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Physics
Letters
B
www.elsevier.com/locate/physletb
Measurement
of
B
0smeson
production
in
pp
and
PbPb
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 ra c t Articlehistory: Received6October2018Receivedinrevisedform27June2019 Accepted4July2019
Availableonline9July2019 Editor:M.Doser
Keywords:
Physics
Quarkgluonplasma Bmeson
Openheavy-flavor
Theproductioncrosssections ofB0s mesonsandchargeconjugatesaremeasuredinproton-proton(pp) and PbPb collisions via the exclusive decay channel B0s→J/ψφ→μ+μ−K+K− at a center-of-mass energyof5.02 TeVpernucleonpairandwithintherapidityrange|y| <2.4 usingtheCMSdetectorat theLHC.Theppmeasurementisperformedasafunctionoftransversemomentum(pT)oftheB0smesons intherangeof7to50 GeV/c andiscomparedtothepredictionsofperturbativeQCDcalculations.The B0
s productionyield inPbPbcollisions is measuredintwo pT intervals, 7to 15 and 15 to50 GeV/c, andcomparedtotheyieldinppcollisionsinthesamekinematicregion.Thenuclearmodificationfactor (RAA)is foundtobe1.5±0.6(stat) ±0.5(syst) for7–15 GeV/c, and 0.87±0.30(stat) ±0.17(syst) for 15–50 GeV/c, respectively. Withincurrent uncertainties,the B0
s results are consistent withmodels of strangenessenhancement,andsuppressionbypartonenergyloss,asobservedfortheB+mesons.
PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3.
1. Introduction
Relativistic heavy ion collisions allow the study of quantum chromodynamics (QCD) at high energy densityand temperature. Under such extreme conditions, a state consisting of deconfined quarks and gluons, the quark-gluon plasma (QGP) [1,2], is pre-dicted by lattice QCD calculations [3]. The study of the phe-nomenoninwhichtheoutgoingpartonsinteractstronglywiththe QGPandloseenergyby means ofelasticcollisions and medium-inducedgluonradiation [4–8] canprovideinsightsintotheenergy densityanddiffusionpropertiesoftheQGP. Heavyquarks are ef-fective probes to study these properties of the medium. Charm andbeautyquarksthatareprimarilyproducedinhardscatterings atthe early stages ofthe collision are expectedto carry the full evolutionhistory oftheQGP formation [8].On theother handit isexpected [9] that,via theprocess gg→ss,an enhancement of strangenessinathermallyandchemicallyequilibratedQGPshould occurifitstemperatureisabovethestrangequarkmass. Measure-ments attheBNLRHIC oftheproduction ofstrange baryonsand mesons,usingdifferentcollisionsystemsandbeamenergies, pro-vide systematicsupport forthis expectation [10–14]. Because of theinterplaybetweenthepredictedenhancementofstrangequark production and the quenching mechanismof beauty quarks, the measurement of strange beauty particles is important for study-ing the mechanisms of beauty hadronization in heavy ion
colli- E-mailaddress:cms-publication-committee-chair@cern.ch.
sions. In the presence of a medium with increased strangeness content [15,16], the relative yield of B0
s mesons withrespect to
nonstrange beauty mesons at transverse momentum (pT) below
∼15 GeV/c [8,17] canbe enhanced in nucleus-nucleus collisions compared to proton-proton (pp) interactions. This can happen if recombination is a significant factor of beauty hadronization in the QGP [18–20]. The recombination processes, which are con-sidered markers forthe presence of a deconfined medium, were mostrecently testedinthe open charmsector by theALICE Col-laboration [21].Apossiblehintforanenhancementintherelative yield of D+s mesons withrespect tononstrange charmedmesons for pT<8 GeV/c incentralPbPbcollisionsatacenter-of-mass
en-ergyof√sNN=5.02 TeVpernucleonpairwasobserved.
The productionof B0s mesons was previously measured atthe CERNLHCbytheCMSCollaborationinppcollisionsata center-of-massenergyof√s=7 TeV [22] andinproton-lead(pPb)collisions at√sNN=5.02 TeV [23].Inthisletter,wereportthefirst
measure-ment of exclusive B0s meson decays ever performed in nucleus-nucleus collisions and inpp collisions at 5.02 TeV.The pp mea-surement isperformed asa function of pT andcompared to the
predictions of fixed-order plus next-to-leading order logarithmic (FONLL)perturbativeQCDcalculations [24–26].Thenuclear modi-ficationfactor(RAA)ofBs0 mesons,whichisdefinedastheratioof
the yield in PbPb collisions with respect to that in pp collisions scaled by the corresponding number of binary nucleon-nucleon (NN) collisions,isshown. Thecomparisonbetweenthe RAA ofB0s
mesonsandthatofB+mesonsmeasuredbyCMSatthesame en-ergy [27] isalsopresented.
https://doi.org/10.1016/j.physletb.2019.07.014
The B0s meson and its charge conjugate are measured in the rapidityrange|y|<2.4 viathe reconstructionofthedecay chan-nelB0s→J/ψφ→μ+μ−K+K−,which hasthe branchingfraction
B = (3.12±0.24)×10−5 [28].Theppmeasurementisperformed
as a function of the B0s pT in three intervals, 7–15, 15–20, and
20–50 GeV/c.ThePbPbproductionyieldandthe RAAmeasurement
areperformedintwo pT intervals, 7–15and15–50 GeV/c,
inclu-sivelyforallevents(i.e.,0–100%centrality,thedegreeofoverlapof thetwo collidingnuclei).Throughout theletter, unlessotherwise specified,the y and pTvariablesgivenarethoseoftheB0s mesons.
Thisanalysisdoesnotdistinguishbetweenthechargeconjugates.
2. Experimentalapparatusanddatasample
The central feature of the CMS detector is a superconduct-ing solenoid, which provides a magnetic field of 3.8 T. Within the solenoidvolume are a silicon tracker that measures charged particles in the pseudorapidity range |η|<2.5, a lead tungstate crystal electromagnetic calorimeter, and a brass and scintillator hadroncalorimeter.Forchargedparticlesof1<pT<10 GeV/c and
|η|<1.4,thetrackresolutions aretypically1.5%in pT and25–90
(45–150) μm in the transverse (longitudinal) impact parameter [29]. Muonsare measured in the range|η|<2.4, withdetection planes made using three technologies: drift tubes, cathode strip chambers,andresistive-plate chambers. Themuon reconstruction algorithmstartsbyfindingtracksinthemuondetectors,whichare thenfittedtogetherwithtracksreconstructedinthesilicontracker to form “global muons”.Matching muons to tracks measured in the silicon tracker results in a relative pT resolution for muons
with20<pT<100 GeV/c of1.3–2.0%inthebarrel(|η|<1.2)and
better than6% inthe endcaps (1.6<|η|<2.4). Formuons with higher pT up to1 TeV/c,the pT resolutioninthe barrelisbetter
than10% [30].The hadronforward(HF)calorimeteruses steelas an absorber and quartz fibers as the sensitive material. The two halves of the HF are located 11.2 m away from the interaction point,one oneach end, providingtogether coverage intherange 3.0<|η|<5.2.Inthisanalysis,theHFinformationisusedfor per-forming an offline event selection. A detailed description of the CMSexperimentandcoordinatesystemcanbefoundinRef. [31].
Several Monte Carlo (MC) simulated event samples are used to evaluate background components, signal efficiencies, and de-tector acceptance corrections. The simulations include samples containing only the B0s meson decay channels being measured, andsampleswithinclusive(promptandnonprompt) J/ψmesons. Proton-protoncollisionsaregeneratedwith pythia8v212 [32] tune CUETP8M1 [33] and propagated through the CMS detectorusing the Geant4 package [34]. The decay of the B0s mesons is mod-eled with evtgen 1.3.0 [35], and final-state photon radiation in the B0
s decays is simulated with photos 2.0 [36]. For the PbPb
MCsamples,each pythia8eventisembeddedintoaPbPbcollision eventgeneratedwith hydjet 1.8 [37],whichistunedtoreproduce globaleventproperties,suchasthe charged-hadron pT spectrum
and particle multiplicity. For both samples, the signal pT shape
is reweighted to match the one from FONLL. For both p p and PbPb dataandMC samples,the dimuonand ditrack mass distri-butions/resolutionsareconsistent.
Eventswerecollectedwiththesametriggerduringtheppand PbPbdataacquisition,requiringthepresenceoftwomuon candi-dates(withnoexplicitmomentumthreshold)incoincidencewith a bunch crossing. Forthe offline analysis, events have to pass a setofselectioncriteriadesignedtorejecteventsfrombackground processes(beam-gas collisions and beamscraping events) as de-scribed inRef. [38]. Events are requiredto have atleast one re-constructed primary interaction vertex, formed by two or more tracks,withadistancefromthecenterofthenominalinteraction
region of less than 15 cm along the beam axis. In PbPb colli-sions, the shapes of the clusters in the pixel detector have to be compatiblewiththose expected fromparticles producedby a PbPbcollision [39].Inordertoselecthadroniccollisions,thePbPb events arealso requiredto have atleastthree towers in each of the HF detectors with energy deposits of more than 3 GeV per tower. The combinedefficiencyforthiseventselection, including the remaining non-hadronic contamination, is (99±2)%. Values higherthan100%are possible,reflectingthepotentialpresenceof ultra-peripheral(i.e.,non-hadronic)collisionsintheselectedevent sample. The PbPb sample corresponds to an integrated luminos-ityofapproximately351 μb−1.Thisvalueisindicativeonly,asthe
PbPb yield is normalized by the total number of minimum bias eventssampled, NMB[38].Theppdatasetcorrespondstoan
inte-gratedluminosityof28.0 pb−1,whichisknowntoanaccuracyof
±2.3%fromtheuncertaintyinthecalibrationbasedona vander Meer scan [40]. The average number of additional collisions per bunchcrossing isapproximately0.9forpp andlessthan0.01 for PbPb data.The presenceofmultiple collisions isfound tohavea negligibleeffectonthemeasurement.
3. Signalextraction
TheanalysisprocedureiscommonforppandPbPbdata. Kine-matic limits are imposed on the single muons so that their re-construction efficiency stays above 10%. These limits are pμT > 3.5 GeV/c for|ημ|<1.2, pμT >1.8 GeV/c for2.1≤ |ημ|<2.4,and linearlyinterpolatedinthe1.2<|ημ|<2.1 region.Themuonsare
alsorequiredtomatchthemuonsthattriggeredtheeventonline, andtopass selectioncriteriaoptimized forlow pT (the so-called
soft selection [30]).Twomuonsofopposite sign(OS), withan in-variantmasswithin±150 MeV/c2oftheworld-averageJ/ψmeson
mass [28] areselectedtoreconstructaJ/ψ candidate,withamass resolution of typically 18–55 MeV/c2, depending on the dimuon rapidityandpT.TheOSmuonpairsarefittedwithacommon
ver-tex constraintandare kept if thep-value ofthe χ2 ofthe fit is
greater than 1%, thus lowering the background from charm and beautyhadronsemileptonicdecays.Similarly, theφmeson candi-dates are formed withacommon vertexconstraintbetweentwo OS charged-particle tracks with pT>300(150) MeV/c for PbPb
(p p) sample, both requiredto pass standard selections [38]. The invariant mass,with a resolution of ∼3.9(3.4) MeV/c2 forPbPb
(p p)data,isrequiredtobewithin15 MeV/c2 oftheworld-average φ mesonmass [28]. TheB0
s mesoncandidatesare constructedby
combiningtheJ/ψandφcandidatesandrequiringthatthey orig-inatefromacommonvertex.Withoutusingparticleidentification, assumptions need to be made about the masses of the charged particles. Thedifference betweenthe naturalwidth(according to PDG [41])andthemeasuredwidth(reflectingdetectorresolution) ofthepeaksismuchbiggerfortheJ/ψ mesonthanfortheφ me-son. Therefore, in calculating the mass ofthe B0s candidates, the two charged particles are always assumed to have the mass of charged kaons, andthe muon pair is assumedto have the mass ofaJ/ψmeson.
The B0s candidates are selected according to their daughter chargedparticletrackkinematics,the χ2probabilityoftheirdecay
vertex(the probability forthe muon tracks fromthe J/ψ meson decay and the other charged particle tracks to originate from a commonvertex),thedistancebetweentheprimaryanddecay ver-tices (normalized byits uncertainty), andthepointingangle(the anglebetweenthelinesegmentconnectingtheprimaryanddecay vertices andthe momentumvector ofthe B0
s meson). The
selec-tion is optimized separately for pp and PbPb results as well as each individual pT bin, using a multivariate technique that
Fig. 1. InvariantmassdistributionsofB0s candidatesinpp(left)andPbPb(right)collisionsmeasuredintherange|y|<2.4 andinthe pT rangeof7–15 GeV/c.The χ2
dividedbythenumberofdegreesoffreedom(nDOF)isalsogiven.
Fig. 2. InvariantmassdistributionsofB0
s candidatesinpp(left)andPbPb(right)collisionsmeasuredintherange|y|<2.4 andinthepTrangeof15–50 GeV/c.The χ2
dividedbythenumberofdegreesoffreedom(nDOF)isalsogiven.
maximizethe statisticalsignificanceofthe B0
s mesonsignals. The
B0s signal samples are takenfrom simulation.The signal samples are scaled to the number of B0s candidates predicted by FONLL
calculationscorresponding totheintegratedluminosityofthe an-alyzeddatasample.Thisnormalizationisnotusedwhen perform-ingtheBDTtraining.Thebackgroundsamplesforthemultivariate training are taken from data sidebands of the B0s meson invari-antmass(0.2<|MμμKK−MB0
s,PDG|<0.3 GeV/c
2),whichisabout
5σ away fromthePDGB0s massvalue.The optimalselection cri-terion is the working point with the highest signal significance (Ns/√(Ns+Nb), where Ns (Nb) are the expected signal
(back-ground) candidate yields from the simulated signal (data side-bands)withinthemassrange|MμμKK−MB0
s,PDG|<0.08 GeV/c
2.
TherawyieldsofB0s mesonsinppandPbPbcollisions are ex-tractedusinganextendedunbinnedmaximumlikelihoodfittothe invariantmassdistributionoftheB0s candidatesinthemassrange 5–6 GeV/c2. The estimation ofthe statisticaluncertainties ofthe
fittedraw yields isbased on thesecond derivativesof the nega-tivelog-likelihoodfunction.Examplesoffitstotheinvariantmass distributionsinppandPbPbcollisions areshowninFigs.1and2 forthe pT regions 7–15and15–50 GeV/c,respectively.Thesignal
shapeismodeledbytwoGaussianfunctionswithacommonmean
(which isafree parametertogetherwiththeamplitude),and dif-ferentwidthsindividuallydeterminedfromMCsimulationsforthe ppandPbPbresults.TherelativecontributionofthetwoGaussian functionstothesignalyieldisalsofixedatthevaluegivenbythe MCsample.Thebackgroundisdominatedbyrandomcombinations ofpromptandnonpromptJ/ψcandidateswithextraparticlesand it ismodeledby afirst-orderpolynomial,asdeterminedby stud-ies oftheinclusiveJ/ψ MC sample.Peakingstructuresthat could arisefromthebackgroundcontaminationofotherBmesondecays (e.g.,B0→J/ψK∗0)werefoundtobenegligibleasaconsequence ofthetightselectiononthemassoftheφcandidate.
The differential crosssection forB0
s production in|y|<2.4 is
computedineach pTintervalaccordingto
dσB0s dpT |y|<2.4 =1 2 1 B L 1 pT N(B 0 s+B 0 s) pp (pT) αpp(pT)pp(pT) | y|<2.4 , (1)
forppdata,andforPbPbdataaccordingto
1 TAA dNB0s PbPb dpT |y|<2.4
=1 2 1 BNMBTAA 1 pT × N(B0s+B 0 s) PbPb (pT) αPbPb(pT)PbPb(pT) | y|<2.4 . (2) The N(B0s+B 0 s)
pp,PbPb is therawsignalyield extractedineach pT interval
of width pT, (α, )pp,PbPb represents the corresponding
accep-tancetimesefficiency,andBisthebranchingfractionofthedecay chain. For the pp cross section, L represents the integrated lu-minosity, andfor the PbPb cross section, NMB is the number of
minimumbiaseventsand TAA isthenuclearoverlapfunction [43].
The TAA is equal to the number of NN binary collisions divided
by theNN total inelasticcross section, andit can be interpreted astheNN-equivalentintegratedluminosityperheavyioncollision. The TAA valueforinclusivePbPbcollisions at√sNN=5.02 TeVis
(5.6±0.2)mb−1 asestimatedfromanMCGlaubermodel [38,43]. Assumingthat, in thekinematic regionaccessible by the present measurement,theB0
s andB 0
s productioncross sectionsareequal,
thefactor 1/2accountsfor thefact that the yields are measured forparticlesandantiparticlesaddedtogether,butthecrosssection isgivenforonespeciesonly.
4. Systematicuncertainties
Thecrosssectionmeasurementsareaffectedbyseveralsources ofsystematicuncertaintiesarising fromthesignal extraction, cor-rections, B, L, NMB, and TAA determination. Unless mentioned
otherwise,thesameprocedures wereusedtoestimate the uncer-taintiesforthep pandPbPbresults.Theuncertaintyofthesignal modelingisevaluatedbyconsideringfourfitvariations:(i) increas-ing/decreasing thewidthparameters determined fromsimulation by 4% (the maximum relative statistical uncertainty ofthe fitted widthparameteramongall pT bins fromp p andPbPbdata); (ii)
usingasingle Gaussianfunction; (iii)usingasumofthree Gaus-sian functions with a common mean, and, (iv) fixing the mean of the Gaussian function to the value determined from simula-tion. The uncertainty in the modeling of the background shapes isalsoevaluated byvarying theprobability distributionfunctions usedtodescribethebackgroundtoahigher-orderpolynomialand exponential function. The maximum of the signal variations and themaximumof allthe backgroundvariations are propagated as systematicuncertainties.Forthep presults,thesystematic uncer-taintyduetotheselectionoftheB0
s mesoncandidatesisestimated
bycomparingtheBDT-obtainednominalresultwiththeresults us-inga cut-based method(arectangularcut)that uses theGenetic Algorithmtodeterminethebestcutvalueforeachparameter [42]. Thesamesignal andbackgroundshape parametrizationareused, and the same analysis parameters are optimized as in the BDT nominalmethod.The significanceis similarforthe two methods (∼8) forthe p p bins.This provides an estimate of the potential difference betweendifferentselection criteria. The full difference between the two methods is propagated as a systematic uncer-tainty.For the PbPb results,because of the small signal indata, inordertominimizetheimpactofstatisticalfluctuations,a differ-entapproachwastaken. Inthiscase, theB0s selectionuncertainty wasestimatedusingthe ppdatasample, asthefull differencein theyield betweenthep presultswiththeBDTtrainedonthep p sample(the nominalresult)andtheresultswiththe BDTtrained onthePbPbsample(theselectionusedforthePbPbresults).
Thebin-by-binsystematicuncertaintiesassociatedwiththe ac-ceptance correction are estimated by varying the shape of the generated B0s meson pT and y spectra. For the purpose of the
systematicstudies only, both data andMC are splitinto four pT
andy bins. Theratiobetweendataandsimulated pT spectra
(in-cludingtheirstatisticaluncertainties)isusedtogenerate pseudo-experiments (‘toys’). Each toy is fit with a polynomial, which is
Table 1
Summaryofsystematicuncertaintiesinpercentage(%)fromeachsourceinppand PbPbanalyses. Collisionsystem pp PbPb pTinterval(GeV/c) [7,15] [15,20] [20,50] [7,15] [15,50] Signalmodeling 2.5 0.7 0.7 4.2 3.5 Backgroundmodeling 3.4 1.6 1.6 8.7 0.68 B0 sselection 15 2.6 2.6 19 8.6 B0 sacceptance 1.7 1.4 1.7 1.7 1.7 B0sefficiency 6.5 0.5 0.9 7.9 3.8 MCsamplesize 0.8 0.8 0.5 4.9 2.1 Muontrigger, reconstruction,and identification 4.4 3.3 3.0 5.1 3.8
Hadrontrackingefficiency 8 8 8 12 12 Total 19 9.4 9.3 26 16 Branchingfractions 7.6
Numberofminimumbias eventsinPbPbdata – 2 TAA – +2.8/−3.4 Integratedluminosityofpp data 2.3 –
then used to reweight the MC B0
s meson pT spectra. A new
ac-ceptance value is calculated for each modified shape, for each kinematicbin.Therootmeansquare (RMS)ofallacceptances de-termined viatoys ispropagated asthe systematicuncertaintyby choosing the maximumRMS value emerging fromthe pT and y
shapevariations.Becauseofthesmallsignalavailable,forthePbPb resultsthep p ratioisusedtogeneratethetoys. Thereisalsoan uncertaintyassignedtoaccountforpotentialbiasintheefficiency calculationsfromtheFONLLsimulationsoftheB0s meson pTshape.
Thisuncertaintyiscalculatedasthedifferencebetweenthe nomi-nalresultsandthoseobtainedbygeneratingthe pythia pT shape.
An additional uncertainty comes from the finite size of the MC samples. This is determined by the statisticaluncertainty of the simulatedsignal,afterapplyingallselectioncriteria.
The uncertainty in the efficiency of the muon trigger, recon-struction, andidentification isevaluated bin-by-bin usingcontrol samples indata [44]. Arelative systematicuncertainty of4% per hadrontrackinppcollisions [29] and6%inPbPbcollisions [38] is alsoconsidered,toaccountfortheuncertaintyinthetrack recon-structionefficiency.Thisuncertaintypropagatesto8%and12%for theB0s measurementinppandPbPb,respectively. Thesystematic uncertaintyinthecrosssection measurementiscomputedasthe suminquadratureofthedifferentcontributionsmentionedabove. TheuncertaintyintheB0s mesondecayB is7.6% [28].The uncer-taintyfor NMB accountsfortheinefficiencyoftheeventselection
andthe triggerinselecting hadronicevents [38]. The TAA
uncer-tainty is +2.8%, −3.4% [38]. Inthe calculationsofthe systematic uncertainties oftheB0
s meson RAA andtheRAA ratiobetweenB0s
andB+,correlated uncertaintiesfromthe trackandmuon recon-structionandidentificationarepartiallycanceled.
Thevaluesforeachsystematicuncertaintysourcearelisted in Table1.
5. Results
InFig.3andinthetoppanelofFig.4,the pT-differential
pro-duction crosssectionsinpp andPbPb collisions measuredin the interval |y|<2.4 are presented. The pp results are compared to the predictions of FONLL calculations [26]. The FONLL reference cross section isobtained by multiplying the FONLL totalb quark production [24–26] by the world-average production fraction of B0s of10.3% [28]. The B0s FONLL predictionis consistentwith the
measuredB0
Fig. 3. ThepT-differentialproductioncrosssectionofB0s inppcollisionsat
√
s=
5.02 TeVinthreepTintervalsfrom7to50 GeV/c.Theverticalbars(boxes)
cor-respondtostatistical(systematic)uncertainties.Theglobalsystematicuncertainty, listedinthelegendandnotincludedinthepoint-to-pointuncertainties,comprises theuncertaintiesintheintegratedluminositymeasurementandinthebranching fractionB.TheppcrosssectioniscomparedtoFONLLcalculations [26] represented bythecoloredyellowboxeswiththeheightsindicatingthetheoreticaluncertainty.
spectrumhasasmalleruncertaintythanthatoftheFONLL calcu-lation.
The nuclear modificationfactor RAA,shown inFig. 4,is
com-putedas: RAA(pT)= 1 TAA dNB0s PbPb dpT dσB0s pp dpT . (3) The B0
s meson RAA is 1.5±0.6(stat)±0.5(syst) for 7–15 GeV/c,
and0.87±0.30(stat)±0.17(syst)for15–50 GeV/c,respectively.In the bottompanel of Fig. 4, the RAA of B+ mesons froma
previ-ousmeasurement [27] isalsoshown.ComparedtotheB+mesons, there is an indication of an enhancement for B0s mesons, which wouldbe the expectationinthe presenceof acontribution from beautyrecombinationwithstrangequarksinheavyioncollisions. However, the B0s RAA values arecompatible withunity andtheir
largeuncertaintiesdonotexcludeasignificantsuppression.The pT
dependenceof RAAiscomparedtotheB0s predictionofa
perturba-tiveQCD basedmodelthat includesbothcollisionalandradiative energyloss,(CUJET3.0) [45–47],andatransportmodelbasedona Langevinequation that includescollisionalenergyloss andheavy quark diffusion in the medium, (TAMU) [17,48]. The difference betweenthe two models below pT∼15 GeV reflects the
contri-bution from recombination processes, which are included in the TAMU but not in the CUJET3.0 model.The results measured for
pT>7 GeV/c havethe powerto disentanglethetwo models,
al-beit afteran increase inprecision,which canbe achievedwitha biggerdatasample.
Tofurtherquantifythesignificanceofapossibleenhancement ofthe B0s/B+ ratioin PbPb withrespect to pp collisions, the ra-tio betweenthe B0
s and the B+ RAA is also calculated,canceling
thesystematicuncertaintysourcesthatarecommontoboth mea-surements(acceptance,trackingefficiency,andmuon-related).The B+ RAAwithawider pTbinning(15–50 GeV/c)isobtainedbyaB+
yield weighted averageof theresults fromthree pT bins (15–20,
20–30and30–50 GeV/c)presentedinpreviouswork [27].The re-sultisshowninFig.5.The ratiois 4.0±1.8(stat)±1.3(syst) for 7–15 GeV/c, and 1.8±0.7(stat)±0.3(syst) for 15–50 GeV/c, re-spectively.AssumingaGaussiandistributionwithmeanandwidth equaltothatofthe RAAratioanditsuncertainty(including
statis-ticalandsystematiccomponentsaddedinquadrature),the
hypoth-Fig. 4. (top)ThepT-differentialproductioncrosssectionofB0s mesonsinpp
colli-sionsandthe pT-differentialcorrectedyieldofB0s mesonsscaledbyTAAinPbPb
collisionsat√sNN=5.02 TeVintwopTintervalsfrom7to50 GeV/c.Thevertical
bars(boxes)correspondtostatistical(systematic)uncertainties.Theglobal system-aticuncertaintycomprisestheuncertaintiesinTAA,NMB,andB.(bottom)The
nu-clearmodificationfactorRAAofB0smeasuredinPbPbcollisionsat√sNN=5.02 TeV
from 7to50 GeV/c.Theverticalbars(boxes) correspondto statistical (system-atic)uncertainties.TheB+ RAAmeasurement [27] isalsoshownforcomparison.
Theglobalsystematicuncertainty,representedbythegreyboxat RAA=1,
com-prisestheuncertaintiesintheintegratedluminositymeasurementand TAAvalue.
TwoB0s theoreticalcalculationsarealsoshownforcomparison:TAMU [17,48] and
CUJET3.0 [45–47].ThelinewidthofthetheoreticalcalculationfromRefs. [17,48] representsthesizeofitsstatisticaluncertainty.
esisof theratio valuesbeingconsistent withunity (no enhance-ment)istestedwitha χ2 test.Theresultingp-valuesare18%and
28%for7–15and15–50 GeV/c,respectively.Thisshowsthat,with a p-value cutoffof5%,thescenarioofnoenhancementcannotbe rejected. This analysisdemonstrates the capability ofperforming a fullyreconstructedB0s measurementinPbPbcollisions withthe CMSdetector.
6. Summary
Thefirstmeasurementofthedifferentialproductioncross sec-tion of B0s mesons(including both charge conjugates) in bothpp andPbPbcollisionsatacenter-of-massenergyof5.02 TeVper nu-cleon pair ispresented. The B0
s and B 0
s mesons are studied with
the CMS detector at the LHC in the rapidity range |y|<2.4 via the reconstructionof oneoftheir exclusive hadronicdecay chan-nels, B0s→J/ψφ→μ+μ−K+K−. The nuclear modification factor
Fig. 5. ThenuclearmodificationfactorRAAratiobetweenB0s andB+ measuredin
PbPbcollisionsat√sNN=5.02 TeVfrom7to50 GeV/c.TwoB0s theoretical
calcula-tionsarealsoshownforcomparison:TAMU [17,48],andCUJET3.0 [45–47].
7 to 50 GeV/c,inclusively for0–100% event centrality. A hintof an enhancement of the B0
s/B+ ratio in PbPb with respect to pp
collisions is seen. More precise measurements of the B0s andB± mesons RAA with the upcoming high-luminosity LHC heavy ion
runscould providefurtherconstraintsontherelevance of recom-bination,a markerof deconfined matter, forbeauty hadron pro-duction,and unambiguous informationabout themechanisms of beautyhadronizationinheavyioncollisions.
Acknowledgements
WecongratulateourcolleaguesintheCERNaccelerator depart-ments for the excellent performance of the LHC and thank the technicalandadministrativestaffs atCERN andatother CMS in-stitutes for their contributions to the success of the CMS effort. Inaddition,wegratefullyacknowledgethecomputingcentersand personneloftheWorldwideLHCComputingGridfordeliveringso effectivelythecomputinginfrastructure essential toour analyses. Finally, we acknowledge the enduring support for the construc-tionandoperationofthe LHCandtheCMSdetectorprovided by thefollowingfundingagencies: BMBWFandFWF(Austria);FNRS andFWO (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,ERCIUT,andERDF(Estonia);Academy ofFinland,MEC,andHIP(Finland);CEAandCNRS/IN2P3(France); BMBF, DFG, and HGF (Germany); GSRT (Greece); NKFIA (Hun-gary);DAEandDST (India);IPM(Iran);SFI(Ireland);INFN (Italy); MSIPandNRF(Republic ofKorea);MES (Latvia);LAS (Lithuania); MOE and UM (Malaysia); BUAP, CINVESTAV, CONACYT, LNS, SEP, andUASLP-FAI(Mexico);MOS(Montenegro);MBIE(NewZealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna);MON,ROSATOM,RAS,RFBR,andNRCKI(Russia);MESTD (Serbia);SEIDI,CPAN,PCTI,andFEDER(Spain);MoSTR (SriLanka); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR, and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASUand SFFR(Ukraine); STFC (United Kingdom);DOE andNSF (USA).
Individuals have received support from the Marie-Curie pro-gramme and the European Research Council and Horizon 2020 Grant, contract No. 675440 (European Union); the A.G. Leventis Foundation;theA. P. SloanFoundation;the Alexandervon Hum-boldt Foundation; the Belgian Federal Science Policy Office; the Fonds pour la Formation à la Recherche dansl’Industrie et dans
l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium); the F.R.S.-FNRS and FWO (Belgium) under the “Excellence of Science - EOS” - be.h projectn.30820817; theMinistryofEducation,Youth andSports (MEYS) of the Czech Republic; the Lendület (“Momentum”) Pro-gramme and the János Bolyai Research Scholarship of the Hun-garianAcademyofSciences,theNewNationalExcellenceProgram ÚNKP,theNKFIAresearchgrants123842,123959,124845,124850 and125105 (Hungary); the Council ofScience andIndustrial Re-search, India; the HOMING PLUS programme of the Foundation forPolishScience,cofinancedfromEuropeanUnion,European Re-gional Development Fund, the Mobility Plus programme of the Ministry of Science and Higher Education, the National Science Center (Poland), contracts Harmonia 2014/14/M/ST2/00428, Opus 2014/13/B/ST2/02543, 2014/15/B/ST2/03998, and 2015/19/B/ST2/ 02861,Sonata-bis2012/07/E/ST2/01406;theNationalPriorities Re-search Program by Qatar National Research Fund; the Programa EstataldeFomento delaInvestigación CientíficayTécnica de Ex-celencia María de Maeztu, grant MDM-2015-0509 and the Pro-grama Severo Ochoa del Principado de Asturias; the Thalis and Aristeia programmes cofinanced by EU-ESF andthe Greek NSRF; theRachadapisekSompotFundforPostdoctoralFellowship, Chula-longkornUniversityandtheChulalongkornAcademic intoIts2nd CenturyProjectAdvancement Project(Thailand);theWelch Foun-dation,contractC-1845;andtheWestonHavensFoundation(USA).
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TheCMSCollaboration
A.M. Sirunyan,A. Tumasyan
YerevanPhysicsInstitute,Yerevan,Armenia
W. Adam, F. Ambrogi, E. Asilar,T. Bergauer, J. Brandstetter, M. Dragicevic,J. Erö,A. Escalante Del Valle, M. Flechl,R. Frühwirth1, V.M. Ghete, J. Hrubec, M. Jeitler1, N. Krammer,I. Krätschmer,D. Liko,
T. Madlener, I. Mikulec,N. Rad, H. Rohringer, J. Schieck1,R. Schöfbeck, M. Spanring, D. Spitzbart,
A. Taurok,W. Waltenberger, J. Wittmann, C.-E. Wulz1, M. Zarucki
InstitutfürHochenergiephysik,Wien,Austria
V. Chekhovsky, V. Mossolov,J. Suarez Gonzalez
InstituteforNuclearProblems,Minsk,Belarus
E.A. De Wolf,D. Di Croce, X. Janssen, J. Lauwers,M. Pieters,H. Van Haevermaet, P. Van Mechelen,
N. Van Remortel
S. Abu Zeid,F. Blekman, J. D’Hondt, I. De Bruyn, J. De Clercq, K. Deroover, G. Flouris, 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, G. Fasanella,L. Favart,
R. Goldouzian, A. Grebenyuk,A.K. Kalsi,T. Lenzi, J. Luetic, N. Postiau,E. Starling, L. Thomas,
C. Vander Velde, P. Vanlaer,D. Vannerom, Q. Wang
UniversitéLibredeBruxelles,Bruxelles,Belgium
T. Cornelis,D. Dobur, A. Fagot,M. Gul, I. Khvastunov2,D. Poyraz, C. Roskas, D. Trocino, M. Tytgat,
W. Verbeke,B. Vermassen, M. Vit, N. Zaganidis
GhentUniversity,Ghent,Belgium
H. Bakhshiansohi,O. Bondu, S. Brochet,G. Bruno, C. Caputo, P. David,C. Delaere, M. Delcourt,
B. Francois,A. Giammanco, G. Krintiras,V. Lemaitre, A. Magitteri, A. Mertens, M. Musich,
K. Piotrzkowski,A. Saggio, M. Vidal Marono, S. Wertz, J. Zobec
UniversitéCatholiquedeLouvain,Louvain-la-Neuve,Belgium
F.L. Alves,G.A. Alves,M. Correa Martins Junior, G. Correia Silva,C. Hensel, A. Moraes,M.E. Pol, P. Rebello Teles
CentroBrasileirodePesquisasFisicas,RiodeJaneiro,Brazil
E. Belchior Batista Das Chagas, W. Carvalho,J. Chinellato3, E. Coelho, E.M. Da Costa, G.G. Da Silveira4,
D. De Jesus Damiao,C. De Oliveira Martins, S. Fonseca De Souza, H. Malbouisson, D. Matos Figueiredo,
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 Manganote3,F. Torres Da Silva De Araujo, A. Vilela Pereira
UniversidadedoEstadodoRiodeJaneiro,RiodeJaneiro,Brazil
S. Ahujaa,C.A. Bernardesa, L. Calligarisa,T.R. Fernandez Perez Tomeia,E.M. Gregoresb, P.G. Mercadanteb,S.F. Novaesa,Sandra Padulaa
aUniversidadeEstadualPaulista,SãoPaulo,Brazil bUniversidadeFederaldoABC,SãoPaulo,Brazil
A. Aleksandrov, 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. Fang5, X. Gao5,L. Yuan
BeihangUniversity,Beijing,China
M. Ahmad, J.G. Bian, G.M. Chen,H.S. Chen, M. Chen, Y. Chen, C.H. Jiang, D. Leggat,H. Liao, Z. Liu,
F. Romeo,S.M. Shaheen6,A. Spiezia, J. Tao, Z. Wang, E. Yazgan, H. Zhang,S. Zhang6,J. Zhao
InstituteofHighEnergyPhysics,Beijing,China
Y. Ban, G. Chen, A. Levin,J. Li, L. Li,Q. Li, Y. Mao, S.J. Qian, D. Wang,Z. Xu
Y. Wang
TsinghuaUniversity,Beijing,China
C. Avila,A. Cabrera, C.A. Carrillo Montoya, L.F. Chaparro Sierra, C. Florez, C.F. González Hernández,
M.A. Segura Delgado
UniversidaddeLosAndes,Bogota,Colombia
B. Courbon, N. Godinovic, D. Lelas,I. Puljak, T. Sculac
UniversityofSplit,FacultyofElectricalEngineering,MechanicalEngineeringandNavalArchitecture,Split,Croatia
Z. Antunovic, M. Kovac
UniversityofSplit,FacultyofScience,Split,Croatia
V. Brigljevic,D. Ferencek, K. Kadija,B. Mesic, A. Starodumov7, T. Susa
InstituteRudjerBoskovic,Zagreb,Croatia
M.W. Ather,A. Attikis, M. Kolosova, G. Mavromanolakis,J. Mousa, C. Nicolaou, F. Ptochos, P.A. Razis,
H. Rykaczewski
UniversityofCyprus,Nicosia,Cyprus
M. Finger8, M. Finger Jr.8
CharlesUniversity,Prague,CzechRepublic
E. Ayala
EscuelaPolitecnicaNacional,Quito,Ecuador
E. Carrera Jarrin
UniversidadSanFranciscodeQuito,Quito,Ecuador
A. Ellithi Kamel9, M.A. Mahmoud10,11,Y. Mohammed10
AcademyofScientificResearchandTechnologyoftheArabRepublicofEgypt,EgyptianNetworkofHighEnergyPhysics,Cairo,Egypt
S. Bhowmik, A. Carvalho Antunes De Oliveira,R.K. Dewanjee, K. Ehataht, M. Kadastik, M. Raidal,
C. Veelken
NationalInstituteofChemicalPhysicsandBiophysics,Tallinn,Estonia
P. Eerola, H. Kirschenmann,J. Pekkanen,M. Voutilainen
DepartmentofPhysics,UniversityofHelsinki,Helsinki,Finland
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, J.L. Faure, F. Ferri, S. Ganjour, A. Givernaud, P. Gras,
G. Hamel de Monchenault, P. Jarry,C. Leloup,E. Locci, J. Malcles,G. Negro, J. Rander, A. Rosowsky,
M.Ö. Sahin,M. Titov
A. Abdulsalam12,C. Amendola, I. Antropov, F. Beaudette, P. Busson, C. Charlot, R. Granier de Cassagnac,
I. Kucher, A. Lobanov, J. Martin Blanco, C. Martin Perez,M. Nguyen, C. Ochando, G. Ortona, P. Paganini,
P. Pigard,J. Rembser, R. Salerno,J.B. Sauvan, Y. Sirois, A.G. Stahl Leiton, A. Zabi,A. Zghiche
LaboratoireLeprince-Ringuet,Ecolepolytechnique,CNRS/IN2P3,UniversitéParis-Saclay,Palaiseau,France
J.-L. Agram13,J. Andrea, D. Bloch,J.-M. Brom, E.C. Chabert,V. Cherepanov, C. Collard, E. Conte13, J.-C. Fontaine13,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,N. Chanon, R. Chierici,D. Contardo, P. Depasse, H. El Mamouni,
J. Fay, L. Finco,S. Gascon, M. Gouzevitch, G. Grenier, B. Ille, F. Lagarde, I.B. Laktineh,H. Lattaud, M. Lethuillier,L. Mirabito, S. Perries,A. Popov14,V. Sordini, G. Touquet, M. Vander Donckt, S. Viret
UniversitédeLyon,UniversitéClaudeBernardLyon1,CNRS-IN2P3,InstitutdePhysiqueNucléairedeLyon,Villeurbanne,France
T. Toriashvili15
GeorgianTechnicalUniversity,Tbilisi,Georgia
I. Bagaturia16
TbilisiStateUniversity,Tbilisi,Georgia
C. Autermann,L. Feld, M.K. Kiesel, K. Klein, M. Lipinski,M. Preuten, M.P. Rauch,C. Schomakers, J. Schulz,
M. Teroerde,B. Wittmer, V. Zhukov14
RWTHAachenUniversity,I.PhysikalischesInstitut,Aachen,Germany
A. Albert, D. Duchardt, M. Erdmann,S. Erdweg, T. Esch, R. Fischer,S. Ghosh, A. Güth, T. Hebbeker,
C. Heidemann,K. Hoepfner,H. Keller, L. Mastrolorenzo,M. Merschmeyer, A. Meyer,P. Millet,
S. Mukherjee,T. Pook,M. Radziej, H. Reithler, M. Rieger, A. Schmidt,D. Teyssier, S. Thüer
RWTHAachenUniversity,III.PhysikalischesInstitutA,Aachen,Germany
G. Flügge,O. Hlushchenko, T. Kress, A. Künsken, T. Müller,A. Nehrkorn, A. Nowack, C. Pistone, O. Pooth,
D. Roy, H. Sert, A. Stahl17
RWTHAachenUniversity,III.PhysikalischesInstitutB,Aachen,Germany
M. Aldaya Martin,T. Arndt, C. Asawatangtrakuldee, I. Babounikau, K. Beernaert,O. Behnke, U. Behrens,
A. Bermúdez Martínez, D. Bertsche, A.A. Bin Anuar, K. Borras18,V. Botta, A. Campbell,P. Connor,
C. Contreras-Campana, V. Danilov,A. De Wit, M.M. Defranchis, C. Diez Pardos, D. Domínguez Damiani,
G. Eckerlin,T. Eichhorn, A. Elwood, E. Eren, E. Gallo19, A. Geiser, A. Grohsjean, M. Guthoff,M. Haranko,
A. Harb,J. Hauk, H. Jung,M. Kasemann, J. Keaveney, C. Kleinwort,J. Knolle, D. Krücker, W. Lange,
A. Lelek,T. Lenz, J. Leonard, K. Lipka,W. Lohmann20, R. Mankel, I.-A. Melzer-Pellmann,A.B. Meyer,
M. Meyer,M. Missiroli, G. Mittag, J. Mnich, V. Myronenko,S.K. Pflitsch, D. Pitzl,A. Raspereza,
M. Savitskyi,P. Saxena,P. Schütze, C. Schwanenberger, R. Shevchenko, A. Singh,H. Tholen, O. Turkot,
A. Vagnerini,G.P. Van Onsem, R. Walsh, Y. Wen,K. Wichmann,C. Wissing, O. Zenaiev
DeutschesElektronen-Synchrotron,Hamburg,Germany
R. Aggleton,S. Bein, L. Benato, A. Benecke, V. Blobel, T. Dreyer, E. Garutti,D. Gonzalez, P. Gunnellini,
J. Haller, A. Hinzmann, A. Karavdina,G. Kasieczka, R. Klanner, R. Kogler,N. Kovalchuk, S. Kurz,
A. Reimers, O. Rieger,C. Scharf, P. Schleper, S. Schumann, J. Schwandt, J. Sonneveld,H. Stadie,
G. Steinbrück, F.M. Stober,M. Stöver, A. Vanhoefer, B. Vormwald, I. Zoi
UniversityofHamburg,Hamburg,Germany
M. Akbiyik, C. Barth,M. Baselga, S. Baur, E. Butz,R. Caspart, T. Chwalek, F. Colombo, W. De Boer,
A. Dierlamm, K. El Morabit,N. Faltermann, B. Freund,M. Giffels, M.A. Harrendorf,F. Hartmann17,
S.M. Heindl,U. Husemann, F. Kassel17,I. Katkov14, S. Kudella, H. Mildner, S. Mitra, M.U. Mozer, Th. Müller, M. Plagge, G. Quast, K. Rabbertz,M. Schröder, I. Shvetsov, G. Sieber,H.J. Simonis, R. Ulrich,
S. Wayand,M. Weber, T. Weiler, S. Williamson, C. Wöhrmann, R. Wolf
KarlsruherInstitutfuerTechnologie,Karlsruhe,Germany
G. Anagnostou, G. Daskalakis,T. Geralis,A. Kyriakis, D. Loukas, G. Paspalaki,I. Topsis-Giotis
InstituteofNuclearandParticlePhysics(INPP),NCSRDemokritos,AghiaParaskevi,Greece
G. Karathanasis,S. Kesisoglou, P. Kontaxakis, A. Panagiotou, I. Papavergou, N. Saoulidou, E. Tziaferi, K. Vellidis
NationalandKapodistrianUniversityofAthens,Athens,Greece
K. Kousouris,I. Papakrivopoulos, G. Tsipolitis
NationalTechnicalUniversityofAthens,Athens,Greece
I. Evangelou, C. Foudas,P. Gianneios, P. Katsoulis, P. Kokkas, S. Mallios,N. Manthos, I. Papadopoulos, E. Paradas, J. Strologas,F.A. Triantis, D. Tsitsonis
UniversityofIoánnina,Ioánnina,Greece
M. Bartók21,M. Csanad, N. Filipovic, P. Major, M.I. Nagy, G. Pasztor, O. Surányi,G.I. Veres
MTA-ELTELendületCMSParticleandNuclearPhysicsGroup,EötvösLorándUniversity,Budapest,Hungary
G. Bencze,C. Hajdu, D. Horvath22,Á. Hunyadi, F. Sikler,T.Á. Vámi, V. Veszpremi, G. Vesztergombi†
WignerResearchCentreforPhysics,Budapest,Hungary
N. Beni, S. Czellar, J. Karancsi23,A. Makovec, J. Molnar,Z. Szillasi
InstituteofNuclearResearchATOMKI,Debrecen,Hungary
P. Raics, Z.L. Trocsanyi,B. Ujvari
InstituteofPhysics,UniversityofDebrecen,Debrecen,Hungary
S. Choudhury, J.R. Komaragiri, P.C. Tiwari
IndianInstituteofScience(IISc),Bangalore,India
S. Bahinipati24, C. Kar,P. Mal, K. Mandal, A. Nayak25,D.K. Sahoo24,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,
R. Kumar,P. Kumari, M. Lohan, A. Mehta, K. Sandeep, S. Sharma,J.B. Singh, A.K. Virdi, G. Walia
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
R. Bhardwaj26, M. Bharti26, R. Bhattacharya,S. Bhattacharya, U. Bhawandeep26, D. Bhowmik, S. Dey,
S. Dutt26,S. Dutta, S. Ghosh, K. Mondal, S. Nandan, A. Purohit,P.K. Rout, A. Roy,S. Roy Chowdhury,
G. Saha,S. Sarkar, M. Sharan, B. Singh26, S. Thakur26
SahaInstituteofNuclearPhysics,HBNI,Kolkata,India
P.K. Behera
IndianInstituteofTechnologyMadras,Madras,India
R. Chudasama, D. Dutta, V. Jha, V. Kumar, P.K. Netrakanti, L.M. Pant, P. Shukla
BhabhaAtomicResearchCentre,Mumbai,India
T. Aziz,M.A. Bhat, S. Dugad, G.B. Mohanty, N. Sur, B. Sutar, R.K. Verma
TataInstituteofFundamentalResearch-A,Mumbai,India
S. Banerjee, S. Bhattacharya, S. Chatterjee,P. Das, M. Guchait,Sa. Jain, S. Karmakar, S. Kumar,
M. Maity27,G. Majumder, K. Mazumdar, N. Sahoo,T. Sarkar27
TataInstituteofFundamentalResearch-B,Mumbai,India
S. Chauhan,S. Dube, V. Hegde, A. Kapoor, K. Kothekar, S. Pandey, A. Rane, S. Sharma
IndianInstituteofScienceEducationandResearch(IISER),Pune,India
S. Chenarani28, E. Eskandari Tadavani,S.M. Etesami28, M. Khakzad, M. Mohammadi Najafabadi,
M. Naseri, F. Rezaei Hosseinabadi, B. Safarzadeh29, M. Zeinali
InstituteforResearchinFundamentalSciences(IPM),Tehran,Iran
M. Felcini,M. Grunewald
UniversityCollegeDublin,Dublin,Ireland
M. Abbresciaa,b, C. Calabriaa,b, A. Colaleoa, D. Creanzaa,c,L. Cristellaa,b, N. De Filippisa,c,
M. De Palmaa,b, A. Di Florioa,b, F. Erricoa,b,L. Fiorea,A. Gelmia,b, G. Iasellia,c, M. Incea,b,S. Lezkia,b, G. Maggia,c, M. Maggia,G. Minielloa,b,S. Mya,b,S. Nuzzoa,b, A. Pompilia,b, G. Pugliesea,c,R. Radognaa, A. Ranieria,G. Selvaggia,b,A. Sharmaa,L. Silvestrisa, R. Vendittia,P. Verwilligena,G. Zitoa
aINFNSezionediBari,Bari,Italy bUniversitàdiBari,Bari,Italy cPolitecnicodiBari,Bari,Italy
G. Abbiendia,C. Battilanaa,b,D. Bonacorsia,b, L. Borgonovia,b,S. Braibant-Giacomellia,b,
R. Campaninia,b,P. Capiluppia,b,A. Castroa,b, F.R. Cavalloa, S.S. Chhibraa,b,C. Cioccaa,G. Codispotia,b, M. Cuffiania,b,G.M. Dallavallea, F. Fabbria,A. Fanfania,b,E. Fontanesi, P. Giacomellia,C. Grandia, L. Guiduccia,b,S. Lo Meoa,S. Marcellinia, G. Masettia, A. Montanaria, F.L. Navarriaa,b,A. Perrottaa, F. Primaveraa,b,17,A.M. Rossia,b, T. Rovellia,b,G.P. Sirolia,b, N. Tosia
aINFNSezionediBologna,Bologna,Italy bUniversitàdiBologna,Bologna,Italy
S. Albergoa,b, A. Di Mattiaa,R. Potenzaa,b,A. Tricomia,b,C. Tuvea,b
aINFNSezionediCatania,Catania,Italy bUniversitàdiCatania,Catania,Italy
G. Barbaglia,K. Chatterjeea,b,V. Ciullia,b,C. Civininia,R. D’Alessandroa,b, E. Focardia,b, G. Latino, P. Lenzia,b, M. Meschinia, S. Paolettia,L. Russoa,30, G. Sguazzonia,D. Stroma,L. Viliania
aINFNSezionediFirenze,Firenze,Italy bUniversitàdiFirenze,Firenze,Italy
L. Benussi, S. Bianco, F. Fabbri,D. Piccolo
INFNLaboratoriNazionalidiFrascati,Frascati,Italy
F. Ferroa, F. Raveraa,b,E. Robuttia, S. Tosia,b
aINFNSezionediGenova,Genova,Italy bUniversitàdiGenova,Genova,Italy
A. Benagliaa, A. Beschib, L. Brianzaa,b, F. Brivioa,b, V. Cirioloa,b,17,S. Di Guidaa,b,17, M.E. Dinardoa,b, S. Fiorendia,b,S. Gennaia,A. Ghezzia,b,P. Govonia,b,M. Malbertia,b, S. Malvezzia, A. Massironia,b, D. Menascea,F. Monti, L. Moronia,M. Paganonia,b, D. Pedrinia,S. Ragazzia,b,T. Tabarelli de Fatisa,b,
D. Zuoloa,b
aINFNSezionediMilano-Bicocca,Milano,Italy bUniversitàdiMilano-Bicocca,Milano,Italy
S. Buontempoa, N. Cavalloa,c, A. De Iorioa,b,A. Di Crescenzoa,b, F. Fabozzia,c,F. Fiengaa, G. Galatia, A.O.M. Iorioa,b, W.A. Khana,L. Listaa, S. Meolaa,d,17, P. Paoluccia,17, C. Sciaccaa,b, E. Voevodinaa,b
aINFNSezionediNapoli,Napoli,Italy bUniversitàdiNapoli‘FedericoII’,Napoli,Italy cUniversitàdellaBasilicata,Potenza,Italy dUniversitàG.Marconi,Roma,Italy
P. Azzia,N. Bacchettaa,D. Biselloa,b,A. Bolettia,b,A. Bragagnolo,R. Carlina,b, P. Checchiaa, M. Dall’Ossoa,b,P. De Castro Manzanoa, T. Dorigoa,U. Dossellia,F. Gasparinia,b,U. Gasparinia,b, A. Gozzelinoa, S.Y. Hoh, S. Lacapraraa,P. Lujan, M. Margonia,b, A.T. Meneguzzoa,b,J. Pazzinia,b,
P. Ronchesea,b,R. Rossina,b,F. Simonettoa,b,A. Tiko, E. Torassaa,M. Zanettia,b,P. Zottoa,b,G. Zumerlea,b
aINFNSezionediPadova,Padova,Italy bUniversitàdiPadova,Padova,Italy cUniversitàdiTrento,Trento,Italy
A. Braghieria,A. Magnania,P. Montagnaa,b, S.P. Rattia,b,V. Rea, M. Ressegottia,b, C. Riccardia,b, P. Salvinia, I. Vaia,b, P. Vituloa,b
aINFNSezionediPavia,Pavia,Italy bUniversitàdiPavia,Pavia,Italy
M. Biasinia,b, G.M. Bileia,C. Cecchia,b,D. Ciangottinia,b,L. Fanòa,b,P. Laricciaa,b, R. Leonardia,b, E. Manonia, G. Mantovania,b, V. Mariania,b,M. Menichellia,A. Rossia,b,A. Santocchiaa,b, D. Spigaa
aINFNSezionediPerugia,Perugia,Italy bUniversitàdiPerugia,Perugia,Italy
K. Androsova,P. Azzurria,G. Bagliesia,L. Bianchinia,T. Boccalia,L. Borrello, R. Castaldia, M.A. Cioccia,b, R. Dell’Orsoa,G. Fedia, F. Fioria,c, L. Gianninia,c,A. Giassia, M.T. Grippoa,F. Ligabuea,c, E. Mancaa,c, G. Mandorlia,c, A. Messineoa,b, F. Pallaa,A. Rizzia,b, P. Spagnoloa, R. Tenchinia,G. Tonellia,b,
A. Venturia, P.G. Verdinia
aINFNSezionediPisa,Pisa,Italy bUniversitàdiPisa,Pisa,Italy
cScuolaNormaleSuperiorediPisa,Pisa,Italy
L. Baronea,b,F. Cavallaria, M. Cipriania,b,D. Del Rea,b, E. Di Marcoa,b, M. Diemoza,S. Gellia,b,
E. Longoa,b, B. Marzocchia,b,P. Meridiania, G. Organtinia,b,F. Pandolfia, R. Paramattia,b, F. Preiatoa,b, S. Rahatloua,b,C. Rovellia,F. Santanastasioa,b
aINFNSezionediRoma,Rome,Italy bSapienzaUniversitàdiRoma,Rome,Italy
N. Amapanea,b, R. Arcidiaconoa,c,S. Argiroa,b,M. Arneodoa,c,N. Bartosika,R. Bellana,b, C. Biinoa,
N. Cartigliaa, F. Cennaa,b,S. Comettia,M. Costaa,b, R. Covarellia,b,N. Demariaa,B. Kiania,b,C. Mariottia, S. Masellia, E. Migliorea,b,V. Monacoa,b,E. Monteila,b,M. Montenoa, M.M. Obertinoa,b,L. Pachera,b,
N. Pastronea,M. Pelliccionia,G.L. Pinna Angionia,b, A. Romeroa,b, M. Ruspaa,c,R. Sacchia,b, K. Shchelinaa,b, V. Solaa,A. Solanoa,b,D. Soldia,b,A. Staianoa
aINFNSezionediTorino,Torino,Italy bUniversitàdiTorino,Torino,Italy
cUniversitàdelPiemonteOrientale,Novara,Italy
S. Belfortea,V. Candelisea,b, M. Casarsaa,F. Cossuttia,A. Da Rolda,b,G. Della Riccaa,b,F. Vazzolera,b, A. Zanettia
aINFNSezionediTrieste,Trieste,Italy bUniversitàdiTrieste,Trieste,Italy
D.H. Kim,G.N. Kim, M.S. Kim, J. Lee,S. Lee, S.W. Lee, C.S. Moon, Y.D. Oh, S.I. Pak,S. Sekmen, D.C. Son, Y.C. Yang
KyungpookNationalUniversity,Daegu,RepublicofKorea
H. Kim,D.H. Moon,G. Oh
ChonnamNationalUniversity,InstituteforUniverseandElementaryParticles,Kwangju,RepublicofKorea
J. Goh31, T.J. Kim
HanyangUniversity,Seoul,RepublicofKorea
S. Cho,S. Choi, Y. Go, D. Gyun,S. Ha,B. Hong, Y. Jo,K. Lee, K.S. Lee, S. Lee, J. Lim, S.K. Park,Y. Roh
KoreaUniversity,Seoul,RepublicofKorea
H.S. Kim
SejongUniversity,Seoul,RepublicofKorea
J. Almond,J. Kim, J.S. Kim, H. Lee,K. Lee, K. Nam,S.B. Oh, B.C. Radburn-Smith, S.h. Seo, U.K. Yang,
H.D. Yoo,G.B. Yu
SeoulNationalUniversity,Seoul,RepublicofKorea
D. Jeon, H. Kim,J.H. Kim, J.S.H. Lee, I.C. Park
UniversityofSeoul,Seoul,RepublicofKorea
Y. Choi,C. Hwang, J. Lee,I. Yu
SungkyunkwanUniversity,Suwon,RepublicofKorea
V. Dudenas, A. Juodagalvis,J. Vaitkus
VilniusUniversity,Vilnius,Lithuania
I. Ahmed,Z.A. Ibrahim, M.A.B. Md Ali32,F. Mohamad Idris33,W.A.T. Wan Abdullah, M.N. Yusli,
Z. Zolkapli
NationalCentreforParticlePhysics,UniversitiMalaya,KualaLumpur,Malaysia
J.F. Benitez, A. Castaneda Hernandez,J.A. Murillo Quijada
UniversidaddeSonora(UNISON),Hermosillo,Mexico
H. Castilla-Valdez,E. De La Cruz-Burelo, M.C. Duran-Osuna, I. Heredia-De La Cruz34,R. Lopez-Fernandez,
J. Mejia Guisao,R.I. Rabadan-Trejo,M. Ramirez-Garcia, G. Ramirez-Sanchez, R. Reyes-Almanza,
A. Sanchez-Hernandez
S. Carrillo Moreno, C. Oropeza Barrera, F. Vazquez Valencia
UniversidadIberoamericana,MexicoCity,Mexico
J. Eysermans, I. Pedraza, H.A. Salazar Ibarguen, C. Uribe Estrada
BenemeritaUniversidadAutonomadePuebla,Puebla,Mexico
A. Morelos Pineda
UniversidadAutónomadeSanLuisPotosí,SanLuisPotosí,Mexico
D. Krofcheck
UniversityofAuckland,Auckland,NewZealand
S. Bheesette,P.H. Butler
UniversityofCanterbury,Christchurch,NewZealand
A. Ahmad, M. Ahmad, M.I. Asghar,Q. Hassan, H.R. Hoorani, A. Saddique,M.A. Shah, M. Shoaib,M. Waqas
NationalCentreforPhysics,Quaid-I-AzamUniversity,Islamabad,Pakistan
H. Bialkowska, M. Bluj,B. Boimska, T. Frueboes,M. Górski, M. Kazana, M. Szleper, P. Traczyk,P. Zalewski
NationalCentreforNuclearResearch,Swierk,Poland
K. Bunkowski,A. Byszuk35, K. Doroba,A. Kalinowski, M. Konecki,J. Krolikowski, M. Misiura,
M. Olszewski, A. Pyskir,M. Walczak
InstituteofExperimentalPhysics,FacultyofPhysics,UniversityofWarsaw,Warsaw,Poland
M. Araujo, P. Bargassa,C. Beirão Da Cruz E Silva, A. Di Francesco, P. Faccioli, B. Galinhas,M. Gallinaro, J. Hollar, N. Leonardo,M.V. Nemallapudi, J. Seixas,G. Strong,O. Toldaiev, D. Vadruccio, J. Varela
LaboratóriodeInstrumentaçãoeFísicaExperimentaldePartículas,Lisboa,Portugal
S. Afanasiev,P. Bunin, M. Gavrilenko, I. Golutvin, I. Gorbunov, A. Kamenev,V. Karjavine, A. Lanev,
A. Malakhov,V. Matveev36,37,P. Moisenz, V. Palichik,V. Perelygin, S. Shmatov, S. Shulha, N. Skatchkov,
V. Smirnov, N. Voytishin, A. Zarubin
JointInstituteforNuclearResearch,Dubna,Russia
V. Golovtsov, Y. Ivanov, V. Kim38,E. Kuznetsova39, P. Levchenko,V. Murzin, V. Oreshkin,I. Smirnov,
D. Sosnov,V. Sulimov, L. Uvarov, S. Vavilov, A. Vorobyev
PetersburgNuclearPhysicsInstitute,Gatchina(St.Petersburg),Russia
Yu. Andreev,A. Dermenev, S. Gninenko, N. Golubev, A. Karneyeu,M. Kirsanov, N. Krasnikov,
A. Pashenkov,D. Tlisov, A. Toropin
InstituteforNuclearResearch,Moscow,Russia
V. Epshteyn, V. Gavrilov, N. Lychkovskaya,V. Popov, I. Pozdnyakov, G. Safronov, A. Spiridonov,
A. Stepennov, V. Stolin, M. Toms,E. Vlasov, A. Zhokin
InstituteforTheoreticalandExperimentalPhysics,Moscow,Russia
T. Aushev
MoscowInstituteofPhysicsandTechnology,Moscow,Russia
R. Chistov40,M. Danilov40,P. Parygin, D. Philippov,S. Polikarpov40,E. Tarkovskii
V. Andreev,M. Azarkin, I. Dremin37,M. Kirakosyan, S.V. Rusakov, A. Terkulov
P.N.LebedevPhysicalInstitute,Moscow,Russia
A. Baskakov,A. Belyaev, E. Boos,A. Demiyanov,A. Ershov, A. Gribushin, O. Kodolova,V. Korotkikh,
I. Lokhtin,I. Miagkov, S. Obraztsov,S. Petrushanko, V. Savrin, A. Snigirev, I. Vardanyan
SkobeltsynInstituteofNuclearPhysics,LomonosovMoscowStateUniversity,Moscow,Russia
A. Barnyakov41, V. Blinov41, T. Dimova41,L. Kardapoltsev41, Y. Skovpen41
NovosibirskStateUniversity(NSU),Novosibirsk,Russia
I. Azhgirey,I. Bayshev,S. Bitioukov, D. Elumakhov, A. Godizov, V. Kachanov, A. Kalinin, D. Konstantinov,
P. Mandrik,V. Petrov, R. Ryutin, S. Slabospitskii, A. Sobol, S. Troshin, N. Tyurin, A. Uzunian,A. Volkov
InstituteforHighEnergyPhysicsofNationalResearchCentre‘KurchatovInstitute’,Protvino,Russia
A. Babaev,S. Baidali, V. Okhotnikov
NationalResearchTomskPolytechnicUniversity,Tomsk,Russia
P. Adzic42,P. Cirkovic, D. Devetak,M. Dordevic, J. Milosevic
UniversityofBelgrade,FacultyofPhysicsandVincaInstituteofNuclearSciences,Belgrade,Serbia
J. Alcaraz Maestre,A. Álvarez Fernández, I. Bachiller,M. Barrio Luna, J.A. Brochero Cifuentes,M. Cerrada,
N. Colino, B. De La Cruz,A. Delgado Peris,C. Fernandez Bedoya, J.P. Fernández Ramos, J. Flix, M.C. Fouz,
O. Gonzalez Lopez,S. Goy Lopez, J.M. Hernandez, M.I. Josa, D. Moran, A. Pérez-Calero Yzquierdo,
J. Puerta Pelayo, I. Redondo,L. Romero, M.S. Soares,A. Triossi
CentrodeInvestigacionesEnergéticasMedioambientalesyTecnológicas(CIEMAT),Madrid,Spain
C. Albajar, J.F. de Trocóniz
UniversidadAutónomadeMadrid,Madrid,Spain
J. Cuevas,C. Erice, J. Fernandez Menendez, S. Folgueras,I. Gonzalez Caballero, J.R. González Fernández,
E. Palencia Cortezon,V. Rodríguez Bouza, S. Sanchez Cruz, P. Vischia,J.M. Vizan Garcia
UniversidaddeOviedo,Oviedo,Spain
I.J. Cabrillo, A. Calderon, B. Chazin Quero,J. Duarte Campderros, M. Fernandez,P.J. Fernández Manteca,
A. García Alonso,J. Garcia-Ferrero,G. Gomez, A. Lopez Virto, J. Marco, C. Martinez Rivero,
P. Martinez Ruiz del Arbol,F. Matorras, J. Piedra Gomez, C. Prieels, T. Rodrigo, A. Ruiz-Jimeno,
L. Scodellaro,N. Trevisani, I. Vila, R. Vilar Cortabitarte
InstitutodeFísicadeCantabria(IFCA),CSIC-UniversidaddeCantabria,Santander,Spain
N. Wickramage
UniversityofRuhuna,DepartmentofPhysics,Matara,SriLanka
D. Abbaneo, B. Akgun,E. Auffray, G. Auzinger, P. Baillon, A.H. Ball, D. Barney, J. Bendavid,M. Bianco,
A. Bocci, C. Botta,E. Brondolin, T. Camporesi, M. Cepeda, G. Cerminara, E. Chapon, Y. Chen, G. Cucciati,
D. d’Enterria, A. Dabrowski,N. Daci, V. Daponte, A. David,A. De Roeck, N. Deelen, M. Dobson,
M. Dünser,N. Dupont,A. Elliott-Peisert, P. Everaerts,F. Fallavollita43,D. Fasanella, G. Franzoni, J. Fulcher,
W. Funk, D. Gigi,A. Gilbert, K. Gill,F. Glege, M. Guilbaud, D. Gulhan, J. Hegeman, C. Heidegger,
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