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Search for a pseudoscalar boson decaying into a Z boson and the 125 GeV Higgs boson in ℓ+ℓ- b anti-b final states


Academic year: 2021

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125 GeV





bb final




a r t i c l e i n f o a b s t ra c t

Articlehistory: Received18April2015

Receivedinrevisedform25June2015 Accepted7July2015

Availableonline9July2015 Editor:M.Doser Keywords: CMS Higgs 2HDM MSSM BSM

ResultsarereportedonasearchfordecaysofapseudoscalarAbosonintoaZbosonandalightscalarh boson,wheretheZbosondecaysintoapairofoppositely-chargedelectronsormuons,andthehboson decays intobb.Thesearchis basedondata fromproton–proton collisions atacenter-of-mass energy √s

=8 TeV collectedwith theCMS detector, corresponding toan integratedluminosity of 19.7 fb−1. Thehbosonisassumedtobethestandardmodel-likeHiggsbosonwithamassof125 GeV.Withno evidencefor signal,upperlimits are obtainedonthe productoftheproductioncrosssectionand the branchingfractionoftheAbosonintheZhchannel.Resultsarealsointerpretedinthecontextoftwo Higgsdoubletmodels.

©2015CERNforthebenefitoftheCMSCollaboration.PublishedbyElsevierB.V.Thisisanopenaccess articleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3.

1. Introduction

The discovery of a scalar boson at the CERN LHC [1–3] with properties in agreement with those predicted by the standard model(SM) raisesthe question ofwhethertheHiggs sector con-sistsofonlyonephysicalstate,asexpectedintheSM,orwhether additionalbosonsarealsoinvolved.

Anextension oftheSM Higgssector isprovided intwoHiggs doubletmodels(2HDM)[4],whichintroduceasecond scalar dou-bletinadditiontotheonefromtheSM.Differentformulationsof 2HDMpredict differentcouplings of the two doublets to quarks andto leptons.In Type-I 2HDM, all fermions coupleto only one Higgsdoublet, while in Type-II, up- and down-typequarks cou-pleto different doublets.One example ofa Type-II 2HDMis the minimal supersymmetric standard model [5], despite that super-symmetry is not explicitly required in 2HDM. The second Higgs doublet entails the presence of five physical states: two neutral, CP-evenstates,representingalighth andaheavyH boson;a neu-tral,CP-oddA boson;andtwochargedscalarH±bosons.The light-estscalarh isassumedtobethebosonobservedattheLHCata massof125 GeV[6–9].Ifthemassesoftheheavierbosonsareat orbelowtheTeV scale,theycanbeaccessibleattheLHC.Searches forthisextendedsectorcanbeperformedeitherbymeasuringthe valuesofthecouplingsofthediscoveredh bosontootherSM par-ticles[10–12], orvia direct searches infinal states disfavored by


theSM[13].A waytoprobethiskindofnewphysicsistherefore to search forbosons that decay into final statesthat contain an SM-likeHiggsboson.

ThispaperdescribesasearchforaheavypseudoscalarA boson that decays into a Z and an h boson, both on-shell, withthe Z bosondecayingintoapairof+− leptons ( beinge or μ),and theh bosonintobb.Inmost2HDMformulations[4],theA boson isproducedpredominantlythroughgluon–gluonfusionanddecays toon-shellZ andh bosons,providedthatthemassoftheA boson satisfiesmAmh+mZ≈216 GeV.Thischannelisexpectedtobe viableformA smallerthantwice thetopquark mass(mt), where thedecayA→Zh isgenerallydominant,but,dependingonmodel parameters,itcanalsobesensitiveatlargervaluesofmA.Theh→ bb decayhasalargebranchingfractionformostoftheparameter spacein2HDM[11].A similaranalysishasbeenrecentlypublished byATLAS[14].

The analysis strategy is to reconstruct the Z, h, and A bo-son candidates fromthevisibledecay products intheevent. The signal would manifest itself as a peak in the four-body invari-ant mass (mbb) spectrum over an expected SM continuum. Ir-reduciblebackgroundscorrespondtoZ bosonproductionwithtwo accompanying b quark jets, and tt events in the dileptonic final state.Thesebackgroundsareevaluatedandnormalizeddirectly us-ing appropriate controlregions indata.The h bosonproduced in association with a Z boson provides a contribution to the back-ground,butitdiffersfromsignalbecausethembbmassdoesnot containaresonantpeak.Signalsensitivityisimprovedby exploit-ingtheknownvalueoftheh bosonmass,usingittorescalethejet


0370-2693/©2015CERNforthebenefitoftheCMSCollaboration.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3.


momentatomatchthevalueexpectedforthedijetinvariantmass. In addition,optimal signal efficiencyandbackground rejectionis achievedusing a multivariate discriminator. Results are extracted through a two-dimensional (2D) fitto mbb andthe discrimina-toroutput;upperlimitsarepresentedontheproductofthetotal crosssectionandtheA→Zh,Z→ ,andh→bb branching frac-tionsforapseudoscalarboson,andinterpretedwithinthe2HDM.

2. CMS detector

A detailed description of the CMS detector, together with a definition of the coordinate system and kinematic variables, can be found in Ref. [15]. The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, provid-ing a magneticfield of3.8 T. The field volume contains asilicon pixelandstrip tracker,a homogeneouselectromagnetic calorime-ter(ECAL),andasamplinghadroncalorimeter(HCAL),each com-posedof abarrel andtwo endcapsections.Muonsare measured ingas-ionizationdetectorsembeddedinthesteelflux-returnyoke outsidethesolenoid.

Thesilicontrackermeasureschargedparticleswithinthe pseu-dorapidityrangeof|η|<2.5.Fornon-isolatedparticleswith trans-versemomentaof1<pT<10 GeV and|η|<1.4,thetrack resolu-tionsaretypically1.5%in pT,andbetween25–90and45–150 μm, respectively,intransverseandlongitudinalimpactparameters rel-ative to the production vertex [16]. The ECAL consists of lead tungstate crystals that provide a coverage up to |η|<3.0. The massresolutionforZ→e+e− decayswhen bothelectrons are in the ECAL barrel is 1.6%, and is 2.6% when both electrons are in theendcaps.TheHCALhasalternating layersofbrassasabsorber andplasticscintillators, and coversthe rangeof |η|<3.0,which is extendedto |η|5.2 throughforward calorimetry. Muonsare measured in the range of |η|<2.4, withdetection planes made usingthreetechnologies:drifttubes,cathode-stripchambers, and resistive-plate chambers. Matching muonsto tracks measured in thesilicontrackerprovidesa pT resolutionof1.3–2.0%formuons with20<pT<100 GeV in thebarrel andbetter than 6% inthe endcaps.

3. Data and simulation

Data used forthisanalysiswere collected usingdouble-muon and double-electron triggers, with pT thresholds set to 17 and 8 GeV for the highest and next highest pT lepton, respectively, andanisolationrequirementusedintheelectrontriggerto main-tain an acceptable rate. The analyzed events correspond to an integratedluminosity of19.7±0.5 fb−1 ofpp collisions at√s=

8 TeV[17].

SignalsamplesandSMbackgroundprocessesZ+jets,W+jets, and tt + jets or a vector boson (ttV ) are simulated using the MadGraph5.1[18] MonteCarlo(MC)generator;multijetsand di-bosons (V V, with V , V being W or Z) are generated using LO pythia6.4[19]andtheCTEQ6L[20]partondistributionfunctions (PDF).Singletopquarkproduction,andSMHiggsbosonproduction inassociation with an electroweak vector boson (V h)are gener-ated using the next-to-leading-order (NLO) powheg 1.0 [21–23] MC generator and the MSTW2008NLO PDF [24]. Parton shower-ing and hadronization are performed with pythia using the Z2∗ tune [25]. The generated MC events, including additional pp in-teractions(pileup)occurringinthebunchcrossing containingthe high-pT scatter, are processed through a full detectorsimulation basedon Geant4[26]andreconstructedwiththesamealgorithms asusedfordata.

The pseudoscalarA boson isassumed tobe produced via the gluon–gluon fusionprocess andto havea narrowwidth. The

va-lidityofthenarrow-widthapproximationisdiscussedinSection7. The branching fraction B(A→Zh) is set to 100%, and similarly onlytheZ bosondecaysintoelectronsormuons,andtheh boson decaysintoapairofbb quarks,areconsidered.Otherdecaymodes have negligible efficiencyfor passing the selections. The mass of thelightHiggsbosonissettomh=125 GeV,whilethesearchfor theA bosonisperformedinthemassrangefrom225to600 GeV, abovewhichtheefficiencytoreconstructtwoseparatejetsfromh decaybecomestoosmallbecauseofitsincreasedmomentum.

4. Event reconstruction

A global reconstruction of the event is achieved using a particle-flow (PF)technique,whichreconstructs andidentifies in-dividualparticles emerging fromeach collision usinginformation fromallCMSsubdetectors[27,28].

Electron candidates are reconstructed for |η|<2.5 by match-ingenergydepositionsintheECALwithreconstructedtracks[29]. Theidentificationreliesonamultivariatetechniquethatcombines observables sensitive to theamount ofbremsstrahlung along the electrontrajectory,thecompatibilityofthemeasuredposition, di-rection and momentum of the reconstructed track in the inner tracker,andtheenergydepositionreconstructedintheECAL clus-ter.Additionalrequirementsareimposedtoremoveelectrons pro-ducedbyphotonconversionsinthedetectormaterial.

Muons are reconstructed within |η|<2.4, combining infor-mation from both the silicon tracker and the outer muon spec-trometer[30],requiringsmallenergydepositionsinthe calorime-ters [31]. Muon candidates have to fulfill restrictive selection criteria basedonthequalityandtheimpactparameterofthetrack, aswellasonthenumberofhitsobservedinthetrackerandmuon systems.

An isolation variable is defined for each lepton through the scalarsumoverthe pT ofallPFcandidates,excluding thelepton, within a coneofR=(η)2+ (ϕ)2<0.4 aroundthe lepton direction, where ϕ is theazimuthal anglein radians, subtracting the pileupcontribution [32], andthendividing by thelepton pT. The lepton is rejected if the isolation exceeds 0.15 forelectrons and0.12formuons.

Jetsare formed fromall particles,chargedandneutral, recon-structed throughthePFalgorithm,andclusteredwiththeanti-kT algorithm[33,34]withadistanceparameterof0.5.Jetenergy cor-rections are determined from dijet and Z + jet events, and appliedtoboth dataandsimulation[35].Theimbalancein trans-versemomentumiscalculatedasthenegativeofthevectorialsum oftransversemomentaofallthePFcandidates,anditsmagnitude isdenotedasEmissT [36].

Thecombinedsecondaryvertex(CSV)btaggingalgorithm[37] is used to identify jets that originate from b quarks. This algo-rithmcombinesinformationfromtrackimpactparametersrelative totheprimaryandsecondary(displaced)verticesintoalikelihood discriminant.Twostandardworkingpointsaresetonthe discrimi-nant,correspondingtorestrictive(tight)andless-restrictive(loose) thresholdsthatprovideonaverage50%and80%btagging efficien-cies, with respective misidentification probabilities of about 0.1% and10%forlight-flavor jets,andabout5%and25%forcjets. The CSV distributionis correctedinsimulation totake intoaccount a difference atthe percentlevel inalgorithm performance fordata andsimulation.

5. Event selection

Events are required to have at least two electrons or two muons within the geometrical acceptanceregions, andto satisfy the reconstruction, identification, andisolation requirements. The


Table 1

Scale factorsfor thefour main backgrounds obtainedfromafittothecontrolregions. Re-porteduncertaintiesarestatisticalinnature.

Background Scale factor Z+jets 1.069±0.002 Z+b 0.945±0.012 Z+bb 1.008±0.020 tt 0.984±0.010

pTthresholdissetto20 GeV fortheleptonwithhighestpT,andto 10 GeV fortheleptonwithnext-highestpT.TheZ bosoncandidate is formed fromthe two highest-pT,opposite-charge, same-flavor leptons, andmusthave an invariant masslarger than 50 GeV.In addition,atleasttwo jetsare requiredwith pT>20 GeV, within

|η|<2.4, andwith angular separation relative to each lepton of R>0.5.Theh bosoncandidateisformedfromthetwojetsthat havethe highestvaluesof theb taggingdiscriminant. Additional jetsintheeventareignored.

Signal events are expected to have at least one jet b-tagged withthetight and onewith theloose CSV workingpoints;after btagging application, the contribution frompileup jets becomes negligible. The invariant masses of the two leptons and of the two jets are required to be compatiblewith those of the Z bo-son(75<m<105 GeV)andh boson(90<mbb<140 GeV),and thevalueoftheEmissT intheeventhastobecompatiblewithzero. Aftertheseselections,thesignal efficienciesrangefrom10.0% for

mA=250 GeV to20.7% formA=600 GeV.

Dedicated control regions are definedto check both the nor-malizationsanddistributions of themostimportant backgrounds byinvertingtheselectionsusedtoenhancesignal.Drell–Yan back-grounds (from qq→Z/γ→ +production) are considered separately as a function of the number of b jets, distinguishing Z+ jets(nobjets),Z+b (1bjet)andZ+bb (2bjets).The cor-responding control regions are selected by requiring 80<m< 100 GeV, EmissT <40 GeV, vetoing of dijet masses close to the Higgsboson massof 90<mj j<140 GeV, andapplyingdifferent b-taggingselections. Inthe Z+jetscontrolregion,nocutoffsare appliedonbtaggingdiscriminators.TheZ+b controlregion con-tainseventswithone bjetfulfillingthetight CSVworkingpoint, andnootherjetspassingtheloosethreshold.Eventsthatenterthe Z+bb controlregionshouldhaveatleasttwob-taggedjets,with onepassing thetight andthe otherthe looseworkingpoint.The tt controlregionis definedbyinverting them and EmissT selec-tions,droppingtherequirementofthedijetmass,andrequiringat leastonetightandonelooseb-taggedjet.

Thescalefactors thatare usedtocorrectthe normalizationof Drell–Yan and tt backgrounds, reported in Table 1, are obtained froma simultaneous likelihood fit to data andsimulation in the fourcontrolregions andare appliedinthefollowing stepsofthe analysis. Multijet contamination in control and signal regions is evaluated withdata by invertinglepton isolation criteria, andits contributionis found to be negligible. The yield of the V h, ttV , andsingle topproductionthrough thes channelare calculatedat NLO[38,39],whiletheother singletopchannelsanddibosonsare normalizedtothe measured crosssections[40–42].A mismodel-ing insimulation,observedinthecontrolregionsrelativetodata, iscorrectedby reweighting withalinearfunction theevent cen-tralitydistribution(defined asthe ratioof thesums inscalar pT andtheenergyofthetwo leptonsandtwojetsintherestframe ofthefourobjects)inallMonteCarloevents,improvingthe over-allagreementbetweensimulationanddata.

Animportantfeatureofthe signalis thatthe twobjets orig-inatefromthe decayoftheh boson,whose massisknownwith betterprecision thanthat providedby thebb invariantmass

res-Fig. 1. Simulateddistributionsformbbbefore(dottedlines)andafterthekinematic


Table 2

Summaryofsystematicuncertainties.Normalization:sourcesofsystematic uncer-taintyandtheireffectinpercentonthenormalizationofsignalandbackground distributions.Shape:sourcesofsystematicuncertaintyandtherangeoftheir ef-fectinpercentonrelativechangesmadeintheformofthebackgroundandsignal distributions.

Sources Backgrounds Signal Drell–Yan, tt Others


Control region fitting <2.4% – –

Extrapolation 2–13% – –

Lepton and trigger efficiency – 2.5% 2.5% Jet energy scale – 5.7% 3.8–0.2% Jet energy resolution – 3.2% 0.8–0.5%

b tagging – 4.9% 3.6–3.2% Unclustered energy – 1.9% 1.4–1.0% Pileup – 0.9% 1.2% PDF – 4.3% 4.0–7.9% Cross section – 9.2–15% – Integrated luminosity – 2.6% 2.6% Shape

Jet energy scale <4% <8% Jet energy resolution <2% <4%

b tagging <4% <8%

Factorization and renormalization scales <6% 6–10% Monte Carlo reweighting <15% – Monte Carlo statistics 1–4% –

olution [43]. The measured jet pT, η, and ϕ values are there-forevaried accordingto their resolution,ina kinematicfit based on Lagrange multipliers, to constrain the dijet invariant mass to

mh=125 GeV.Thefit χ2isusedinsubsequentstepsofthe anal-ysisasadiscriminantinplaceofmbb.Thekinematicfitimproves therelativefour-body invariantmassresolutionfrom6.3%to1.2% and4.0%to1.9%,respectively,forthesmallestandlargestvaluesof

mA,centeringthepeaksaroundtheir nominalvalues,asshownin

Fig. 1.TheeffectofthekinematicfitislargeratlowmA,wherethe constraint on the Higgs invariant mass has the largest contribu-tion.Althoughboththebackgroundandsignalmbbdistributions aremodifiedbythekinematicfit,thesignalsignificanceinamass windowclosetotheinvestigatedA bosonmassincreasesbya fac-toroftwoatthelowestmassandby34%atthehighestmass.The resultingjetthree-momentaareusedtoredefineallthekinematic variablesintheevent.

Discriminationofsignalfrombackgroundsisachievedthrough a multivariate discriminant. Simulated mass points are divided


Fig. 2. BDToutputsandinvariantmassdistributionsinthelow,intermediate,andhighmassregions.ThembbplotsareforBDT>0.6,weightedbyS/(S+B)ineachBDT

bin.Histogramsforsignalarenormalizedtotheexpectedexclusionlimitat95%confidencelevel.Statisticalandsystematicuncertaintiesinsimulatedsamplesareshownas well.Eithertheratio(left)orthedifference(right)betweendataandSMbackgroundisgivenatthebottomofeachpanel.


into three mass regions: low (mA=225,250, and 275 GeV), in-termediate (mA=300,325, and 350 GeV), andhigh mass (mA= 400,500, and 600 GeV). Three boosteddecision trees (BDT) [44] aretrainedseparately,oneforeachregion.TheinputsofeachBDT consistof16discriminatingvariables,selectedfromalistofmore than40variables:the pT oftheZ andh bosoncandidates,the χ2 ofthekinematicfit,thesignificanceofEmiss

T [36],thedilepton in-variantmass,theR separationandthe“twist”angle(definedas tan−1ϕ/η)betweenthetwo bjets[45],their CSV discrimina-torvalues,theflightdirectionsoftheZ bosonandofthebeamin therest frame of the A boson(cosθ∗), the decayangle ofthe Z bosonrelative toits flightdirectionintherestframeoftheZ bo-son(cosθ1),whichissensitivetothetransversepolarizationofthe Z bosonalongitsflight direction,theangleofthepullvector[46, 47]ofthehighest-pT jet,whichexploitsthecolor connection be-tweenthe two bquarks originatingfromtheh boson, thescalar sum of Emiss

T and the pT of jets and leptons in the event (ST), the number of jets with pT>20 GeV, the event centrality, and aplanarity[45].ThedistributioninBDToutputsfordata,for simu-latedsignal(S),andfortheexpectedSMbackground(B)eventsare showninFig. 2,weightingeachentryinthembbdistributionby theexpectedS/(S+B)ratiooftheBDTbininthesignal-sensitive regionwithBDT>0.6.

6. Systematic uncertainties

Thesensitivityoftheanalysisiscurrentlylimitedbythe avail-abledata,andnotbysystematicuncertainties.

Theuncertaintiesinthenormalizationsofthefourmain back-grounds(Z + jets, Z+b, Z+bb,and tt) originateboth fromthe fitsinthecontrolregionsandfromtheextrapolationtothesignal region.TheformerarereportedinTable 1,andthelatteris evalu-atedthroughasimultaneouslikelihoodfittodataandtosimulated yieldsinseveralstatisticallyindependentregions, obtainedby al-teringtheselectionsusedtodefinethefourcontrolregions.A 13% normalizationuncertaintyduetothisextrapolationisassignedto Z+jets,12% toZ+b,2.1% toZ+bb,and6.2%tott events. Nor-malizationuncertainties forother SM backgroundscorrespond to theonesontheirmeasuredortheoreticalcrosssections.

Theuncertaintiesinleptonreconstruction,identification, isola-tion,andtriggerefficienciesareevaluatedthroughspecificstudies ofeventswithmassesintheregionoftheZ peak.Uncertaintiesin backgroundorsignalnormalizationanddistributiondueto uncer-taintiesinjetenergyscaleandresolution[35]andbtaggingscale factors [37] are estimated by changing the corresponding values by±1 standarddeviation(σ).Additional systematicuncertainties affecting the normalization of backgrounds and signal from the choiceofPDF[48,49],contributionsfrompileup,EmissT fluctuations becauseof the presence ofunclustered energy in theevent, and integratedluminosity [17]are alsoconsideredintheanalysisand arereportedinTable 2(Normalization).

Resultsareextractedfromananalysisbasedonabinned like-lihoodfittothetwo-dimensional(2D)distributionofmbbversus BDT. Dependence on jet energy scale and resolution, b tagging, aswellasfactorizationandrenormalizationscales arepropagated tothe2D-templates,takingintoaccountthecorrelationsbetween thetwovariables.TheimpactofreweightingtheMonteCarlo dis-tributions isconsidered asan additionalsource ofbackgroundin modeling theuncertainty.Finally,theuncertaintyfromthelimited numberofsimulatedeventsistreatedasinRef. [50].Thesources ofsystematicuncertainty affecting theforms of the distributions aresummarizedinthefirstcolumnofTable 2(Shape).Thesecond and third columns indicate the respective ranges in the relative impact in percent, obtained by the changes implemented in the backgroundandsignalcontributions.

Fig. 3. Observedandexpected95%CLupperlimitonσAB(A→Zh→ bb)asa


sys-tematicuncertainties.Thegreenandyellowbandsarethe±1 and±2σuncertainty bandsontheexpectedlimit.(Forinterpretationofthereferencestocolorinthis figurelegend,thereaderisreferredtothewebversionofthisarticle.)

The systematicuncertainty withthe largestimpacton the ex-pectedlimitisfromthereweightingofthebackground(accounting for a 6% difference on the expected limit, depending on mA), which isfollowed by thelimitations inthe numberof simulated events (4%), and the factorization and renormalization scales (2%).Theeffectoftheothersourcesissmall(1%).

7. Results and their interpretation

Resultsareobtainedfromthecombinedsignalandbackground fit to the binned two-dimensional distribution of the four-body invariant mass mbb and the BDT output in the signal-sensitive (BDT>0.6) region. With no evidence of significant deviation from background expectations, the asymptoticmodified frequen-tistmethodis usedtodetermine thelimit atthe95% confidence level(CL)onthecontributionfromsignal,treating systematic un-certaintiesasnuisanceparametersthat areintegratedoverinthe fit[51–54].

The observed limit, as well asthe expected limit and its rel-ative ±1 and ±2σ bands ofuncertainty, are reportedas a func-tion oftheA boson mass inFig. 3 for σAB(A→Zh→ bb),i.e. the product of the cross section and the A→Zh, h→bb, and Z→  branching fractions, with=e or μ. The limits are ob-tainedby considering theA bosonproduced via thegluon–gluon fusion process in the narrow-width approximation. Interpolated mass points are obtained as in Ref. [55], and numerical values are reportedin Table 3. A signalupper limitat 95% CL isset on

σAB(A→Zh→ bb),excludingfrom10to30 fb formA nearthe kinematicthreshold,≈8 fb formA≈2mt,andupto ≈3 fb at the highend(600 GeV)oftheconsideredmassrange.Comparable lim-itshavebeenrecentlyobtainedforthesamechannelbytheATLAS Collaboration[14].Themostsignificantexcessatmbb=560 GeV hasalocalsignificanceof2.6σ,whichbecomesaglobal1.1σ sig-nificancetakingintoaccountthelook-elsewhere effect[56].

FormA>2mt,the widthof theA boson dependsstrongly on themodelparameters.Differentlimitsareprovidedbytakinginto accountthenaturalwidthoftheA boson( A)inthereconstructed

mbb,leavingtheBDTunchanged.Fig. 4showstheexclusionlimit above2mt foranaveragewidthof30 GeV,andthedependenceof theobserved limiton A formA=500 GeV.Thelocalandglobal


Table 3

Observedandexpected95%CLupperlimitsonσAB(A→Zh→ bb)asafunctionofmAinthenarrow-widthapproximation,includingstatisticalandsystematic


mA[GeV] 225 250 275 300 325 350 400 500 600

Observed [fb] 17.9 16.8 14.8 19.5 10.1 8.84 3.29 3.35 2.61 Expected [fb] 17.9 18.1 16.4 13.6 10.0 7.84 5.27 2.79 1.93

Fig. 4. Observedandexpected95%CLupperlimitonσAB(A→Zh→ bb)for A=30 GeV asafunctionofmA(top),andformA=500 GeV asafunctionofthe

widthoftheA boson(bottom).

significance at mbb=560 GeV become, respectively, 2.9σ and 1.5σ,assuming A=30 GeV.

As an independentcross-check ofthe 2D fit, thesignal is ex-tractedbyapplyingtwo complementarystrategies,basedon one-dimensionalfits.Thefirstoneconsistsoffittingthembb distribu-tion,afterselectingeventsinasignal-enrichedregionbyapplying aBDT>0.8 selection.The secondreliesonfits totheBDT distri-butions, afterselecting eventswithin the resolutionofthe signal

mbb peak. The two methods give upper limitscompatible with thosefromthe2Dfit,but10to20%lessstringent.

The results are interpreted in terms of Type-I and Type-II 2HDMformulations [4]. The B(A→Zh) and B(h→bb) branch-ing fractions and the signal cross sections are computed at next-to-next-to-leading-order (NNLO) with SuShi 1.2.0 [57] and 2hdmc 1.6.4[58],respectively, usingtheMSTW2008LO,NLO, and NNLO sets ofPDF. The B(Z→ ) branching fraction, with =e or μ, is taken from the measured value [59]. Both gluon–gluon fusionandassociatedproductionwithbquarkshavebeen

consid-Fig. 5. Observed and expected(together with ±1,2σ uncertainty bands) exclu-sionlimitforType-I(top)andType-II(bottom)models,asafunctionoftanβand cosα).Contoursarederivedfromtheprojectiononthe2HDMparameterspace forthemA=300 GeV signalhypothesis;theobservedlimitiscloseto1σ above

theexpectedlimit,asshowninFig. 3.

ered. The latter isrescaled to the fusion process, taking account ofthedifferenceinacceptanceforsignal,aswellastheefficiency for selecting dijetpairs in the presence of combinatorial contri-butions from additional b quarks in the event. The parameters used forthe models are:mh=125 GeV,mH=mH± =mA, m212=



0.1≤tanβ≤100,and−1≤cosα)≤1,usingtheconvention 0< βα<π,where tanβ and α are, respectively, the ratioof thevacuumexpectationvalues, andthemixingangle ofthe two Higgsdoublets[4].

The observed limit, together with the expected limit and its relative±1 and±2σ uncertaintybands,areshowninFig. 5, inter-pretedinType-IandType-II2HDMformA=300 GeV.A sizeable fractionof the 2HDMphase spaceis excluded at a 95% CL with respecttothepreviousCMSsearches[13].

8. Summary

A search is presented for new physics in the extended Higgs sector, in signaturesexpected fromdecays of a pseudoscalar bo-son A into a Z bosonand anSM-like h boson,withthe Z boson decayinginto+− (beingeithere or μ)andtheh bosoninto bb.Differenttechniquesareemployedtoincreasethesensitivityto signal,exploitingthepresenceofthethreeresonancesA,Z,andh todiscriminateagainststandard modelbackgrounds.Upperlimits ata95%CLaresetontheproductofanarrowpseudoscalarboson crosssection andbranchingfraction σAB(A→Zh→ bb),which exclude30to3 fb at thelow andhighendsofthe 250–600 GeV massrange.Results arealsopresentedasafunctionofthewidth oftheA boson. Interpretationsare giveninthecontext ofType-I andType-II 2HDM formulations,thereby reducing the parameter spaceforextensionsofthestandardmodel.


WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the technicalandadministrativestaffs atCERN andatother CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcentersand personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythecomputinginfrastructure essential toour analyses. Finally, we acknowledge the enduring support for the construc-tionandoperationofthe LHCandtheCMSdetectorprovided by thefollowingfundingagencies:BMWFWandFWF(Austria);FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES(Bulgaria);CERN;CAS,MOST,andNSFC(China);COLCIENCIAS (Colombia);MSESandCSF(Croatia);RPF(Cyprus);MoER,ERCIUT andERDF(Estonia); AcademyofFinland,MEC, andHIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic ofKorea); LAS (Lithuania);MOE andUM (Malaysia); CINVESTAV, CONACYT,SEP,andUASLP-FAI(Mexico);MBIE(NewZealand);PAEC (Pakistan);MSHEandNSC(Poland);FCT(Portugal);JINR(Dubna); MON,RosAtom,RASandRFBR(Russia);MESTD(Serbia);SEIDIand CPAN(Spain);SwissFundingAgencies(Switzerland);MST(Taipei); ThEPCenter,IPST,STARandNSTDA(Thailand);TÜBITAK and TAEK (Turkey);NASUandSFFR(Ukraine);STFC (UnitedKingdom);DOE andNSF(USA).

Individuals have received support from the Marie-Curie pro-gramandtheEuropeanResearchCouncilandEPLANET(European Union); the Leventis Foundation; the A.P. Sloan Foundation; the AlexandervonHumboldt Foundation;theBelgianFederal Science Policy Office; the Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); theMinistryofEducation, YouthandSports (MEYS)ofthe Czech Republic;theCouncilofScienceandIndustrialResearch,India;the HOMING PLUSprogram ofthe Foundation forPolish Science, co-financed from European Union, Regional Development Fund; the

CompagniadiSanPaolo(Torino); theConsorzioperlaFisica (Tri-este); MIUR project 20108T4XTM (Italy); the Thalis and Aristeia programs cofinanced by EU-ESF and the Greek NSRF; and the National Priorities Research Program by Qatar National Research Fund.


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J.-L. Agram17,J. Andrea, A. Aubin,D. Bloch, J.-M. Brom,M. Buttignol, E.C. Chabert,N. Chanon, C. Collard, E. Conte17,J.-C. Fontaine17, D. Gelé, U. Goerlach,C. Goetzmann, A.-C. Le Bihan, J.A. Merlin2,K. Skovpen, P. Van Hove

InstitutPluridisciplinaireHubertCurien,UniversitédeStrasbourg,UniversitédeHauteAlsaceMulhouse,CNRS/IN2P3,Strasbourg,France S. Gadrat


S. Beauceron,N. Beaupere, C. Bernet8, G. Boudoul2,E. Bouvier, S. Brochet, C.A. Carrillo Montoya, J. Chasserat, R. Chierici,D. Contardo, B. Courbon, P. Depasse, H. El Mamouni, J. Fan, J. Fay, S. Gascon, M. Gouzevitch,B. Ille, I.B. Laktineh,M. Lethuillier, L. Mirabito,A.L. Pequegnot, S. Perries,

J.D. Ruiz Alvarez,D. Sabes,L. Sgandurra, V. Sordini, M. Vander Donckt, P. Verdier,S. Viret, H. Xiao UniversitédeLyon,UniversitéClaudeBernardLyon1,CNRS-IN2P3,InstitutdePhysiqueNucléairedeLyon,Villeurbanne,France

Z. Tsamalaidze10


C. Autermann,S. Beranek, M. Edelhoff,L. Feld, A. Heister, M.K. Kiesel, K. Klein, M. Lipinski, A. Ostapchuk, M. Preuten,F. Raupach, J. Sammet, S. Schael, J.F. Schulte,T. Verlage, H. Weber, B. Wittmer, V. Zhukov5 RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany

M. Ata, M. Brodski,E. Dietz-Laursonn, D. Duchardt, M. Endres,M. Erdmann, S. Erdweg, T. Esch, R. Fischer,A. Güth, T. Hebbeker,C. Heidemann, K. Hoepfner, D. Klingebiel,S. Knutzen, P. Kreuzer, M. Merschmeyer,A. Meyer, P. Millet,M. Olschewski, K. Padeken, P. Papacz,T. Pook, M. Radziej, H. Reithler,M. Rieger, L. Sonnenschein, D. Teyssier,S. Thüer


V. Cherepanov, Y. Erdogan,G. Flügge, H. Geenen, M. Geisler, W. Haj Ahmad, F. Hoehle,B. Kargoll, T. Kress,Y. Kuessel, A. Künsken, J. Lingemann2,A. Nehrkorn, A. Nowack, I.M. Nugent,C. Pistone, O. Pooth,A. Stahl


M. Aldaya Martin,I. Asin, N. Bartosik, O. Behnke,U. Behrens, A.J. Bell,K. Borras, A. Burgmeier, A. Cakir, L. Calligaris,A. Campbell, S. Choudhury, F. Costanza, C. Diez Pardos,G. Dolinska, S. Dooling,T. Dorland, G. Eckerlin,D. Eckstein, T. Eichhorn, G. Flucke,E. Gallo, J. Garay Garcia, A. Geiser, A. Gizhko,

P. Gunnellini, J. Hauk, M. Hempel18,H. Jung, A. Kalogeropoulos, O. Karacheban18, M. Kasemann, P. Katsas, J. Kieseler, C. Kleinwort,I. Korol, W. Lange, J. Leonard,K. Lipka, A. Lobanov, W. Lohmann18, R. Mankel, I. Marfin18,I.-A. Melzer-Pellmann, A.B. Meyer, G. Mittag, J. Mnich, A. Mussgiller,

S. Naumann-Emme,A. Nayak,E. Ntomari, H. Perrey,D. Pitzl, R. Placakyte, A. Raspereza,

P.M. Ribeiro Cipriano,B. Roland, M.Ö. Sahin,J. Salfeld-Nebgen, P. Saxena, T. Schoerner-Sadenius, M. Schröder,C. Seitz, S. Spannagel, K.D. Trippkewitz, C. Wissing


V. Blobel, M. Centis Vignali, A.R. Draeger,J. Erfle, E. Garutti,K. Goebel, D. Gonzalez, M. Görner,J. Haller, M. Hoffmann,R.S. Höing,A. Junkes, R. Klanner, R. Kogler, T. Lapsien, T. Lenz, I. Marchesini,D. Marconi, D. Nowatschin, J. Ott, F. Pantaleo2,T. Peiffer, A. Perieanu, N. Pietsch,J. Poehlsen, D. Rathjens,C. Sander, H. Schettler,P. Schleper, E. Schlieckau, A. Schmidt, M. Seidel, V. Sola,H. Stadie, G. Steinbrück, H. Tholen, D. Troendle,E. Usai, L. Vanelderen, A. Vanhoefer


M. Akbiyik, C. Barth, C. Baus,J. Berger, C. Böser,E. Butz, T. Chwalek, F. Colombo, W. De Boer, A. Descroix, A. Dierlamm, M. Feindt,F. Frensch, M. Giffels, A. Gilbert,F. Hartmann2,U. Husemann, F. Kassel2,

I. Katkov5, A. Kornmayer2, P. Lobelle Pardo, M.U. Mozer, T. Müller,Th. Müller, M. Plagge, G. Quast, K. Rabbertz,S. Röcker, F. Roscher, H.J. Simonis,F.M. Stober, R. Ulrich, J. Wagner-Kuhr,S. Wayand, T. Weiler, C. Wöhrmann, R. Wolf


G. Anagnostou, G. Daskalakis,T. Geralis,V.A. Giakoumopoulou, A. Kyriakis, D. Loukas, A. Markou, A. Psallidas, I. Topsis-Giotis


A. Agapitos, S. Kesisoglou, A. Panagiotou, N. Saoulidou, E. Tziaferi UniversityofAthens,Athens,Greece

I. Evangelou, G. Flouris,C. Foudas, P. Kokkas, N. Loukas, N. Manthos, I. Papadopoulos,E. Paradas, J. Strologas


G. Bencze,C. Hajdu, A. Hazi,P. Hidas, D. Horvath19,F. Sikler, V. Veszpremi, G. Vesztergombi20, A.J. Zsigmond


N. Beni, S. Czellar, J. Karancsi21,J. Molnar, J. Palinkas, Z. Szillasi InstituteofNuclearResearchATOMKI,Debrecen,Hungary

M. Bartók22,A. Makovec, P. Raics, Z.L. Trocsanyi UniversityofDebrecen,Debrecen,Hungary

P. Mal, K. Mandal, N. Sahoo, S.K. Swain NationalInstituteofScienceEducationandResearch,Bhubaneswar,India

S. Bansal, S.B. Beri,V. Bhatnagar, R. Chawla, R. Gupta,U. Bhawandeep, A.K. Kalsi,A. Kaur, M. Kaur, R. Kumar,A. Mehta, M. Mittal, N. Nishu, J.B. Singh, G. Walia


Ashok Kumar, Arun Kumar, A. Bhardwaj,B.C. Choudhary, R.B. Garg,A. Kumar, S. Malhotra, M. Naimuddin,K. Ranjan, R. Sharma,V. Sharma


S. Banerjee, S. Bhattacharya, K. Chatterjee,S. Dey, S. Dutta, Sa. Jain, Sh. Jain,R. Khurana, N. Majumdar, A. Modak, K. Mondal, S. Mukherjee,S. Mukhopadhyay, A. Roy, D. Roy, S. Roy Chowdhury, S. Sarkar, M. Sharan


A. Abdulsalam, R. Chudasama, D. Dutta, V. Jha, V. Kumar, A.K. Mohanty2, L.M. Pant,P. Shukla, A. Topkar BhabhaAtomicResearchCentre,Mumbai,India

T. Aziz, S. Banerjee, S. Bhowmik23,R.M. Chatterjee, R.K. Dewanjee, S. Dugad, S. Ganguly,S. Ghosh, M. Guchait,A. Gurtu24,G. Kole, S. Kumar, B. Mahakud, M. Maity23, G. Majumder, K. Mazumdar, S. Mitra, G.B. Mohanty, B. Parida, T. Sarkar23,K. Sudhakar, N. Sur, B. Sutar, N. Wickramage25 TataInstituteofFundamentalResearch,Mumbai,India


S. Sharma


H. Bakhshiansohi,H. Behnamian,S.M. Etesami26, A. Fahim27, R. Goldouzian, M. Khakzad,

M. Mohammadi Najafabadi,M. Naseri, S. Paktinat Mehdiabadi, F. Rezaei Hosseinabadi, B. Safarzadeh28, M. Zeinali

InstituteforResearchinFundamentalSciences(IPM),Tehran,Iran M. Felcini,M. Grunewald


M. Abbresciaa,b, C. Calabriaa,b, C. Caputoa,b, S.S. Chhibraa,b, A. Colaleoa, D. Creanzaa,c,L. Cristellaa,b, N. De Filippisa,c,M. De Palmaa,b,L. Fiorea,G. Iasellia,c,G. Maggia,c,M. Maggia, G. Minielloa,b, S. Mya,c, S. Nuzzoa,b, A. Pompilia,b, G. Pugliesea,c,R. Radognaa,b,2, A. Ranieria,G. Selvaggia,b,A. Sharmaa,

L. Silvestrisa,2,R. Vendittia,b,P. Verwilligena

aINFNSezionediBari,Bari,Italy bUniversitàdiBari,Bari,Italy cPolitecnicodiBari,Bari,Italy

G. Abbiendia,C. Battilana, 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,G. Codispotia,b, M. Cuffiania,b,

G.M. Dallavallea,F. Fabbria,A. Fanfania,b,D. Fasanellaa,b, P. Giacomellia, C. Grandia, L. Guiduccia,b, S. Marcellinia, G. Masettia,A. Montanaria,F.L. Navarriaa,b,A. Perrottaa,A.M. Rossia,b,T. Rovellia,b, G.P. Sirolia,b,N. Tosia,b, R. Travaglinia,b

aINFNSezionediBologna,Bologna,Italy bUniversitàdiBologna,Bologna,Italy

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

aINFNSezionediCatania,Catania,Italy bUniversitàdiCatania,Catania,Italy cCSFNSM,Catania,Italy

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

aINFNSezionediFirenze,Firenze,Italy bUniversitàdiFirenze,Firenze,Italy

L. Benussi,S. Bianco, F. Fabbri, D. Piccolo INFNLaboratoriNazionalidiFrascati,Frascati,Italy

V. Calvellia,b, F. Ferroa, M. Lo Veterea,b, E. Robuttia,S. Tosia,b

aINFNSezionediGenova,Genova,Italy bUniversitàdiGenova,Genova,Italy

M.E. Dinardoa,b, S. Fiorendia,b, S. Gennaia,2, R. Gerosaa,b, A. Ghezzia,b,P. Govonia,b, M.T. Lucchinia,b,2, S. Malvezzia, R.A. Manzonia,b, B. Marzocchia,b,2,D. Menascea,L. Moronia,M. Paganonia,b, D. Pedrinia, S. Ragazzia,b,N. Redaellia,T. Tabarelli de Fatisa,b

aINFNSezionediMilano-Bicocca,Milano,Italy bUniversitàdiMilano-Bicocca,Milano,Italy

S. Buontempoa, N. Cavalloa,c,S. Di Guidaa,d,2, M. Espositoa,b, F. Fabozzia,c,A.O.M. Iorioa,b, G. Lanzaa, L. Listaa,S. Meolaa,d,2,M. Merolaa,P. Paoluccia,2,C. Sciaccaa,b,F. Thyssen

aINFNSezionediNapoli,Napoli,Italy bUniversitàdiNapoli‘FedericoII’,Napoli,Italy cUniversitàdellaBasilicata,Potenza,Italy dUniversitàG.Marconi,Roma,Italy


P. Azzia,2, N. Bacchettaa, D. Biselloa,b,A. Brancaa,b, R. Carlina,b,A. Carvalho Antunes De Oliveiraa,b, P. Checchiaa,M. Dall’Ossoa,b,T. Dorigoa,F. Gasparinia,b,U. Gasparinia,b, A. Gozzelinoa,

K. Kanishcheva,c,S. Lacapraraa,M. Margonia,b,A.T. Meneguzzoa,b, J. Pazzinia,b, N. Pozzobona,b, P. Ronchesea,b,F. Simonettoa,b, E. Torassaa,M. Tosia,b, S. Vaninia,b, M. Zanetti,P. Zottoa,b, A. Zucchettaa,b,G. Zumerlea,b

aINFNSezionediPadova,Padova,Italy bUniversitàdiPadova,Padova,Italy cUniversitàdiTrento,Trento,Italy

A. Braghieria,M. Gabusia,b, A. Magnania,S.P. Rattia,b, V. Rea, C. Riccardia,b,P. Salvinia,I. Vaia, P. Vituloa,b

aINFNSezionediPavia,Pavia,Italy bUniversitàdiPavia,Pavia,Italy

L. Alunni Solestizia,b,M. Biasinia,b, G.M. Bileia,D. Ciangottinia,b,2, L. Fanòa,b,P. Laricciaa,b, G. Mantovania,b,M. Menichellia, A. Sahaa, A. Santocchiaa,b,A. Spieziaa,b,2

aINFNSezionediPerugia,Perugia,Italy bUniversitàdiPerugia,Perugia,Italy

K. Androsova,29,P. Azzurria,G. Bagliesia,J. Bernardinia,T. Boccalia,G. Broccoloa,c,R. Castaldia, M.A. Cioccia,29, R. Dell’Orsoa,S. Donatoa,c,2, G. Fedi,L. Foàa,c,†,A. Giassia, M.T. Grippoa,29,

F. Ligabuea,c,T. Lomtadzea,L. Martinia,b,A. Messineoa,b,F. Pallaa, A. Rizzia,b, A. Savoy-Navarroa,30, A.T. Serbana,P. Spagnoloa,P. Squillaciotia,29,R. Tenchinia, G. Tonellia,b,A. Venturia, P.G. Verdinia

aINFNSezionediPisa,Pisa,Italy bUniversitàdiPisa,Pisa,Italy


L. Baronea,b,F. Cavallaria, G. D’imperioa,b,D. Del Rea,b,M. Diemoza, S. Gellia,b,C. Jordaa,E. Longoa,b, F. Margarolia,b,P. Meridiania,F. Michelia,b,G. Organtinia,b, R. Paramattia,F. Preiatoa,b, S. Rahatloua,b, C. Rovellia,F. Santanastasioa,b,L. Soffia,b, P. Traczyka,b,2

aINFNSezionediRoma,Roma,Italy bUniversitàdiRoma,Roma,Italy

N. Amapanea,b, R. Arcidiaconoa,c,S. Argiroa,b,M. Arneodoa,c,R. Bellana,b, C. Biinoa, N. Cartigliaa, S. Casassoa,b, M. Costaa,b,R. Covarellia,b, A. Deganoa,b, N. Demariaa,L. Fincoa,b,2, B. Kiania,b, C. Mariottia, S. Masellia, E. Migliorea,b,V. Monacoa,b,M. Musicha, M.M. Obertinoa,c, L. Pachera,b, N. Pastronea,M. Pelliccionia, G.L. Pinna Angionia,b,A. Romeroa,b, M. Ruspaa,c, R. Sacchia,b, A. Solanoa,b, A. Staianoa, U. Tamponia

aINFNSezionediTorino,Torino,Italy bUniversitàdiTorino,Torino,Italy


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

aINFNSezionediTrieste,Trieste,Italy bUniversitàdiTrieste,Trieste,Italy

S. Chang, A. Kropivnitskaya,S.K. Nam KangwonNationalUniversity,Chunchon,RepublicofKorea

D.H. Kim,G.N. Kim, M.S. Kim,D.J. Kong, S. Lee, Y.D. Oh,A. Sakharov, D.C. Son KyungpookNationalUniversity,Daegu,RepublicofKorea

H. Kim,T.J. Kim, M.S. Ryu ChonbukNationalUniversity,Jeonju,RepublicofKorea


S. Song


S. Choi, Y. Go,D. Gyun, B. Hong,M. Jo, H. Kim,Y. Kim, B. Lee, K. Lee,K.S. Lee, S. Lee, S.K. Park,Y. Roh KoreaUniversity,Seoul,RepublicofKorea

H.D. Yoo


M. Choi,J.H. Kim, J.S.H. Lee, I.C. Park, G. Ryu UniversityofSeoul,Seoul,RepublicofKorea

Y. Choi,Y.K. Choi,J. Goh, D. Kim, E. Kwon, J. Lee, I. Yu SungkyunkwanUniversity,Suwon,RepublicofKorea

A. Juodagalvis,J. Vaitkus VilniusUniversity,Vilnius,Lithuania

Z.A. Ibrahim, J.R. Komaragiri, M.A.B. Md Ali31, F. Mohamad Idris,W.A.T. Wan Abdullah NationalCentreforParticlePhysics,UniversitiMalaya,KualaLumpur,Malaysia

E. Casimiro Linares, H. Castilla-Valdez,E. De La Cruz-Burelo, I. Heredia-de La Cruz32, A. Hernandez-Almada,R. Lopez-Fernandez, G. Ramirez Sanchez, A. Sanchez-Hernandez CentrodeInvestigacionydeEstudiosAvanzadosdelIPN,MexicoCity,Mexico

S. Carrillo Moreno, F. Vazquez Valencia UniversidadIberoamericana,MexicoCity,Mexico

S. Carpinteyro, I. Pedraza, H.A. Salazar Ibarguen BenemeritaUniversidadAutonomadePuebla,Puebla,Mexico

A. Morelos Pineda

UniversidadAutónomadeSanLuisPotosí,SanLuisPotosí,Mexico D. Krofcheck

UniversityofAuckland,Auckland,NewZealand P.H. Butler,S. Reucroft


A. Ahmad, M. Ahmad, Q. Hassan,H.R. Hoorani, W.A. Khan,T. Khurshid, M. Shoaib NationalCentreforPhysics,Quaid-I-AzamUniversity,Islamabad,Pakistan

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


G. Brona,K. Bunkowski, K. Doroba, A. Kalinowski, M. Konecki,J. Krolikowski, M. Misiura, M. Olszewski, M. Walczak


P. Bargassa,C. Beirão Da Cruz E Silva, A. Di Francesco, P. Faccioli, P.G. Ferreira Parracho,M. Gallinaro, L. Lloret Iglesias,F. Nguyen, J. Rodrigues Antunes, J. Seixas,O. Toldaiev, D. Vadruccio, J. Varela, P. Vischia LaboratóriodeInstrumentaçãoeFísicaExperimentaldePartículas,Lisboa,Portugal

S. Afanasiev,P. Bunin,M. Gavrilenko, I. Golutvin,I. Gorbunov, A. Kamenev, V. Karjavin,V. Konoplyanikov, A. Lanev,A. Malakhov,V. Matveev33, P. Moisenz, V. Palichik,V. Perelygin, S. Shmatov, S. Shulha,

N. Skatchkov, V. Smirnov,T. Toriashvili34,A. Zarubin JointInstituteforNuclearResearch,Dubna,Russia

V. Golovtsov, Y. Ivanov, V. Kim35,E. Kuznetsova, P. Levchenko, V. Murzin, V. Oreshkin, I. Smirnov, V. Sulimov, L. Uvarov, S. Vavilov, A. Vorobyev


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


V. Epshteyn, V. Gavrilov, N. Lychkovskaya,V. Popov, I. Pozdnyakov, G. Safronov, A. Spiridonov,E. Vlasov, A. Zhokin


V. Andreev,M. Azarkin36, I. Dremin36,M. Kirakosyan, A. Leonidov36, G. Mesyats,S.V. Rusakov, A. Vinogradov


A. Baskakov,A. Belyaev, E. Boos,V. Bunichev, M. Dubinin37,L. Dudko, A. Ershov, V. Klyukhin, O. Kodolova,I. Lokhtin, I. Myagkov,S. Obraztsov, S. Petrushanko,V. Savrin, A. Snigirev


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. Adzic38, M. Ekmedzic,J. Milosevic,V. Rekovic UniversityofBelgrade,FacultyofPhysicsandVincaInstituteofNuclearSciences,Belgrade,Serbia

J. Alcaraz Maestre, E. Calvo,M. Cerrada,M. Chamizo Llatas, N. Colino, B. De La Cruz,A. Delgado Peris, D. Domínguez Vázquez, A. Escalante Del Valle, C. Fernandez Bedoya,J.P. Fernández Ramos, J. Flix, M.C. Fouz,P. Garcia-Abia, O. Gonzalez Lopez,S. Goy Lopez, J.M. Hernandez, M.I. Josa,

E. Navarro De Martino,A. Pérez-Calero Yzquierdo, J. Puerta Pelayo, A. Quintario Olmeda, I. Redondo, L. Romero,M.S. Soares

CentrodeInvestigacionesEnergéticasMedioambientalesyTecnológicas(CIEMAT),Madrid,Spain C. Albajar, J.F. de Trocóniz, M. Missiroli, D. Moran UniversidadAutónomadeMadrid,Madrid,Spain

H. Brun, J. Cuevas,J. Fernandez Menendez, S. Folgueras, I. Gonzalez Caballero, E. Palencia Cortezon, J.M. Vizan Garcia


J.A. Brochero Cifuentes,I.J. Cabrillo, A. Calderon, J.R. Castiñeiras De Saa, J. Duarte Campderros,

M. Fernandez,G. Gomez, A. Graziano, A. Lopez Virto, J. Marco,R. Marco, C. Martinez Rivero,F. Matorras, F.J. Munoz Sanchez,J. Piedra Gomez, T. Rodrigo, A.Y. Rodríguez-Marrero, A. Ruiz-Jimeno, L. Scodellaro, I. Vila, R. Vilar Cortabitarte


D. Abbaneo, E. Auffray, G. Auzinger, M. Bachtis,P. Baillon, A.H. Ball, D. Barney, A. Benaglia,J. Bendavid, L. Benhabib,J.F. Benitez, G.M. Berruti,G. Bianchi, P. Bloch, A. Bocci, A. Bonato, C. Botta, H. Breuker, T. Camporesi, G. Cerminara, S. Colafranceschi39,M. D’Alfonso, D. d’Enterria, A. Dabrowski,V. Daponte, A. David,M. De Gruttola, F. De Guio, A. De Roeck, S. De Visscher, E. Di Marco, M. Dobson, M. Dordevic, N. Dupont-Sagorin,A. Elliott-Peisert, J. Eugster,G. Franzoni, W. Funk, D. Gigi,K. Gill, D. Giordano, M. Girone,F. Glege, R. Guida, S. Gundacker, M. Guthoff, J. Hammer, M. Hansen,P. Harris, J. Hegeman, V. Innocente, P. Janot, H. Kirschenmann,M.J. Kortelainen, K. Kousouris,K. Krajczar, P. Lecoq,C. Lourenço, N. Magini,L. Malgeri,M. Mannelli, J. Marrouche, A. Martelli,L. Masetti, F. Meijers, S. Mersi,E. Meschi, F. Moortgat,S. Morovic, M. Mulders, M.V. Nemallapudi, H. Neugebauer,S. Orfanelli, L. Orsini, L. Pape, E. Perez,A. Petrilli, G. Petrucciani, A. Pfeiffer,D. Piparo, A. Racz,G. Rolandi40,M. Rovere, M. Ruan, H. Sakulin,C. Schäfer, C. Schwick,A. Sharma,P. Silva, M. Simon, P. Sphicas41, D. Spiga,J. Steggemann, B. Stieger,M. Stoye, Y. Takahashi, D. Treille, A. Tsirou,G.I. Veres20,N. Wardle, H.K. Wöhri,

A. Zagozdzinska42,W.D. Zeuner


W. Bertl,K. Deiters,W. Erdmann, R. Horisberger, Q. Ingram,H.C. Kaestli, D. Kotlinski, U. Langenegger, T. Rohe


F. Bachmair, L. Bäni, L. Bianchini, M.A. Buchmann,B. Casal, G. Dissertori, M. Dittmar, M. Donegà, M. Dünser,P. Eller,C. Grab, C. Heidegger, D. Hits,J. Hoss, G. Kasieczka, W. Lustermann, B. Mangano, A.C. Marini,M. Marionneau, P. Martinez Ruiz del Arbol, M. Masciovecchio, D. Meister, N. Mohr,

P. Musella,F. Nessi-Tedaldi, F. Pandolfi,J. Pata, F. Pauss, L. Perrozzi,M. Peruzzi,M. Quittnat, M. Rossini, A. Starodumov43,M. Takahashi, V.R. Tavolaro, K. Theofilatos, R. Wallny, H.A. Weber


T.K. Aarrestad, C. Amsler44, M.F. Canelli,V. Chiochia,A. De Cosa, C. Galloni, A. Hinzmann, T. Hreus, B. Kilminster,C. Lange, J. Ngadiuba, D. Pinna,P. Robmann, F.J. Ronga,D. Salerno, S. Taroni, Y. Yang UniversitätZürich,Zurich,Switzerland

M. Cardaci,K.H. Chen, T.H. Doan, C. Ferro,M. Konyushikhin, C.M. Kuo, W. Lin, Y.J. Lu, R. Volpe, S.S. Yu NationalCentralUniversity,Chung-Li,Taiwan

P. Chang, Y.H. Chang,Y.W. Chang, Y. Chao,K.F. Chen, P.H. Chen, C. Dietz, F. Fiori, U. Grundler,W.-S. Hou, Y. Hsiung, Y.F. Liu,R.-S. Lu, M. Miñano Moya,E. Petrakou, J.f. Tsai, Y.M. Tzeng,R. Wilken


B. Asavapibhop,K. Kovitanggoon, G. Singh, N. Srimanobhas, N. Suwonjandee ChulalongkornUniversity,FacultyofScience,DepartmentofPhysics,Bangkok,Thailand

A. Adiguzel, S. Cerci45,C. Dozen, S. Girgis, G. Gokbulut, Y. Guler,E. Gurpinar, I. Hos, E.E. Kangal46, A. Kayis Topaksu,G. Onengut47, K. Ozdemir48,S. Ozturk49, B. Tali45, H. Topakli49, M. Vergili, C. Zorbilmez


I.V. Akin,B. Bilin, S. Bilmis, B. Isildak50,G. Karapinar51,U.E. Surat, M. Yalvac, M. Zeyrek MiddleEastTechnicalUniversity,PhysicsDepartment,Ankara,Turkey


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