naumann-Emme, O. Novgorodova,

F. Nowak,J. Olzem, H. Perrey, A. Petrukhin,D. Pitzl, R. Placakyte, A. Raspereza,P.M. Ribeiro Cipriano,

C. Riedl, E. Ron,M.Ö. Sahin, J. Salfeld-Nebgen,R. Schmidt18, T. Schoerner-Sadenius,N. Sen, M. Stein,

R. Walsh, C. Wissing

DeutschesElektronen-Synchrotron,Hamburg,Germany

V. Blobel, H. Enderle,J. Erfle, U. Gebbert,M. Görner, M. Gosselink, J. Haller, K. Heine, R.S. Höing,

G. Kaussen, H. Kirschenmann,R. Klanner, R. Kogler, J. Lange,I. Marchesini, T. Peiffer, N. Pietsch,

D. Rathjens, C. Sander, H. Schettler,P. Schleper, E. Schlieckau, A. Schmidt, M. Schröder, T. Schum,

M. Seidel,J. Sibille19, V. Sola, H. Stadie,G. Steinbrück, J. Thomsen, D. Troendle,L. Vanelderen

UniversityofHamburg,Hamburg,Germany

C. Barth,C. Baus, J. Berger,C. Böser, T. Chwalek, W. De Boer, A. Descroix, A. Dierlamm,M. Feindt,

M. Guthoff2,F. Hartmann2,T. Hauth2, H. Held, K.H. Hoffmann,U. Husemann, I. Katkov5,

J.R. Komaragiri, A. Kornmayer2,P. Lobelle Pardo, D. Martschei, Th. Müller, M. Niegel, A. Nürnberg,

O. Oberst,J. Ott, G. Quast, K. Rabbertz,F. Ratnikov,S. Röcker, F.-P. Schilling, G. Schott, H.J. Simonis,

F.M. Stober,R. Ulrich, J. Wagner-Kuhr, S. Wayand, T. Weiler, M. Zeise

InstitutfürExperimentelleKernphysik,Karlsruhe,Germany

G. Anagnostou, G. Daskalakis,T. Geralis,S. Kesisoglou, A. Kyriakis, D. Loukas, A. Markou, C. Markou,

E. Ntomari

InstituteofNuclearandParticlePhysics(INPP),NCSRDemokritos,AghiaParaskevi,Greece

L. Gouskos,T.J. Mertzimekis,A. Panagiotou, N. Saoulidou, E. Stiliaris

UniversityofAthens,Athens,Greece

X. Aslanoglou,I. Evangelou, G. Flouris, C. Foudas,P. Kokkas, N. Manthos, I. Papadopoulos, E. Paradas

UniversityofIoánnina,Ioánnina,Greece

G. Bencze,C. Hajdu, P. Hidas, D. Horvath20, B. Radics,F. Sikler, V. Veszpremi, G. Vesztergombi21,

A.J. Zsigmond

KFKIResearchInstituteforParticleandNuclearPhysics,Budapest,Hungary

N. Beni, S. Czellar, J. Molnar, J. Palinkas, Z. Szillasi

InstituteofNuclearResearchATOMKI,Debrecen,Hungary

J. Karancsi, P. Raics, Z.L. Trocsanyi,B. Ujvari

UniversityofDebrecen,Debrecen,Hungary

S.K. Swain22

NationalInstituteofScienceEducationandResearch,Bhubaneswar,India

S.B. Beri, V. Bhatnagar,N. Dhingra, R. Gupta, M. Kaur, M.Z. Mehta, M. Mittal, N. Nishu, L.K. Saini,

A. Sharma,J.B. Singh

Ashok Kumar,Arun Kumar, S. Ahuja,A. Bhardwaj, B.C. Choudhary,S. Malhotra, M. Naimuddin,K. Ranjan,

P. Saxena,V. Sharma, R.K. Shivpuri

UniversityofDelhi,Delhi,India

S. Banerjee, S. Bhattacharya, K. Chatterjee,S. Dutta, B. Gomber, Sa. Jain, Sh. Jain,R. Khurana,A. Modak,

S. Mukherjee,D. Roy, S. Sarkar, M. Sharan, A.P. Singh

SahaInstituteofNuclearPhysics,Kolkata,India

A. Abdulsalam,D. Dutta, S. Kailas,V. Kumar, A.K. Mohanty2,L.M. Pant, P. Shukla, A. Topkar

BhabhaAtomicResearchCentre,Mumbai,India

T. Aziz,R.M. Chatterjee, S. Ganguly,S. Ghosh, M. Guchait23,A. Gurtu24,G. Kole, S. Kumar, M. Maity25,

G. Majumder,K. Mazumdar, G.B. Mohanty, B. Parida,K. Sudhakar, N. Wickramage26

TataInstituteofFundamentalResearch–EHEP,Mumbai,India

S. Banerjee, S. Dugad

TataInstituteofFundamentalResearch–HECR,Mumbai,India

H. Arfaei27,H. Bakhshiansohi, S.M. Etesami28,A. Fahim27,H. Hesari, A. Jafari,M. Khakzad,

M. Mohammadi Najafabadi,S. Paktinat Mehdiabadi, B. Safarzadeh29,M. Zeinali

InstituteforResearchinFundamentalSciences(IPM),Tehran,Iran

M. Grunewald

UniversityCollegeDublin,Dublin,Ireland

M. Abbresciaa,b, L. Barbonea,b,C. Calabriaa,b,S.S. Chhibraa,b,A. Colaleoa,D. Creanzaa,c,

N. De Filippisa,c, M. De Palmaa,b, L. Fiorea, G. Iasellia,c, G. Maggia,c, M. Maggia,B. Marangellia,b,

S. Mya,c,S. Nuzzoa,b, N. Pacificoa, A. Pompilia,b,G. Pugliesea,c, G. Selvaggia,b,L. Silvestrisa, G. Singha,b, R. Vendittia,b, P. Verwilligena,G. Zitoa

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

G. Abbiendia,A.C. Benvenutia, D. Bonacorsia,b, S. Braibant-Giacomellia,b,L. Brigliadoria,b,

R. Campaninia,b,P. Capiluppia,b,A. Castroa,b, F.R. Cavalloa,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,2, M. Meneghellia,b,A. Montanaria, F.L. Navarriaa,b,F. Odoricia,A. Perrottaa, F. Primaveraa,b,

A.M. Rossia,b,T. Rovellia,b, G.P. Sirolia,b,N. Tosia,b, R. Travaglinia,b

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

S. Albergoa,b, M. Chiorbolia,b, S. Costaa,b, F. Giordanoa,2, R. Potenzaa,b, A. Tricomia,b, C. Tuvea,b

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

G. Barbaglia,V. Ciullia,b,C. Civininia, R. D’Alessandroa,b, E. Focardia,b,S. Frosalia,b,E. Galloa, S. Gonzia,b, V. Goria,b, P. Lenzia,b, M. Meschinia, S. Paolettia, G. Sguazzonia,A. Tropianoa,b

a

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

L. Benussi,S. Bianco, F. Fabbri, D. Piccolo

P. Fabbricatorea, R. Musenicha,S. Tosia,b

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

A. Benagliaa, F. De Guioa,b, L. Di Matteoa,b, S. Fiorendia,b,S. Gennaia,A. Ghezzia,b, P. Govonia,b, M.T. Lucchinia,b,2,S. Malvezzia,R.A. Manzonia,b,2, A. Martellia,b,2,D. Menascea,L. Moronia, M. Paganonia,b,D. Pedrinia,S. Ragazzia,b, N. Redaellia,T. Tabarelli de Fatisa,b

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

S. Buontempoa, N. Cavalloa,c, A. De Cosaa,b,F. Fabozzia,c, A.O.M. Iorioa,b,L. Listaa, S. Meolaa,d,2,

M. Merolaa, P. Paoluccia,2

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

P. Azzia,N. Bacchettaa,M. Bellatoa,D. Biselloa,b, A. Brancaa,b,R. Carlina,b, P. Checchiaa, T. Dorigoa, M. Galantia,b,2, F. Gasparinia,b, U. Gasparinia,b, P. Giubilatoa,b,F. Gonellaa, A. Gozzelinoa,

K. Kanishcheva,c,S. Lacapraraa,I. Lazzizzeraa,c,M. Margonia,b,A.T. Meneguzzoa,b, F. Montecassianoa,

J. Pazzinia,b, N. Pozzobona,b,P. Ronchesea,b, F. Simonettoa,b,E. Torassaa, M. Tosia,b,S. Vaninia,b, P. Zottoa,b, A. Zucchettaa,b,G. Zumerlea,b

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

M. Gabusia,b, S.P. Rattia,b,C. Riccardia,b,P. Vituloa,b

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

M. Biasinia,b, G.M. Bileia,L. Fanòa,b, P. Laricciaa,b, G. Mantovania,b,M. Menichellia, A. Nappia,b,†, F. Romeoa,b, A. Sahaa, A. Santocchiaa,b,A. Spieziaa,b

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

K. Androsova,30,P. Azzurria,G. Bagliesia,J. Bernardinia,T. Boccalia,G. Broccoloa,c,R. Castaldia,

R.T. D’Agnoloa,c,2,R. Dell’Orsoa,F. Fioria,c,L. Foàa,c, A. Giassia,M.T. Grippoa,30,A. Kraana,F. Ligabuea,c, T. Lomtadzea, L. Martinia,30,A. Messineoa,b,F. Pallaa,A. Rizzia,b,A.T. Serbana,P. Spagnoloa,

P. Squillaciotia,R. Tenchinia, G. Tonellia,b,A. Venturia, P.G. Verdinia, C. Vernieria,c

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

c_{ScuolaNormaleSuperiorediPisa,Pisa,Italy}

L. Baronea,b,F. Cavallaria, D. Del Rea,b,M. Diemoza, M. Grassia,b,2, E. Longoa,b, F. Margarolia,b, P. Meridiania,F. Michelia,b,S. Nourbakhsha,b, G. Organtinia,b, R. Paramattia,S. Rahatloua,b,L. Soffia,b

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

N. Amapanea,b, R. Arcidiaconoa,c,S. Argiroa,b,M. Arneodoa,c,C. Biinoa,N. Cartigliaa,S. Casassoa,b, M. Costaa,b,N. Demariaa, C. Mariottia, S. Masellia, E. Migliorea,b,V. Monacoa,b,M. Musicha,

M.M. Obertinoa,c,G. Ortonaa,b, N. Pastronea,M. Pelliccionia,2, A. Potenzaa,b,A. Romeroa,b, M. Ruspaa,c, R. Sacchia,b, A. Solanoa,b, A. Staianoa, U. Tamponia

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

S. Belfortea,V. Candelisea,b, M. Casarsaa,F. Cossuttia,2,G. Della Riccaa,b, B. Gobboa, C. La Licataa,b, M. Maronea,b, D. Montaninoa,b, A. Penzoa,A. Schizzia,b, A. Zanettia

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

S. Chang,T.Y. Kim, S.K. Nam

KangwonNationalUniversity,Chunchon,RepublicofKorea

D.H. Kim,G.N. Kim, J.E. Kim, D.J. Kong,Y.D. Oh, H. Park, D.C. Son

KyungpookNationalUniversity,Daegu,RepublicofKorea

J.Y. Kim,Zero J. Kim, S. Song

ChonnamNationalUniversity,InstituteforUniverseandElementaryParticles,Kwangju,RepublicofKorea

S. Choi, D. Gyun,B. Hong,M. Jo, H. Kim, T.J. Kim, K.S. Lee, S.K. Park,Y. Roh

KoreaUniversity,Seoul,RepublicofKorea

M. Choi,J.H. Kim, C. Park, I.C. Park, S. Park,G. Ryu

UniversityofSeoul,Seoul,RepublicofKorea

Y. Choi,Y.K. Choi,J. Goh, M.S. Kim, E. Kwon, B. Lee, J. Lee,S. Lee, H. Seo,I. Yu

SungkyunkwanUniversity,Suwon,RepublicofKorea

I. Grigelionis,A. Juodagalvis

VilniusUniversity,Vilnius,Lithuania

H. Castilla-Valdez,E. De La Cruz-Burelo, I. Heredia-de La Cruz31,R. Lopez-Fernandez, J. Martínez-Ortega,

A. Sanchez-Hernandez,L.M. Villasenor-Cendejas

CentrodeInvestigacionydeEstudiosAvanzadosdelIPN,MexicoCity,Mexico

S. Carrillo Moreno, F. Vazquez Valencia

UniversidadIberoamericana,MexicoCity,Mexico

H.A. Salazar Ibarguen

BenemeritaUniversidadAutonomadePuebla,Puebla,Mexico

E. Casimiro Linares, A. Morelos Pineda, M.A. Reyes-Santos

UniversidadAutónomadeSanLuisPotosí,SanLuisPotosí,Mexico

D. Krofcheck

UniversityofAuckland,Auckland,NewZealand

A.J. Bell,P.H. Butler, R. Doesburg, S. Reucroft, H. Silverwood

UniversityofCanterbury,Christchurch,NewZealand

M. Ahmad, M.I. Asghar,J. Butt, H.R. Hoorani, S. Khalid, W.A. Khan, T. Khurshid, S. Qazi,M.A. Shah,

M. Shoaib

NationalCentreforPhysics,Quaid-I-AzamUniversity,Islamabad,Pakistan

H. Bialkowska,B. Boimska, T. Frueboes,M. Górski, M. Kazana, K. Nawrocki, K. Romanowska-Rybinska,

NationalCentreforNuclearResearch,Swierk,Poland

G. Brona, K. Bunkowski, M. Cwiok,W. Dominik, K. Doroba, A. Kalinowski, M. Konecki,J. Krolikowski,

M. Misiura, W. Wolszczak

InstituteofExperimentalPhysics,FacultyofPhysics,UniversityofWarsaw,Warsaw,Poland

N. Almeida, P. Bargassa, A. David,P. Faccioli, P.G. Ferreira Parracho,M. Gallinaro, J. Rodrigues Antunes,

J. Seixas2, J. Varela, P. Vischia

LaboratóriodeInstrumentaçãoeFísicaExperimentaldePartículas,Lisboa,Portugal

S. Afanasiev,P. Bunin, I. Golutvin, I. Gorbunov, A. Kamenev, V. Karjavin, V. Konoplyanikov,G. Kozlov,

A. Lanev,A. Malakhov,V. Matveev, P. Moisenz, V. Palichik, V. Perelygin, S. Shmatov, N. Skatchkov,

V. Smirnov, A. Zarubin

JointInstituteforNuclearResearch,Dubna,Russia

S. Evstyukhin,V. Golovtsov, Y. Ivanov, V. Kim, P. Levchenko,V. Murzin, V. Oreshkin, I. Smirnov,

V. Sulimov, L. Uvarov, S. Vavilov, A. Vorobyev,An. Vorobyev

PetersburgNuclearPhysicsInstitute,Gatchina(St.Petersburg),Russia

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

A. Toropin

InstituteforNuclearResearch,Moscow,Russia

V. Epshteyn, M. Erofeeva, V. Gavrilov, N. Lychkovskaya,V. Popov, G. Safronov, S. Semenov, A. Spiridonov,

V. Stolin, E. Vlasov, A. Zhokin

InstituteforTheoreticalandExperimentalPhysics,Moscow,Russia

V. Andreev,M. Azarkin, I. Dremin, M. Kirakosyan, A. Leonidov, G. Mesyats, S.V. Rusakov,A. Vinogradov

P.N.LebedevPhysicalInstitute,Moscow,Russia

A. Belyaev,E. Boos, M. Dubinin7, L. Dudko, A. Ershov, A. Gribushin, V. Klyukhin, O. Kodolova,I. Lokhtin,

A. Markina,S. Obraztsov, S. Petrushanko,V. Savrin, A. Snigirev

SkobeltsynInstituteofNuclearPhysics,LomonosovMoscowStateUniversity,Moscow,Russia

I. Azhgirey,I. Bayshev,S. Bitioukov, V. Kachanov, A. Kalinin, D. Konstantinov, V. Krychkine, V. Petrov,

R. Ryutin, A. Sobol, L. Tourtchanovitch,S. Troshin, N. Tyurin, A. Uzunian,A. Volkov

StateResearchCenterofRussianFederation,InstituteforHighEnergyPhysics,Protvino,Russia

P. Adzic32, M. Djordjevic,M. Ekmedzic, D. Krpic32,J. Milosevic

UniversityofBelgrade,FacultyofPhysicsandVincaInstituteofNuclearSciences,Belgrade,Serbia

M. Aguilar-Benitez,J. Alcaraz Maestre, C. Battilana,E. Calvo, M. Cerrada,M. Chamizo Llatas2,N. Colino,

B. De La Cruz,A. Delgado Peris,D. Domínguez Vázquez, C. Fernandez Bedoya,J.P. Fernández Ramos,

A. Ferrando, J. Flix, M.C. Fouz,P. Garcia-Abia, O. Gonzalez Lopez,S. Goy Lopez, J.M. Hernandez, M.I. Josa,

G. Merino, E. Navarro De Martino,J. Puerta Pelayo, A. Quintario Olmeda, I. Redondo,L. Romero,

J. Santaolalla, M.S. Soares, C. Willmott

CentrodeInvestigacionesEnergéticasMedioambientalesyTecnológicas(CIEMAT),Madrid,Spain

C. Albajar, J.F. de Trocóniz

H. Brun, J. Cuevas,J. Fernandez Menendez, S. Folgueras, I. Gonzalez Caballero,L. Lloret Iglesias, J. Piedra Gomez

UniversidaddeOviedo,Oviedo,Spain

J.A. Brochero Cifuentes,I.J. Cabrillo, A. Calderon, S.H. Chuang, J. Duarte Campderros, M. Fernandez,

G. Gomez, J. Gonzalez Sanchez, A. Graziano,C. Jorda, A. Lopez Virto,J. Marco, R. Marco,

C. Martinez Rivero,F. Matorras, F.J. Munoz Sanchez,T. Rodrigo, A.Y. Rodríguez-Marrero,A. Ruiz-Jimeno,

L. Scodellaro,I. Vila, R. Vilar Cortabitarte

InstitutodeFísicadeCantabria(IFCA),CSIC-UniversidaddeCantabria,Santander,Spain

D. Abbaneo, E. Auffray, G. Auzinger, M. Bachtis,P. Baillon, A.H. Ball, D. Barney, J. Bendavid,J.F. Benitez,

C. Bernet8, G. Bianchi, P. Bloch,A. Bocci, A. Bonato,O. Bondu, C. Botta, H. Breuker,T. Camporesi,

G. Cerminara, T. Christiansen,J.A. Coarasa Perez, S. Colafranceschi33,D. d’Enterria, A. Dabrowski,

A. De Roeck, S. De Visscher, S. Di Guida, M. Dobson, N. Dupont-Sagorin,A. Elliott-Peisert, J. Eugster,

W. Funk, G. Georgiou, M. Giffels,D. Gigi,K. Gill, D. Giordano, M. Girone, M. Giunta,F. Glege,

R. Gomez-Reino Garrido,S. Gowdy, R. Guida, J. Hammer, M. Hansen,P. Harris, C. Hartl,A. Hinzmann,

V. Innocente, P. Janot, E. Karavakis,K. Kousouris,K. Krajczar, P. Lecoq,Y.-J. Lee, C. Lourenço,N. Magini,

M. Malberti,L. Malgeri,M. Mannelli, L. Masetti, F. Meijers, S. Mersi,E. Meschi, L. Moneta, R. Moser,

M. Mulders, P. Musella,E. Nesvold, L. Orsini, E. Palencia Cortezon,E. Perez,L. Perrozzi, A. Petrilli,

A. Pfeiffer,M. Pierini,M. Pimiä, D. Piparo, M. Plagge, G. Polese, L. Quertenmont,A. Racz, W. Reece,

G. Rolandi34,C. Rovelli35, M. Rovere, H. Sakulin, F. Santanastasio,C. Schäfer, C. Schwick,I. Segoni,

S. Sekmen,A. Sharma,P. Siegrist, P. Silva,M. Simon, P. Sphicas36,D. Spiga, M. Stoye, A. Tsirou,

G.I. Veres21,J.R. Vlimant, H.K. Wöhri, S.D. Worm37,W.D. Zeuner

CERN,EuropeanOrganizationforNuclearResearch,Geneva,Switzerland

W. Bertl,K. Deiters,W. Erdmann, K. Gabathuler,R. Horisberger, Q. Ingram, H.C. Kaestli, S. König,

D. Kotlinski,U. Langenegger, D. Renker, T. Rohe

PaulScherrerInstitut,Villigen,Switzerland

F. Bachmair, L. Bäni, P. Bortignon, M.A. Buchmann,B. Casal, N. Chanon, A. Deisher, G. Dissertori,

M. Dittmar, M. Donegà, M. Dünser, P. Eller,K. Freudenreich, C. Grab, D. Hits, P. Lecomte, W. Lustermann,

A.C. Marini,P. Martinez Ruiz del Arbol, N. Mohr,F. Moortgat, C. Nägeli38,P. Nef, F. Nessi-Tedaldi,

F. Pandolfi,L. Pape, F. Pauss,M. Peruzzi, F.J. Ronga,M. Rossini,L. Sala, A.K. Sanchez, A. Starodumov39,

B. Stieger,M. Takahashi, L. Tauscher†, A. Thea, K. Theofilatos,D. Treille, C. Urscheler, R. Wallny,

H.A. Weber

InstituteforParticlePhysics,ETHZurich,Zurich,Switzerland

C. Amsler40,V. Chiochia, C. Favaro,M. Ivova Rikova, B. Kilminster, B. Millan Mejias, P. Otiougova,

P. Robmann, H. Snoek,S. Taroni, S. Tupputi,M. Verzetti

UniversitätZürich,Zurich,Switzerland

M. Cardaci,K.H. Chen, C. Ferro, C.M. Kuo, S.W. Li, W. Lin, Y.J. Lu, R. Volpe,S.S. Yu

NationalCentralUniversity,Chung-Li,Taiwan

P. Bartalini,P. Chang, Y.H. Chang, Y.W. Chang,Y. Chao, K.F. Chen, C. Dietz, U. Grundler,W.-S. Hou,

Y. Hsiung, K.Y. Kao,Y.J. Lei, R.-S. Lu,D. Majumder, E. Petrakou,X. Shi, J.G. Shiu, Y.M. Tzeng,M. Wang

NationalTaiwanUniversity(NTU),Taipei,Taiwan

B. Asavapibhop,N. Suwonjandee

A. Adiguzel, M.N. Bakirci41, S. Cerci42,C. Dozen, I. Dumanoglu, E. Eskut, S. Girgis, G. Gokbulut,

E. Gurpinar,I. Hos, E.E. Kangal, A. Kayis Topaksu,G. Onengut43,K. Ozdemir, S. Ozturk41, A. Polatoz,

K. Sogut44,D. Sunar Cerci42,B. Tali42,H. Topakli41,M. Vergili

CukurovaUniversity,Adana,Turkey

I.V. Akin, T. Aliev,B. Bilin, S. Bilmis, M. Deniz, H. Gamsizkan, A.M. Guler,G. Karapinar45,K. Ocalan,

A. Ozpineci,M. Serin, R. Sever,U.E. Surat, M. Yalvac, M. Zeyrek

MiddleEastTechnicalUniversity,PhysicsDepartment,Ankara,Turkey

E. Gülmez,B. Isildak46,M. Kaya47,O. Kaya47,S. Ozkorucuklu48,N. Sonmez49

BogaziciUniversity,Istanbul,Turkey

H. Bahtiyar50,E. Barlas, K. Cankocak, Y.O. Günaydin51,F.I. Vardarlı, M. Yücel

IstanbulTechnicalUniversity,Istanbul,Turkey

L. Levchuk,P. Sorokin

NationalScientificCenter,KharkovInstituteofPhysicsandTechnology,Kharkov,Ukraine

J.J. Brooke,E. Clement, D. Cussans, H. Flacher,R. Frazier, J. Goldstein,M. Grimes, G.P. Heath, H.F. Heath,

L. Kreczko, S. Metson,D.M. Newbold37,K. Nirunpong, A. Poll, S. Senkin, V.J. Smith,T. Williams

UniversityofBristol,Bristol,UnitedKingdom

L. Basso52,K.W. Bell, A. Belyaev52,C. Brew, R.M. Brown, D.J.A. Cockerill, J.A. Coughlan, K. Harder,

S. Harper, J. Jackson, E. Olaiya,D. Petyt, B.C. Radburn-Smith, C.H. Shepherd-Themistocleous, I.R. Tomalin,

W.J. Womersley

RutherfordAppletonLaboratory,Didcot,UnitedKingdom

R. Bainbridge,O. Buchmuller, D. Burton,D. Colling, N. Cripps,M. Cutajar, P. Dauncey,G. Davies,

M. Della Negra, W. Ferguson,J. Fulcher, D. Futyan, A. Gilbert,A. Guneratne Bryer, G. Hall,Z. Hatherell,

J. Hays, G. Iles, M. Jarvis, G. Karapostoli, M. Kenzie,R. Lane, R. Lucas37,L. Lyons, A.-M. Magnan,

J. Marrouche, B. Mathias,R. Nandi, J. Nash, A. Nikitenko39,J. Pela, M. Pesaresi, K. Petridis,M. Pioppi53,

D.M. Raymond, S. Rogerson,A. Rose, C. Seez,P. Sharp†,A. Sparrow, A. Tapper, M. Vazquez Acosta,

T. Virdee,S. Wakefield, N. Wardle,T. Whyntie

ImperialCollege,London,UnitedKingdom

M. Chadwick, J.E. Cole, P.R. Hobson, A. Khan,P. Kyberd, D. Leggat,D. Leslie, W. Martin,I.D. Reid,

P. Symonds, L. Teodorescu, M. Turner

BrunelUniversity,Uxbridge,UnitedKingdom

J. Dittmann, K. Hatakeyama,A. Kasmi, H. Liu, T. Scarborough

BaylorUniversity,Waco,USA

O. Charaf,S.I. Cooper, C. Henderson, P. Rumerio

TheUniversityofAlabama,Tuscaloosa,USA

A. Avetisyan, T. Bose,C. Fantasia, A. Heister, P. Lawson, D. Lazic, J. Rohlf, D. Sperka, J. St. John,L. Sulak

BostonUniversity,Boston,USA

J. Alimena,S. Bhattacharya, G. Christopher,D. Cutts, Z. Demiragli,A. Ferapontov, A. Garabedian,

U. Heintz, S. Jabeen, G. Kukartsev, E. Laird,G. Landsberg, M. Luk, M. Narain, M. Segala, T. Sinthuprasith,