Searches for a heavy scalar boson H decaying to a pair of 125 GeV Higgs bosons hh or for a heavy pseudoscalar boson A decaying to Zh, in the final states with h -> tau tau

UNIVERSIDADE ESTADUAL DE CAMPINAS

SISTEMA DE BIBLIOTECAS DA UNICAMP

REPOSITÓRIO DA PRODUÇÃO CIENTIFICA E INTELECTUAL DA UNICAMP

Versão do arquivo anexado / Version of attached file:

Versão do Editor / Published Version

Mais informações no site da editora / Further information on publisher's website:

https://www.sciencedirect.com/science/article/pii/S0370269316000757

DOI: 10.1016/j.physletb.2016.01.056

Direitos autorais / Publisher's copyright statement:

©2016

by Elsevier. All rights reserved.

DIRETORIA DE TRATAMENTO DA INFORMAÇÃO

Cidade Universitária Zeferino Vaz Barão Geraldo

CEP 13083-970 – Campinas SP

Fone: (19) 3521-6493

http://www.repositorio.unicamp.br

Searches

for

a

heavy

scalar

boson

H

decaying

to

a

pair

of

125 GeV

Higgs

bosons

hh

or

for

a

heavy

pseudoscalar

boson A

decaying

to Zh,

in

the

final

states

with

h

→

τ τ

.

CMS

Collaboration



CERN,Switzerland

a

r

t

i

c

l

e

i

n

f

o

a

b

s

t

r

a

c

t

Articlehistory: Received5October2015

Receivedinrevisedform10January2016 Accepted26January2016

Availableonline9February2016 Editor:M.Doser Keywords: CMS Physics MSSM τ Higgs

AsearchforaheavyscalarbosonHdecayingintoapairoflighterstandard-model-like125 GeVHiggs bosons hh andasearchforaheavypseudoscalarboson AdecayingintoaZandanhbosonarepresented. The searches are performedon adata set corresponding toan integrated luminosity of19.7 fb−1 _of

pp collisiondataatacentre-of-massenergyof8 TeV,collectedbyCMSin2012.A finalstateconsisting oftwo

τ

leptonsandtwobjetsisusedtosearchfortheH→hh decay.A finalstateconsistingoftwo

τ

leptonsfromtheh bosondecay,andtwoadditionalleptonsfromtheZ bosondecay,isusedtosearch forthedecayA_→Zh.Theresultsareinterpretedinthecontextoftwo-Higgs-doubletmodels.Noexcess isfoundabovethestandardmodelexpectationandupperlimitsaresetontheheavybosonproduction crosssectionsinthemassranges260<mH<350 GeV and220<mA<350 GeV.

©2016CERNforthebenefitoftheCMSCollaboration.PublishedbyElsevierB.V.Thisisanopenaccess articleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

1. Introduction

ThediscoveryofadditionalHiggsbosonsattheLHCwould pro-vide directevidence ofphysics beyondthe standardmodel (SM). ThereareseveraltypesofmodelsthatrequiretwoHiggsdoublets [1–3].Forexample theminimal supersymmetricextension ofthe SM(MSSM)requiresthe introductionofanadditionalHiggs dou-blet,whereoneHiggsdoublet couplestoup-typequarksandthe othertodown-typequarks[4–11].Thisleads tothepredictionof fiveHiggsparticles:onelightandoneheavyCP-evenHiggsboson, handH,oneCP-oddHiggsbosonA,andtwochargedHiggsbosons H±[2,12].Themassesandcouplingsofthesebosonsare interre-latedand,attreelevel,canbedescribedbytwoparameters,which areoftenchosentobethemassofthepseudoscalarbosonmA and

theratioofthevacuumexpectationvaluesoftheneutral compo-nentsofthe twoHiggsdoublets tan

β

.However, radiative correc-tions[13–17]introducedependenciesonotherparametersnamely themassofthetopquarkmt,thescaleofthesoftsupersymmetry

breakingmassesMSUSY,thehiggsinomassparameter

μ

,thewino

mass parameter M2, the third-generation trilinear couplings, At,

Ab,and Aτ ,themass ofthe gluinomg˜,andthe third-generation

sleptonmassparameterM_˜

3.

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

Direct searchesfortheneutralMSSM Higgsbosons havebeen performed by the CMS and ATLAS Collaborations [18–20] using thebenchmarkscenarios proposedinRef.[21].Inthesescenarios theparameters involvedintheradiativecorrectionsfortheHiggs bosonmassesandcouplingshavebeenfixed,andonlythetwo pa-rametersmA andtan

β

remainfree.Thevalue ofMSUSY wasfixed

ataround 1 TeV, whichproduces a lightest CP-evenHiggs boson with a mass mh lower than the observed Higgs boson mass of

125.09

±

0.21

(stat)

±

0.11

(syst)

GeV[22],forvaluesoftanβ



6. If, however,MSUSY ismuch largerthan1 TeV, assuggestedby

the non-observationsofSUSY partner particles attheLHC sofar, low valuesof tan

β

canproduce an h boson withmh



125 GeV [23,24].TheinterpretationoftheHiggsbosonmeasurementsinthe framework oftherecentlydevelopedMSSM benchmarkscenarios [24–27] suggests that the mass of the CP-odd Higgs boson, mA,

can be smaller than 2mt. In the mass region below 2mt and at

low valuesof tanβ,the decaymode oftheheavy scalar H

→

hh andthatofthepseudoscalarA

→

Zh canhavesizeablebranching fractions.

Thisencouragesaprogrammeofsearchesintheso-called“low tan

β”

channels[23,28]:

•

for220 GeV

<

mA

<

2mt:A

→

Zh;

•

for260 GeV

<

mA

<

2mt:H

→

hh;

•

formA

>

2mt:A/H

→

t

¯

t.

http://dx.doi.org/10.1016/j.physletb.2016.01.056

0370-2693/©2016CERNforthebenefitoftheCMSCollaboration.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

218 CMS Collaboration / Physics Letters B 755 (2016) 217–244

The decay modes H

→

hh and A

→

Zh, studied in this pa-per, are alsopresentin other typesoftwo-Higgs-doublet models (2HDM)[2,3].Therearedifferenttypesof2HDMwiththosemost similar to the MSSM (i.e. whereup-type fermions coupleto one doublet and down-type fermions to the other) being “Type II” 2HDM.Thediscovery ofaHiggsbosonattheLHC[29–31] witha massaround125 GeV pushesthe2HDMparameterspacetowards eitherthealignmentordecouplinglimits[24].Intheselimitsthe propertiesofh areSM-like.

Inthealignment limitof2HDMwhen cos(β

−

α

)



1 (where

α

is themixinganglebetweenthetwo neutralscalarfields),the Hhh and AZh couplings vanish at Born level [32]. However, in the MSSM, the Hhh and AZh couplings do not vanish, even in thealignmentlimit,becauseofthelargeradiativecorrectionsthat arise in the model. In the decoupling limit of 2HDM the scalar HiggsbosonH hasaverylargemassandthedecayH

→

t

¯

t domi-nates[32].

Thispaperreportsthe resultsofsearches forthedecays H

→

hh

→

bb

τ τ

and A

→

Zh

→ 

τ τ

(where



denotes

μμ

or ee). Thechoiceof

τ

pairfinalstatewasdrivenbyitsquiteclean signa-tureandbythemostrecentresults,whichgavestrongerevidence ofthe125 Higgsbosoncouplingtothefermions[33].Thisanalysis exploitssimilartechniquesasusedforthesearchfortheSMHiggs boson at 125 GeV [34] and several different

τ τ

signatures are studied.Forthechannel H

→

hh

→

bb

τ τ

,the

μτ

h,e

τ

h,and

τ

h

τ

h

final states are used,where

τ

h denotes the visibleproducts ofa

hadronicallydecaying

τ

,whereasforthechannelA

→

Zh

→ 

τ τ

, the

μτ

h,e

τ

h,

τ

h

τ

h,ande

μ

finalstatesareselected.

SearchesforthedecaysH

→

hh,andA

→

Zh havealreadybeen performedbytheATLAS [35–38]andCMSCollaborations[39–41] indi-photon,multileptonandbb finalstates.

This analysishas the powerto bring important results inthe low tanβ region for the mA range, which has been previously

discussed andwhere theseprocesses havean enhanced sensitiv-ity [23]. This region has not yet been excluded by the direct or indirectsearches fora heavy scalaror pseudoscalarHiggsboson, that have been mentioned above, therefore the described decay modeslooktobequitepromising.

Forsimplicityofthepaper,weareneitherindicatingthecharge oftheleptonsnortheparticle–antiparticlenatureofquarks.

2. TheCMSdetector,simulationanddatasamples

A detailed description of the CMS detector can be found in Ref. [42]. The central feature of the CMS apparatus is a super-conductingsolenoidof6 m internal diameterproviding afield of 3.8 T.Withinthefieldvolumeareasiliconpixelandstriptracker, a crystal electromagnetic calorimeter (ECAL), and a brass/scintil-lator hadron calorimeter. Muons are measured in gas-ionisation detectorsembeddedinthesteelreturnyokeofthemagnet.

TheCMScoordinatesystemhastheorigincentred atthe nom-inalcollision pointandis orientedsuch thatthe x-axispoints to thecentre oftheLHCring,they-axispointsverticallyupwardand the z-axisisinthedirectionofthebeam. Theazimuthal angle

φ

ismeasuredfromthex-axisinthexy planeandtheradial coordi-nateinthisplaneisdenotedby r.Thepolarangle

θ

isdefinedin therz planeandthepseudorapidityis

η

= −

ln

[

tan(θ/2)

]

[42].The momentumcomponenttransversetothebeamdirection,denoted by pT,iscomputedfromthex- and y-components.

Thefirstlevel(L1)oftheCMStriggersystem,composedof cus-tomhardware processors, usesinformationfromthecalorimeters andmuondetectorstoselectthemostinterestingeventsinafixed time interval of less than 4 μs. The high-level Trigger processor farm decreases the L1 accept rate from around 100 kHz to less than1 kHz beforedatastorage.

Thedatausedforthissearchwere recordedwiththeCMS de-tectorinproton–protoncollisionsattheCERNLHCandcorrespond to an integrated luminosity of19.7 fb−1 at acentre-of-mass en-ergy of

√

s

=

8 TeV. The H

→

hh signals are modelled with the pythia6.4.26[43] eventgeneratorwhilethe A

→

Zh signalswere modelled with MadGraph 5.1 [44]. When modelling background processes,the MadGraph 5.1generatorisusedforZ

+

jets,W

+

jets, t

¯

t,anddibosonproduction,and powheg 1.0[45–48]forsingle top quark production.The powheg and MadGraph generators are in-terfacedwith pythia forpartonshoweringandfragmentationusing the Z2*tune [49].All generators are interfacedwith tauola[50] forthe simulationof the

τ

decays.All generatedeventsare pro-cessed through a detailed simulation of the CMS detector based on Geant4 [51] andare reconstructed with the samealgorithms as the data. Parton distribution functions (PDFs) CT10 [52] or CTEQ6L1[53]fortheprotonareused,dependingonthegenerator inquestion, togetherwithMSTW2008[54] accordingto PDF4LHC prescriptions[55].

3. Eventreconstruction

Duringthe2012LHCrun therewere anaverageof21proton– proton interactions per bunch crossing. The collision vertex that maximises the sumofthe squares ofmomenta components per-pendiculartothebeamline(transverse momenta)ofalltracks as-sociated withit,



p2

T, is taken to be the vertex of the primary

hard interaction.The otherverticesare categorisedaspileup ver-tices.

A particle-flow algorithm [56,57] is used to reconstruct indi-vidual particles, i.e. muons, electrons, photons, charged hadrons andneutralhadrons,usinginformationfromallCMSsubdetectors. Composite objects such as jets, hadronically decaying

τ

leptons, andmissingtransverseenergyarethenconstructedusingthelists ofindividualparticles.

Muonsare reconstructed byperforming a simultaneousglobal trackfit to hitsinthe silicontracker andthemuon system [58]. Electronsare reconstructedfromclustersofECALenergydeposits matched to hits in the silicontracker [59].Muons andelectrons assumed to originate from W or Z bosondecays are required to be spatially isolatedfromother particles [59,60].The presenceof charged and neutral particles from pileup vertices is taken into account in the isolation requirement of both muons and elec-trons. Muon andelectron identification and isolation efficiencies aremeasuredviathetag-and-probetechnique[61]usinginclusive samples of Z

→ 

events from data and simulation. Correction factors are applied to account for differences between data and simulation.

Jets are reconstructed fromall particles using the anti-kT jet

clustering algorithm implemented in fastjet [62,63] with a dis-tance parameter of 0.5. The contribution to the jet energy from particles originatingfrom pileup vertices is removed following a procedure based on the effective jet area described in Ref. [64]. Furthermore, jet energy corrections are applied as a function of jet pT and

η

correcting jet energies to the generator level

re-sponse ofthe jet, on average. Jets originatingfrom pileup inter-actions areremoved by amultivariate pileupjetidentification al-gorithm[65].

The missingtransverse momentum vector



pmiss

T is definedas

the negative vector sumofthe transversemomenta ofall recon-structedparticlesinthevolumeofthedetector(electrons,muons, photons, andhadrons). Its magnitudeis referred toas Emiss

T . The

Emiss

T reconstructionisimprovedbytakingintoaccountthejet

en-ergyscalecorrectionsandthe

φ

modulation,duetocollisions not beingatthenominalcentreofCMS[66].A multivariateregression correctionof Emiss

hadron-plus-stripsalgorithm[68],whichconsiderscandidateswith one chargedpion andup to two neutralpions, or threecharged pions. The neutral pions are reconstructed as “strips” of elec-tromagnetic particles taking into account possible broadening of calorimeterenergydepositionsinthe

φ

directionfromphoton con-versions.The

τ

h candidatesthat are alsocompatiblewithmuons

orelectronsarerejected.Jetsoriginatingfromthehadronisation of quarksandgluonsaresuppressedbyrequiringthe

τ

hcandidateto

beisolated.Thecontributionofchargedandneutralparticlesfrom pileupinteractionsisremovedwhencomputingtheisolation.

4. Eventselection

Theeventsare selectedwitha combinationof electron,muon and

τ

trigger objects [34,59,60,69]. The identification criteria of these objects were progressively tightened and their transverse momentum thresholds raised asthe LHC instantaneous luminos-ityincreasedoverthedatatakingperiod.A tag-and-probemethod wasusedtomeasuretheefficienciesofthesetriggersindataand simulation,andcorrectionfactorsareappliedtothesimulation.

Electrons,muons,and

τ

hareselectedusingthecriteriadefined

intheCMSsearch fortheSM Higgsbosonat125 GeV[34]. Spe-cificrequirementsfortheselectionoftheH

→

hh

→

bb

τ τ

andthe A

→

Zh

→ 

τ τ

channelsaredescribedbelow.

4.1.EventselectionofH

→

hh

→

bb

τ τ

IntheH

→

hh

→

bb

τ τ

channel,the threemostsensitive final statesare analysed, distinguished by the decaymode of the two

τ

leptonsoriginatingfromtheh boson(

μτ

h,e

τ

hand

τ

h

τ

h).

Inthe

μτ

hande

τ

hfinalstates,eventsareselectedwithamuon

with pT

>

20 GeV and

|

η

|

<

2.1 or an electron of pT

>

24 GeV

and

|

η

|

<

2.1,and an oppositely charged

τ

h of pT

>

20 GeV and

|

η

|

<

2.3. To reduce the Z

→

μμ

,

ee contamination, events with twomuonsorelectronsof pT

>

15 GeV,ofopposite charges,and

passinglooseisolationcriteriaarerejected.

In the

μτ

h and e

τ

h final states, the transverse mass of the

muonorelectronand



pmiss_T

mT

=



2pTEmissT

(

1

−

cos

φ),

(1)

where pT isthelepton transversemomentumand

φ

isthe

dif-ferenceintheazimuthalanglebetweentheleptonmomentumand



pmiss_T ,isrequiredto be lessthan 30 GeV to rejecteventscoming fromW

+

jets andt

¯

t backgrounds.ThemT distributionforthe

μτ

h

finalstateisshowninFig. 1.

In the

τ

h

τ

h final state, events with two oppositely charged

hadronically decaying

τ

leptons with pT

>

45 GeV and

|

η

|

<

2.1

areselected.

Inadditiontothe

τ τ

selection,each selectedeventmust con-tain atleast two jetswith pT

>

20 GeV and

|

η

|

<

2.4.These pT

and

η

requirementsare necessary to selectjetsthat have a well definedvalueoftheCSVdiscriminator(Section3),whichis impor-tant forcategorisingsignal-like events withtwo b jet candidates comingfromthe125 GeV Higgsbosondecayingtobb.

Fig. 1. DistributionofmTforeventsintheμτh finalstate,containingatleasttwo

additionaljets.TheW+jets backgroundisincludedinthe“electroweak”category. MultijeteventsareindicatedasQCD.TheH→hh→bbτ τselectionrequiresmT<

30 GeV fortheμτhandeτhfinalstates.

Simulationstudiesshowthatthemajorityofsignaleventswill have at least one jet passing the medium working point of the CSVdiscriminator.ThejetsareorderedbyCSVdiscriminatorvalue, suchthattheleadingandsubleadingjetsaredefinedasthosewith the two highest CSV values. Then the events are separated into categories,definedas:

•

2jet–0tagwhen neithertheleading norsubleadingjet passes themediumCSVworkingpoint.Onlyasmallamountofsignal iscollectedinthiscategory,whichisbackground-dominated.

•

2jet–1tag when only the leading but not the subleading jet

passesthemediumCSVworkingpoint.

•

2jet–2tagwhenboththeleadingandsubleadingjetspassthe mediumCSVworkingpoint.

Thesignalextractionisperformedusingthedistributionofthe reconstructedmassoftheHbosoncandidate.

4.2. EventselectionofA

→

Zh

→ 

τ τ

IntheA

→

Zh

→ 

τ τ

channeleight finalstatesareanalysed. ThesearecategorisedaccordingtothedecaymodeoftheZboson andthe decaymode ofthe

τ

leptons originatingfromthe h bo-son.

The Z bosonis reconstructedfrom twosame-flavour, isolated, andoppositelychargedelectronsormuons.IntheZ

→

μμ

(ee) fi-nalstatethemuons(electrons)arerequiredtohave

|

η

|

<

2.4 (2.5) with pT

>

20 GeV for the leading lepton and pT

>

10 GeV for

the subleading lepton. The invariant mass of the two leptons is required to be between60 GeV and 120 GeV. When more than onepairofleptonssatisfythesecriteria,thepairwithaninvariant massclosesttotheZbosonmassisselected.

AftertheZ candidatehasbeenchosen,theh

→

τ τ

decayis se-lectedbycombiningthedecayproductsofthetwo

τ

leptonsinthe four final states

μτ

h

,

e

τ

h

,

τ

h

τ

h

,

e

μ

.The combination of thelarge

contributionfromtheirreducibleZZ backgroundandofthesmall branching fractions ofleptonic taudecays makes the

μμ

andee final stateslesssensitivetothe signal,andthereforethey arenot used in the analysis. Depending on the final state, a muonwith

pT

>

10 GeV and

|

η

|

<

2.4, or an electron of pT

>

10 GeV and

220 CMS Collaboration / Physics Letters B 755 (2016) 217–244

Fig. 2. DistributionofthevariableLh

Tforeventsintheτhτh finalstate.The

re-duciblebackgroundisestimatedfromdata,insteadtheZZirreduciblebackground fromsimulation.

formanoppositely chargedpair.Eventswithadditionallight lep-tonssatisfyingtheserequirementsarerejected.

A requirement on Lh_T, which is the scalar sum of the visible transverse momenta of the two

τ

candidates originating from the h boson, is applied to lower the reducible background from misidentifiedleptonsaswellastheirreduciblebackgroundfrom ZZ production.The thresholdsofthisrequirementdepend onthe fi-nalstate andhavebeen choseninsuch awayastooptimisethe sensitivityoftheanalysistothepresenceofan A

→

Zh signal for A masses between 220 and350 GeV. The distribution of Lh

T for

eventsinthe



τ

h

τ

hfinalstatecanbeseeninFig. 2.

In order to reduce the t

¯

t background, eventscontaining a jet with pT

>

20 GeV,

|

η

|

<

2.4 and passing the medium working

pointoftheCSVbtaggingdiscriminatorareremoved.

Thefourfinalobjectsarefurtherrequiredtobeseparatedfrom eachother by

R

=



(

η

)

2

_{+ (}

_ϕ

₎

2 _{largerthan 0.5(where}

_ϕ

_is

inradians),andtocomefromthesameprimaryvertex.

Inthischannelthesignalextractionisperformedusingthe dis-tributionofthereconstructedmassoftheAbosoncandidate.

5. Backgroundestimation

5.1. BackgroundestimationforH

→

hh

→

bb

τ τ

ThebackgroundstotheH

→

hh

→

bb

τ τ

finalstateconsist pre-dominantlyoft

¯

t events,followedbyZ

→

τ τ

+

jets events,W

+

jets events, and QCD multijet events, with other small contributions from Z

→ 

, diboson, and single top quark production.The es-timation of the shapes of the reconstructed H mass and of the yields of the major backgrounds isobtained fromdata wherever possible.

TheZ

→

τ τ

process constitutesanirreduciblebackgrounddue to its final state involving two

τ

leptons, whichonly differ from theh

→

τ τ

signalbyhavinganinvariantmassclosertothemass ofthe Z bosoninstead ofthe Higgsboson. Requiringtwo jetsin the eventgreatly reduces this backgroundand the btagging re-quirements reduce it even further. Nevertheless, it still remains an important source of background events, in particular in the 2jet–1tag and2jet–0tag categories. This background isestimated usingasampleofZ

→

μμ

eventsfromdata,obtainedbyrequiring two oppositely charged isolated muons, where the reconstructed

Fig. 3. Distributionsofthereconstructedfour-bodymasswiththekinematicfitafter applyingmassselectionsonmτ τandmbbintheμτhchannel.Theplotsareshown

foreventsinthe2jet–0tag(top),2jet–1tag(middle),and2jet–2tag(bottom) cate-gories.Theexpectedsignalscaledbyafactor10isshownsuperimposedasanopen dashedhistogramfortanβ=2 andmH=300 GeV inthelowtanβscenarioofthe

MSSM.Expectedbackgroundcontributionsareshownforthevaluesofnuisance pa-rameters(systematicuncertainties)obtainedafterfittingthesignalplusbackground hypothesistothedata.

Fig. 4. Distributionsofthereconstructedfour-bodymasswiththekinematicfitafter applyingmassselectionsonmτ τandmbbintheeτhchannel.Theplotsareshown

foreventsinthe2jet–0tag(top),2jet–1tag(middle),and2jet–2tag(bottom) cate-gories.Theexpectedsignalscaledbyafactor10isshownsuperimposedasanopen dashedhistogramfortanβ=2 andmH=300 GeV inthelowtanβscenarioofthe

MSSM.Expectedbackgroundcontributionsareshownforthevaluesofnuisance pa-rameters(systematicuncertainties)obtainedafterfittingthesignalplusbackground hypothesistothedata.

Fig. 5. Distributionsofthereconstructedfour-bodymasswiththekinematicfitafter applyingmassselectionsonmτ τandmbbintheτhτhchannel.Theplotsareshown

foreventsinthe2jet–0tag(top),2jet–1tag(middle),and2jet–2tag(bottom) cate-gories.Theexpectedsignalscaledbyafactor10isshownsuperimposedasanopen dashedhistogramfortanβ=2 andmH=300 GeV inthelowtanβscenarioofthe

MSSM.Expectedbackgroundcontributionsareshownforthevaluesofnuisance pa-rameters(systematicuncertainties)obtainedafterfittingthesignalplusbackground hypothesistothedata.

222 CMS Collaboration / Physics Letters B 755 (2016) 217–244

Fig. 6. InvariantmassdistributionsfordifferentfinalstatesoftheA→Zh processwhereZ decaystoee.Theexpectedsignalscaledbyafactor5isshownsuperimposed asanopendashedhistogramfortanβ=2 andmA=300 GeV inthelowtanβscenarioofMSSM.Expectedbackgroundcontributionsareshownforthevaluesofnuisance

parameters(systematicuncertainties)obtainedafterfittingthesignalplusbackgroundhypothesistothedata.(Forinterpretationofthereferencestocolourinthisfigure, thereaderisreferredtothewebversionofthisarticle.)

muons are replaced by the reconstructed particles from simu-lated

τ

decays. A correction for a contamination from t

¯

t events is applied to the Z

→

μμ

selection. Thistechnique substantially reduces the systematic uncertainties dueto the jet energy scale andthe missingtransverse energy, asthese quantities are mod-elledwithdata.

Forthet

¯

t background,bothshapeandnormalisationaretaken from Monte Carlo simulation (MC), and the results are checked against data ina control region wherethe presence of t

¯

t events isenhanced by requiringe

μ

in thefinal state insteadof aditau, andatleastonebtaggedjet.

Another significant source of background is from QCD multi-jetevents,whichcanmimicthesignalinvariousways, e.g.where oneormorejetsaremisidentifiedas

τ

h.Inthe

μτ

hande

τ

h

chan-nels,the shapeoftheQCD backgroundisestimatedusingan ob-servedsample ofsame-sign (SS)

τ τ

events.Theyield isobtained by scaling theobserved numberof SSevents by theratio ofthe opposite-sign(OS)to SSeventyields obtainedina QCD-enriched regionwithrelaxedleptonisolation.Inthe

τ

h

τ

hchannel,theshape

isobtainedfromOS eventswithrelaxed

τ

isolation. The yieldis obtained by scaling these events by the ratio of SS events with tighterandrelaxed

τ

isolation.

In the

μτ

h and e

τ

h channels, W

+

jets events in which there

isa jetmisidentified asa

τ

h are anothersizeablesourceof

back-ground. The W

+

jets shape is modelledusing MC simulationand the yieldisestimatedusinga controlregion ofeventswithlarge

mTclosetotheW mass.Inthe

τ

h

τ

hchannelthisbackgroundhas

been foundto be lessrelevantandits shape andyieldare taken fromMCsimulation.

The contribution of Drell–Yan production of muon and elec-tron pairs is estimatedfrom simulationafter rescaling the simu-latedyieldtothatmeasuredfromobservedZ

→

μμ

events.Inthe e

τ

hchannel, theZ

→

ee simulationisfurthercorrectedusingthe

e

→

τ

h misidentification ratemeasured indata using a

tag-and-probetechnique[61]onZ

→

ee events.

Finally the contributions of other minor backgrounds such as diboson and single top quark events are estimatedfrom simula-tion. Possible contributions fromSM Higgs boson production are estimatedandfoundtohaveanegligibleeffectonthefinalresult.

5.2. BackgroundestimationforA

→

Zh

→ 

τ τ

The backgrounds to the A

→

Zh channel can be divided into a reduciblecomponentandanirreduciblecomponentwhich con-tributeinequalparts.

Fig. 7. InvariantmassdistributionsfordifferentfinalstatesoftheA→Zh processwhereZ decaystoμμ.Theexpectedsignalscaledbyafactor5isshownsuperimposed asanopendashedhistogramfortanβ=2 andmA=300 GeV inthelowtanβscenarioofMSSM.Expectedbackgroundcontributionsareshownforthevaluesofnuisance

parameters(systematicuncertainties)obtainedafterfittingthesignalplusbackgroundhypothesistothedata.(Forinterpretationofthereferencestocolourinthisfigure, thereaderisreferredtothewebversionofthisarticle.)

Thepredominant source ofirreducible backgroundis from ZZ production that yields exactly the same final states as the ex-pectedsignal. Other “rare” sources ofirreducible background are SMHiggsbosonassociatedproductionwithaZ boson,t

¯

tZ produc-tionwheretheZ bosondecaysintoamuonoranelectronpairand both top quarksdecay leptonically (to e,

μ

,or

τ

h), andtriboson

events(WWZ,WZZ,ZZZ). The contributions ofall theirreducible backgrounds after the final selection are estimated from simula-tion.

Thereduciblebackgroundshaveatleastoneleptoninthefinal statethatisduetoamisidentifiedjetthatpassesthelepton iden-tification.In



τ

h

τ

hfinalstates,thereduciblebackgroundis

essen-tiallycomposed ofZ

+

jetsevents withatleast twojets, whereas in



μτ

h and

e

τ

hfinal states,the maincontributionto the

re-duciblebackgroundcomesfromWZ

+

jetswiththreelightleptons. Thecontributionfromtheseprocessestothefinalselectedevents isestimatedusingcontrolsamplesindata.

Theprobabilities fora jet that passesrelaxedlepton selection criteriatopassthefinalidentificationandisolationcriteriaof elec-trons,muons, and

τ

leptonsare measuredin a signal-freeregion

asafunctionofthetransversemomentumoftheobjectclosestto thecandidate, f

(

pfake_T

).

Inthisregion,eventsarerequiredtopass all thefinal stateselections, exceptthatthe reconstructed

τ

can-didates are required to have the same sign and to pass relaxed identificationandisolationcriteria. Thiseffectivelyeliminates any possiblesignal,whilemaintainingroughly thesameproportionof reduciblebackgroundevents.

Inordertousethemisidentificationprobabilities f

(

pfake T

),

side-bands are defined for each channel, where, unlike the relaxed criterion, the final identification or isolation criterion is not sat-isfied for one or more of the final state lepton candidates. The number of reducible background events due to a lepton being misidentified in the final selection is estimated by applying the weight f

(

pfake

T

)/(1

−

f

(

pfakeT

))

to the observed events with

lep-toncandidatesinthesidebandthatsatisfytherelaxedbutnotthe finalidentificationorisolationcriterion.Finally,thereducible back-groundshape ofthe reconstructedA mass isobtainedfroma SS signal-free region wherethe

τ

candidates havethe same charge andrelaxedisolationcriteria.PossiblecontributionsfromSMHiggs bosonproductionareestimatedandfoundtohaveanegligible ef-fectonthefinalresult.

224 CMS Collaboration / Physics Letters B 755 (2016) 217–244

Fig. 8. Upperlimitsat95%CLontheH→hh→bbτ τ crosssectiontimesbranchingfractionfortheμτh(topleft),eτh(topright),τhτh(bottomleft),andforfinalstates

combined(bottomright).

6. Systematicuncertainties

The shape of the reconstructed mass of the A and H boson candidates, used for signal extraction, and the normalisation are sensitivetovarioussystematicuncertainties.

The main contributions to the normalisation uncertainty that affectthe signal andthe simulated backgrounds include the un-certaintyinthetotalintegratedluminosity,whichamountsto2.6% [70], andthe identificationandtriggerefficiencies ofmuons(2%) andelectrons (2%). The

τ

h identificationefficiency has a 6%

un-certainty(8%inthe

τ

h

τ

hchannel),whichismeasuredinZ/

γ

∗

→

τ τ

→

μτ

h eventsusinga tag-and-probetechnique. Thereis a3%

uncertaintyintheefficiencyonthe hadronicpartofthe

μτ

h and

e

τ

h triggers,anda4.5%uncertaintyoneachofthetwo

τ

h

candi-datesrequiredbythe

τ

h

τ

htrigger.Thebtaggingefficiencyhasan

uncertaintyof2–7%,andthemistag rateforlight-flavourpartons is accurate to 10–20% depending on

η

and pT [67]. The

back-groundnormalisation uncertainties fromthe estimation methods discussedinSection5arealsoconsidered.IntheH

→

hh

→

bb

τ τ

channel this uncertainties amount to 2–40% depending on the eventcategoryandonthefinalstate.Theuncertaintiesofreducible backgroundstotheA

→

Zh channelareestimatedbyevaluatingan

individual uncertainty for each lepton misidentification rate and applyingittothebackgroundcalculation.Thisamountsto15–50% depending on the final



τ τ

state considered. The main uncer-tainty in the estimation of the ZZ background arises from the theoreticaluncertaintyintheZZ productioncrosssection.

Uncertaintiesthat contribute to variations inthe shape ofthe mass spectrum include the jet energy scale, which varies with jet pT andjet

η

[71],andthe

τ

lepton(3%)energyscale[34].

Theoretical uncertainties onthe crosssection forsignal derive fromPDFandQCDscaleuncertaintiesanddependonthechoiceof signalhypothesis.Formodelindependentresultsnochoiceofcross sectionismadeandhencenotheoreticaluncertaintiesare consid-ered.FortheMSSMinterpretationtheuncertaintiesdependonmA

andtanβ andamountto2–3%forPDFuncertaintiesand5–9%for scale uncertainties, evaluated as described in [27] andusing the PDF4LHC recommendations [55]. No theoretical uncertainties are consideredinthe2HDMinterpretation.

7. Resultsandinterpretation

The ditau(mττ ) massisreconstructedusinga dedicated algo-rithmcalled SVFit[72],whichcombinesthevisiblefour-vectorsof

Fig. 9. Upperlimitsat95%CLoncrosssectiontimesbranchingfractiononA→Zh→LLτ τ foreμ(topleft),μτh (topright),eτh(bottomleft),andτhτh(bottom

right)finalstates.

the

τ

leptoncandidatesaswellasthe Emiss_T andits experimental resolutioninamaximumlikelihoodestimator.

Forthe H

→

hh

→

bb

τ τ

process, the chosen distribution for signalextractionisthefour-bodymass.Thedecayproducts ofthe twoh bosonsneedtofulfillstringentkinematicconstraints,dueto thesmallnaturalwidthoftheh.Theseconstraintscanbeusedin akinematic fit inorder toimprove theevent reconstruction and tobetterseparatesignaleventsfrombackground.Thecollinear ap-proximationfor the decay products of the

τ

leptons isassumed inthefit,sincethe

τ

leptons arehighlyboostedasthey originate froman objectthat isheavy when comparedto their ownmass. Furthermore,it is assumed that the reconstruction of the direc-tionsofallfinalstateobjectsisaccurateandtheuncertaintiescan beneglected comparedto theuncertainties ontheenergy recon-struction.Inthedecayofthetwo

τ

leptons,atleasttwoneutrinos are involved and there is no precise measurement of the origi-nal

τ

lepton energies. Forthisreason, the

τ

lepton energies are constrainedfromthebalanceofthefittedH bosontransverse mo-mentumandthereconstructedtransversalrecoildeterminedfrom

Emiss_T reconstructionalgorithms,asdescribedinSec.3.The recon-structedmassobtainedwiththekinematicfitisdenotedbymkinfit_H

(seetheSupplementarymaterialforadetaileddescription).

The signal-to-background ratio is greatly improved by select-ing events that are consistent with a mass of 125 GeV for both thedijet(mbb)massandtheditaumass(mττ )reconstructedwith

SVFit.The mass windows of theselections are optimised to col-lect as much signal as possible while rejecting a large part of the background. They correspond to 70

<

mbb

<

150 GeV and

90

<

mττ

<

150 GeV.TheinvariantmassdistributionsoftheH bo-sonindifferentfinalstatesareshowninFigs. 3,4 and 5.

For the A

→

Zh

→ 

τ τ

process, the A boson mass is recon-structed from the four-vector information of the Z boson can-didate and the four-vector information of the h boson candi-date as obtainedfrom SVFit. The invariant mass distributions of the A boson in the different final states are shown in Figs. 6 and 7. The



τ

h

τ

h final states have a comparable contribution

from reducible and irreducible backgrounds, while the

e

μ

fi-nal states are dominated by the irreducible ZZ production. The backgroundlabelledas“rare”collects togetherthesmaller contri-butions fromthe triboson processesasdiscussed inthe previous section.

In neithersearch do the invariant massspectra show any ev-idence ofa signal.Model independentupper limitsat95% confi-dencelevel(CL)onthecrosssectiontimesbranching fractionare

226 CMS Collaboration / Physics Letters B 755 (2016) 217–244

Fig. 10. Upperlimitsat95%CLoncrosssectiontimesbranchingfractiononA→ Zh→LLτ τforallτ τ finalstatescombined(top)andcomparisonofthedifferent finalstates(bottom).

setusingabinned maximumlikelihoodfitforthesignalplus back-ground andbackground-only hypotheses.Thelimitsaredetermined using the CLs method [73,74] and the procedure is described in

Refs.[75,76].

Systematicuncertaintiesaretakenintoaccountasnuisance pa-rameters in the fit procedure: normalisation uncertainties affect the signal and backgroundyields. Uncertaintieson the

τ

energy scaleandjetenergyscalearepropagatedasshapeuncertainties.

The model independent expected and observed cross section times branching fraction limits for the H

→

hh

→

bb

τ τ

process areshowninFig. 8andfortheA

→

Zh

→

LL

τ τ

processinFigs. 9 and10whereL

=

e,

μ

or

τ

inordertoreflectthe smallZ

→

τ τ

contributiontothesignalacceptance.

We interpret the observed limits on the cross section times branchingfractionintheMSSMand2HDMframeworks,discussed inSection1.

IntheMSSMweinterprettheminthe“lowtanβ”scenario[27, 78]inwhichthevalueofMSUSY isincreaseduntilthemassofthe

lightestHiggsbosonisconsistentwith125 GeV overarangeoflow tan

β

andmA values.The exclusionregionin themA–tan

β

plane

forthecombinationofthe H

→

hh

→

bb

τ τ

andA

→

Zh

→ 

τ τ

Fig. 11. The95%CLexclusionregioninthemA–tanβplaneforthelowtanβ

sce-narioasdiscussedintheintroduction,combiningtheresultsoftheH→hh→bbτ τ

and theA→Zh→ τ τ analysis.Theareahighlighted inblue belowthe black curvemarkstheobservedexclusion.Thedashedcurveandthegreybandsshow theexpectedexclusionlimitwiththerelativeuncertainty.Theredareawiththe back-slashlinesatthelower-leftcorneroftheplotindicatestheregionexcludedby themassoftheSM-likescalarbosonbeing125 GeV.Thelimitfallsoffrapidlyas mAapproaches350 GeV becausedecaysoftheA totwotopquarksarebecoming

kinematicallyallowed.(Forinterpretationofthereferencestocolourinthisfigure legend,thereaderisreferredtothewebversionofthisarticle.)

analyses,insuchascenario,isshowninFig. 11.Thelimitfallsoff rapidlyasmAapproaches350 GeV becausedecaysoftheA totwo

topquarksarebecomingkinematicallyallowed.

The interpretationoftheobserved limitsinaType II2HDMis performedinthe“physicsbasis”.The inputstothisinterpretation are the physicalHiggs boson masses(mh,mH, mA,mH±),the

ra-tioofthevacuumexpectationenergies(tan

β),

theCP-evenHiggs mixingangle(

α

) andm2

12

=

m2A

[

tanβ/(1

+

tan

β

2

)

]

.Forsimplicity

weassumethatmH

=

mA

=

mH±.

The cross sections andbranching fractionsin the2HDMwere calculated as described by the LHC Higgs Cross Section Working Group [77,78].The exclusionregions,calculatedusingthe combi-nation ofthe H

→

hh

→

bb

τ τ

andA

→

Zh

→ 

τ τ

analyses, in the cos(β

−

α

)

vs. tan

β

plane forsuch a Type II2HDMscenario withaheavy Higgsbosonmassof300 GeV areshowninFig. 12. ThiscanbecomparedtoFig. 5inRef.[41].

8. Summary

A search for a heavy scalar Higgs boson (H) decaying into a pairofSM-likeHiggsbosons(hh)andasearchforaheavyneutral pseudoscalarHiggsboson (A)decayingintoa Z bosonanda SM-like Higgsboson(h), havebeenperformedusingeventsrecorded by theCMS experiment atthe LHC. The data set corresponds to anintegratedluminosityof19.7 fb−1,recordedat8 TeV centre-of-massenergyin2012.Noevidenceforasignalhasbeenfoundand exclusion limitson the production cross section times branching fraction forthe processes H

→

hh

→

bb

τ τ

andA

→

Zh

→

LL

τ τ

are presented. The results are also interpreted in the context of theMSSMand2HDMmodels.

Fig. 12. The95%CLexclusionregionsinthecos(β−α)vs.tanβplaneof2HDM Type IImodelformA=mH=300 GeV,combiningtheresultsofthe H→hh→

bbτ τ andA→Zh→ τ τ analysis.Theareashighlightedinblueboundedbythe blackcurvesmarktheobservedexclusion.Thedashedcurvesandthegreybands showtheexpectedexclusionlimitwiththerelativeuncertainty.(Forinterpretation ofthereferencestocolourinthisfigurelegend,thereaderisreferredtotheweb versionofthisarticle.)

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 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);TUBITAKandTAEK (Turkey);NASUandSFFR(Ukraine);STFC (UnitedKingdom);DOE andNSF(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

doctoral Fellowship,Chulalongkorn University(Thailand); andthe WelchFoundation,contractC-1845.

Appendix A. Supplementarymaterial

Supplementarymaterialrelatedtothisarticlecanbefound on-lineathttp://dx.doi.org/10.1016/j.physletb.2016.01.056.

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CMSCollaboration

V. Khachatryan,

A.M. Sirunyan,

A. Tumasyan

YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam,

E. Asilar,

T. Bergauer,

J. Brandstetter,

E. Brondolin,

M. Dragicevic,

J. Erö,

M. Flechl,

M. Friedl,

R. Frühwirth

1

,

V.M. Ghete,

C. Hartl,

N. Hörmann,

J. Hrubec,

M. Jeitler

1

,

V. Knünz,

A. König,

M. Krammer

1

,

I. Krätschmer,

D. Liko,

T. Matsushita,

I. Mikulec,

D. Rabady

2

,

B. Rahbaran,

H. Rohringer,

J. Schieck

1

,

R. Schöfbeck,

J. Strauss,

W. Treberer-Treberspurg,

W. Waltenberger,

C.-E. Wulz

1

InstitutfürHochenergiephysikderOeAW,Wien,Austria

V. Mossolov,

N. Shumeiko,

J. Suarez Gonzalez

NationalCentreforParticleandHighEnergyPhysics,Minsk,Belarus

S. Alderweireldt,

T. Cornelis,

E.A. De Wolf,

X. Janssen,

A. Knutsson,

J. Lauwers,

S. Luyckx,

S. Ochesanu,

R. Rougny,

M. Van De Klundert,

H. Van Haevermaet,

P. Van Mechelen,

N. Van Remortel,

A. Van Spilbeeck

UniversiteitAntwerpen,Antwerpen,Belgium

S. Abu Zeid,

F. Blekman,

J. D’Hondt,

N. Daci,

I. De Bruyn,

K. Deroover,

N. Heracleous,

J. Keaveney,

S. Lowette,

L. Moreels,

A. Olbrechts,

Q. Python,

D. Strom,

S. Tavernier,

W. Van Doninck,

P. Van Mulders,

G.P. Van Onsem,

I. Van Parijs

VrijeUniversiteitBrussel,Brussel,Belgium

P. Barria,

H. Brun,

C. Caillol,

B. Clerbaux,

G. De Lentdecker,

H. Delannoy,

G. Fasanella,

L. Favart,

A.P.R. Gay,

A. Grebenyuk,

G. Karapostoli,

T. Lenzi,

A. Léonard,

T. Maerschalk,

A. Marinov,

L. Perniè,

A. Randle-conde,

T. Reis,

T. Seva,

C. Vander Velde,

P. Vanlaer,

R. Yonamine,

F. Zenoni,

F. Zhang

3

UniversitéLibredeBruxelles,Bruxelles,Belgium

K. Beernaert,

L. Benucci,

A. Cimmino,

S. Crucy,

D. Dobur,

A. Fagot,

G. Garcia,

M. Gul,

J. Mccartin,

A.A. Ocampo Rios,

D. Poyraz,

D. Ryckbosch,

S. Salva,

M. Sigamani,

N. Strobbe,

M. Tytgat,

W. Van Driessche,

E. Yazgan,

N. Zaganidis

GhentUniversity,Ghent,Belgium

S. Basegmez,

C. Beluffi

4

,

O. Bondu,

S. Brochet,

G. Bruno,

R. Castello,

A. Caudron,

L. Ceard,

G.G. Da Silveira,

C. Delaere,

D. Favart,

L. Forthomme,

A. Giammanco

5

,

J. Hollar,

A. Jafari,

P. Jez,

M. Komm,

V. Lemaitre,

A. Mertens,

C. Nuttens,

L. Perrini,

A. Pin,

K. Piotrzkowski,

A. Popov

6

,

L. Quertenmont,

M. Selvaggi,

M. Vidal Marono

230 CMS Collaboration / Physics Letters B 755 (2016) 217–244

N. Beliy,

G.H. Hammad

UniversitédeMons,Mons,Belgium

W.L. Aldá Júnior,

G.A. Alves,

L. Brito,

M. Correa Martins Junior,

M. Hamer,

C. Hensel,

C. Mora Herrera,

A. Moraes,

M.E. Pol,

P. Rebello Teles

CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

E. Belchior Batista Das Chagas,

W. Carvalho,

J. Chinellato

7

,

A. Custódio,

E.M. Da Costa,

D. De Jesus Damiao,

C. De Oliveira Martins,

S. Fonseca De Souza,

L.M. Huertas Guativa,

H. Malbouisson,

D. Matos Figueiredo,

L. Mundim,

H. Nogima,

W.L. Prado Da Silva,

A. Santoro,

A. Sznajder,

E.J. Tonelli Manganote

7

,

A. Vilela Pereira

UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

S. Ahuja

a

,

C.A. Bernardes

b

,

A. De Souza Santos

b

,

S. Dogra

a

,

T.R. Fernandez Perez Tomei

a

,

E.M. Gregores

b

,

P.G. Mercadante

b

,

C.S. Moon

a

,

8

,

S.F. Novaes

a

,

Sandra S. Padula

a

,

D. Romero Abad,

J.C. Ruiz Vargas

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A. Aleksandrov,

R. Hadjiiska,

P. Iaydjiev,

M. Rodozov,

S. Stoykova,

G. Sultanov,

M. Vutova

InstituteforNuclearResearchandNuclearEnergy,Sofia,Bulgaria

A. Dimitrov,

I. Glushkov,

L. Litov,

B. Pavlov,

P. Petkov

UniversityofSofia,Sofia,Bulgaria

M. Ahmad,

J.G. Bian,

G.M. Chen,

H.S. Chen,

M. Chen,

T. Cheng,

R. Du,

C.H. Jiang,

R. Plestina

9

,

F. Romeo,

S.M. Shaheen,

J. Tao,

C. Wang,

Z. Wang,

H. Zhang

InstituteofHighEnergyPhysics,Beijing,China

C. Asawatangtrakuldee,

Y. Ban,

Q. Li,

S. Liu,

Y. Mao,

S.J. Qian,

D. Wang,

Z. Xu,

W. Zou

StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

C. Avila,

A. Cabrera,

L.F. Chaparro Sierra,

C. Florez,

J.P. Gomez,

B. Gomez Moreno,

J.C. Sanabria

UniversidaddeLosAndes,Bogota,Colombia

N. Godinovic,

D. Lelas,

I. Puljak,

P.M. Ribeiro Cipriano

UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia

Z. Antunovic,

M. Kovac

UniversityofSplit,FacultyofScience,Split,Croatia

V. Brigljevic,

K. Kadija,

J. Luetic,

S. Micanovic,

L. Sudic

InstituteRudjerBoskovic,Zagreb,Croatia

A. Attikis,

G. Mavromanolakis,

J. Mousa,

C. Nicolaou,

F. Ptochos,

P.A. Razis,

H. Rykaczewski

UniversityofCyprus,Nicosia,Cyprus

M. Bodlak,

M. Finger

10

,

M. Finger Jr.

10

J. Härkönen,

V. Karimäki,

R. Kinnunen,

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

J. Talvitie,

T. Tuuva

LappeenrantaUniversityofTechnology,Lappeenranta,Finland

M. Besancon,

F. Couderc,

M. Dejardin,

D. Denegri,

B. Fabbro,

J.L. Faure,

C. Favaro,

F. Ferri,

S. Ganjour,

A. Givernaud,

P. Gras,

G. Hamel de Monchenault,

P. Jarry,

E. Locci,

M. Machet,

J. Malcles,

J. Rander,

A. Rosowsky,

M. Titov,

A. Zghiche

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

I. Antropov,

S. Baffioni,

F. Beaudette,

P. Busson,

L. Cadamuro,

E. Chapon,

C. Charlot,

T. Dahms,

O. Davignon,

N. Filipovic,

A. Florent,

R. Granier de Cassagnac,

S. Lisniak,

L. Mastrolorenzo,

P. Miné,

I.N. Naranjo,

M. Nguyen,

C. Ochando,

G. Ortona,

P. Paganini,

P. Pigard,

S. Regnard,

R. Salerno,

J.B. Sauvan,

Y. Sirois,

T. Strebler,

Y. Yilmaz,

A. Zabi

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

J.-L. Agram

16

,

J. Andrea,

A. Aubin,

D. Bloch,

J.-M. Brom,

M. Buttignol,

E.C. Chabert,

N. Chanon,

C. Collard,

E. Conte

16

,

X. Coubez,

J.-C. Fontaine

16

,

D. Gelé,

U. Goerlach,

C. Goetzmann,

A.-C. Le Bihan,

J.A. Merlin

2

,

K. Skovpen,

P. Van Hove

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

S. Gadrat

CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France

S. Beauceron,

C. Bernet,

G. Boudoul,

E. Bouvier,

C.A. Carrillo Montoya,

R. Chierici,

D. Contardo,

B. Courbon,

P. Depasse,

H. El Mamouni,

J. Fan,

J. Fay,

S. Gascon,

M. Gouzevitch,

B. Ille,

F. Lagarde,

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

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

T. Toriashvili

17

GeorgianTechnicalUniversity,Tbilisi,Georgia

Z. Tsamalaidze

10

TbilisiStateUniversity,Tbilisi,Georgia

C. Autermann,

S. Beranek,

M. Edelhoff,

L. Feld,

A. Heister,

M.K. Kiesel,

K. Klein,

M. Lipinski,

A. Ostapchuk,

M. Preuten,

F. Raupach,

S. Schael,

J.F. Schulte,

T. Verlage,

H. Weber,

B. Wittmer,

V. Zhukov

6