Production of Lambda+c baryons in proton-proton and lead-lead collisions at sqrt(s_NN) = 5.02 TeV

Contents lists available atScienceDirect

Physics

Letters

B

www.elsevier.com/locate/physletb

Production

of



+

_c

baryons

in

proton-proton

and

lead-lead

collisions

at

√

s

_NN

=

5.02

TeV

.The

CMS

Collaboration



CERN,Switzerland

a

r

t

i

c

l

e

i

n

f

o

a

b

s

t

r

a

c

t

Articlehistory: Received7June2019

Receivedinrevisedform17February2020 Accepted18February2020

Availableonline25February2020 Editor: M.Doser

Keywords:

CMS Physics

Lambda(c)baryons Nuclearmodificationfactor Heavyflavor

The transverse momentum (pT) spectra of inclusively produced +c baryons are measured via the exclusivedecaychannel



+c →pK−π+usingtheCMSdetectorattheLHC.Spectraaremeasuredasa functionoftransversemomentuminproton-proton(pp)and lead-lead(PbPb)collisionsata nucleon-nucleon center-of-mass energy of 5.02 TeV. The measurement is performed within the +c rapidity interval|y|

<

1 inthe pT rangeof5–20 GeV/c inpp and10–20 GeV/c inPbPb collisions.The observed yields of



+

c for pT of10–20 GeV/c suggesta suppression incentral PbPb collisionscompared topp collisions scaledbythenumber ofnucleon-nucleon(NN)interactions. The



+c/D0 productionratioin pp collisionsiscomparedtotheoreticalmodels.InPbPb collisions,thisratioisconsistentwiththeresult frompp collisionsintheircommonpTrange.

©2020TheAuthor(s).PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

1. Introduction

Measurements of heavy-quark production provide unique in-puts in understanding the parton energy loss and the degree of thermalization in the quark-gluon plasma (QGP) [1] formed in high energy heavy ion collisions. Compared to light quarks, dif-ferentenergy loss mechanisms [2] are expectedto dominatethe interactionbetweenheavyquarksandthemedium.Besidesthe in-mediuminteractions,adetailedstudyofthehadronizationprocess iscriticalfortheinterpretation ofexperimental data.In relativis-ticheavy ion collisions, in addition tothe fragmentation process present in proton-proton (pp) collisions, hadron production can alsooccurviacoalescence,wherepartonscombinewitheachother whiletraversingtheQGPmediumoratthephaseboundary [3,4]. At high transverse momentum (pT



6 GeV/c), the probability of

coalescence is reduced, and therefore the hadronization process is expected to be dominated by fragmentation. In the interme-diate pT region (2



pT



6 GeV/c), a significant enhancement of

thebaryon-to-meson ratioisobserved inheavy ioncollisions for hadronswithup,down,orstrangequarks [5,6].Thisenhancement, anditsdependenceoncentrality(i.e.,thedegreeofoverlapofthe two colliding nuclei) can be explained in a scenario with had-ronizationvia coalescence. Furthermore,elliptic flow, the second Fouriercomponent of the azimuthal distribution of emitted par-ticles, is found to roughly scale with the number of constituent

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

quarks in the pT range of 2–5 GeV/c at RHIC [7], an observation

whichisalsoconsistentwiththeexpectationforcoalescence. A significant contribution of coalescence to the hadronization of charm quarks fromthe QGP medium is supported by various measurementsofcharmoniumandopencharmproductionatRHIC andLHCenergies [8–16].Onesuchobservableisthenuclear mod-ification factor, RAA, which isthe ratio ofthe yield in heavy ion

collisionstothatinpp collisionsscaledbythenumberof nucleon-nucleon (NN)interactions. At RHIC,the RAA forJ

/

ψ

mesonswith

pT

≤

7 GeV/c produced in AuAu collisions decreases significantly

fromperipheraltocentralcollisions [8].Incontrast,inhigher en-ergy PbPb collisionsatthe LHC,the J

/

ψ

RAA has amuch smaller

centralitydependence [9,10].ThedifferencebetweentheAuAu and PbPb resultscan beexplained bya larger coalescenceprobability inPbPb collisionsbecauseofthelargernumberofproducedcharm andanti-charmquarksatthehighercenter-of-massenergy.ForD0 mesonproductioninAuAu collisions, RAA isobservedtoincrease

with

p

T upto1.5 GeV/c anddecreasewith

p

Tfrom2to6 GeV/c,an

effectthatcanbequalitativelyreproducedbymodelsinvolving co-alescence [11,12].AttheLHC,themeasurementsofD0 _R

AAandD0

azimuthalanisotropy [13–16] arewellexplainedbymodels involv-ing coalescence. The relative coalescence contribution to baryon productionisexpectedtobemoresignificantthanformesons be-cause oftheir larger number of constituentquarks. In particular, modelsinvolvingcoalescenceofcharmandlight-flavorquarks pre-dictalargeenhancementinthe



+_c

/

D0 productionratioinheavy ioncollisionsrelativetopp collisionsandalsopredictthatthe en-hancement has a strong pT dependence [17–20]. Comparison of https://doi.org/10.1016/j.physletb.2020.135328



+_c baryon productionin pp and lead-lead (PbPb)collisions can thus shed new light on understanding heavy-quark transport in the medium and heavy-quark hadronization via coalescence. All discussions of



+_c andD0 alsoincludethe corresponding charge conjugatestates.

Recently, the productionof



+_c baryons fora variety of colli-sion configurations has been measured in a similar pT range by

theLHC experimentsALICE andLHCbinthe central andforward rapidityregions,respectively [21–24].Bothexperimentsmeasured the



+_c pT-differentialcrosssectionsinpp collisionsata

center-of-massenergy of

√

s

=

7TeV and compared them to theoretical predictionsusingthenext-to-leadingorderGeneralizedMass Vari-ableFlavorNumberScheme [25].TheLHCbresultsfortherapidity range2

.

0

<

y

<

4

.

5 werefoundtobecompatiblewiththeory [23], whiletheALICEvaluesfor

|

y

|

<

0

.

5 were largerthanthe predic-tions [21].TheALICEexperimentalsoreported



+_c

/

D0 production ratios in7 TeV pp collisions, aswell asin proton-lead(pPb) and PbPb collisionsatanNNcenter-of-massenergyof

√

s_NN

=

5

.

02TeV. TheALICEratiosfrompp andpPbcollisions [21] werefoundtobe above the corresponding LHCb values [24] (however in different rapidity ranges), withthelatter agreeing withtheoretical predic-tions.The ALICE



+_c

/

D0 productionratiofor6

<

pT

<

12 GeV/c in

PbPb collisionswasmeasuredtobelargerthaninpp andpPb col-lisions [22], and this difference can be described using a model involvingonlycoalescence inhadronization [20].The ALICE mea-surementsof the RAA of



+c baryonsinpPb andPbPb collisions

were found to be compatiblewithunity andless thanunity, re-spectively, buthave limitedpower to constrain models owing to largeuncertainties [21,22].

Inthisletter,we reportmeasurementsofinclusive



+_c baryon productionin pp and PbPb collisionsathigh pT where inclusive

refers tobothprompt (directlyproduced incharmquark hadron-ization orfrom strong decays of excited charmed hadron states) andnonprompt(fromb hadrondecays)production.Thedatawere collectedat

√

s_NN

=

5

.

02TeV in2015usingtheCMSdetector.The



+_c baryonsare reconstructed in thecentral region (

|

y

|

<

1) via thehadronicdecaychannel



+_c

→

pK−

π

+.The pT spectrumand



+_c

/

D0 productionratioaremeasuredinthe pT ranges5–20and

10–20 GeV/c in pp and PbPb collisions, respectively. The



+_c

/

D0

production ratios use the corresponding CMS measurements of promptD0 production [14].Centrality binsforPbPb collisionsare giveninpercentagerangesofthetotalinelastichadroniccross sec-tion, with the 0–30% centrality bin corresponding to the 30% of collisionshavingthe largestoverlapofthetwo nuclei.The values of RAA areobtainedforthree centralityintervals:0–100%,0–30%,

and30–100%. 2. TheCMSdetector

The central feature of the CMS apparatus is a superconduct-ing solenoidof 6 m internal diameter, providinga magnetic field of3.8 T. Withinthe solenoidvolume are a silicon tracker,a lead tungstatecrystalelectromagneticcalorimeter,andabrassand scin-tillator hadron calorimeter, each composed of a barrel and two endcapsections.Thetrackermeasureschargedparticleswithinthe pseudorapidity range

|

η

|

<

2

.

5 and the calorimeters record de-posited energy forparticles with

|

η

|

<

3

.

0. Two forward hadron (HF) calorimeters use steel as an absorber and quartz fibers as thesensitivematerial.ThetwoHFcalorimetersarelocated11.2 m fromthe interaction region, one on each end, and together they extendthecalorimetercoveragefrom

|

η

|

=

3

.

0 to5.2.EachHF cal-orimeterconsistsof432readouttowers,containinglongandshort quartz fibersrunning parallelto thebeam, providing information on the shower energy and the relative contribution originating fromhadronsversuselectronsandphotons.Adetaileddescription oftheCMSexperimentcanbefoundinRef. [26].

3. Eventreconstructionandsimulatedsamples

The total transverseenergy depositedin bothHF calorimeters isusedtodeterminethecollisioncentralityinPbPb collisionsand was utilized by the triggers for both data sets included in this analysis [27]. Onetrigger selected minimum-bias(MB) eventsby requiring transverse energy deposits in one (both) HF calorime-tersaboveapproximately1 GeV forpp

(

PbPb

)

collisions.Asnotall MBeventscouldbesaved,anadditionaltriggerselectedthemore peripheralcentralityregionof30–100%forPbPb events.The inte-gratedluminositiesofpp collisions,PbPb collisionswithcentrality 0–100%,andPbPb collisionswithcentrality30–100%are38 nb−1, 44

μ

b−1,and102

μ

b−1,respectively.

The trackreconstruction algorithms usedin thisstudy for pp and PbPb collisions are described in Refs. [28] and [29], respec-tively.InPbPb collisions,minormodificationsaremadetothepp reconstructionalgorithminordertoaccommodatethemuchlarger trackmultiplicities.Tracksarerequiredtohavearelative

p

T

uncer-taintyoflessthan30%inPbPb collisionsand10%inpp collisions. In PbPb collisions,tracksmustalsohaveatleast11hitsand sat-isfyastringentfitqualityrequirement,specificallythatthe

χ

2 _per

degree offreedom belessthan 0.15timesthenumberoftracker layerswithahit.

Fortheoffline analysis,eventsmustpassselection criteria de-signed to rejectevents frombackgroundprocesses (beam-gas in-teractions and nonhadronic collisions), as described in Ref. [29]. Events are required to have at least one reconstructed primary interactionvertex [28] withadistancefromthecenterofthe nom-inalinteractionregion oflessthan 15 cm alongthebeamaxis.In addition,inPbPb collisions,theshapesoftheclustersinthepixel detectorhavetobecompatiblewiththoseexpectedfromparticles produced at the primary vertex location [30]. The PbPb collision eventsare alsorequiredto haveatleastthreetowers ineach HF detectorwithenergydepositsofmorethan3GeVpertower.These criteriaselect

(

99

±

2

)

% ofinelastichadronicPbPb collisions. Frac-tions above 100%reflect thepossiblepresence ofultra-peripheral (nonhadronic)collisionsintheselectedeventsample.

MonteCarlo(MC)simulatedeventsamplesareusedtooptimize theselectioncriteria,calculatetheacceptancetimesefficiency,and estimate thesystematicuncertainties.Proton-protoncollisions are generated with pythia 8.212 [31] tune CUETP8M1 [32], hereafter referred toas pythia 8, andincludesbothpromptandnonprompt



+_c baryonevents.ForthePbPb MCsamples,each pythia 8event containing a



+_c baryon isembedded intoa PbPb collisionevent generatedwithhydjet_{1.8 [33],whichistunedtoreproduceglobal} eventpropertiessuchasthecharged-hadron

p

Tspectrumand

par-ticlemultiplicity.The



+_c

→

pK−

π

+decayisperformedbyevtgen 1.3.0 [34] throughfoursub-channels:



+_c

→

pK∗

(

892

)

0

→

pK−

π

+,



+_c

→ (

1232

)

++K−

→

pK−

π

+,



+_c

→ (

1520

)

π

+

→

pK−

π

+,

and



+_c

→

pK−

π

+ (nonresonant), with no modeling of inter-ference between the sub-channels. All particles are propagated throughtheCMSdetectorusingthe Geant4package [35]. 4. Signalextraction

The



+_c

→

pK−

π

+ candidates are reconstructed by selecting three charged tracks with

|

η

|

<

1

.

2 and a net charge of

+

1. All tracks must have pT

>

0

.

7

(

1

.

0

)

GeV/c for pp (PbPb) events.

Fig. 1. Invariantmassdistributionof+c candidateswith pT=5–6 GeV/c (left),10–20 GeV/c (middle)inpp collisions,and pT=10–20 GeV/c inPbPb collisionswithinthe

centralityrange0–100%(right).Thesolidlinerepresentsthefullfitandthedashedlinerepresentsthebackgroundcomponent.

Astheeventmultiplicities forpp andPbPb collisionsare sub-stantiallydifferent,theselectioncriteriawereoptimizedseparately. Intheoptimization,simulatedeventsinwhichareconstructed



+_c

candidateis matchedto a generated



+_c baryon are used asthe signal sample, and data events from the mass sideband region are used as the background sample. Requirements are made on three topological and three kinematic variables. The three topo-logical criteria are: the

χ

2 _{probability of the vertex fit to the}

threechargedtracks makingup the



+_c candidate,the angle be-tween the



+_c candidate momentum and the vector connecting the production anddecay vertices in radians (

α

), and the sepa-ration between the two vertices. While more than one collision per bunch crossing is rare in PbPb collisions, it is common in pp collisions. Therefore, two-dimensional variables in the trans-verseplanewithrespecttothebeamlineareusedfor

α

anddecay lengthinpp collisions,whilethree-dimensionalvariableswith re-spectto the primary vertexare used for PbPb collisions. Forthe PbPb events,thetopologicalrequirementsare

χ

2_{probabilityabove}

20%,

α

<

0

.

1,anddecaylengthgreaterthan3.75

σ

,where

σ

isthe uncertaintyintheseparation.Forpp events,thecorresponding re-quirementsare

χ

2_{probabilityabove8%,}

_α

_<

₀

_.

_{4,anddecaylength}

greaterthan2.25

σ

.Thekinematicrequirementsarekaon(proton) pTdividedbythe



+c candidatepT greaterthan0.14(0.28)forall

eventsandpion pT divided bythe



+c candidatepT greaterthan

0.12forPbPb events.

The



+_c baryon yields in each pT interval are obtained from

unbinnedmaximumlikelihoodfits totheinvariantmass distribu-tionintherangeof2.11–2.45 GeV/c2.The signalshapeismodeled by the sumof two Gaussian functionswiththe same mean,but differentwidthsthat are fixed onthe basis ofthesimulated sig-nalsample.Onefitparameterscalesbothwidthstoaccommodate a potential difference inthe mass resolution betweensimulation anddata,withtheexceptionofthelowest pTregion(5–6 GeV/c)in

thepp data,wherethisparameterwas found tocauseinstability inthefitandtheunmodifiedmassresolutionfromthesimulation was used.The background ismodeled witha third-order Cheby-shevpolynomial.Representativeinvariantmassdistributionsinpp andPbPb collisionsareshowninFig.1.

The



+_c baryondifferentialcrosssectioninpp collisionsis de-finedas: d

σ

+c pp dpT







|y|<1

=

1 2

L

pT

B

N+c pp

|

|y|<1 A

,

(1) where N+c

pp

|

|y|<1 is the



c+ yield extractedin each pT bin,

L

is

theintegratedluminosity,



pT isthe widthofeach pT bin,

B

is

thebranchingfractionofthedecay,and A

istheproductofthe acceptanceandefficiency.Thefactorof1/2accountsforaveraging

Table 1

SummaryoftheNcoll,TAA,andNpartvaluesforthreePbPb centralityranges.

Centrality TAA[mb−1] Npart Ncoll

0–30% 15.41+0.33 −0.47 270.7+ 3.2 −3.4 1079+ 74 −78 30–100% 1.41+0.09 −0.06 46.8+ 2.4 −1.2 98+ 8 −6 0–100% 5.61+₋00..1619 114.0+ 2.6 −2.6 393+ 26 −28

theparticleandantiparticlecontributions.Thenormalized



+_c pT

spectruminPbPb collisionsisdefinedas:

1



TAA



dN+c PbPb dpT







_| y|<1

=

1



TAA



1 2Nevents



pT

B

N+c PbPb

|

|y|<1 A

,

(2)

where Nevents isthe number of MB eventsused for the analysis

(correctedbythe99%selectionefficiency)and



TAA



isthenuclear

overlapfunction,whichisequaltotheaveragenumberofNN bi-nary collisions (



Ncoll



) divided by theNNinelastic crosssection,

andcan be interpreted asthe NN-equivalentintegrated luminos-ity per heavy ion collision. The values of



TAA



,



Ncoll



, and the

average numberof participatingnucleons (



Npart



) are calculated

usingaMonteCarloGlaubermodel [36],inwhichtheNNinelastic crosssection(70 mb)isusedasaninput parameter.Theaverages ofthese quantitiesover theevents inthe givencentralityranges arelistedinTable1.

ThenuclearmodificationfactorRAAiscomputedas:

RAA

(

pT

)

=

1



TAA



dN+c PbPb dpT



d

σ

+c pp dpT

.

(3)

The values of A

are obtained from MC simulation as a frac-tion in which the denominator is the number of generated



+_c

baryons with

|

y

|

<

1 and the numerator is the number of re-constructed



+_c candidates that pass the selection criteria and are matched to a generated



+_c baryon. The simulation includes both prompt andnonprompt



+_c baryonsestimated from pythia 8 andcontains an appropriately weighted combinationof decays in the four known sub-channels. For the pp simulation, the pT

spectrum of the generated



+_c baryons is weighted to match a fit to the observed data (iterating until convergence is reached). For pp collisions, A

increases from 7 to 19% as pT increases.

As the PbPb results are given for just one pT range, an

alter-native method is used to correct the pT spectra in simulation.

Under the transverse mass scaling hypothesis (mT scaling) [37],

the



+_c baryon pT spectrum is obtained for the 0–100%

cen-tralityregion fromthe D0 measurements [14] usingthefunction m2

_(

+

c

)

+

p2T

(

+c

)

=

m2

(

D0

)

+

p2T

(

D

centrality distribution in simulation is reweighted to match the data.Thereisoneadditionalcorrectionappliedto A

forthePbPb data set. Previous CMS results have found more suppression for promptthannonpromptD0mesons [14,38],whichcanbe quanti-fiedfor10

<

pT

<

20 GeV/c as

R

nonpromptAA

/

R

prompt

AA

=

1

.

66

±

0

.

38.As

nonpromptbaryonstendtohavegreater

p

Tanddecayfartherfrom

thecollision point than promptbaryons,the requirementforthe decaylengthsignificanceresultsinavalueof A

thatislargerfor nonpromptbaryons. Changingthenonprompt fractionto account forthedifferentsuppression increases A

by 15%. After applying thecorrections, A

=

5% forPbPb collisions.

5. Systematicuncertainties

Systematic uncertainties arise from the extraction of the raw signal yield, the ability of the MC simulation to reproduce the combinedacceptanceandefficiency,thebranching fractionofthe decaymode,andtheintegratedluminosity.Unlessotherwise indi-cated,systematicuncertainties are combined by addingthe indi-vidualcontributionsinquadrature.

The systematicuncertainty inthe signal yields is obtainedby varying the modeling functionsthat are used for the signal and background contributions. The background function is changed from the default third- to second- and fourth-order Chebyshev polynomials,withthemaximumdifferenceinyieldbetweenthese twoalternativefunctionsandthedefaultfitfunctiontakenasthe systematicuncertainty. Thisamounts to 4–10% and7–9% forpp indifferent pT binsandPbPb collisionsinthreecentralityclasses,

respectively.The defaultsignal modelfunctionis thesumoftwo Gaussian functions with parameters chosen as described in Sec-tion 4.Forthe pp (PbPb) collision data,the alternative modelis a triple (single) Gaussian function with similar procedures used fortheparameters. Asthe signal widthisfixed foreventsinthe lowest



+_c pTbinforpp collisions,anadditionalsystematic

uncer-taintyisassessedbyvaryingthewidthby

±

40%,correspondingto themaximumdeviationswithrespecttothesimulationobserved inother

p

T binsinpp andPbPb collisions.Theuncertaintydueto

themodelingofthesignalis3–28%forpp collisionsand2–4%for PbPb collisions.

FivesourcesofsystematicuncertaintiesassociatedwiththeMC modelingofthedataareevaluated.Thefirstuncertaintymeasures the effect of the selection criteria variation. We define a double ratioas:

DR =

NData(varied) NData(nominal)



NMC(varied) NMC(nominal)

,

(4)

where NData(nominal) and NData(varied) are the yields obtained

fromdata using thedefault andalternative selection criteria, re-spectively,and

N

MC(nominal) and

N

MC(varied) arethe

correspond-ing yields fromthe simulatedevents.Foreach of thetopological selection criteria, the doubleratio is evaluated atmany different values of the selection criterion. The specific ranges for pp col-lision eventsare

>

1

.

5

σ

to

>

6

σ

,

>

5% to

>

45%, and

<

0

.

1 tono cut for decay length, vertex fit probability, and

α

, respectively. The correspondingranges forPbPb collision eventsare

>

2

.

5

σ

to

>

8

σ

,

>

5% to

>

45%, and

<

0

.

05 to

<

0

.

2.Forallbutthe

α

cut in PbPb collisions,

DR

isplottedasafunctionoftheselectionvalue and fit to a linear function. The systematic uncertainty is taken as the difference between unity and the value ofthe fitted line atthepoint wherenoselectionisapplied.Forthe

α

requirement inPbPb collisions,thesystematicuncertaintyisobtainedfromthe biggestdifferencesbetweenunityandthevalueof

DR

fromallof thealternativeselectionvalues.Combiningtheresultsofthethree topologicalselectioncriteriasystematicuncertaintiesinquadrature resultsinuncertaintiesof6% forthe pp datasetand19% forthe PbPb datasets.

The second uncertainty arises from a potential mismodeling of the pT distribution of



+c baryonsbecause A

isstrongly

de-pendent on the



+_c pT. In pp collisions,the default pT shape is

derived from the data. ForPbPb collisions, the default pT shape

is obtained from mT scaling of the measured D0 pT spectrum.

For each dataset, two alternative pT spectra,one from pythia 8

andonefrom pythia 8withcolorreconnection(describedin Sec-tion6)areconsideredandthemaximumdeviationin A

istaken asthesystematicuncertainty.Theresultingsystematicuncertainty is0–3%forpp collisionsand5.2%forPbPb collisions.

The third uncertainty arisesfrom impreciseknowledge of the resonantsubstructureofthepK−

π

+decaymode [39].The calcula-tionofA

usestheappropriatelyweightedsumofthefourknown sub-channelsandthesystematicuncertaintyassociatedwiththisis evaluated by determining A

foreach sub-channelandrandomly adjustingtheweightsbytheuncertaintiesofeachbranching frac-tion. Theindividual values of A

vary by about

±

30% relative to theaverage.Thesystematicuncertaintyisobtainedfromthe stan-darddeviationofaGaussianfittothedifferentaverage A

values andis8%forbothpp andPbPb events.

ThefourthuncertaintyassociatedwiththeMCmodelingofthe dataisthetrackreconstructionefficiency,whichis4%forpp colli-sions [14] and5%forPbPb collisions [40].Astherearethreetracks inthe



+_c decay,thecorrespondinguncertaintiesonthemeasured pT spectra are 12 and 15% for pp and PbPb, respectively, while

for the



+_c

/

D0 _{productionratio, the uncertainties are 4 and 5%,}

respectively.

The fifth uncertaintyarises frompossible mismodeling of the nonpromptcomponent, namely



+_c fromb hadrondecays,inthe inclusive



+_c sample. The inclusive A

is the weighted sum of prompt and nonprompt A

according to the prompt and non-promptfractions.Asfoundusingthestandard pythia 8MCsample, the nonprompt A

isgenerally3–4timeslargerthan theprompt A

and so an incorrect nonprompt fraction in pythia 8 will re-sultin an incorrect A

for theinclusivesample. To evaluatethis systematic uncertainty, an alternative method is used to obtain the final resultthat doesnot rely onthe pythia 8 predictionfor thenonpromptfraction.Agenerator-only pythia 8sampleof non-prompt



+_c events is reweighted to matchthe pT-differential b

hadroncrosssectionfromafixed-orderplusnext-to-leading loga-rithm (FONLL) calculation [41].The resulting pT-differentialcross

section for nonprompt



+_c baryons is multiplied by the appro-priate luminosity,branchingfractions,and A

fornonprompt



+_c

eventstoobtainanestimateofthenumberofreconstructed non-prompt



+_c baryonsineach

p

Tbin.Subtractingthisvaluefromthe

measurednumberofreconstructed



+_c baryonsgivesthenumber ofreconstructedprompt



+_c baryons.Thesereconstructedprompt yields are then corrected using the prompt A

aswell as lumi-nosityandbranchingfractionstoestimatethe pT-differentialcross

sectionforprompt



+_c baryons.Finally,thetwocrosssectionsgive an alternativeestimate ofthenonpromptfractionineach pT bin,

and therefore an alternative estimate of the weighted inclusive A

value. The systematic uncertainty is taken as the difference between the nominal and alternative A

values.The nonprompt fractionforeventspassingthepp selectioncriteriaisfoundtobe 28–34%forthenominalscenario(pythia 8only)and4–7%forthe alternative method,withhighervaluesassociatedwithlarger



+_c

pT. The resultingsystematicuncertaintyvaries byonly

±

1% as a

function of pT soan averagevalue of18%isusedforall pT bins.

The samemethodisapplied tothePbPb dataset,wherethe sys-tematic uncertainty is found to be 25% as a result of the more stringent selectioncriteria. For PbPb collisions, an additional sys-tematic uncertaintyis assessed by takingthe difference between applying and not applying the correction for different values of RAA fornonpromptandprompt



+c baryonsasdiscussedin

The overall



+_c

→

pK−

π

+ branching fraction uncertainty is 5.3% [39]. The uncertainties in the integrated luminosity in pp collisions and the MB selection efficiency in PbPb collisions are 2.3% [42] and2.0% [29],respectively.The uncertaintiesin TAA are

listedinTable1.

Forthemeasurementofthe pTspectra,theuncertainties

asso-ciatedwiththe



+_c

→

pK−

π

+branchingfractionandsubresonant contributions,theluminosityandMBselectionefficiency,andthe nonprompt fraction contribute only to the overall normalization andarelabeledglobaluncertainties.Addingthesecontributionsin quadratureyields globaluncertaintiesof21% (31%)forpp

(

PbPb

)

collisions. In measuring the nuclear modification factor RAA, the

uncertaintiesassociated withthebranching fractionand subreso-nantcontributionscancelandthenonpromptfractionuncertainty partially cancels. In calculating the



+_c

/

D0 production ratio, the uncertaintiesassociated withD0 fromtheyield extraction, selec-tioncriteriaefficiency, and pT shape are obtainedfromRef. [14],

while the uncertainties in the integrated luminosity in pp colli-sionsandtheMBselectionefficiencyinPbPb collisionscancel. 6. Resultsanddiscussion

Fig.2 shows the pT-differential crosssection ofinclusive



+_c

baryon production in pp collisions for the range of 5

<

pT

<

20 GeV/c andthe

T

AA-scaledyieldsinPbPb collisionsfortherange

of10

<

pT

<

20 GeV/c, forthree centrality classes.The 21% (31%)

normalizationuncertaintyforthepp (PbPb)resultsisnotincluded in the boxes representing the systematic uncertainties for each datapoint.Whiletheshapeofthe pT distributioninpp collisions

isconsistentwiththeinclusiveproductioncalculationfrom pythia 8 using tune CUETP8M1 and activating the “SoftQCD:nondiffrac-tive”processes,thedataaresystematicallyhigher.The hadroniza-tionin pythia 8 can be modified by addinga colorreconnection (CR)mechanisminwhichthefinalpartonsinthestring fragmen-tation are considered to be color connected in such a way that thetotalstringlengthbecomesasshortaspossible [43]. The cal-culationsusingthe recommendedcolorreconnectionmodelfrom Ref. [43] are consistent with our pT-differential cross section in

pp collisions.The pT-differential cross section inpp collisions is

alsocomparedtotheGM-VFNSperturbativeQCDcalculations [44], whichincludesonlyprompt



+_c baryonproduction.TheGM-VFNS predictionissignificantlybelowourdataforpT

<

10 GeV/c,similar

tothedifferencefoundbyALICE [21]. pythia 8predictsthat8–15% of generated



+_c baryons arise from b hadrons, with the low (high)valuecorrespondingtothe



+_c pTinterval5

<

pT

<

6 GeV/c

(

10

<

pT

<

20 GeV/c

)

.Therefore,accountingfortheeffectsof

non-prompt



+_c productionwill onlymarginally reduce the disagree-mentwiththeGM-VFNSprediction.

Thenuclear modification factor RAA forinclusive



+c baryons

in the pT range 10–20 GeV/c is shown in Fig. 3 as a function of

the numberof participating nucleons



Npart



for PbPb collisions.

The resultssuggest that



+_c is suppressed in PbPb collisions for pT

>

10 GeV/c,butnoconclusioncanbedrawnbecauseofthelarge

uncertainties.Thedifferencein

R

AAvaluesbetweenthe0–30%and

30–100%centralityrangesisconsistentwithanenhanced suppres-sioninthemorecentralPbPb collisions.

Fig.4showsthe



+_c

/

D0productionratioasafunctionof

p

Tfor

pp collisions andPbPb collisions inthe centrality range0–100%. Theproductionratiofound frompp collisionsissimilar inshape versus pT butaboutthreetimeslargerinmagnitudecomparedto

the calculation from pythia 8.212tune CUETP8M1. Results using theMonash2013 [45] tunearefoundtobe consistentwiththose fromtheCUETP8M1tune.Besidesprovidingareasonable descrip-tionof



+_c baryon pT-differentialcrosssections,Fig.4showsthat

calculationsusinga colorreconnection modelareconsistentwith ourresultsforthe



+_c

/

D0 productionratioinpp collisions.

Fig. 2. The pT-differentialcrosssectionsforinclusive+c productioninpp

colli-sionsandtheTAA-scaledyieldsforthreecentralityregionsofPbPb collisions.The

boxesanderrorbarsrepresentthesystematicandstatisticaluncertainties, respec-tively.ThePbPb datapointsareshiftedinthehorizontalaxisforclarity.Predictions forpp collisionsaredisplayedfor pythia 8withtheCUETP8M1tune(opencrosses), pythia8withcolorreconnection [43] (openstars),andGM-VFNS [44] (opencircles labeled“JHEP12(2017)021”)alongwithratiostothedatainthelowertwopanels. The pythia 8(GM-VFNS)predictionsareforinclusive(prompt)+c production.The

errorbarsontheGM-VFNSpredictionaccountforthescalevariationuncertainty. Thelowerpanelsshowthedata-to-predictionratioforpp collisionswithinnerand outererrorbarscorrespondingtothestatisticalandtotaluncertaintyinthedata, respectively,andtheshadedboxatunityindicatingthe21%normalization uncer-tainty.TheshadedboxesinthebottompanelrepresenttheGM-VFNSuncertainty.

Fig. 3. ThenuclearmodificationfactorRAAversusNpartforinclusive+c

produc-tion.TheerrorbarsrepresentthePbPb yieldstatisticaluncertainties.Theboxesat eachpointincludethePbPb systematicuncertaintiesassociatedwiththesignal ex-traction,pTspectrum,selectioncriteria,trackreconstruction,andTAA.Thebandat

unitylabeledpp uncertaintyincludesthesesameuncertaintiesforthepp data (ex-ceptforTAA)plustheuncertaintiesinpp yieldandluminosity.Thebandatunity

Fig. 4. Theratiooftheproduction crosssectionsofinclusive+c topromptD0

versuspTfrompp collisionsaswellas0–100%centralityPbPb collisions.Theboxes

anderrorbarsrepresentthe systematicand statisticaluncertainties,respectively. ThePbPb datapointisshiftedinthe horizontalaxisfor clarity.The20and31% normalizationuncertaintiesinpp andPbPb collisions,respectively,arenotincluded intheboxesrepresentingthesystematicuncertaintiesforeachdatapoint.Theopen crossesandopenstarsrepresentthepredictionsof pythia 8withtheCUETP8M1 tuneandwithcolorreconnection [43],respectively.Thesolidanddashedlinesare thecalculationsforprompt+c overpromptD

0

productionratiofromRef. [20] and Ref. [46],respectively.Allpredictionsareforpp collisions.

Thepp dataarealsocomparedwithtwopredictionswhichare for the prompt



+_c over D0 production ratio.Calculations using a modelthat includes both coalescenceandfragmentation inpp collisions [20] areshowninFig.4by thesolid line. Comparedto the data, this model predicts a stronger dependence on pT and

underestimatesthe measurements.Anotherrecentmodel [46] at-tempts to usea statistical hadronization approachto explain the large



+_c

/

D0 _{production ratio as arising from}

_

+

c baryons that

are produced fromthe decayof excited charm baryon statesnot includedinRef. [39] andarethereforenotincludedinthe hadron-izationsimulation in pythia 8.The predictionofthismodel, also showninFig.4bythedashedline,providesareasonable descrip-tionofthedatafor pT

<

10 GeV/c.

WhiletheALICEresultsindicateanenhancementinthe



+_c

/

D0 productionratiointhe

p

Trangeof6–12 GeV/c forPbPb [22]

com-paredtopPbandpp collisions,theCMSPbPb measurementinthe pT range 10–20 GeV/c is consistent with the pp result.This lack

ofan enhancement maysuggest that there isno significant con-tribution fromthe coalescence process for pT

>

10 GeV/c in PbPb

collisions. 7. Summary

The

p

T-differentialcrosssectionsof



+c baryons,includingboth

promptandnonpromptcontributions, havebeenmeasuredinpp andPbPb collisionsatanucleon-nucleoncenter-of-massenergyof 5.02 TeV.Theshape ofthe pT distribution inpp collisionsiswell

described by the pythia 8eventgenerator. Ahintofsuppression of



+_c productionfor10

<

pT

<

20 GeV/c isobservedinPbPb when

comparedto pp data,withcentral PbPb eventsshowingstronger suppression. This is consistent with the suppression observed in D0 meson measurements, which is understoodto originate from the strong interaction betweenthe charm quark andthe quark-gluon plasma. The



+_c

/

D0 _{production ratios in pp collisions are}

consistentwithamodelobtainedbyaddingcolorreconnectionin hadronization to pythia 8, and also with a model that includes enhancedcontributions fromthedecayofexcited charmbaryons. The



+_c

/

D0 productionratios inpp andPbPb collisions for pT

=

10–20 GeV/c arefoundtobeconsistentwitheachother.Thesetwo observations may suggest that the coalescence process doesnot playasignificantrolein



+_c baryonproductioninthis

p

T range.

Acknowledgements

WethankV.Grecoforprovidingthetheoreticalcalculationsof the



+_c

/

D0 productionratiosusedforcomparisonswithour mea-surementsinpp collisions.

WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the technical andadministrativestaffs atCERNand atother CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcentresand personneloftheWorldwideLHCComputingGridfordeliveringso effectively thecomputinginfrastructure essentialto our analyses. Finally, we acknowledge the enduring support for the construc-tion andoperationofthe LHCandtheCMSdetectorprovided by the followingfundingagencies: BMBWFandFWF(Austria);FNRS and FWO (Belgium); CNPq, CAPES,FAPERJ, FAPERGS, andFAPESP (Brazil); MES (Bulgaria); CERN; CAS, MOST, and NSFC (China); COLCIENCIAS (Colombia); MSES and CSF (Croatia); RPF (Cyprus); SENESCYT (Ecuador); MoER, ERC IUT, PUT and ERDF (Estonia); AcademyofFinland,MEC,andHIP(Finland);CEAandCNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); NK-FIA (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy);MSIPandNRF(RepublicofKorea);MES(Latvia);LAS (Lithuania);MOEandUM(Malaysia);BUAP,CINVESTAV,CONACYT, LNS,SEP,andUASLP-FAI(Mexico);MOS(Montenegro);MBIE(New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portu-gal);JINR(Dubna);MON,ROSATOM, RAS,RFBR,andNRCKI (Rus-sia);MESTD(Serbia);SEIDI,CPAN,PCTI,andFEDER(Spain);MoSTR (Sri Lanka); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter,IPST,STAR, andNSTDA(Thailand);TUBITAKandTAEK (Turkey);NASU andSFFR (Ukraine);STFC(United Kingdom);DOE andNSF(USA).

theRachadapisekSompotFundforPostdoctoralFellowship, Chula-longkornUniversity andthe ChulalongkornAcademicintoIts 2nd CenturyProjectAdvancementProject(Thailand);TheWelch Foun-dation,contractC-1845;andtheWestonHavensFoundation(USA). References

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TheCMSCollaboration

A.M. Sirunyan

†

,

A. Tumasyan

YerevanPhysicsInstitute,Yerevan,Armenia

W. Adam,

F. Ambrogi,

T. Bergauer,

J. Brandstetter,

M. Dragicevic,

J. Erö,

A. Escalante Del Valle,

M. Flechl,

R. Frühwirth

1

,

M. Jeitler

1

,

N. Krammer,

I. Krätschmer,

D. Liko,

T. Madlener,

I. Mikulec,

N. Rad,

J. Schieck

1

,

R. Schöfbeck,

M. Spanring,

D. Spitzbart,

W. Waltenberger,

J. Wittmann,

C.-E. Wulz

1

,

M. Zarucki

InstitutfürHochenergiephysik,Wien,Austria

V. Drugakov,

V. Mossolov,

J. Suarez Gonzalez

InstituteforNuclearProblems,Minsk,Belarus

M.R. Darwish,

E.A. De Wolf,

D. Di Croce,

X. Janssen,

J. Lauwers,

A. Lelek,

M. Pieters,

H. Rejeb Sfar,

H. Van Haevermaet,

P. Van Mechelen,

S. Van Putte,

N. Van Remortel

UniversiteitAntwerpen,Antwerpen,Belgium

F. Blekman,

E.S. Bols,

S.S. Chhibra,

J. D’Hondt,

J. De Clercq,

D. Lontkovskyi,

S. Lowette,

I. Marchesini,

S. Moortgat,

L. Moreels,

Q. Python,

K. Skovpen,

S. Tavernier,

W. Van Doninck,

P. Van Mulders,

I. Van Parijs

VrijeUniversiteitBrussel,Brussel,Belgium

D. Beghin,

B. Bilin,

H. Brun,

B. Clerbaux,

G. De Lentdecker,

H. Delannoy,

B. Dorney,

L. Favart,

A. Grebenyuk,

A.K. Kalsi,

J. Luetic,

A. Popov,

N. Postiau,

E. Starling,

L. Thomas,

C. Vander Velde,

P. Vanlaer,

D. Vannerom,

Q. Wang

UniversitéLibredeBruxelles,Bruxelles,Belgium

T. Cornelis,

D. Dobur,

I. Khvastunov

2

,

C. Roskas,

D. Trocino,

M. Tytgat,

W. Verbeke,

B. Vermassen,

M. Vit,

N. Zaganidis

GhentUniversity,Ghent,Belgium

O. Bondu,

G. Bruno,

C. Caputo,

P. David,

C. Delaere,

M. Delcourt,

A. Giammanco,

G. Krintiras,

V. Lemaitre,

A. Magitteri,

K. Piotrzkowski,

J. Prisciandaro,

A. Saggio,

M. Vidal Marono,

P. Vischia,

J. Zobec

UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium

F.L. Alves,

G.A. Alves,

G. Correia Silva,

C. Hensel,

A. Moraes,

P. Rebello Teles

CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil

E. Belchior Batista Das Chagas,

W. Carvalho,

J. Chinellato

3

,

E. Coelho,

E.M. Da Costa,

G.G. Da Silveira

4

,

D. De Jesus Damiao,

C. De Oliveira Martins,

S. Fonseca De Souza,

L.M. Huertas Guativa,

H. Malbouisson,

J. Martins

5

,

D. Matos Figueiredo,

M. Medina Jaime

6

,

M. Melo De Almeida,

C. Mora Herrera,

L. Mundim,

H. Nogima,

W.L. Prado Da Silva,

L.J. Sanchez Rosas,

A. Santoro,

A. Sznajder,

M. Thiel,

E.J. Tonelli Manganote

3

,

F. Torres Da Silva De Araujo,

A. Vilela Pereira

UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil

S. Ahuja

a

,

C.A. Bernardes

a

,

L. Calligaris

a

,

T.R. Fernandez Perez Tomei

a

,

E.M. Gregores

b

,

D.S. Lemos,

P.G. Mercadante

b

,

S.F. Novaes

a

,

SandraS. Padula

a

A. Aleksandrov,

G. Antchev,

R. Hadjiiska,

P. Iaydjiev,

A. Marinov,

M. Misheva,

M. Rodozov,

M. Shopova,

G. Sultanov

InstituteforNuclearResearchandNuclearEnergy,BulgarianAcademyofSciences,Sofia,Bulgaria

A. Dimitrov,

L. Litov,

B. Pavlov,

P. Petkov

UniversityofSofia,Sofia,Bulgaria

W. Fang

7

,

X. Gao

7

,

L. Yuan

BeihangUniversity,Beijing,China

M. Ahmad,

G.M. Chen,

H.S. Chen,

M. Chen,

C.H. Jiang,

D. Leggat,

H. Liao,

Z. Liu,

S.M. Shaheen

8

,

A. Spiezia,

J. Tao,

E. Yazgan,

H. Zhang,

S. Zhang

8

,

J. Zhao

InstituteofHighEnergyPhysics,Beijing,China

A. Agapitos,

Y. Ban,

G. Chen,

A. Levin,

J. Li,

L. Li,

Q. Li,

Y. Mao,

S.J. Qian,

D. Wang

StateKeyLaboratoryofNuclearPhysicsandTechnology,PekingUniversity,Beijing,China

Z. Hu,

Y. Wang

TsinghuaUniversity,Beijing,China

C. Avila,

A. Cabrera,

L.F. Chaparro Sierra,

C. Florez,

C.F. González Hernández,

M.A. Segura Delgado

UniversidaddeLosAndes,Bogota,Colombia

D. Giljanovi ´c,

N. Godinovic,

D. Lelas,

I. Puljak,

T. Sculac

UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia

Z. Antunovic,

M. Kovac

UniversityofSplit,FacultyofScience,Split,Croatia

V. Brigljevic,

S. Ceci,

D. Ferencek,

K. Kadija,

B. Mesic,

M. Roguljic,

A. Starodumov

9

,

T. Susa

InstituteRudjerBoskovic,Zagreb,Croatia

M.W. Ather,

A. Attikis,

E. Erodotou,

A. Ioannou,

M. Kolosova,

S. Konstantinou,

G. Mavromanolakis,

J. Mousa,

C. Nicolaou,

F. Ptochos,

P.A. Razis,

H. Rykaczewski,

D. Tsiakkouri

UniversityofCyprus,Nicosia,Cyprus

M. Finger

10

,

M. Finger Jr.

10

,

A. Kveton,

J. Tomsa

CharlesUniversity,Prague,CzechRepublic

E. Ayala

EscuelaPolitecnicaNacional,Quito,Ecuador

E. Carrera Jarrin

UniversidadSanFranciscodeQuito,Quito,Ecuador

M.A. Mahmoud

11

,

12

,

Y. Mohammed

11

AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt

S. Bhowmik,

A. Carvalho Antunes De Oliveira,

R.K. Dewanjee,

K. Ehataht,

M. Kadastik,

M. Raidal,

C. Veelken

P. Eerola,

L. Forthomme,

H. Kirschenmann,

K. Osterberg,

J. Pekkanen,

M. Voutilainen

DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland

F. Garcia,

J. Havukainen,

J.K. Heikkilä,

T. Järvinen,

V. Karimäki,

R. Kinnunen,

T. Lampén,

K. Lassila-Perini,

S. Laurila,

S. Lehti,

T. Lindén,

P. Luukka,

T. Mäenpää,

H. Siikonen,

E. Tuominen,

J. Tuominiemi

HelsinkiInstituteofPhysics,Helsinki,Finland

T. Tuuva

LappeenrantaUniversityofTechnology,Lappeenranta,Finland

M. Besancon,

F. Couderc,

M. Dejardin,

D. Denegri,

B. Fabbro,

J.L. Faure,

F. Ferri,

S. Ganjour,

A. Givernaud,

P. Gras,

G. Hamel de Monchenault,

P. Jarry,

C. Leloup,

E. Locci,

J. Malcles,

J. Rander,

A. Rosowsky,

M.Ö. Sahin,

A. Savoy-Navarro

13

,

M. Titov

IRFU,CEA,UniversitéParis-Saclay,Gif-sur-Yvette,France

C. Amendola,

F. Beaudette,

P. Busson,

C. Charlot,

B. Diab,

R. Granier de Cassagnac,

I. Kucher,

A. Lobanov,

C. Martin Perez,

M. Nguyen,

C. Ochando,

P. Paganini,

J. Rembser,

R. Salerno,

J.B. Sauvan,

Y. Sirois,

A. Zabi,

A. Zghiche

LaboratoireLeprince-Ringuet,CNRS/IN2P3,EcolePolytechnique,InstitutPolytechniquedeParis,France

J.-L. Agram

14

,

J. Andrea,

D. Bloch,

G. Bourgatte,

J.-M. Brom,

E.C. Chabert,

C. Collard,

E. Conte

14

,

J.-C. Fontaine

14

,

D. Gelé,

U. Goerlach,

M. Jansová,

A.-C. Le Bihan,

N. Tonon,

P. Van Hove

UniversitédeStrasbourg,CNRS,IPHCUMR7178,Strasbourg,France

S. Gadrat

CentredeCalculdel’InstitutNationaldePhysiqueNucleaireetdePhysiquedesParticules,CNRS/IN2P3,Villeurbanne,France

S. Beauceron,

C. Bernet,

G. Boudoul,

C. Camen,

N. Chanon,

R. Chierici,

D. Contardo,

P. Depasse,

H. El Mamouni,

J. Fay,

S. Gascon,

M. Gouzevitch,

B. Ille,

Sa. Jain,

F. Lagarde,

I.B. Laktineh,

H. Lattaud,

M. Lethuillier,

L. Mirabito,

S. Perries,

V. Sordini,

G. Touquet,

M. Vander Donckt,

S. Viret

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

A. Khvedelidze

10

GeorgianTechnicalUniversity,Tbilisi,Georgia

Z. Tsamalaidze

10

TbilisiStateUniversity,Tbilisi,Georgia

C. Autermann,

L. Feld,

M.K. Kiesel,

K. Klein,

M. Lipinski,

D. Meuser,

A. Pauls,

M. Preuten,

M.P. Rauch,

C. Schomakers,

J. Schulz,

M. Teroerde,

B. Wittmer

RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany

A. Albert,

M. Erdmann,

S. Erdweg,

T. Esch,

B. Fischer,

R. Fischer,

S. Ghosh,

T. Hebbeker,

K. Hoepfner,

H. Keller,

L. Mastrolorenzo,

M. Merschmeyer,

A. Meyer,

P. Millet,

G. Mocellin,

S. Mondal,

S. Mukherjee,

D. Noll,

A. Novak,

T. Pook,

A. Pozdnyakov,

T. Quast,

M. Radziej,

Y. Rath,

H. Reithler,

M. Rieger,

A. Schmidt,

S.C. Schuler,

A. Sharma,

S. Thüer,

S. Wiedenbeck

RWTHAachenUniversity,III.PhysikalischesInstitutA,Aachen,Germany

G. Flügge,

W. Haj Ahmad

15

,

O. Hlushchenko,

T. Kress,

T. Müller,

A. Nehrkorn,

A. Nowack,

C. Pistone,

O. Pooth,

D. Roy,

H. Sert,

A. Stahl

16

M. Aldaya Martin,

C. Asawatangtrakuldee,

P. Asmuss,

I. Babounikau,

H. Bakhshiansohi,

K. Beernaert,

O. Behnke,

U. Behrens,

A. Bermúdez Martínez,

D. Bertsche,

A.A. Bin Anuar,

K. Borras

17

,

V. Botta,

A. Campbell,

A. Cardini,

P. Connor,

S. Consuegra Rodríguez,

C. Contreras-Campana,

V. Danilov,

A. De Wit,

M.M. Defranchis,

C. Diez Pardos,

D. Domínguez Damiani,

G. Eckerlin,

D. Eckstein,

T. Eichhorn,

A. Elwood,

E. Eren,

E. Gallo

18

,

A. Geiser,

J.M. Grados Luyando,

A. Grohsjean,

M. Guthoff,

M. Haranko,

A. Harb,

N.Z. Jomhari,

H. Jung,

A. Kasem

17

,

M. Kasemann,

J. Keaveney,

C. Kleinwort,

J. Knolle,

D. Krücker,

W. Lange,

T. Lenz,

J. Leonard,

J. Lidrych,

K. Lipka,

W. Lohmann

19

,

R. Mankel,

I.-A. Melzer-Pellmann,

A.B. Meyer,

M. Meyer,

M. Missiroli,

G. Mittag,

J. Mnich,

A. Mussgiller,

V. Myronenko,

D. Pérez Adán,

S.K. Pflitsch,

D. Pitzl,

A. Raspereza,

A. Saibel,

M. Savitskyi,

V. Scheurer,

P. Schütze,

C. Schwanenberger,

R. Shevchenko,

A. Singh,

H. Tholen,

O. Turkot,

A. Vagnerini,

M. Van De Klundert,

G.P. Van Onsem,

R. Walsh,

Y. Wen,

K. Wichmann,

C. Wissing,

O. Zenaiev,

R. Zlebcik

DeutschesElektronen-Synchrotron,Hamburg,Germany

R. Aggleton,

S. Bein,

L. Benato,

A. Benecke,

V. Blobel,

T. Dreyer,

A. Ebrahimi,

A. Fröhlich,

C. Garbers,

E. Garutti,

D. Gonzalez,

P. Gunnellini,

J. Haller,

A. Hinzmann,

A. Karavdina,

G. Kasieczka,

R. Klanner,

R. Kogler,

N. Kovalchuk,

S. Kurz,

V. Kutzner,

J. Lange,

T. Lange,

A. Malara,

D. Marconi,

J. Multhaup,

M. Niedziela,

C.E.N. Niemeyer,

D. Nowatschin,

A. Perieanu,

A. Reimers,

O. Rieger,

C. Scharf,

P. Schleper,

S. Schumann,

J. Schwandt,

J. Sonneveld,

H. Stadie,

G. Steinbrück,

F.M. Stober,

M. Stöver,

B. Vormwald,

I. Zoi

UniversityofHamburg,Hamburg,Germany

M. Akbiyik,

C. Barth,

M. Baselga,

S. Baur,

T. Berger,

E. Butz,

R. Caspart,

T. Chwalek,

W. De Boer,

A. Dierlamm,

K. El Morabit,

N. Faltermann,

M. Giffels,

P. Goldenzweig,

A. Gottmann,

M.A. Harrendorf,

F. Hartmann

16

,

U. Husemann,

S. Kudella,

S. Mitra,

M.U. Mozer,

Th. Müller,

M. Musich,

A. Nürnberg,

G. Quast,

K. Rabbertz,

M. Schröder,

I. Shvetsov,

H.J. Simonis,

R. Ulrich,

M. Weber,

C. Wöhrmann,

R. Wolf

KarlsruherInstitutfuerTechnologie,Karlsruhe,Germany

G. Anagnostou,

P. Asenov,

G. Daskalakis,

T. Geralis,

A. Kyriakis,

D. Loukas,

G. Paspalaki

InstituteofNuclearandParticlePhysics(INPP),NCSRDemokritos,AghiaParaskevi,Greece

M. Diamantopoulou,

G. Karathanasis,

P. Kontaxakis,

A. Panagiotou,

I. Papavergou,

N. Saoulidou,

A. Stakia,

K. Theofilatos,

K. Vellidis

NationalandKapodistrianUniversityofAthens,Athens,Greece

G. Bakas,

K. Kousouris,

I. Papakrivopoulos,

G. Tsipolitis

NationalTechnicalUniversityofAthens,Athens,Greece

I. Evangelou,

C. Foudas,

P. Gianneios,

P. Katsoulis,

P. Kokkas,

S. Mallios,

K. Manitara,

N. Manthos,

I. Papadopoulos,

J. Strologas,

F.A. Triantis,

D. Tsitsonis

UniversityofIoánnina,Ioánnina,Greece

M. Bartók

20

,

M. Csanad,

P. Major,

K. Mandal,

A. Mehta,

M.I. Nagy,

G. Pasztor,

O. Surányi,

G.I. Veres

MTA-ELTELendületCMSParticleandNuclearPhysicsGroup,EötvösLorándUniversity,Budapest,Hungary

G. Bencze,

C. Hajdu,

D. Horvath

21

,

F. Sikler,

T.Ã. Vámi,

V. Veszpremi,

G. Vesztergombi

†

WignerResearchCentreforPhysics,Budapest,Hungary

N. Beni,

S. Czellar,

J. Karancsi

20

,

A. Makovec,

J. Molnar,

Z. Szillasi

InstituteofNuclearResearchATOMKI,Debrecen,Hungary

P. Raics,

D. Teyssier,

Z.L. Trocsanyi,

B. Ujvari

T.F. Csorgo,

W.J. Metzger,

F. Nemes,

T. Novak

EszterhazyKarolyUniversity,KarolyRobertCampus,Gyongyos,Hungary

S. Choudhury,

J.R. Komaragiri,

P.C. Tiwari

IndianInstituteofScience(IISc),Bangalore,India

S. Bahinipati

23

,

C. Kar,

G. Kole,

P. Mal,

V.K. Muraleedharan Nair Bindhu,

A. Nayak

24

,

S. Roy Chowdhury,

D.K. Sahoo

23

,

S.K. Swain

NationalInstituteofScienceEducationandResearch,HBNI,Bhubaneswar,India

S. Bansal,

S.B. Beri,

V. Bhatnagar,

S. Chauhan,

R. Chawla,

N. Dhingra,

R. Gupta,

A. Kaur,

M. Kaur,

S. Kaur,

P. Kumari,

M. Lohan,

M. Meena,

K. Sandeep,

S. Sharma,

J.B. Singh,

A.K. Virdi

PanjabUniversity,Chandigarh,India

A. Bhardwaj,

B.C. Choudhary,

R.B. Garg,

M. Gola,

S. Keshri,

Ashok Kumar,

S. Malhotra,

M. Naimuddin,

P. Priyanka,

K. Ranjan,

Aashaq Shah,

R. Sharma

UniversityofDelhi,Delhi,India

R. Bhardwaj

25

,

M. Bharti

25

,

R. Bhattacharya,

S. Bhattacharya,

U. Bhawandeep

25

,

D. Bhowmik,

S. Dey,

S. Dutta,

S. Ghosh,

M. Maity

26

,

K. Mondal,

S. Nandan,

A. Purohit,

P.K. Rout,

A. Roy,

G. Saha,

S. Sarkar,

T. Sarkar

26

,

M. Sharan,

B. Singh

25

,

S. Thakur

25

SahaInstituteofNuclearPhysics,HBNI,Kolkata,India

P.K. Behera,

P. Kalbhor,

A. Muhammad,

P.R. Pujahari,

A. Sharma,

A.K. Sikdar

IndianInstituteofTechnologyMadras,Madras,India

R. Chudasama,

D. Dutta,

V. Jha,

V. Kumar,

D.K. Mishra,

P.K. Netrakanti,

L.M. Pant,

P. Shukla

BhabhaAtomicResearchCentre,Mumbai,India

T. Aziz,

M.A. Bhat,

S. Dugad,

G.B. Mohanty,

N. Sur,

RavindraKumar Verma

TataInstituteofFundamentalResearch-A,Mumbai,India

S. Banerjee,

S. Bhattacharya,

S. Chatterjee,

P. Das,

M. Guchait,

S. Karmakar,

S. Kumar,

G. Majumder,

K. Mazumdar,

S. Sawant

TataInstituteofFundamentalResearch-B,Mumbai,India

S. Chauhan,

S. Dube,

V. Hegde,

A. Kapoor,

K. Kothekar,

S. Pandey,

A. Rane,

A. Rastogi,

S. Sharma

IndianInstituteofScienceEducationandResearch(IISER),Pune,India

S. Chenarani

27

,

E. Eskandari Tadavani,

S.M. Etesami

27

,

M. Khakzad,

M. Mohammadi Najafabadi,

M. Naseri,

F. Rezaei Hosseinabadi

InstituteforResearchinFundamentalSciences(IPM),Tehran,Iran

M. Felcini,

M. Grunewald

UniversityCollegeDublin,Dublin,Ireland

M. Abbrescia

a

,

b

,

C. Calabria

a

,

b

,

A. Colaleo

a

,

D. Creanza

a

,

c

,

L. Cristella

a

,

b

,

N. De Filippis

a

,

c

,

M. De Palma

a

,

b

,

A. Di Florio

a

,

b

,

L. Fiore

a

,

A. Gelmi

a

,

b

,

G. Iaselli

a

,

c

,

M. Ince

a

,

b

,

S. Lezki

a

,

b

,

G. Maggi

a

,

c

,

M. Maggi

a

,

G. Miniello

a

,

b

,

S. My

a

,

b

,

S. Nuzzo

a

,

b

,

A. Pompili

a

,

b

,

G. Pugliese

a

,

c

,

R. Radogna

a

,

A. Ranieri

a

,

G. Selvaggi

a

,

b

,

L. Silvestris

a

,

R. Venditti

a

,

P. Verwilligen

a