ϒ production in p–Pb collisions at sNN=8.16 TeV

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Physics

Letters

B

www.elsevier.com/locate/physletb

ϒ

production

in

p–Pb collisions

at

√

s

_NN

=

8

.

16 TeV

.

ALICE

Collaboration



a

r

t

i

c

l

e

i

n

f

o

a

b

s

t

r

a

c

t

Articlehistory:

Received16November2019 Receivedinrevisedform29April2020 Accepted11May2020

Availableonline20May2020 Editor:D.F.Geesaman

ϒproductioninp–Pb interactionsisstudiedatthecentre-of-massenergypernucleon–nucleoncollision

√_s

NN=8.16 TeVwiththeALICEdetectorattheCERNLHC.Themeasurementisperformedreconstructing bottomonium resonances via their dimuon decay channel, in the centre-of-mass rapidity intervals 2.03<ycms<3.53 and −4.46<ycms<−2.96, down to zero transverse momentum. In this work, results on the ϒ(1S) production cross section as a function of rapidity and transverse momentum are presented.Thecorresponding nuclearmodificationfactorshows asuppression oftheϒ(1S)yields with respectto pp collisions, bothat forward and backwardrapidity. Thissuppression is stronger in the low transverse momentumregionand shows nosignificantdependence on the centralityofthe interactions. Furthermore,the ϒ(2S)nuclearmodificationfactorisevaluated,suggestingasuppression similartothatoftheϒ(1S).Afirstmeasurementoftheϒ(3S)hasalsobeenperformed.Finally,resultsare comparedwithpreviousALICEmeasurementsinp–Pb collisionsat√sNN=5.02 TeVandwiththeoretical calculations.

©2020EuropeanOrganizationforNuclearResearch.PublishedbyElsevierB.V.Thisisanopenaccess articleundertheCCBYlicense(http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

1. Introduction

Quarkoniumresonances,i.e.boundstatesofaheavy quark(Q) andanti-quark(Q),are well-known probes ofthe formation ofa quark–gluon plasma (QGP) which can occur in heavy-ions colli-sions.The high colour-charge densityreachedin such a medium can,infact,screenthebinding forcebetweentheQ andQ, lead-ingtoatemperature-dependentmeltingofthequarkoniumstates accordingtotheirbindingenergies [1].

A suppression of bottomonium resonances, the bound states formedbyb andb quarks,wasobservedinPb–Pb collisions,atthe LHCenergiesof

√

sNN

=

2

.

76 TeVand

√

sNN

=

5

.

02 TeVbythe

AL-ICE [2,3] andCMS [4–6] experiments.Allthe

ϒ

resonancesshowa reductionintheirproductionyieldscomparedtopp interactionsat thesamecentre-of-massenergy,scaledbythenumberofnucleon– nucleoncollisions.Furthermore,themagnitudeofthesuppression issignificantly differentforthe threeresonances anditincreases fromthe tightly bound

ϒ

(1S) to the loosely bound

ϒ

(3S) [4–6], asexpectedinasequentialsuppressionscenario,withthebinding energies ofthe

ϒ

states rangingbetween

∼

1 GeV forthe

ϒ

(1S) to

∼

0.2 GeV forthe

ϒ

(3S) [7].Modifications tothebottomonium productionmight also be induced by cold nuclear matter (CNM) mechanismsnotrelatedtotheformationoftheQGP.The modifica-tionofthequarkandgluonstructurefunctionsfornucleonsinside nuclei, modelled either via nuclear parton distribution functions

 _{E-mailaddress:alice-publications@cern.ch.}

(nPDFs) [8–11] orthrougha ColorGlassCondensateeffective the-ory [12],orthecoherentenergylossoftheQQ pairduringitspath throughthecoldnuclearmedium [13] areexamplesofCNMeffects whichcaninfluencequarkoniumproduction [14].Thesizeofthese effects isusually assessed inproton–nucleus collisions. These in-teractionsalsoallow forthe investigationofadditionalfinal state mechanisms,whichcanmodifytheproductioninparticularofthe morelooselyboundresonances [15–17].

ALICE haspublished results on themodification of the

ϒ

(1S) production yields as a function of the centre-of-mass rapidity ( ycms) using the 2013 p–Pb collisions data sample at

√

sNN

=

5

.

02 TeV [18]. The size of the observed suppression was found to be similarin theforward andbackward rapidity regions. The-oretical calculations based on the aforementioned CNM mecha-nismsfairly describetheforward- ycms measurements, whilethey

slightly overestimate the results obtained at backward rapidity. Furthermore, the measurement of the

ϒ

(2S) to

ϒ

(1S) ratio [18],

ϒ

(2S)/

ϒ

(1S),wasconsistent,albeitwithinlargeuncertainties,with the one obtained in pp collisions [19], suggesting CNM effects of the same size on the two resonances both at forward and backward rapidity. Consistent results were also obtained by the LHCb experiment [20] in a similar kinematic region. However, it should be notedthat ATLAS [21] and CMS [22] measurements of

ϒ

(2S)/

ϒ

(1S)atmidrapidity suggest astronger suppressionofthe

ϒ

(2S) withrespect to the

ϒ

(1S) state, as expected if final state effectsareatplay [15].

In2016,theLHCdeliveredp–Pb collisionsat

√

sNN

=

8

.

16 TeV.

The increase both in integrated luminosity, about a factor of 2

https://doi.org/10.1016/j.physletb.2020.135486

0370-2693/©2020EuropeanOrganizationforNuclearResearch.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBYlicense (http://creativecommons.org/licenses/by/4.0/).FundedbySCOAP3_.

larger than the one collected in 2013, and in the bottomonium productioncrosssection,duetothehighercentre-of-massenergy, allowsamoredetailedstudyoftheproductionofthe

ϒ

states.In thispaper,resultsonthe

ϒ

(1S)productionasafunction of ycms,

transverse momentum (pT) and centrality of the collisions will

bediscussedandcomparedwiththemeasurements performedin p–Pb collisions at

√

sNN

=

5

.

02 TeV and with theoretical

calcu-lations. A comparison of the

ϒ

(2S) and

ϒ

(3S) to

ϒ

(1S) produc-tionyields andnuclearmodification factors,integratedover ycms,

pT andcentrality, will alsobe presented.Finally, the resultswill

be compared with the corresponding measurements obtained by LHCbatthesameenergy [23].Itshouldbenotedthatallthe pre-sentedresultsrefer tothe

ϒ

inclusiveproduction,i.e.to

ϒ

either produced directlyor coming fromthe feed-downof higher-mass excitedstates.

2. Experimentalapparatusanddatasample

AdetaileddescriptionoftheALICEapparatusandperformance can be found in [24,25].The forwardmuon spectrometer [26] is themaindetectorusedinthisanalysis. Itconsistsoffivetracking stations madeoftwo planes ofCathode PadChambers each, fol-lowedby two triggerstations each one composed by two planes ofResistivePlateChambers.A10interaction-length(

λI

)absorber, placed in front of the tracking system, filters out most of the hadrons produced in the collisions. Low-momentum muons and hadrons escaping the first absorber are stopped by a second 7.2

λI

-thickiron wall,placedinfrontofthetriggerstations.The mo-mentumoftheparticlesisevaluatedbymeasuringtheircurvature in a dipole magnet with a 3 T

×

m integrated field. The muon spectrometermeasuresmuonsinthepseudorapidityinterval

−

4

<

η

<

−

2

.

5 inthelaboratoryreferenceframe.Italsoprovidessingle and unlike- or like-sign dimuon triggers based on the detection inthetriggersystemofoneortwomuons, respectively,havinga transversemomentum higherthana programmablethresholdset to pT,μ

=

0

.

5 GeV

/

c. This threshold is not sharp and the single muontriggerefficiencyreachesa plateauvalue of

∼

98%atabout pT,μ

∼

1

.

5 GeV

/

c.

Theprimaryinteractionvertexofthecollisionisreconstructed usingthetwoinnermostlayers oftheInner TrackingSystem (Sil-icon PixelDetector, SPD) [27], extending overthe pseudorapidity intervals

|

η

|

<

2 and

|

η

|

<

1

.

4,respectively. TheV0detector [28], composed oftwosets ofscintillatorscovering thepseudorapidity intervals2

.

8

<

η

<

5

.

1 and

−

3

.

7

<

η

<

−

1

.

7,provides the lumi-nosity measurement, which can also be obtained independently fromthe information of the T0 Cherenkovdetectors [29], cover-ingtheregions4

.

6

<

η

<

4

.

9 and

−

3

.

3

<

η

<

−

3.TheV0detector is also used to provide the minimum bias (MB) trigger, defined by thecoincidence of signalsinthe two sets ofscintillators. The triggerconditionusedinthisanalysisisbasedonthecoincidence oftheMBtriggerwiththeunlike-signdimuonone(

μμ

-MB).The removalof beam-inducedbackground isbased on thetiming in-formation provided by the V0 and by two sets of Zero Degree Calorimeters (ZDC) [30] placedat

±

112.5 m fromtheinteraction point,alongthebeamline.TheZDCsarealsousedforthecentrality estimationasit willbe discussed inSec. 3.Finally,forthe study of the

ϒ

productionas a function of the centrality of the colli-sions, pile-upevents inwhich two ormoreinteractions occur in thesamecollidingbunchareremovedusingtheinformationfrom SPDandV0.

Further selection criteria, commonly adopted in the ALICE quarkonium analyses (see e.g. [18,31]), are applied to the muon tracks forming thedimuon pair. Muon tracks must havea pseu-dorapidity value in the range

−

4

<

η

μ

<

−

2

.

5, corresponding to the muon spectrometer acceptance, and they should point to the interaction vertex to remove fake tracks and particles not

directlyproducedinbeam–beaminteractions.Theirtransverse co-ordinate atthe end of the front absorber (Rabs) must be within

17

.

6 cm

<

Rabs

<

89

.

5 cm,to removemuonsnot passingthe

ho-mogeneous regionoftheabsorber.Finally,tracksreconstructedin thetrackingchambersofthemuonspectrometershouldmatchthe tracksegmentsreconstructedinthetriggersystem.Thismatching request helpsto furtherrejecthadron contamination andensures thatthereconstructedmuonsfulfillthetriggercondition.

Thedatawerecollectedwithtwobeamconfigurationsobtained byinvertingthedirectionsoftheprotonandPbbeamscirculating insidetheLHC.Inthiswayitwaspossibletocoverbothaforward (2

.

03

<

ycms

<

3

.

53) and a backward (

−

4

.

46

<

ycms

<

−

2

.

96)

dimuonrapidityinterval,wherethepositive(negative) ycmsrefers

to the proton (Pb) beam going towards the muon spectrometer. The collected integrated luminosities for the corresponding data samples, referred to asp–Pb (forward rapidity) andPb–p (back-ward rapidity) in the following, are

L

_intpPb

=

8

.

4

±

0

.

2 nb−1 and

L

Pbp

int

=

12

.

8

±

0

.

3 nb− 1 _[32].

3. Dataanalysis

The results presented in this paper are based on an analysis proceduresimilartotheonedescribedin[18] forthestudyofthe

ϒ

productioninp–Pb collisionsat

√

sNN

=

5

.

02 TeV.

The

ϒ

(1S),

ϒ

(2S) and

ϒ

(3S) production cross sections, cor-rected by the branching ratio for the decay in a muon pair (B

.

R

.

ϒ→μ+μ−),areobtained,foragiven(



ycms,



pT)interval,as

d2

σ

ϒ pPb dycmsdpT

=

Nϒ

L

intpPb

× (

A

×

ε

)

× 

ycms

× 

pT

×

B

.

R

.

ϒ→μ+μ−

,

(1) where Nϒ isthenumberofsignalcountsand( A

×

ε

)isthe

cor-responding acceptance andefficiency correction inthe kinematic binunderstudy,whilethebranchingratiosare(2

.

48

±

0

.

05)%for

ϒ

(1S),(1

.

93

±

0

.

17)%for

ϒ

(2S)and(2

.

18

±

0

.

21)%for

ϒ

(3S) [33]. The number of

ϒ(

nS

)

is obtained by fitting the unlike-sign dimuon invariant mass spectrum with a combination of signal shapes to describe the

ϒ

resonances and an empirical function to modelthe background.More in detail, the background is de-scribed by several combinations of exponential and polynomial functionsorbyaGaussianfunctionwithamass-dependentwidth. For the resonance shapes, extended Crystal Ball functions [34], withpower-lawtails ontherightandleftsidesofthemasspeak are used. Alternatively, pseudo-Gaussian functions with a mass-dependent width are also adopted [34]. The same signal shape is chosen for all the

ϒ

states. The mass of the

ϒ

(1S) and its width

σ

ϒ(1S) are free parameters of the fit, while the mass and

thewidthofthe

ϒ

(2S)and

ϒ

(3S)statesareboundtothoseofthe

ϒ

(1S) in the following way:mϒ(nS)

=

mϒ(1S)

+ (

mPDG_ϒ(nS)

−

mPDG_ϒ(1S)

)

and

σ

ϒ(nS)

=

σ

ϒ(1S)

×

σ

ϒ(nS)MC

/

σ

ϒ(1S)MC .ThemassvaluemPDGϒ(nS)istaken

from [33] and

σ

MC

ϒ(nS) is the widthof theresonance asevaluated

froma fit,withtheaforementioned signalfunctions, tothe spec-trum obtained from the Monte Carlo (MC) simulation also used forthe ( A

×

ε

) correction. Dueto thesignal-over-background ra-tio oftheorder of

∼

0.7(

∼

1) inp–Pb (Pb–p), measured ina 3

σ

region around the

ϒ

(1S) mass, the non-Gaussian tails ofthe ex-tended CrystalBallfunctioncannotbekeptasfreeparametersof the fits. Hence, they are tuned on pp data at

√

s

=

13 TeV, the largest datasample collected byALICEso far,or,alternatively, on p–Pb or pp MCsimulations at

√

sNN

=

8

.

16 TeVand

√

s

=

8 TeV,

respectively. The sametails areadopted forthe

ϒ

(2S)and

ϒ

(3S) mass shapes.Examplesof thefitto theinvariant massspectrum, forboththep–Pb andPb–p samples,areshowninFig.1.

Fig. 1. Invariant massspectraofunlike-signdimuons,integratedoverpT,forPb–p (leftpanel)andp–Pb (rightpanel)collisions.Theshapesoftheϒ(1S),ϒ(2S)andϒ(3S)

resonancesareshown(dash-dottedlines),togetherwiththebackgroundfunction(dashedline)andthetotalfit(solidline).

Thenumber of

ϒ

candidates, Nϒ, isevaluated asthe average

ofthevaluesobtainedbyvaryingthesignalandbackground func-tionsaswellasthefittingintervals(6 GeV/c2

<

mμμ

<

13 GeV

/

c2 or7 GeV/c2

<

mμμ

<

12 GeV

/

c2).Thestatisticaluncertaintiesare calculatedas the average ofthe statistical uncertainties over the various fits andthe standard deviationof the distributionof the Nϒ valuesprovides thesystematicuncertainties onthesignal

ex-traction.Forthe

ϒ

(2S)and

ϒ

(3S)cases,anadditionalcontribution tothe systematicuncertaintyis included,to account forpossible variationsoftheirwidthwithrespecttothatofthe

ϒ

(1S).In par-ticular,theirwidthsareallowedtovarybetweenaminimumvalue

σ

ϒ(1S)andamaximumvalue

σ

ϒ(1S)

×

σ

ϒ(nS)MC

/

σ

ϒ(1S)MC ,wherethe

ra-tio

σ

MC ϒ(nS)

/

σ

MC

ϒ(1S) is obtained from MC simulations alternative to

theonesusedforthe( A

×

ε

)correction,i.e.basedondifferent

ϒ

kinematicinput shapes,asitwillbe discussedlateron.Afurther 5%systematicuncertaintyisalsoincludedtoaccountforpossible residualdiscrepanciesbetweenthedetectorresolutioninMC and inthedata.

The total number of

ϒ

(1S), integrated over the full kine-matic range, amounts to Nϒ(1S)

=

909

±

62

(

stat

.)

±

58

(

syst

.)

and Nϒ(1S)

=

918

±

55

(

stat

.)

±

51

(

syst

.)

for the forward and

backward-rapidity regions, respectively. Corresponding values for

ϒ

(2S)are Nϒ(2S)

=

192

±

39

(

stat

.)

±

17

(

syst

.)

andNϒ(2S)

=

194

±

34

(

stat

.)

±

16

(

syst

.)

,while forthe

ϒ

(3S)the valuesare Nϒ(3S)

=

48

±

36

(

stat

.)

±

8

(

syst

.)

and Nϒ(3S)

=

95

±

30

(

stat

.)

±

12

(

syst

.)

.

Thesystematicuncertainty, amountingto

∼

6% forthe

ϒ

(1S)and

∼

8% for the

ϒ

(2S), is dominated by the choice of the tail pa-rameters inthe fit functionsand, in the

ϒ

(2S) case, also by the allowed range of variation forthe

σ

ϒ(2S).In the

ϒ

(3S) case, the

systematic uncertainties are slightly larger, amounting to

∼

17% at forward rapidity and

∼

12% at backward rapidity. For pT- or

ycms-differential

ϒ

(1S)studies,thesystematicuncertaintieshavea

similarsize,reaching

∼

15%onlyinthehighestpT bin(8 GeV

/

c

<

pT

<

15 GeV

/

c).

Theacceptanceandefficiencycorrection iscalculatedina MC simulation, based on the GEANT3 transport code [35]. The MC simulation is performed on a run-by-run basis to closely follow theevolutionoftheperformanceofthedetectorsduringthedata taking.The

ϒ

(1S)aregeneratedusingrapidityandtransverse mo-mentum distributions tuned on p–Pb or Pb–p data at

√

sNN

=

8

.

16 TeV,throughaniterativeprocedure [31].The pTandycms

in-tegrated( A

×

ε

)amountsto0

.

300

±

0

.

006 forthe

ϒ

(1S)atforward rapidityand0

.

273

±

0

.

007 atbackwardrapidity,wherethequoted uncertaintiesaresystematic,thestatisticaluncertaintiesbeing

neg-ligible.Thelower( A

×

ε

)valuesmeasuredinthePb–p period,with respecttothep–Pb one,areduetodetectorinstabilitieswhich af-fected temporarily the behaviour of two tracking chambers. The limitedsize ofthedata sample donot allowfora similartuning ofthe pT and ycmsdistributions ondataforthe

ϒ

(2S)and

ϒ

(3S)

resonances,hencethesameshapesasforthe

ϒ

(1S)areused.The resulting( A

×

ε

) valuesshowanegligible differencewithrespect tothe

ϒ

(1S)ones.Thesystematicuncertaintieson( A

×

ε

)include contributions relatedto the choiceof the MC pT and ycms input

distributions forthe

ϒ

statesandto the evaluationofthe track-ingandtriggerefficiencies.Thesystematicuncertaintiesassociated to theMC

ϒ

inputshapesare evaluated asthemaximum differ-encebetweenthe( A

×

ε

) evaluatedwiththeaforementionedMC tunedondataandthevaluesextractedfromalternative MC sam-ples based on pT and ycms

ϒ

distributions either measured by

the LHCb experimentin pp collisions at

√

s

=

8 TeV [36] or ob-tained fromexisting CDF andLHC pp measurements [37–39] via aproceduresimilartotheonedescribedin [40].Nuclear shadow-ing is alsoincluded toaccount for its influenceon the bottomo-nium kinematic distributions. These systematic uncertainties for thethreeresonancesvarybetween1%and1.8%.Theyhavea neg-ligible pT-dependence,whilethey reachup to4% attheedges of

therapidityintervals.Thesystematicuncertaintyonthetrigger ef-ficiencyconsistsoftwocontributions,onerelatedtotheevaluation oftheintrinsicefficiencyofeach muon-triggerchamber (1%)and onetosmalldifferencesbetweenthetriggerresponsefunction es-timated via data andMC (0.6% inp–Pb and 0.2% in Pb–p, when integrating over ycms and pT). This last source of uncertainty is

below1%alsoforthe pT or ycms-differentialstudies.The

system-atic uncertainty associatedto the tracking efficiencyis evaluated comparingthedimuontrackingefficienciescomputedbothindata andMC.Theseefficiencies arecomputedcombiningtheefficiency of each single muon-tracking chamber, obtained relying on the redundancyofthetrackingsystem.Theresultingsystematic uncer-taintiesamountto1%forp–Pb and2%forPb–p,forboththe ycms

andpTdifferentialstudiesandforresultsintegratedoverthe

kine-maticdomain.Finally,an additional1% systematicuncertaintyon thechoice ofthe

χ

2 _{cut onthematchingbetweenthetracks}

re-constructedinthetrackingandinthetriggersystemsisincluded. Thesystematicuncertaintiesassociatedtothetrigger,trackingand matching efficiencies are considered to be identical forboth the

ϒ

(1S)and

ϒ

(2S)resonances.

The integrated luminosities are obtained as

Lint

=

NMB/

σ

MB.

Thenumberofequivalentminimumbiasevents,NMB,isevaluated

triggerbyafactorFnorm,correspondingtotheinverseofthe

prob-abilityofhavingatriggereddimuoninaMBevent [31].This quan-tityiscomputed,run byrun,astheratiobetweenthenumberof collected MB triggers andthe number oftimesthe dimuon trig-gerconditionisverified intheMBtrigger sample.Onceaveraged over all the runs, considering as weight the number of

μμ

-MB triggers in each run, Fnorm amounts to 679

±

7 at forward

ra-pidity and 372

±

4 at backward rapidity.The quoted uncertainty (1%)issystematicandaccountsfordifferencescomingfroman al-ternative evaluation method, based on the information provided by the level-0 trigger scalers, as detailed in [41]. The V0-based MB cross section (

σ

MB) is measured from a van der Meer scan,

andit amounts to 2

.

09

±

0

.

04 b forthe p–Pb configuration and 2

.

10

±

0

.

04 bforthePb–p one [32].Intheluminosity systematic uncertaintyquotedinTable1,theuncertaintieson Fnorm and

σ

MB

arecombined,togetherwitha1.1%(0.6%)contributionduetothe differencebetweentheluminositiesobtainedwiththeV0andT0 detectorsinthep–Pb (Pb–p)configurations [32].

The nuclear effects on the

ϒ

production are studied compar-ing the corresponding p–Pb production cross section to the one measured inpp collisions, d2

σ

ϒ

pp

/

dycmsdpT, obtainedatthe same

centre-of-mass energyandscaledby the atomicmassnumberof thePbnucleus( APb

=

208),throughtheso-callednuclear

modifi-cationfactorRpPb,definedas

RpPb

=

d2

σ

ϒ

pPb

/

dycmsdpT

APb

×

d2

σ

ppϒ

/

dycmsdpT

.

(2)

The proton–proton reference is based on the LHCb measure-ments of the bottomonium production cross section in pp col-lisions at

√

s

=

8 TeV [36], in

−

4

.

5

<

ycms

<

−

2

.

5 and 2

<

ycms

<

4, corrected by a factor to account for the slightly

dif-ferent centre-of-mass energies of the interactions. This correc-tion factor is evaluated interpolating the LHCb measurements at

√

s

=

7, 8 and 13 TeV [36,42], as detailed in [43]. It amounts to 1

.

02 for both the

ϒ

(1S) and

ϒ

(2S), showing a negligible ycms dependence and varying by 1% from low to high pT.

A systematic uncertainty on the determination of this factor (1%) is assigned, based on the choice of the different functions used for the energy-interpolation. The

ϒ

production cross sec-tions in pp collisions at

√

s = 8 TeV are also measured by ALICE [44]. The results show good agreement with the corre-sponding LHCb values, but unlike the LHCb measurements, they cover a slightly narrower rapidity region, 2

.

5

<

ycms

<

4, which

does not match the rapidity coverage of the p–Pb measure-ments.The

σ

ppϒ(1S)crosssections,integratedover pT andycms,are

98

.

5

±

0

.

1

(

stat

.)

±

3

.

4

(

syst

.)

nb in therange 2

.

03

<

ycms

<

3

.

53

and62

.

0

±

0

.

1

(

stat

.)

±

2

.

1

(

syst

.)

nb intherange

−

4

.

46

<

ycms

<

−

2

.

96.The corresponding cross sections forthe

ϒ

(2S) are about afactor3smaller,being

σ

ppϒ(2S)

=

31

.

9

±

0

.

1

(

stat

.)

±

2

.

9

(

syst

.)

nb

atforwardrapidityand19

.

7

±

0

.

05

(

stat

.)

±

1

.

8

(

syst

.)

nb at back-ward rapidity. The

ϒ

(3S) production cross sections are

σ

ppϒ(3S)

=

12

.

9

±

0

.

1

(

stat

.)

±

1

.

3

(

syst

.)

nb at forward rapidity and 8

.

3

±

0

.

1

(

stat

.)

±

0

.

8

(

syst

.)

nb atbackwardrapidity.

Thelarge datasample collected in p–Pb collisionsin 2016 al-lowsthe

ϒ

(1S)productionalsotobe studiedasafunctionofthe collisioncentrality.Thecentralitydeterminationisbasedona hy-brid model, as discussed in detail in [45]. In this approach, the centralityisdetermined by measuringthe energyreleasedinthe ZDC positioned in the Pb-going direction. For each ZDC-selected centralityclass,theaveragenumberofcollisions



Ncoll



isobtained

as



Ncoll



= 

Npart



-1, assuming the charged particle multiplicity

measuredatmidrapidity isproportional tothenumberof partic-ipantnucleons, Npart. The centrality classes usedin this analysis

correspondto2–20%,20–40%,40–60%and60–90%oftheMBcross

section. The 0–2% most central collisions are excluded from this analysisbecausethefractionofeventscomingfrompile-upinthe ZDC islarge in thiscentrality interval anda residual contamina-tionmightstillbepresentinspiteoftheappliedpile-uprejection cuts [46].

Forcentralitystudies,themodification inducedby thenuclear matter onthe

ϒ

(1S)productionisquantifiedthrough thenuclear modificationfactordenotedbyQpPb,tobedistinguishedfromRpPb

since potentialbiasesfromthecentralityestimation,unrelated to nucleareffects,mightbepresent [45].The QpPbisdefinedas

QpPb

=

Nϒ

B

.

R

.

ϒ→μ+μ−

×

NMB

× (

A

×

ε

)

× 

TpPb

 ×

σ

ppϒ

.

(3)

The quantities entering Eq. (3) are evaluated accordingto the previouslydiscussedprocedure,withfewminordifferences.When extractingthe

ϒ

(1S)signal,forexample,nosignificantvariationof the

ϒ

(1S) widthas a function of the collision centrality is fore-seen.Hence forcentralitystudies,the

ϒ

(1S)widthisfixed tothe valueobtainedinthefittothecentrality-integratedinvariantmass spectrum.Theuncertaintyassociatedtothechoiceofthewidthis accounted forin the evaluationof the systematicuncertainty on the signal extraction. No significant centralitydependence is ex-pected for the ( A

×

ε

) either, so the centrality-integrated values arealsousedforallthecentralityclasses.Toevaluatethenumber ofMBeventsineachcentralityclassi, Finormisobtainedfromthe

centrality-integrated quantity scaled by the ratio of the number of minimum bias and dimuon-triggered events in each central-ityintervalwithrespecttothecorrespondingcentralityintegrated quantities,

(

Ni_MB

/

NMB)/(N_μμi _−MB

/

Nμμ−MB).Alternatively, Fi

norm is

computed directly foreach centralityclass and a further 1% dif-ference betweenthetwoapproachesisincludedinthesystematic uncertainty. The statisticaluncertainty on Fi

norm is negligible.

Fi-nally,



TpPb



isthecentrality-dependentaveragenuclearthickness

function,computedwiththeGlauberframework [45,47].

Thesystematicuncertaintiesenteringthecrosssectionand nu-clearmodificationfactorevaluationaresummarisedinTable1.

When RpPb is computedasafunction of pT or ycms,the

sys-tematicuncertaintiesonthesignalextraction,tracking,triggerand matching efficiencies, MC input shapesand a fractionof the un-certainty on the pp reference are considered as bin-by-bin un-correlated.Onthecontrary,thecorrelatedcontributionstothepp referenceandtheluminosityuncertainties, whicharecommonto thep–Pb orPb–p systems,areconsideredascorrelatedover pTor

ycms.IntheQpPbevaluation,theuncertaintiesonsignalextraction,

on the MC input shapes and on



TpPb



depend on the

central-ity ofthe collision,while theother uncertainties arecommon to all classesand,therefore,consideredascorrelatedover centrality. Evenifmostcentraleventsarenotincludedinthisanalysis,a fur-ther 2%centrality-uncorrelated systematicuncertaintyisassigned to the QpPb values,to account for residual pile-up which might

still introduce abias inthe measurement.Thissystematic uncer-tainty is evaluated by comparing the expected pile-up fraction, computedfromthepile-upprobability associatedtotheobserved interactionrate,andtheamountofpile-upeventsremovedbythe eventselection procedure. Forthe

ϒ

(2S)and

ϒ

(3S)studies, sim-ilar valuesofthe systematicuncertainties areobtained, the main differencebeingthelargersignalextractionuncertainties.

4. Results

The inclusive

ϒ

(1S)production crosssectionsareevaluated in therapidityregions2

.

03

<

ycms

<

3

.

53 and

−

4

.

46

<

ycms

<

−

2

.

96

Table 1

Systematicuncertainties,inpercentage,onthethreeϒcrosssectionsandnuclearmodificationfactorsforbothp–PbandPb–pcollisions.Rangesinparenthesesreferto themaximumvariationasafunctionofcentrality, ycms or pT.Whennorangesarespecified,the quotedvaluesarevalidforboththe integratedandthedifferential

measurements.ErrortypeImeansthattheuncertaintiesarecorrelatedover pTor ycms,whileerrortypeIIreferstouncertaintiescorrelatedversuscentrality.Ifnoerror

typeisspecified,theuncertaintiesareconsideredasuncorrelated.Theuncertaintiesontheppreferenceandluminosityresultfromthecombinationofycms-uncorrelated

andcorrelatedcontributions.Forthesystematicuncertaintyontheluminositydetermination,thetwoterms,definedaccordingto [32],areseparatelyquotedinthetable, butcombinedwhenresultsareshowninthefigures.UncertaintiesontheB.R.aretakenfrom [33].

Sources ϒ(1S) ϒ(2S) ϒ(3S)

p–Pb Pb–p p–Pb Pb–p p–Pb Pb–p

Signal extraction 6.4 (5.1–15.9) 5.7 (5.5–8.5) 8.8 8.4 17.4 12.6

Trigger efficiency (II) 1.2 (1.1–1.3) 1.0 (1.0–1.1) 1.2 1.0 1.2 1.0

Tracking efficiency (II) 1.0 2.0 1.0 2.0 1.0 2.0

Matching efficiency (II) 1.0 1.0 1.0 1.0 1.0 1.0

MC inputs 1.0 (0.5–4.0) 1.0 (0.4–4.0) 1.3 1.6 1.4 1.8 pp reference (II) 0.2 (0.1–0.4) 0.2 (0.1–0.4) 0.2 0.3 0.2 0.2 pp reference (I,II) 2.8 2.8 2.8 LpPb int (II) 2.1 2.2 2.1 2.2 2.1 2.2 LpPb int (I,II) 0.5 0.7 0.5 0.7 0.5 0.7 Pile-up 2.0 2.0 – – TpPb 2.1–5.8 – – B.R. (I) 2.0 8.8 9.6

σ

_pPbϒ(1S)

(

2

.

03

<

ycms

<

3

.

53

)

=

14

.

5

±

1

.

0

(

stat

.)

±

1

.

0

(

uncor

.

syst

.)

±

0

.

3

(

cor

.

syst

.)

μ

b

,

σ

_pPbϒ(1S)

(

−

4

.

46

<

ycms

<

−

2

.

96

)

=

10

.

5

±

0

.

6

(

stat

.)

±

0

.

7

(

uncor

.

syst

.)

±

0

.

2

(

cor

.

syst

.)

μ

b

.

The corresponding values forthe

ϒ

(2S) production cross sec-tionsare:

σ

_pPbϒ(2S)

(

2

.

03

<

ycms

<

3

.

53

)

=

3

.

9

±

0

.

8

(

stat

.)

±

0

.

4

(

uncor

.

syst

.)

±

0

.

3

(

cor

.

syst

.)

μ

b

,

σ

_pPbϒ(2S)

(

−

4

.

46

<

ycms

<

−

2

.

96

)

=

2

.

8

±

0

.

5

(

stat

.)

±

0

.

3

(

uncor

.

syst

.)

±

0

.

3

(

cor

.

syst

.)

μ

b

,

andforthe

ϒ

(3S)are:

σ

_pPbϒ(3S)

(

2

.

03

<

ycms

<

3

.

53

)

=

0

.

87

±

0

.

66

(

stat

.)

±

0

.

15

(

uncor

.

syst

.)

±

0

.

08

(

cor

.

syst

.)

μ

b

,

σ

_pPbϒ(3S)

(

−

4

.

46

<

ycms

<

−

2

.

96

)

=

1

.

24

±

0

.

39

(

stat

.)

±

0

.

15

(

uncor

.

syst

.)

±

0

.

12

(

cor

.

syst

.)

μ

b

.

The systematic uncertainties have two terms, one correlated andoneuncorrelatedasafunctionofrapidity.

Thedatacollectedinp–Pb collisionsat

√

sNN

=

8

.

16 TeVallow

forthemeasurementofthe

ϒ

(1S)productioncrosssections differ-entiallyin ycmsbinsorin pT intervals,upto pT

<

15 GeV/c.The

resultingcrosssectionsareshowninFig.2asafunctionof rapid-ity,integratedovertransversemomentum,andinFig.3,asa func-tionofpT,intheforward- andbackward-rapidityregions.Inthese

figures,asinallthefollowingones,thestatisticaluncertaintiesare shownasverticalerrorbars,whilethesystematicuncertaintiesare representedasboxesaround thepoints.Thehorizontalerrorbars correspondtothe ycms orpT binwidths.Thecrosssections

eval-uatedatforward andbackwardrapidities are comparedwiththe pp ones, obtainedthrough theaforementioned interpolation pro-cedure, scaled by the Pbatomic mass number. The comparison showsthatintheforward-rapidityregionthe

ϒ

(1S)crosssections aresmaller thanthe pp ones, inparticular atlow pT, suggesting

thepresenceofCNMeffectsatplayinp–Pb collisions.Onthe con-trary, inthe backward-rapidity rangethe pp and the p–Pb cross

Fig. 2.ϒ(1S),ϒ(2S)andϒ(3S)differentialcrosssectionsasafunctionofycms in

p–Pb collisionsat√sNN=8.16 TeV.Thecorrespondingpp referencecrosssections,

obtainedthroughtheproceduredescribedinSec.3andscaledbyAPb,areshown

asbands.

Fig. 3.ϒ(1S)differentialcrosssectionasafunctionofpT,atforward(closed

sym-bols)andbackward(opensymbols)rapidity,at√sNN=8.16 TeV.Thepp reference

crosssection,obtainedthroughtheproceduredescribedinSec.3andscaledbyAPb,

Fig. 4. Ratio ofϒ(nS)overϒ(1S)yieldsinp–Pb collisionsat√sNN=8.16 TeVand

inpp collisionsat√s =8TeV [36].

sectionsare closerandnucleareffectsseemtohavea less promi-nentrole.

The limitedavailable datasample allows fortheevaluationof the

ϒ

(2S)and

ϒ

(3S)crosssectionsintheforwardand backward-rapidityregions onlyintegratingoverthecorresponding ycms and

pT ranges,asshownin Fig.2. Asuppression withrespect tothe

corresponding pp reference cross sections, scaled by APb, is

ob-served.

Giventhe relatively small mass difference betweenthe

ϒ

(1S) and

ϒ

(2S) (or

ϒ

(3S)) resonances, most of the systematic uncer-tainties, exceptthose on the signal extraction andon the choice of the pT- and ycms-input shapesused in the MC, cancel inthe

ratiooftheresonanceyields,multipliedbytheirbranchingratios, definedas

[ϒ(

nS

)/ϒ(

1S

)

]

pPb

=

Nϒ(nS)

/(A

×

ε

)

ϒ(nS)

Nϒ(1S)

/(A

×

ε

)

ϒ(1S)

.

Thevalues ofthe

ϒ

(2S)over

ϒ

(1S)ratio,obtained atforward andbackwardrapidity,aresimilar:

[ϒ(

2S

)/ϒ(

1S

)

]

pPb

(

2

.

03

<

ycms

<

3

.

53

)

=

0

.

21

±

0

.

05

(

stat

.)

±

0

.

02

(

syst

.),

[ϒ(

2S

)/ϒ(

1S

)

]

pPb

(

−

4

.

46

<

ycms

<

−

2

.

96

)

=

0

.

21

±

0

.

04

(

stat

.)

±

0

.

01

(

syst

.).

AsshowninFig.4,theratio

[ϒ(

2S

)/ϒ(

1S

)

]

pPbat

√

sNN

=

8

.

16 TeV

is compatible, within uncertainties, with the results obtained by the LHCbCollaboration in pp collisionsat

√

s =8 TeV [36], ina slightlywiderkinematicrange(2

<

ycms

<

4

.

5,pT

<

15 GeV/c).

Similarconclusionscanbeobtainedfromthecomparisonofthe

ϒ

(3S) over

ϒ

(1S) ratio, also shown in Fig. 4. The corresponding valuesatforwardandbackwardrapidityare:

[ϒ(

3S

)/ϒ(

1S

)

]

pPb

(

2

.

03

<

ycms

<

3

.

53

)

=

0

.

053

±

0

.

039

(

stat

.)

±

0

.

007

(

syst

.),

[ϒ(

3S

)/ϒ(

1S

)

]

pPb

(

−

4

.

46

<

ycms

<

−

2

.

96

)

=

0

.

102

±

0

.

032

(

stat

.)

±

0

.

009

(

syst

.).

The size of nuclear effects in p–Pb collisions can be bet-terquantified through thenuclear modification factor definedin Eq. (2). The numericalvalues forthe

ϒ

(1S) RpPb inthe

forward-andinthebackward-rapidityregions,integratingover pT,are:

Fig. 5. ϒ(1S) RpPb values at √sNN=8.16 TeV compared to those obtainedat

√

sNN=5.02 TeVinthesame ycms interval [18].Allsystematicuncertaintiesare

consideredasuncorrelatedbetweentheresults at√sNN=8.16 TeVand√sNN=

5.02 TeV.TheRpPbvaluesatthetwoenergiesareslightlydisplacedhorizontallyto

improvevisibility.

Rϒ(1S)_pPb

(

2

.

03

<

ycms

<

3

.

53

)

=

0

.

71

±

0

.

05

(

stat

.)

±

0

.

05

(

uncor

.

syst

.)

±

0

.

02

(

cor

.

syst

.),

Rϒ(1S)_pPb

(

−

4

.

46

<

ycms

<

−

2

.

96

)

=

0

.

81

±

0

.

05

(

stat

.)

±

0

.

05

(

uncor

.

syst

.)

±

0

.

02

(

cor

.

syst

.),

where(uncor. syst.)and(cor.syst.)refertouncorrelatedand cor-relatedsystematicuncertaintiesasafunctionofrapidity.

Themeasured RpPbvalues,showninFig.5,indicatea

suppres-sionofthe

ϒ

(1S)productioninp–Pb collisions,withrespecttothe one inpp collisions,bothatforwardandbackwardrapidity,with aslightlystrongersuppressionatforward ycms.The RpPbisfound

tobe4.0

σ

and2.4

σ

belowunityinp–Pb andPb–p collisions, re-spectively.TheresultsarecompatiblewiththecorrespondingRpPb

valuesmeasured inp–Pb collisionsat

√

sNN

=

5

.

02 TeV [18],also

showninFig.5.Fromthecomparisonbetweentheresultsobtained atthetwoenergies,animprovementintheprecisionofthe

ϒ

(1S) RpPb measurementsat

√

sNN

=

8

.

16 TeVcanbenoticed,giventhe

reduced size of the statistical and systematic uncertainties. The improvementofthelattercontributionismainlyrelatedtothe re-duction inthe uncertaintiesassociatedtothe trackingefficiencies andtorefinementsinthedeterminationofthepp reference [18].

The rapidity dependence of the

ϒ

(1S) RpPb, explored in

nar-rower ycms intervals, is showninFig. 6,confirming the

suppres-sionalreadyobservedinthe ycms-integratedcase.The resultsare

also compared with the

ϒ

(1S) LHCb measurements [23] at the samecentre-of-massenergyandinslightlywiderkinematicranges (

−

4

.

5

<

ycms

<

−

2

.

5 and2

<

ycms

<

4, pT<25 GeV/c).Fair

agree-mentbetweenthetwosetsofresultscanbeseen.

The pT dependence of the

ϒ

(1S) RpPb is shown in Fig. 7.

A slightdecreaseofthe

ϒ

(1S)nuclearmodificationfactor,with de-creasingpT,isobserved.Thebehaviourissimilarbothatbackward

andforwardrapidities.

The ycmsand pT dependenceofthe

ϒ

(1S) RpPb arecompared,

in Fig. 6 andFig. 7, to severalmodels (referred in the following asnuclearshadowingmodels), basedonEPS09 [8],nCTEQ15 [10] or EPPS16 [9] sets of nuclear parton distribution functions. The EPS09 next-to-leading order (NLO) parametrisation is combined withaNLOColourEvaporationModel(CEM) [48],whichdescribes the

ϒ

production. The corresponding uncertainty bands, shown in Fig. 6 and Fig. 7, are dominated by the uncertainties of the EPS09 parametrisation.The nCTEQ15 andthe EPPS16 NLO nPDFs

Fig. 6.ϒ(1S)RpPb valuesat √sNN=8.16 TeVcomparedwith thecorresponding

LHCbresults [23],asafunctionof ycms. The RpPb valuesarealsocomparedto

modelcalculationsbasedonseveralimplementationsofnuclearshadowing(EPS09 NLO [8,14,48],EPPS16andnCTEQ15 [9–11,49–51])andonpartoncoherentenergy losspredictions,with or without the inclusionof the EPS09shadowing contri-bution [13,14].Atheoreticalmodelincludingashadowingcontributionbasedon nCTEQ15nPDFsontopofasuppressioninducedbycomoverinteractions [15,52] isalsoshown.FortheLHCbresults,theverticalerrorbarsrepresentthequadratic sumofthestatisticalandsystematicuncertainties.

sets are implemented following the Bayesian reweighting proce-duredescribed in[11,49–51]. Theuncertaintybands,inthiscase, representthe convolution ofthe uncertainties on the nPDFs sets andthose onthe factorisationscales.It canbe observedthat the shadowingcalculationsdescribefairlywellthepTandycms

depen-denceof the

ϒ

(1S) nuclear modification factor in 2

.

03

<

ycms

<

3

.

05, while they overestimate the results obtained in

−

4

.

46

<

ycms

<

−

2

.

96. Furthermore,while the pT dependenceof the

AL-ICE measurements indicate slightly stronger cold nuclear matter effectsatlow pT,theshadowingcalculationssuggestaflatter

be-haviour.Finally,the ycms dependenceoftheRpPbisalsocompared

witha model which includes the effects of parton coherent en-ergy loss withor without the contribution ofthe EPS09 nuclear shadowing [13,14].The modelpredicts amild dependenceofthe energylossmechanismonrapidity.Whenthe nuclearshadowing contributionisincluded,themodeldescribestheforward-rapidity results,whileitslightlyoverestimatesthebackward-rapidity RpPb.

The

ϒ

(1S) RpPb isalsocomparedwithatheoretical modelwhich

includesa shadowing contribution,based on the nCTEQ15 setof nPDFs, on top of a suppression of the

ϒ

(1S) production due to interactionswithcomovingparticles [15,52].Theuncertainties as-sociatedtothistheoreticalcalculationincludeasmallcontribution fromtheuncertaintyonthecomoverscrosssectionandare domi-natedbytheuncertaintiesontheshadowing.Alsointhiscasethe calculationslightlyoverestimatestheALICEmeasurementsat back-ward ycms,whileatforward ycms thedataagreewiththemodel.

Itcan benotedthat the interpretationofthe

ϒ

(1S)behaviour in p–Pb collisionswouldalsobenefitfromapreciseknowledge,sofar stillaffectedbylargeuncertainties,ofthefeed-downcontribution oftheexcitedstatesintothe

ϒ

(1S).

The

ϒ

(1S)nuclearmodificationfactorisevaluatedasafunction ofthe collision centrality. The QpPb results, shown inFig. 8, are

presentedasafunctionoftheaveragenumberofcollisions,



Ncoll



anditcanbeobservedthatbothatforwardandbackwardrapidity the

ϒ

(1S)centralitydependenceisratherflat.

Finally,thenuclearmodificationfactorisalsoevaluatedforthe

ϒ

(2S) and

ϒ

(3S) resonances, in the forward and backward- ycms

intervals,asshowninFig.9.Thecorresponding

ϒ

(2S) RpPbvalues

are:

Rϒ(2S)_pPb

(

2

.

03

<

ycms

<

3

.

53

)

=

0

.

59

±

0

.

12

(

stat

.)

±

0

.

05

(

uncor

.

syst

.)

±

0

.

02

(

cor

.

syst

.)

Rϒ(2S)_pPb

(

−

4

.

46

<

ycms

<

−

2

.

96

)

=

0

.

69

±

0

.

12

(

stat

.)

±

0

.

05

(

uncor

.

syst

.)

±

0

.

02

(

cor

.

syst

.)

the

ϒ

(2S)suppressionbeingcompatiblewithunitywithin3.1

σ

at forward ycms and2.3

σ

atbackward ycms.The

ϒ

(3S) RpPb values

are:

Rϒ(3S)_pPb

(

2

.

03

<

ycms

<

3

.

53

)

=

0

.

32

±

0

.

24

(

stat

.)

±

0

.

06

(

uncor

.

syst

.)

±

0

.

01

(

cor

.

syst

.)

Rϒ(3S)_pPb

(

−

4

.

46

<

ycms

<

−

2

.

96

)

=

0

.

71

±

0

.

23

(

stat

.)

±

0

.

09

(

uncor

.

syst

.)

±

0

.

02

(

cor

.

syst

.)

The

ϒ

(3S)suppressioniscompatiblewithunitywithin2.7

σ

at for-ward ycms and1.2

σ

atbackward ycms.Thedifferenceinthe RpPb

of the

ϒ

(2S) and

ϒ

(1S) amounts to 0.5

σ

in both rapidity inter-vals, suggesting, in p–Pb collisions, a similar modification ofthe production yields of the two

ϒ

states, with respect to pp colli-sions.Unfortunately, thelargeuncertainties onthe

ϒ

(3S)prevent robust conclusions on the behaviour of the most loosely bound bottomonium state. The model which includes both the nuclear shadowingcontribution(nCTEQ15)andinteractionswithcomoving particles [15,52] suggestsa smalldifference between thenuclear modificationfactorsofthethree

ϒ

states.Thisdifferenceisslightly moreimportantinthebackward-rapidityrange,whileitbecomes negligible at forward ycms. By evaluating the ratio of the

ϒ(

nS

)

to

ϒ

(1S)nuclearmodificationfactors,theshadowingcontribution andmostofthetheory uncertainties,aswell assome ofthe un-certainties on the data, cancel out. The shape of the theoretical calculation is, hence, mainly driven by the interactions withthe comovingparticles,whichaffectmostlytheexcited

ϒ

statesinthe backward rapidity region. Asshown inthe lower panel ofFig. 9, theALICEmeasurementsandthemodelareinfairagreement,even iftheuncertaintiesonthedatadonotyetallowafirmconclusion ontheroleofcomoverstobedrawn.

5. Conclusions

TheALICEmeasurementsoftherapidity,transversemomentum and centrality dependence of the inclusive

ϒ

(1S) nuclear modi-fication factor in p–Pb collisions at

√

sNN

=

8

.

16 TeV have been

presented. The results show a suppression of the

ϒ

(1S) yields, with respect to the ones measured inpp collisions atthe same centre-of-massenergy.The RpPb valuesaresimilaratforwardand

backward rapiditywitha slightlystronger suppressionatlow pT,

whileinbothrapidity intervalsthereisnoevidencefora central-itydependenceofthe

ϒ

(1S)QpPb.Theresultsobtainedat

√

sNN

=

8

.

16 TeV are similar within uncertainties to those measured by ALICEinp–Pb collisionsat thelower energyof

√

sNN

=

5

.

02 TeV

andshowa goodagreementwiththeLHCbmeasurements atthe samecentre-of-massenergy.Modelsbasedonnuclearshadowing, coherentparton energylossor interactions withcomoving parti-clesfairlydescribethedataatforwardrapidity,whiletheytendto overestimatethe RpPb atbackward ycms.The

ϒ

(2S) RpPb hasalso

beenmeasured, showingastrong suppression,similar totheone measuredforthe

ϒ

(1S) inthetwoinvestigatedrapidityintervals. Finally,afirstmeasurementofthe

ϒ

(3S)hasalsobeenperformed, evenifthelargeuncertaintiespreventadetailedcomparisonofits behaviour in p–Pb collisions with respect to the other bottomo-niumstates.Thesenewbottomoniummeasurements representan

Fig. 7.ϒ(1S)RpPbasafunctionofpTforPb–p (leftpanel)andp–Pb collisions(rightpanel).TheRpPbvaluesarecomparedwiththeoreticalcalculationsbasedonEPS09

NLO [14,48],nCTEQ15andEPPS16 [9–11,49–51] shadowingimplementations.Detailsonthetheoryuncertaintybandsarediscussedinthetext.

Fig. 8.ϒ(1S) QpPbas a function ofNcoll, for Pb–p (left panel) and p–Pb collisions (right panel).

importantbaseline forthe understanding ofthe role of CNM ef-fectsinp–Pb collisionsandopenup thewayforfutureprecision analyseswiththeupcomingLHCRun3andRun4datataking pe-riods.

Declarationofcompetinginterest

Theauthorsdeclarethattheyhavenoknowncompeting finan-cialinterestsorpersonalrelationshipsthatcouldhaveappearedto influencetheworkreportedinthispaper.

Acknowledgements

The ALICE Collaboration would like to thank all its engineers andtechnicians fortheir invaluablecontributionstothe construc-tion of the experiment and the CERN accelerator teams for the outstanding performance of the LHC complex. The ALICE Collab-oration gratefully acknowledges the resources and support pro-videdbyall GridcentresandtheWorldwide LHCComputingGrid (WLCG) collaboration. The ALICE Collaboration acknowledges the followingfundingagencies fortheirsupport inbuildingand run-ningtheALICEdetector:A.I.AlikhanyanNationalScience Labora-tory(YerevanPhysicsInstitute)Foundation(ANSL),State Commit-teeofScienceandWorldFederationofScientists(WFS),Armenia;

Austrian Academy of Sciences, Austrian Science Fund (FWF): [M 2467-N36] and Nationalstiftung für Forschung, Technologie und Entwicklung,Austria;MinistryofCommunicationsandHigh Tech-nologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq), Fi-nanciadora de Estudose Projetos (Finep),Fundação de Amparo à Pesquisa do Estado de São Paulo(FAPESP) andUniversidade Fed-eraldoRioGrandedoSul(UFRGS),Brazil;MinistryofEducationof China (MOEC), MinistryofScience &Technology ofChina (MSTC) and NationalNatural Science Foundation of China (NSFC), China; Ministry of Science and Education and Croatian Science Founda-tion,Croatia;CentrodeAplicacionesTecnológicasyDesarrollo Nu-clear (CEADEN), Cubaenergía, Cuba;Ministry of Education, Youth and Sports of the Czech Republic, Czech Republic; The Danish Council for Independent Research | Natural Sciences, the Villum Fonden and Danish National Research Foundation (DNRF), Den-mark; HelsinkiInstitute ofPhysics(HIP), Finland;Commissariatà l’Énergie Atomique (CEA),Institut National de Physique Nucléaire et de Physique des Particules (IN2P3) and Centre Nationalde la Recherche Scientifique (CNRS) and Région des Pays de la Loire, France; Bundesministerium für Bildung und Forschung (BMBF) andGSIHelmholtzzentrumfürSchwerionenforschungGmbH, Ger-many;GeneralSecretariatforResearchandTechnology,Ministryof

Fig. 9.ϒ(1S),ϒ(2S)andϒ(3S)RpPbat√sNN=8.16 TeVasafunctionofycms.The

RpPbvaluesofthethreeresonancesareslightlydisplacedhorizontallytoimprove

visibility.Theoreticalcalculations includingnCTEQ15shadowingcontributionand interactionsbetweentheϒstatesandcomovingparticles [15,52] arealsoshown foralltheresonances.Thegreyboxaroundunityrepresentstheglobaluncertainty commontothethreeϒstates.Inthelowerpanel,theratiooftheϒ(2S)toϒ(1S) andϒ(3S)toϒ(1S)RpPbisshown,togetherwithacalculationbasedonthe

afore-mentionedtheorymodel [15,52].

Education,Research andReligions,Greece; NationalResearch De-velopmentandInnovationOffice,Hungary;DepartmentofAtomic Energy, Government of India (DAE), Department of Science and Technology, Government of India (DST), University Grants Com-mission,GovernmentofIndia(UGC) andCouncil ofScientificand Industrial Research (CSIR), India; Indonesian Institute of Science, Indonesia;CentroFermi- MuseoStoricodellaFisicaeCentroStudi e Ricerche Enrico Fermi and Instituto Nazionale di Fisica Nucle-are (INFN),Italy; Institute forInnovativeScience andTechnology, Nagasaki Institute of Applied Science (IIST), Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) and JapanSocietyforthePromotionofScience(JSPS)KAKENHI,Japan; Consejo Nacional de Ciencia (CONACYT) y Tecnología, through FondodeCooperaciónInternacionalenCienciayTecnología (FON-CICYT)andDirecciónGeneralde Asuntosdel PersonalAcademico (DGAPA),Mexico; Nederlandse OrganisatievoorWetenschappelijk Onderzoek(NWO),Netherlands; The ResearchCouncil ofNorway, Norway; Commission on Science and Technology for Sustainable Development in the South (COMSATS), Pakistan; Pontificia Uni-versidad Católicadel Perú, Peru; Ministry of Science and Higher EducationandNationalScience Centre,Poland;Korea Institute of ScienceandTechnology Information andNationalResearch Foun-dation of Korea (NRF), Republic of Korea; Ministry of Education andScientificResearch,InstituteofAtomicPhysicsandMinistryof ResearchandInnovationandInstituteofAtomicPhysics,Romania; Joint Institute for Nuclear Research (JINR), Ministry of Education andScience of the Russian Federation, National Research Centre KurchatovInstitute,RussianScienceFoundationandRussian Foun-dation forBasic Research, Russia; Ministry ofEducation, Science, ResearchandSportoftheSlovak Republic, Slovakia; National Re-searchFoundationofSouthAfrica,SouthAfrica; SwedishResearch Council (VR) and Knut & Alice Wallenberg Foundation (KAW), Sweden;EuropeanOrganizationforNuclearResearch,Switzerland; Suranaree University of Technology (SUT), National Science and TechnologyDevelopmentAgency(NSDTA)andOfficeoftheHigher Education Commission under NRU project of Thailand, Thailand; TurkishAtomic Energy Agency (TAEK),Turkey; NationalAcademy ofSciences ofUkraine,Ukraine; ScienceandTechnology Facilities

Council (STFC), United Kingdom; National Science Foundation of theUnitedStatesofAmerica(NSF) andUnitedStatesDepartment of Energy, Office of Nuclear Physics (DOE NP), United States of America.

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