Measurement of the inelastic cross section in proton-lead collisions at root s(NN)=5.02 TeV

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Physics

Letters

B

www.elsevier.com/locate/physletb

Measurement

of

the

inelastic

cross

section

in

proton–lead

collisions

at

√

s

=

5

.

02

TeV

Availableonline16June2016 Editor:M.Doser Keywords: CMS Forwardphysics Proton–lead Crosssection

The inelastic hadroniccross sectionin proton–leadcollisions at acentre-of-mass energypernucleon pairof5.02 TeVismeasuredwiththeCMSdetectorattheLHC. Thedata sample,correspondingtoan integratedluminosityofL=12.6±0.4 nb−1,hasbeencollectedwithanunbiasedtriggerforinclusive particleproduction.Thecrosssectionisobtainedfromthemeasurednumberofproton–leadcollisions withhadronicactivityproducedinthepseudorapidityranges3<η<5 and/or−5<η<−3,corrected forphoton-inducedcontributions,experimentalacceptance,andotherinstrumentaleffects.Theinelastic cross sectionis measuredto beσinel(pPb)=2061±3(stat)±34(syst)±72(lumi) mb.VariousMonte

Carlogenerators,commonlyusedinheavyionandcosmicrayphysics,arefoundtoreproducethedata withinuncertainties.Thevalueofσinel(pPb) iscompatiblewiththatexpectedfromtheproton–proton

crosssectionat5.02 TeVscaledupwithinasimpleGlauberapproachtoaccountformultiplescatterings intheleadnucleus,indicatingthatfurthernetnuclearcorrectionsaresmall.

©2016TheAuthor.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

1. Introduction

Themeasurementof theinelasticcrosssection inproton–lead collisions, σinel(pPb), ata centre-of-massenergyper nucleonpair of5.02 TeV performed by theCMS experimentat theCERN LHC is presented. The inelastic cross section (also called “particle-production”[1]or“absorption” [2]crosssectioninprevious stud-ies) is defined to include all hadronic events, including contri-butions from diffractive processes, except those from the quasi-elastic excitation of the lead nucleus—estimated to amount to about 100 mb for the pPb system [3]. Inelastic electromagnetic (photon–proton) collisions are also excluded from the measure-ment.

Whilebeingone ofthemostinclusiveobservablesinhadronic collisions, the inelastic cross section is one of the least theo-retically accessible quantities, as it cannot be determined from first-principlescalculationsofthetheoryofthestronginteraction, quantum chromodynamics. In proton–proton (pp) and nucleus– nucleuscollisionsattheLHC,particlesproducedinhadronic inter-actionscomemostlyfromthehadronisationofquarksandgluons, eitherproducedin semi-hardscatterings (“minijets”)[4]or emit-tedatveryforwardrapiditiesfrom“spectator”partons,aswell as from soft diffractive processes in “peripheral” interactions. From

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

the measured inelasticproton–proton (or nucleon–nucleon) cross sectionatagivencollisionenergy,onecantheoreticallyderivethe corresponding proton–nucleusandnucleus–nucleuscrosssections bymeansofGlauber [5,6]orGribov–Regge[7]multiple-scattering approaches that take into account the known transverse matter profile ofnuclei. Key quantities forthe experimental comparison between nucleus–nucleus and pp collisions—such as the nuclear overlapfunction,thenumberofnucleon–nucleoncollisionsandof participantnucleons [8,9]—arealso commonlycomputedthrough suchapproaches.ValidatingtheGlauberandGribov–Regge predic-tionswithproton–nucleuscollisionsatLHCenergieshasimportant implications beyond collider physics. Such approaches constitute crucialingredientsintheMonteCarlomodellingofcosmicrayair showersatthehighestenergies [10],forwhichtheinelasticcross sectionsmeasured in thelaboratory mustbe extrapolated overa wideenergyrange.Infact,theinelasticproton–air(mostlyproton– nitrogen andproton–oxygen) cross section introduces one of the largestuncertaintiesforairshowersimulations[11,12].

The Glauber multiple-collision model, based on the eikonal limit(i.e.straight-linetrajectoriesofthecollidingnucleons),isthe simplestand mosteconomical approach oftenused to derive in-clusiveproton–nucleus quantitiesfromthepp crosssectionsand, vice versa,to obtainpp cross sectionsfromthecosmic ray mea-surements [13]. However, some ofthe approximationsapplied in the model—foremostthe absence ofshort-range nucleon correla-tions [14] and of inelastic screening [15]—impact the computed

http://dx.doi.org/10.1016/j.physletb.2016.06.027

0370-2693/©2016TheAuthor.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).Fundedby SCOAP3_.

cross section values. This is observed for fixed-target proton– carbon data [16–20] and estimated for collider [21,22] as well as ultra-high cosmic ray [13] energies, where corrections to the proton–air crosssection of theorder of10% havebeen obtained. Short-range correlationsincrease thenumberofnucleon–nucleon collisions at small impact parameters yielding a larger nucleus– nucleus cross section. On the other hand, screening affects the numberof nucleons that are diffractively excited in themultiple collisions but revert back to their ground state before the scat-tering process is completed, thereby reducing the nuclear cross section.Differentimplementationsofsucheffectsexistinthe cur-rent hadronic interaction models [15,23–29]. A measurement of

σinel in pPbcollisions at theLHC can test ifthe precision ofthe standard Glauber calculation is sufficient, and at which energies correctionstotheGlauberapproachmaybecomerelevant.

2. ExperimentalsetupandMonteCarlosimulations

The measurement presentedhere is basedon pPb data taken with the CMS experiment at the LHC at the beginning of 2013. A detaileddescriptionoftheapparatuscan befound in[30].The main detector used in this analysis is the hadron forward (HF) calorimeterthatcoversthepseudorapidityinterval3<|η|<5.The calorimeteriscomposed ofquartz fibresina steelmatrixwitha 0.175×0.175 segmentation inthe azimuthal angle φ (in radians) and pseudorapidity η. The quartz fibres pick up the Cherenkov light produced by the chargedcomponent of showers. This light isthen measuredby photodetectortubes.The hadronicand elec-tromagneticsignalsofeachsegment,asderivedfromfibresoftwo differentlengthsanddepths,arecombinedtoformatower signal. Thedatausedinthisanalysiscompriseanintegrated luminos-ityof L=12.6±0.4 nb−1. Thisdataset combinesthe integrated luminositiesofthetwo possibledirectionsoftheprotonandlead beams: 5.0±0.2 nb−1 and 7.6±0.3 nb−1,for theproton beam goingrespectivelyintheclockwise(negative η)andanticlockwise (positive η) direction.The eventsare collectedusing anunbiased trigger, only requiring the presence of both beams in the inter-action point, asdetermined by the “Beam Pickup Timingforthe eXperiments”(BPTX)devices.Detectornoiseisstudiedwithevents that are randomlyread out in the absenceofboth beams inthe detector. The luminosity determination technique was calibrated by means of a vander Meer scan [31] forboth beam directions independently,withanuncertaintyof3.5%[32].

A Monte Carlo event simulation based on a Geant4 detec-tor description [33] is used to model the experimental response and derive the reconstruction efficiencies. Different event gen-erators are used to simulate hadronic proton–nucleus collisions. Three models are based on the Gribov–Regge formalism: dpm-jet 3.06 [34], epos-lhc [25], and qgsjetii–04 [26]; and a fourth one is based on a minijet+Glauber approach: hijing 1.383 [35]. Inaddition,particleproductionfromphoton–proton(γp) interac-tions in “ultraperipheral” collisions, at impact parameters larger than the sum of proton and lead radii, needs to be taken into account [36]. Given the large Pb ion charge, and the associated large“equivalentphotonflux”ofitselectromagneticfield [36], in-elasticphoton–protoncollisions resultinanon-negligibleparticle productioncontribution.Pure photon–photon interactions, mostly producing exclusive electron–positron pairs, and photon–nucleus interactions (where the photon emitted from the protoncollides with the Pb ion) have orders-of-magnitude smaller visible cross sectionsandareneglected.Photon–protonprocessesaregenerated with the starlight programme [37] combined either with dpm-jet3.05or pythia 6.4.26[38].

3. Eventselectionandanalysis

In this analysis three types of cross sections are measured: (i) σobs afterremoval ofnoise and correction forpileup, (ii) σvis afterfurtherremovalofelectromagneticcontributionsand transla-tionintoahadron-levelquantity,and(iii)σinelincludingthefinal extrapolationtothetotalinelastichadroniccrosssection.Two dif-ferent approachesare used to determinethe numberof inelastic events: (1) a single-arm event selectionthat requires a localised calorimetric energysignal above a giventhreshold inthe HF de-tector either at positive or negative pseudorapidities, and (2) a double-arm event selectionthat requiresalocalised signal above thresholdinbothHF detectors.The advantageofusingthesetwo event selections is that they have very different sensitivities to diffractiveandphoton–protoneventsaswellastodetectornoise. Denoting by EHF+ (EHF-) the highest energy measured in an HF toweratpositive(negative)pseudorapidity,aneventistaggedasa candidateforaninelasticcollisionifithasavalueof

EHF=



max(EHF+,EHF-) for single-arm selection

min(EHF+,EHF-) for double-arm selection

(1)

aboveagiventhreshold.

The observed distribution of EHF is well reproduced by the combined hadronic inelastic, photon–proton, and detector noise contributionsasshowninthetop(bottom)panelofFig. 1forthe single-arm(double-arm)selection. The sizeofthe various contri-butions totheHFenergydepositionisdetermined fromdataand simulations.The signalisidentifiedasthat comingfromhadronic collisions whereas the backgrounds arise from electromagnetic photon–protoninteractionsanddetectornoise.Theexpected num-ber of photon–protoncollisions is Nγp= fγpσγpL,where fγp is thefractionofsimulatedphoton–protoneventspassing the selec-tionand σγp isthepredicted starlight crosssection.Thenumber ofmisidentifiedeventsproducedbyelectronicnoise inthe detec-tor is Nnoise=N fnoise, where fnoise isthe fractionofevents read out randomly in the absence of beams that pass the selection criteria, and N is thenumber of eventsrecorded withthe unbi-asedtrigger.TheestimateofNnoise includesNobs+noise=Nobsfnoise eventsthatcontainalsoanobservedinelasticcollision,whereNobs is the number of observed inelastic events. The double-counted events are explicitly subtracted from Nnoise. The uncertainty on

Nnoise is derived fromvariations indifferent data-taking periods.

The background induced by beam-gas collisions is found to be negligible deduced from the fractionof eventsselected with the triggerindicatingthepresenceofasingle beamintheinteraction point.

Of thenumber ofinelastic hadroniccollisions, Ninel, theones that are observed by the detector and pass the event selec-tion are defined as Nhad. The purity of the event selection is Nhad/Nhad+Nγp+Nnoise



,andtheacceptanceisgivenbythe ra-tio acc=Nhad/Ninel.Both the purity andtheacceptance depend on the energy threshold used for the selection. Higher purity is achievedforthedouble-armselection,sincephoton–proton inter-actions lead to atypical final state where mostofthe secondary products are asymmetricallyemittedtowards thedirectionofthe protonbeam.Noiseeventsarealsosuppressedbythecoincidence requirement. Theacceptanceisingeneralsmallerforthe double-arm selection due to the smaller chance of selecting diffractive events characterised by large rapidity gaps devoid of activity in oneorbothHFsides.

The dependence of acc on the HF tower energy threshold is showninFig. 2.Forthesingle-armselectiontheworkingpointis chosentobeEHF>8 GeV.Thisvalueistheresultofacompromise betweenacceptance(about93–94%)andcontamination,whilethe

Fig. 1. Distributionoftheenergy depositedinthe HFcalorimeter(EHF)for the

single-arm (top) and double-arm (bottom) event selections. The data sample, shownexemplarilyforoneperiodwithstablerunconditions,comprises1.31 nb−1

recordedwith anunbiasedtrigger.Thecontributionfromnoise isobtainedfrom a random trigger normalised to the same number of triggers as that in the collisiondata. The averagenumber ofphoton–proton processes simulated with starlight+dpmjet and starlight+pythia istreatedasbackgroundandstackedon top.Fourhadronicinteractionmodels(epos, dpmjet, hijing,and qgsjetii)are over-laidandnormalisedtothenumberofdataeventswith EHF>10 GeV,wherethe

contributionfromthebackgroundissmall.Theverticallinerepresentsthe thresh-oldenergyof8 GeV(4 GeV)forthesingle-arm(double-arm)selectionusedinthis analysis.

probability to have a tower above the threshold does not de-pendmuchonthebeamdirection.Thedouble-armselectionuses EHF>4 GeV yielding 99% purity and91% acceptance.The value acc fora specific EHF thresholdis determinedby averaging over theresultsofthe epos and qgsjetii models. The resultsof hijing and dpmjet, which do not include nuclear effects for diffraction, arenotconsideredforthispurpose.Indeed,wehaveverifiedthat bothlattermodelsareunabletodescribethevery-forwardenergy spectrameasuredwiththeCASTORdetector(−6.6<η<−5.2)in eventswithlargerapiditygaps,whichareparticularlysensitiveto diffractiveinteractions.

The uncertainties on the acc and Nγp values are estimated fromthemaximumabsolutedifferencesobtainedfromtheresults of different eventgenerators, averaged over a wide EHF interval between2and10 GeV.Theuncertaintieson acc are0.005 (0.014) andof Nγp/L are 11 mb (0.05 mb) forthe single-arm (double-arm)eventselections.

Fig. 2. Acceptanceversuspurityofthe twoeventselections,asderivedfromthe epos and qgsjetii generators. The symbols indicate different values ofthe EHF

thresholds.Thechosenthresholdsaremarkedwithsquares.

In this analysis no vertex reconstruction is performed and theimpact ofcontributionsfromadditionalpileup (PU)collisions recorded in any given event is consistently evaluated with the HF detector. The number of simultaneous collisions is Poisson-distributedwithan expectationvalue corresponding to the inter-action probability λ. If one collision is selected with probability

acc, then i simultaneous collisions are selected with probability Pi≈1− (1−acc)i.The approximation assumedintheequation,

whichdoesnotaccount forenergydepositsofmultipleeventsin theHF towers,was verifiedto bevalidby meansofa toy Monte Carlosimulation.The numberofcollisions isthen correctedwith the factor fPU=accλ/

∞

 i=1

PiPoisson(i;λ). The interaction

proba-bility λ, which amounts to 2–8% depending on the data-taking period, is calculatedrecursively from the ratio ofthe number of inelasticeventstothenumberofunbiasedtriggers.Thepileup cor-rectionincreasesthemeasuredcrosssectionby2%forbothevent selections, and introduces an uncertainty on the final pPb cross sectionthatissmallerthan0.1%.

Tofacilitatethedirectcomparisonoftheresultstomodel pre-dictions, detector level quantities, such as EHF, are translated to hadron-level quantities. For this purpose, pHF is defined equiva-lently to Eq. (1)but replacing EHF by the largestabsolute value amongthemomenta,|p|,ofallgeneratedfinal-stateparticles(with lifetimes above 1 cm/c), within the pseudorapidity intervals of the HF calorimeters (3<|η|<5), excluding muons and neutri-nos.A correctionfactorcvis,obtainedfromsimulations,isusedto translate themeasuredcrosssection intoahadron-level quantity, defined by the ratio of the number ofvisible events, which ful-filagivenrequirementon pHF,tothenumberofobservedevents, whichpasstheselectiononEHF.Thus,cvisislargerthanunityfor requiringpHF>0,butwillapproachzeroforveryhighthresholds. Thethresholdcanbechosenfreely,andforthepresentanalysisthe requirementontheminimalvalue of pHF ischosen suchthat the fractionsofeventspassing thisselectionandpassingthat on EHF areequal.Thefactorcvisthenbecomes equaltounityandhasno numericaleffectonthecentralvalueofthederivedcrosssection. This procedure leads to the choice ofselecting events that fulfil therequirementpHF>21.3 GeV/c (11.3 GeV/c)forthesingle-arm (double-arm)analysis.Forthechosen thresholds,themeanofthe cvisvaluesofallfourhadronicinteractionmodelsisunityandthe slight dependenceon models is takeninto account as a system-aticuncertaintyoncvisequaltothestandarddeviationofthefour values.

Table 1

Centralvaluesanduncertaintiesforthetwoeventselectionsfornoisecrosssectioncontribution(Nnoise/L) andthefractionofnoiseevents( fnoise)asderivedfromdata.Additionally,thequantitiesacceptance(acc),

electromagneticcrosssectioncontribution(Nγp/L),andhadron-levelcorrectionfactor(cvis)asderivedfrom

simulationsarelisted.

Selection Nnoise/L[mb] fnoise acc Nγp/L[mb] cvis

Single-arm 102±25 (2.0±0.5)×10−3 _{0.939±0.005 63±11 1.000±0.004}

Double-arm 9±3 (1.8±0.8)×10−4 _{0.910±0.014 0.33±0.05 1.000±0.002}

Thevaluesoftheacceptance,backgrounds,andcorrection fac-torsaresummarisedinTable 1.

Thenumberofobservedinelasticevents,Nobs,isderived from thenumberofeventspassingtheeventselection,Nsel,andis cor-rectedfornoise (Nnoise), doublecounting(Nobs+noise), andpileup ( fPU).Dividingthisnumberbytheintegratedluminosityyieldsthe observed crosssection:

σobs= Nobs

L =



Nsel−Nnoise+Nobs+noise

 fPU

L . (2)

UsingtherelationNobs+noise=Nobsfnoise oneobtains

σobs= 1 L Nsel−Nnoise 1/fPU−fnoise . (3)

The visible cross section for hadronic collisions is derived by subtracting the photon–proton contamination and applying the correction factor cvis. Its numerical value is, by definition,equal tothepartoftheobservedcrosssectionrelatedtohadronic colli-sions: σvis= 1 L Nsel−Nnoise−Nγp 1/fPU− fnoise cvis. (4)

Theinelastic crosssectionisobtainedbycorrectingforthe lim-iteddetectoracceptance(acc):

σinel= 1 L Nsel−Nnoise−Nγp 1/fPU−fnoise 1 acc . (5)

Theratioofthevisiblehadroniccrosssectionobtainedwiththe single-armselection totheoneobtainedwiththedouble-arm se-lection is sensitive to the fraction of diffractive pPb events. The measured value of this ratioallows one to constrain the diffrac-tive cross section, σdiff, in the models. In order to be compati-blewithin 2 standard deviations ofthe data,the epos diffractive cross section cannot be scaled up or down by more than ±13% from its default value, while for qgsjetii those limits are ±20%. Thispropagates intoan acc(σdiff) uncertaintyon σinel, conserva-tively assumed to be symmetric, of 0.8% (1.1%). Forthis andthe following uncertainties,the first numberis relatedto the single-armselection andthebracketedone tothedouble-armselection. Themodel-dependenceoftheacceptancecorrectionsresultsinan uncertaintyfor acc(models)of0.5% (1.6%)forthe twoselections, respectively.

Since less than half of the diffractive events, mostly with a high-mass diffractivesystem, pass the hadron-level selection,the uncertainty on cvis is smaller than that on acc. The 1 stan-dard deviation differences found among the four hadronic inter-actionmodels onthehadron-level correction,cvis,propagate into uncertainties on σvis of 0.4% (0.2%) for the single-arm (double-arm)selection.Thesubtractionofphoton–protonevents(withthe Nγp uncertainty shownin Table 1), results in an uncertainty of 0.6% (<0.1%) on σinel and σvis. The uncertainty on Nnoise prop-agates into a 1.3% (0.2%) uncertainty in the final cross sections. The effecton the eventselection of theradiation damage inthe HFfibresisassessed byrescaling thesignalsofthesimulatedHF

Table 2

Listofthesystematicuncertainties,propagatedintothefinalpPb crosssections,forthetwoeventselections.

Source of uncertainty Single-arm Double-arm

Noise subtraction (Nnoise) 1.3% 0.2%

Pileup correction ( fPU) <0.1% <0.1%

Acceptance (acc(models)) 0.5% 1.6%

Acceptance (acc(σdiff)) 0.8% 1.1%

Hadron-level correction (cvis) 0.4% 0.2%

Photon–proton subtraction (Nγp) 0.6% <0.1%

Detector simulation 1.7% 0.8%

HF energy thresholds 0.6% 0.4%

Integrated luminosity (L) 3.5% 3.5%

responsetomatchdatainsegmentsofpseudorapidity.The rescal-ing factorsarecalculatedusingtheaverageresponseproducedby epos_{, hijing, and qgsjetii. These scaling factors are found to be} consistent with the observed radiation damage of HF and range from 1 to 0.67, depending on pseudorapidity. The amount of ra-diation damage is estimatedfroma comparison ofdE/dη distri-butions measured in proton–proton collisions at √s=2.76 TeV recordedin2013andin2010.Thesystematicuncertaintyinduced on the cross section by this approach is estimated by repeat-ing the measurement without the radiation damage correction, which introduces an effect of 1.7% (0.8%) on the cross section. As a further check of the HF tower energy resolution, the cross sections are computed by increasing the selection thresholds to EHF>10 GeV (5 GeV). Toaccount forboth effects, a systematic uncertaintyonthecrosssectionof0.6% (0.4%)isadded.Thecross sections measured for the two beam directions are found to be consistent. Consequently, no dedicated systematic uncertainty is assignedtothiseffect.

Allthedifferentsourcesofuncertaintyofthemeasurementare listed in Table 2 forthe single-armand double-armevent selec-tions. The three derived cross sections have different systematic uncertainties since not all contributions are relevant to each of them. For σinel,all uncertainties butthe one dueto the hadron-level correction contribute. The total uncorrelatedsystematic un-certainty is therefore2.5% (2.2%) forthesingle-arm(double-arm) selection.For σvis,thedominantuncertaintyisduetothe hadron-levelcorrectioninsteadofthecorrectionfor acc.Thevalueofthe uncertainty istherefore reducedto 2.3% (0.9%). Theuncertainties fordetectorsimulationandphoton–protoncorrectiondonot con-tribute to σobs and, hence, its uncertainty becomes 1.4% (0.5%). For all cross sections, a (dominant) integrated luminosity uncer-tainty of3.5%isadded.Themaincontributionsto thelatterarise from the model used to describe the beam profile, the length scale of the beam displacement, and the bunch-to-bunch varia-tions[32].

4. Resultsandsummary

Themeasuredcrosssectionsforthesingle-armanddouble-arm eventselectionsarelistedinTable 3,comparedtothepredictions ofthehadronicinteractionmodels dpmjet, epos,and qgsjetii.Due to the different acceptance, the extrapolations from the

hadron-Table 3

Summaryofcrosssectionsobtainedfromthetwodifferentevent selec-tions.Theacceptancedefinitionfor σvis isbasedonthe productionof

stableparticleswithin3<|η|<5 withmomentum pHF>21.3 GeV/c

(11.3 GeV/c) forthesingle-arm(double-arm)eventselections. Selection σobs(mb) σvis(mb) σinel(mb)

Data Single-arm 2003±76 1937±82 2063±89 Double-arm 1873±66 1872±68 2059±85 epos-lhc Single-arm – 1947 2082 Double-arm – 1883 qgsjetii–04 Single-arm – 2059 2181 Double-arm – 1998 dpmjet3.06 Single-arm – 2116 2166 Double-arm – 2055

Fig. 3. InelastichadroniccrosssectionsforpPbcollisionsasafunctionofthe centre-of-massenergy.Themeasurementdescribedhere(circle,witherrorbarsobtained fromthe quadratic sum ofalluncertainties) iscompared tolower energydata (squaresandtriangles)[2,39,40]andtodifferentmodelpredictions(curves). leveltotheinelasticcrosssection areofdifferentmagnitude,but themodelsreproducewelltheapproximately65 mbdifference be-tweenthetwoselections.Thevaluesoftheinelasticcrosssections obtainedfromthesingle-armanddouble-armmethodsagreewell withintheuncertainties.

Thefinal σinelvalueisobtainedbytakingtheweightedaverage ofthemeasuredvaluesinthetwoeventselections.Thestatistical uncertaintiesandtheuncertaintyontheluminosityarecorrelated betweenthe selections. The degree ofcorrelation among the re-maining systematic uncertainties is much smaller and they are taken as uncorrelated. This yields a final result for the inelastic hadroniccrosssectionof

σinel(pPb)=2061±3(stat)±34(syst)±72(lumi)mb.

ThisresultisshowninFig. 3comparedtoothermeasurements atdifferentcentre-of-massenergiesandtovarioustheoretical pre-dictions. A pPb cross section was also measured by the ALICE Collaboration, amounting to 2090–2120 mb with an uncertainty of70 mb[41].A directcomparisonofthisobservedcrosssection to the one measured in the present analysisis not possible due totheunknowntousALICEdetectoracceptanceandpossible con-taminationfromnoiseandphoton–protoninteractions.

TheinelasticcrosssectionmeasuredbytheCMSexperimentis comparedto the Glauber-model prediction(solid curve inFig. 3) obtained using a pp inelastic cross section at √s=5.02 TeV of 70.0±1.5 mb, derived from the COMPETE parametrisation [42] includingthe measurement of the TOTEMCollaboration at √s=

7 TeV [43] (where the assigned uncertainty is that measured by the latter). The Glauber calculation yields 2130±40 mb and is compatible with the measurement presented here indicating that effects neglected by the calculation (suchas nucleon corre-lations and screening) are either small or approximately cancel out. The experimental result is also consistent with the predic-tionofthe dipsy model[44,45]basedonadipole-modelapproach including parton saturation and multiple-scattering. Among the Gribov–Regge models,the epos predictionis compatiblewiththe measurement within uncertainties, whereas dpmjet and qgsjetii predict a value more than 1 standard deviation above the data, with a larger discrepancy appearing for the σvis cross sections (Table 3). The epos and qgsjetii models are commonly used for cosmic ray air shower simulations. Thus, at the correspond-ing cosmic ray proton energies of Ecr= s/(2mp)=1016.1 eV, where mp is the mass of the proton, there are no indications for data-model deviations above ≈5% in the proton–lead colli-sions studied here. Note, however, that our measurement deals with an ion much heavier than those involved in proton–air in-teractions. Corrections to the Glauber model are possibly larger in the latter case [3,13]. In summary, the measurement of the cross sections in pPb collisions presented here is the first such fully corrected measurement at multi-TeV energies and, thus, provides important constraints on hadronic interaction mod-els commonly used in high-energy heavy ion and cosmic ray physics.

Acknowledgements

WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the technicalandadministrative staffsatCERN andatother CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcentresand personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythe computinginfrastructureessential to ouranalyses. Finally, we acknowledge the enduring support for the construc-tionandoperation oftheLHC andtheCMSdetectorprovidedby 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);Academy ofFinland,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 of Korea); LAS (Lithuania); MOE and UM (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(United Kingdom);DOE andNSF(USA).

Individuals have received support from the Marie-Curie pro-grammeand theEuropean Research CouncilandEPLANET (Euro-pean Union); the Leventis Foundation; the Alfred P. Sloan Foun-dation; the Alexander von Humboldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technolo-gie (IWT-Belgium); the Ministry of Education, Youth and Sports (MEYS) of the Czech Republic; the Council of Science and In-dustrial Research, India; the HOMING PLUS programme of the Foundation for Polish Science, cofinanced from European Union,

Regional Development Fund; the OPUS programme of the Na-tional Science Center (Poland); the Compagnia di San Paolo (Torino); the Consorzio per la Fisica (Trieste); MIUR project 20108T4XTM (Italy); the Thalis and Aristeia programmes cofi-nanced by EU-ESF and the Greek NSRF; the National Priori-ties Research Program by Qatar National Research Fund; the Rachadapisek Sompot Fund for Postdoctoral Fellowship, Chula-longkorn University (Thailand); and the Welch Foundation, con-tractC-1845.

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V. Khachatryan,A.M. Sirunyan, A. Tumasyan Yerevan Physics Institute, Yerevan, Armenia

W. Adam, E. Asilar,T. Bergauer, J. Brandstetter, E. Brondolin, M. Dragicevic, J. Erö,M. Flechl, M. Friedl, R. Frühwirth1, V.M. Ghete, C. Hartl, N. Hörmann, J. Hrubec,M. Jeitler1,V. Knünz, A. König,

M. Krammer1, I. Krätschmer,D. Liko, T. Matsushita,I. Mikulec, D. Rabady2,B. Rahbaran, H. Rohringer, J. Schieck1, R. Schöfbeck, J. Strauss, W. Treberer-Treberspurg,W. Waltenberger, C.-E. Wulz1

Institut für Hochenergiephysik der OeAW, Wien, Austria

V. Mossolov,N. Shumeiko,J. Suarez Gonzalez National Centre for Particle and High Energy Physics, 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 Universiteit Antwerpen, 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

Vrije Universiteit Brussel, Brussel, Belgium

P. Barria, C. Caillol, B. Clerbaux, G. De Lentdecker, H. Delannoy, G. Fasanella, L. Favart, A.P.R. Gay,

A. Grebenyuk,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. Zhang3

Université Libre de Bruxelles, 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 Ghent University, Ghent, Belgium

S. Basegmez, C. Beluffi4, O. Bondu,S. Brochet,G. Bruno, R. Castello,A. Caudron, L. Ceard,

G.G. Da Silveira,C. Delaere, D. Favart,L. Forthomme,A. Giammanco5, J. Hollar,A. Jafari,P. Jez, M. Komm, V. Lemaitre,A. Mertens, C. Nuttens,L. Perrini, A. Pin, K. Piotrzkowski,A. Popov6, L. Quertenmont,

M. Selvaggi,M. Vidal Marono Université Catholique de Louvain, Louvain-la-Neuve, Belgium N. Beliy,G.H. Hammad

Université de Mons, Mons, Belgium

W.L. Aldá Júnior, G.A. Alves,L. Brito,M. Correa Martins Junior, C. Hensel,C. Mora Herrera,A. Moraes, M.E. Pol,P. Rebello Teles

Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, Brazil

E. Belchior Batista Das Chagas, W. Carvalho,J. Chinellato7, 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 Manganote7,A. Vilela Pereira Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil

S. Ahujaa, C.A. Bernardesb, A. De Souza Santosb,S. Dograa, T.R. Fernandez Perez Tomeia,

E.M. Gregoresb, P.G. Mercadanteb,C.S. Moona,8,S.F. Novaesa,Sandra S. Padulaa,D. Romero Abad, J.C. Ruiz Vargas

a_{Universidade Estadual Paulista, São Paulo, Brazil} b_{Universidade Federal do ABC, São Paulo, Brazil}

A. Aleksandrov, V. Genchev†, R. Hadjiiska,P. Iaydjiev, S. Piperov,M. Rodozov, S. Stoykova, G. Sultanov, M. Vutova

Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria

A. Dimitrov, I. Glushkov,L. Litov, B. Pavlov,P. Petkov University of Sofia, Sofia, Bulgaria

M. Ahmad, J.G. Bian, G.M. Chen, H.S. Chen,M. Chen, T. Cheng, R. Du,C.H. Jiang, R. Plestina9,F. Romeo, S.M. Shaheen, J. Tao, C. Wang,Z. Wang, H. Zhang

Institute of High Energy Physics, Beijing, China

C. Asawatangtrakuldee, Y. Ban, Q. Li, S. Liu,Y. Mao, S.J. Qian, D. Wang,Z. Xu, W. Zou State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, China

C. Avila,A. Cabrera, L.F. Chaparro Sierra, C. Florez, J.P. Gomez, B. Gomez Moreno,J.C. Sanabria Universidad de Los Andes, Bogota, Colombia

N. Godinovic, D. Lelas, D. Polic, I. Puljak, P.M. Ribeiro Cipriano University of Split, Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture, Split, Croatia Z. Antunovic, M. Kovac

University of Split, Faculty of Science, Split, Croatia

V. Brigljevic,K. Kadija, J. Luetic, S. Micanovic,L. Sudic Institute Rudjer Boskovic, Zagreb, Croatia

A. Attikis, G. Mavromanolakis, J. Mousa,C. Nicolaou, F. Ptochos, P.A. Razis,H. Rykaczewski University of Cyprus, Nicosia, Cyprus

M. Bodlak,M. Finger10,M. Finger Jr.10 Charles University, Prague, Czech Republic

A.A. Abdelalim11,A. Mahrous12, A. Radi13,14

Academy of Scientific Research and Technology of the Arab Republic of Egypt, Egyptian Network of High Energy Physics, Cairo, Egypt B. Calpas, M. Kadastik, M. Murumaa, M. Raidal, A. Tiko, C. Veelken

National Institute of Chemical Physics and Biophysics, Tallinn, Estonia P. Eerola, J. Pekkanen,M. Voutilainen Department of Physics, University of Helsinki, Helsinki, Finland

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

J. Talvitie,T. Tuuva

Lappeenranta University of Technology, 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,S. Regnard, R. Salerno, J.B. Sauvan, Y. Sirois, T. Strebler, Y. Yilmaz,A. Zabi

Laboratoire Leprince-Ringuet, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France

J.-L. Agram15,J. Andrea, A. Aubin,D. Bloch, J.-M. Brom,M. Buttignol, E.C. Chabert,N. Chanon, C. Collard, E. Conte15,X. Coubez, J.-C. Fontaine15, D. Gelé, U. Goerlach,C. Goetzmann, A.-C. Le Bihan, J.A. Merlin2, K. Skovpen,P. Van Hove

Institut Pluridisciplinaire Hubert Curien, Université de Strasbourg, Université de Haute Alsace Mulhouse, CNRS/IN2P3, Strasbourg, France S. Gadrat

Centre de Calcul de l’Institut National de Physique Nucleaire et de Physique des Particules, CNRS/IN2P3, Villeurbanne, France

S. Beauceron,C. Bernet, G. Boudoul,E. Bouvier, C.A. Carrillo Montoya, J. Chasserat, R. Chierici, D. Contardo, B. Courbon, P. Depasse, H. El Mamouni,J. Fan, J. Fay, S. Gascon, M. Gouzevitch,B. Ille, 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, H. Xiao

Université de Lyon, Université Claude Bernard Lyon 1, CNRS-IN2P3, Institut de Physique Nucléaire de Lyon, Villeurbanne, France T. Toriashvili16

Georgian Technical University, Tbilisi, Georgia I. Bagaturia17

Tbilisi State University, 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. Zhukov6

RWTH Aachen University, I. Physikalisches Institut, Aachen, Germany

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RWTH Aachen University, III. Physikalisches Institut A, Aachen, Germany

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RWTH Aachen University, III. Physikalisches Institut B, Aachen, Germany

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Deutsches Elektronen-Synchrotron, Hamburg, Germany

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G. Steinbrück, H. Tholen, D. Troendle,E. Usai, L. Vanelderen, A. Vanhoefer University of Hamburg, Hamburg, Germany

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

F. Kassel2,I. Katkov6,A. Kornmayer2,P. Lobelle Pardo, B. Maier, H. Mildner, M.U. Mozer, T. Müller, Th. Müller, M. Plagge, G. Quast, K. Rabbertz,S. Röcker, F. Roscher, H.J. Simonis,F.M. Stober, R. Ulrich, J. Wagner-Kuhr, S. Wayand,M. Weber, T. Weiler, C. Wöhrmann, R. Wolf

Institut für Experimentelle Kernphysik, Karlsruhe, Germany

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

Institute of Nuclear and Particle Physics (INPP), NCSR Demokritos, Aghia Paraskevi, Greece

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

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

University of Ioánnina, Ioánnina, Greece

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

Wigner Research Centre for Physics, Budapest, Hungary

N. Beni, S. Czellar, J. Karancsi21,J. Molnar, Z. Szillasi Institute of Nuclear Research ATOMKI, Debrecen, Hungary

M. Bartók22,A. Makovec, P. Raics, Z.L. Trocsanyi,B. Ujvari University of Debrecen, Debrecen, Hungary

P. Mal, K. Mandal, N. Sahoo, S.K. Swain National Institute of Science Education and Research, Bhubaneswar, India

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

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

University of Delhi, Delhi, India

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

Saha Institute of Nuclear Physics, Kolkata, India

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

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

S. Chauhan,S. Dube, S. Sharma

Indian Institute of Science Education and Research (IISER), Pune, India

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

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

Institute for Research in Fundamental Sciences (IPM), Tehran, Iran M. Felcini,M. Grunewald

University College Dublin, Dublin, Ireland

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

a_{INFN Sezione di Bari, Bari, Italy} b_{Università di Bari, Bari, Italy} c_{Politecnico di Bari, Bari, Italy}

G. Abbiendia,C. Battilana2,A.C. Benvenutia,D. Bonacorsia,b, S. Braibant-Giacomellia,b, L. Brigliadoria,b, R. Campaninia,b,P. Capiluppia,b,A. Castroa,b, F.R. Cavalloa, G. Codispotia,b, M. Cuffiania,b,

G.M. Dallavallea,F. Fabbria,A. Fanfania,b,D. Fasanellaa,b, P. Giacomellia, C. Grandia, L. Guiduccia,b, S. Marcellinia, G. Masettia,A. Montanaria,F.L. Navarriaa,b,A. Perrottaa,A.M. Rossia,b,T. Rovellia,b, G.P. Sirolia,b_{,N. Tosi}a,b_{, R. Travaglini}a,b

a_{INFN Sezione di Bologna, Bologna, Italy} b_{Università di Bologna, Bologna, Italy}

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

a_{INFN Sezione di Catania, Catania, Italy} b_{Università di Catania, Catania, Italy} c_{CSFNSM, Catania, Italy}

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

a_{INFN Sezione di Firenze, Firenze, Italy} b_{Università di Firenze, Firenze, Italy}

L. Benussi, S. Bianco, F. Fabbri,D. Piccolo INFN Laboratori Nazionali di Frascati, Frascati, Italy

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

a_{INFN Sezione di Genova, Genova, Italy} b_{Università di Genova, Genova, Italy}

L. Brianza,M.E. Dinardoa,b, S. Fiorendia,b,S. Gennaia,R. Gerosaa,b,A. Ghezzia,b, P. Govonia,b,

S. Malvezzia, R.A. Manzonia,b,B. Marzocchia,b,2,D. Menascea,L. Moronia, M. Paganonia,b,D. Pedrinia, S. Ragazzia,b_{, N. Redaelli}a_{,T. Tabarelli de Fatis}a,b

a_{INFN Sezione di Milano-Bicocca, Milano, Italy} b_{Università di Milano-Bicocca, Milano, Italy}

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

a_{INFN Sezione di Napoli, Napoli, Italy} b_{Università di Napoli ‘Federico II’, Napoli, Italy} c_{Università della Basilicata, Potenza, Italy} d_{Università G. Marconi, Roma, Italy}

P. Azzia,2, N. Bacchettaa, M. Bellatoa, L. Benatoa,b,A. Bolettia,b,A. Brancaa,b, M. Dall’Ossoa,b,2, T. Dorigoa,F. Fanzagoa,F. Gonellaa, A. Gozzelinoa, K. Kanishcheva,c,S. Lacapraraa,M. Margonia,b, G. Marona,29,A.T. Meneguzzoa,b, M. Michelottoa,F. Montecassianoa,M. Passaseoa,J. Pazzinia,b, M. Pegoraroa, N. Pozzobona,b, P. Ronchesea,b,F. Simonettoa,b, E. Torassaa,M. Tosia,b,M. Zanetti, P. Zottoa,b, A. Zucchettaa,b,2

a_{INFN Sezione di Padova, Padova, Italy} b_{Università di Padova, Padova, Italy} c_{Università di Trento, Trento, Italy}

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

a_{INFN Sezione di Pavia, Pavia, Italy} b_{Università di Pavia, Pavia, Italy}

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

a_{INFN Sezione di Perugia, Perugia, Italy} b_{Università di Perugia, Perugia, Italy}

K. Androsova,30,P. Azzurria,G. Bagliesia,J. Bernardinia,T. Boccalia,G. Broccoloa,c,R. Castaldia, M.A. Cioccia,30, R. Dell’Orsoa, S. Donatoa,c,2, G. Fedi,L. Foàa,c,†,A. Giassia, M.T. Grippoa,30,

F. Ligabuea,c,T. Lomtadzea,L. Martinia,b,A. Messineoa,b,F. Pallaa, A. Rizzia,b, A. Savoy-Navarroa,31, A.T. Serbana,P. Spagnoloa,P. Squillaciotia,30,R. Tenchinia, G. Tonellia,b,A. Venturia, P.G. Verdinia

a_{INFN Sezione di Pisa, Pisa, Italy} b_{Università di Pisa, Pisa, Italy}

c_{Scuola Normale Superiore di Pisa, Pisa, Italy}

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

a_{INFN Sezione di Roma, Roma, Italy} b_{Università di Roma, Roma, Italy}

N. Amapanea,b_{, R. Arcidiacono}a,c,2_{, S. Argiro}a,b_{, M. Arneodo}a,c_{, R. Bellan}a,b_{, C. Biino}a_{,N. Cartiglia}a_,

M. Costaa,b,R. Covarellia,b, A. Deganoa,b, N. Demariaa,L. Fincoa,b,2, C. Mariottia, S. Masellia,

M. Pelliccionia, G.L. Pinna Angionia,b,F. Raveraa,b, A. Romeroa,b,M. Ruspaa,c,R. Sacchia,b, A. Solanoa,b, A. Staianoa, U. Tamponia, P.P. Trapania,b

a_{INFN Sezione di Torino, Torino, Italy} b_{Università di Torino, Torino, Italy}

c_{Università del Piemonte Orientale, Novara, Italy}

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

a_{INFN Sezione di Trieste, Trieste, Italy} b_{Università di Trieste, Trieste, Italy}

S. Chang,A. Kropivnitskaya, S.K. Nam Kangwon National University, Chunchon, Republic of Korea

D.H. Kim,G.N. Kim, M.S. Kim, D.J. Kong, S. Lee, Y.D. Oh,A. Sakharov, D.C. Son Kyungpook National University, Daegu, Republic of Korea

J.A. Brochero Cifuentes,H. Kim, T.J. Kim, M.S. Ryu Chonbuk National University, Jeonju, Republic of Korea

S. Song

Chonnam National University, Institute for Universe and Elementary Particles, Kwangju, Republic of Korea

S. Choi, Y. Go,D. Gyun, B. Hong,M. Jo, H. Kim,Y. Kim, B. Lee, K. Lee,K.S. Lee, S. Lee, S.K. Park,Y. Roh Korea University, Seoul, Republic of Korea

H.D. Yoo

Seoul National University, Seoul, Republic of Korea

M. Choi,H. Kim, J.H. Kim, J.S.H. Lee, I.C. Park, G. Ryu University of Seoul, Seoul, Republic of Korea

Y. Choi,Y.K. Choi,J. Goh, D. Kim, E. Kwon, J. Lee, I. Yu Sungkyunkwan University, Suwon, Republic of Korea

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

I. Ahmed,Z.A. Ibrahim, J.R. Komaragiri, M.A.B. Md Ali32,F. Mohamad Idris33,W.A.T. Wan Abdullah, M.N. Yusli

National Centre for Particle Physics, Universiti Malaya, Kuala Lumpur, Malaysia

E. Casimiro Linares, H. Castilla-Valdez,E. De La Cruz-Burelo, I. Heredia-de La Cruz34, A. Hernandez-Almada,R. Lopez-Fernandez, A. Sanchez-Hernandez

Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico S. Carrillo Moreno, F. Vazquez Valencia Universidad Iberoamericana, Mexico City, Mexico

S. Carpinteyro, I. Pedraza, H.A. Salazar Ibarguen Benemerita Universidad Autonoma de Puebla, Puebla, Mexico

A. Morelos Pineda

Universidad Autónoma de San Luis Potosí, San Luis Potosí, Mexico D. Krofcheck

University of Auckland, Auckland, New Zealand P.H. Butler,S. Reucroft

University of Canterbury, Christchurch, New Zealand

A. Ahmad, M. Ahmad, Q. Hassan,H.R. Hoorani, W.A. Khan, T. Khurshid,M. Shoaib National Centre for Physics, Quaid-I-Azam University, Islamabad, Pakistan

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

National Centre for Nuclear Research, Swierk, Poland

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

Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland

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

Laboratório de Instrumentação e Física Experimental de Partículas, Lisboa, Portugal

S. Afanasiev,P. Bunin,M. Gavrilenko, I. Golutvin,I. Gorbunov, A. Kamenev, V. Karjavin,V. Konoplyanikov, A. Lanev,A. Malakhov,V. Matveev35, P. Moisenz, V. Palichik,V. Perelygin, S. Shmatov, S. Shulha,

N. Skatchkov, V. Smirnov,A. Zarubin Joint Institute for Nuclear Research, Dubna, Russia

V. Golovtsov, Y. Ivanov, V. Kim36,E. Kuznetsova, P. Levchenko, V. Murzin, V. Oreshkin, I. Smirnov, V. Sulimov, L. Uvarov, S. Vavilov, A. Vorobyev

Petersburg Nuclear Physics Institute, Gatchina (St. Petersburg), Russia

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

Institute for Nuclear Research, Moscow, Russia

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

Institute for Theoretical and Experimental Physics, Moscow, Russia A. Bylinkin

National Research Nuclear University ‘Moscow Engineering Physics Institute’ (MEPhI), Moscow, Russia

V. Andreev,M. Azarkin37, I. Dremin37,M. Kirakosyan, A. Leonidov37, G. Mesyats,S.V. Rusakov, A. Vinogradov

P.N. Lebedev Physical Institute, Moscow, Russia

A. Baskakov,A. Belyaev, E. Boos,A. Ershov, A. Gribushin, L. Khein, V. Klyukhin, O. Kodolova,I. Lokhtin, O. Lukina, I. Myagkov, S. Obraztsov,S. Petrushanko,V. Savrin, A. Snigirev

I. Azhgirey,I. Bayshev,S. Bitioukov, V. Kachanov, A. Kalinin, D. Konstantinov,V. Krychkine, V. Petrov, R. Ryutin, A. Sobol,L. Tourtchanovitch, S. Troshin, N. Tyurin, A. Uzunian,A. Volkov

State Research Center of Russian Federation, Institute for High Energy Physics, Protvino, Russia P. Adzic38,M. Ekmedzic, J. Milosevic,V. Rekovic University of Belgrade, Faculty of Physics and Vinca Institute of Nuclear Sciences, Belgrade, Serbia

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

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

Centro de Investigaciones Energéticas Medioambientales y Tecnológicas (CIEMAT), Madrid, Spain C. Albajar, J.F. de Trocóniz,M. Missiroli, D. Moran Universidad Autónoma de Madrid, Madrid, Spain

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

Universidad de Oviedo, Oviedo, Spain

I.J. Cabrillo, A. Calderon, J.R. Castiñeiras De Saa, P. De Castro Manzano,J. Duarte Campderros,

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

Instituto de Física de Cantabria (IFCA), CSIC-Universidad de Cantabria, Santander, Spain

D. Abbaneo, E. Auffray, G. Auzinger, M. Bachtis,P. Baillon, A.H. Ball, D. Barney, A. Benaglia,J. Bendavid, L. Benhabib,J.F. Benitez, G.M. Berruti,P. Bloch, A. Bocci, A. Bonato, C. Botta, H. Breuker, T. Camporesi, G. Cerminara, S. Colafranceschi39,M. D’Alfonso, D. d’Enterria, A. Dabrowski,V. Daponte, A. David,

M. De Gruttola,F. De Guio, A. De Roeck, S. De Visscher, E. Di Marco, M. Dobson, M. Dordevic, T. du Pree, N. Dupont,A. Elliott-Peisert, G. Franzoni, W. Funk, D. Gigi,K. Gill, D. Giordano, M. Girone, F. Glege, R. Guida,S. Gundacker, M. Guthoff, J. Hammer, M. Hansen,P. Harris, J. Hegeman, V. Innocente, P. Janot, H. Kirschenmann,M.J. Kortelainen, K. Kousouris,K. Krajczar, P. Lecoq,C. Lourenço, M.T. Lucchini, N. Magini,L. Malgeri,M. Mannelli, A. Martelli,L. Masetti, F. Meijers, S. Mersi, E. Meschi, F. Moortgat, S. Morovic, M. Mulders, M.V. Nemallapudi,H. Neugebauer, S. Orfanelli40, L. Orsini, L. Pape,E. Perez, A. Petrilli, G. Petrucciani,A. Pfeiffer,D. Piparo, A. Racz, G. Rolandi41, M. Rovere,M. Ruan,H. Sakulin, C. Schäfer, C. Schwick,A. Sharma,P. Silva, M. Simon, P. Sphicas42, D. Spiga,J. Steggemann, B. Stieger, M. Stoye,Y. Takahashi, D. Treille, A. Triossi, A. Tsirou,G.I. Veres20, N. Wardle,H.K. Wöhri,

A. Zagozdzinska43,W.D. Zeuner

CERN, European Organization for Nuclear Research, Geneva, Switzerland

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

Paul Scherrer Institut, Villigen, Switzerland

F. Bachmair, L. Bäni, L. Bianchini, M.A. Buchmann,B. Casal, G. Dissertori, M. Dittmar, M. Donegà, M. Dünser,P. Eller,C. Grab, C. Heidegger, D. Hits,J. Hoss, G. Kasieczka, W. Lustermann, B. Mangano, A.C. Marini,M. Marionneau, P. Martinez Ruiz del Arbol, M. Masciovecchio, D. Meister, P. Musella, F. Nessi-Tedaldi, F. Pandolfi,J. Pata, F. Pauss, L. Perrozzi,M. Peruzzi, M. Quittnat,M. Rossini, A. Starodumov44,M. Takahashi, V.R. Tavolaro, K. Theofilatos, R. Wallny

T.K. Aarrestad, C. Amsler45, L. Caminada,M.F. Canelli, V. Chiochia,A. De Cosa, C. Galloni, A. Hinzmann, T. Hreus, B. Kilminster,C. Lange, J. Ngadiuba, D. Pinna,P. Robmann, F.J. Ronga,D. Salerno, S. Taroni, Y. Yang

Universität Zürich, Zurich, Switzerland

M. Cardaci, K.H. Chen,T.H. Doan, C. Ferro,Sh. Jain, R. Khurana,M. Konyushikhin, C.M. Kuo, W. Lin, Y.J. Lu, R. Volpe,S.S. Yu

National Central University, Chung-Li, Taiwan

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

National Taiwan University (NTU), Taipei, Taiwan

B. Asavapibhop, K. Kovitanggoon, G. Singh, N. Srimanobhas,N. Suwonjandee Chulalongkorn University, Faculty of Science, Department of Physics, Bangkok, Thailand

A. Adiguzel, S. Cerci46,C. Dozen, I. Dumanoglu, S. Girgis, G. Gokbulut, Y. Guler, E. Gurpinar,I. Hos, E.E. Kangal47,A. Kayis Topaksu, G. Onengut48,K. Ozdemir49,S. Ozturk50, B. Tali46, H. Topakli50, M. Vergili, C. Zorbilmez

Cukurova University, Adana, Turkey

I.V. Akin, B. Bilin,S. Bilmis, B. Isildak51,G. Karapinar52, U.E. Surat,M. Yalvac, M. Zeyrek Middle East Technical University, Physics Department, Ankara, Turkey

E.A. Albayrak53,E. Gülmez,M. Kaya54, O. Kaya55,T. Yetkin56 Bogazici University, Istanbul, Turkey

K. Cankocak, S. Sen57, F.I. Vardarlı Istanbul Technical University, Istanbul, Turkey

B. Grynyov

Institute for Scintillation Materials of National Academy of Science of Ukraine, Kharkov, Ukraine L. Levchuk,P. Sorokin

National Scientific Center, Kharkov Institute of Physics and Technology, Kharkov, Ukraine

R. Aggleton,F. Ball, L. Beck, J.J. Brooke,E. Clement, D. Cussans,H. Flacher, J. Goldstein,M. Grimes, G.P. Heath, H.F. Heath,J. Jacob, L. Kreczko, C. Lucas, Z. Meng, D.M. Newbold58, S. Paramesvaran,A. Poll, T. Sakuma, S. Seif El Nasr-storey,S. Senkin, D. Smith,V.J. Smith

University of Bristol, Bristol, United Kingdom

K.W. Bell, A. Belyaev59, C. Brew, R.M. Brown, D.J.A. Cockerill, J.A. Coughlan, K. Harder, S. Harper, E. Olaiya,D. Petyt, C.H. Shepherd-Themistocleous, A. Thea, L. Thomas, I.R. Tomalin, T. Williams, W.J. Womersley, S.D. Worm

Rutherford Appleton Laboratory, Didcot, United Kingdom

M. Baber, R. Bainbridge,O. Buchmuller, A. Bundock, D. Burton,S. Casasso,M. Citron, D. Colling, L. Corpe, N. Cripps,P. Dauncey, G. Davies, A. De Wit, M. Della Negra, P. Dunne,A. Elwood, W. Ferguson, J. Fulcher, D. Futyan,G. Hall, G. Iles, G. Karapostoli, M. Kenzie,R. Lane, R. Lucas58, L. Lyons, A.-M. Magnan,

S. Malik,J. Nash, A. Nikitenko44,J. Pela, M. Pesaresi, K. Petridis,D.M. Raymond, A. Richards, A. Rose, C. Seez,A. Tapper, K. Uchida, M. Vazquez Acosta60, T. Virdee,S.C. Zenz