Differential studies of inclusive J/ψ and ψ(2S) production at forward rapidity in Pb-Pb collisions at √sNN=2.76 TeV

JHEP05(2016)179
Published o SISSA by Sp inge
Recei ed:Feb ua y 5, 2016
Accep ed:May 9, 2016
Published:May 31, 2016
Di e en ial s udies o inclusi e J/ψand ψ(2S)
p oduc ion a o wa d apidi y in Pb-Pb collisions a
√sNN = 2.76 TeV
The ALICE collabo a ion
E-mail: [email p o ec ed]
Abs ac : The p oduc ion o J/ψand ψ(2S) was s udied wi h he ALICE de ec o in
Pb-Pb collisions a he LHC. The measu emen was pe o med a o wa d apidi y (2.5<
y < 4) down o ze o ans e se momen um (p ) in he dimuon decay channel. Inclusi e
J/ψyields we e ex ac ed in di e en cen ali y classes and he cen ali y dependence o
he a e age p is p esen ed. The J/ψsupp ession, quan i ied wi h he nuclea modi ica ion
ac o (RAA), was measu ed as a unc ion o cen ali y, ans e se momen um and apidi y.
Compa isons wi h simila measu emen s a lowe collision ene gy and heo e ical models
indica e ha he J/ψp oduc ion is he esul o an in e play be ween colo sc eening
and ecombina ion mechanisms in a decon ined pa onic medium, o a i s had oniza ion.
Resul s on he ψ(2S) supp ession a e p o ided ia he a io o ψ(2S) o e J/ψmeasu ed
in pp and Pb-Pb collisions.
Keywo ds: Hea y Ion Expe imen s, Qua k gluon plasma
A Xi eP in : 1506.08804
Open Access, Copy igh CERN,
o he bene i o he ALICE Collabo a ion.
A icle unded by SCOAP3.
doi:10.1007/JHEP05(2016)179
JHEP05(2016)179
Con en s
1 In oduc ion 2
2 The ALICE de ec o 3
3 Da a sample 4
4 De ini ion o obse ables 5
5 Signal ex ac ion 7
5.1 Muon econs uc ion 7
5.2 J/ψsignal 9
5.3 ψ(2S) signal 11
6 Accep ance and e iciency co ec ion 12
7 Sys ema ic unce ain ies 14
7.1 Signal ex ac ion 14
7.2 Mon e Ca lo inpu pa ame iza ion 15
7.3 Cen ali y dependence o he [ψ(2S)/J/ψ]A×ε15
7.4 T acking e iciency 15
7.5 T igge e iciency 16
7.6 Ma ching e iciency 17
7.7 pp e e ence 17
7.8 No maliza ion 17
7.9 O he s 17
7.10 Summa y 18
8 Inclusi e J/ψ mean ans e se momen um 18
9 Nuclea modi ica ion ac o 21
9.1 Cen ali y dependence o RAA 21
9.2 T ans e se momen um dependence o RAA 24
9.3 Rapidi y dependence o RAA 26
10 [ψ(2S)/J/ψ] a io 27
11 Conclusions 29
A Da a ables 32
The ALICE collabo a ion 42
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JHEP05(2016)179
1 In oduc ion
A high empe a u e, la ice quan um ch omodynamics p edic s he exis ence o a decon-
ined phase o qua ks and gluons whe e chi al symme y is es o ed [1]. This s a e o ma e
is known as he Qua k Gluon Plasma (QGP) [2], and i s cha ac e iza ion is he goal o
ul a- ela i is ic hea y-ion collision s udies.
Among he p obes used o in es iga e he QGP and quan i y i s p ope ies, qua konium
s a es a e one o he mos p ominen and ha e gene a ed a la ge amoun o esul s bo h
heo e ical and expe imen al. Acco ding o he colo -sc eening model [3,4], measu emen
o he in-medium dissocia ion p obabili y o he di e en qua konium s a es could p o ide
an es ima e o he sys em empe a u e. Dissocia ion is expec ed o ake place when he
medium eaches o exceeds he c i ical empe a u e o he phase ansi ion (Tc), depending
on he binding ene gy o he qua konium s a e. In he cha monium (c¯c) amily, he s ongly
bound J/ψ could su i e signi ican ly abo e Tc(1.5–2 Tc) whe eas χcand ψ(2S) mel ing
should occu nea Tc(1.1–1.2 Tc) [5,6]. The de e mina ion o he in-medium qua konium
p ope ies emains a challenging heo e ical ask. In ense and pe sis en in es iga ions
on he heo y side a e ongoing [7]. Sho ly a e qua konium supp ession was sugges ed
as a s ong e idence o QGP o ma ion, he i s ideas o cha monium enhancemen ia
ecombina ion o c and ¯c appea ed [8,9]. Since hen, he J/ψ enhancemen mechanism has
been mo e o malized and quan i a i e p edic ions [10–14] we e made. Since he cha m
qua k densi y p oduced in had onic collisions inc eases wi h ene gy [15], ecombina ion
mechanisms a e p edic ed o gi e ise o a sizable J/ψ p oduc ion a LHC ene gies, which
is likely o pa ially compensa e o exceed he J/ψ supp ession due o colo -sc eening in he
QGP. The obse a ion o J/ψ enhancemen in nucleus-nucleus collisions ia ecombina ion
would cons i u e an e idence o decon inemen and hence o QGP o ma ion. In addi ion,
in o ma ion o he cha ac e iza ion o he QGP can come om he s udy o he ψ(2S)
meson, a s a e which is less s ongly bound and no a ec ed by highe mass cha monium
decays wi h espec o he J/ψ. In he pu e mel ing scena io, he ela i e p oduc ion o
ψ(2S) wi h espec o J/ψ is expec ed o be e y small a he LHC [4], which is no he
case i ecombina ion occu s [16,17].
J/ψ supp ession was obse ed expe imen ally in he mos cen al hea y-nucleus colli-
sions a he SPS [18,19], RHIC [20–23] and LHC [24–28], anging om a cen e -o -mass
ene gy pe nucleon pai (√sNN ) o abou 17 GeV o 2.76 TeV. The ψ(2S) supp ession was
measu ed a he SPS [29] and he LHC [30]. The in e p e a ion o hese esul s is no
s aigh o wa d as hey a e also subjec o o he e ec s, no all ela ed o he p esence
o a QGP. A ac ion o J/ψ o igina es om he s ong and elec omagne ic eed-down o
he χcand ψ(2S). The e o e, a mel ing o hese highe mass s a es be o e hey can decay
in o he J/ψ will lead o an e ec i e supp ession o he J/ψ yield al eady o a medium
ha does no each he J/ψ dissocia ion empe a u e. Assuming cha monium s a es a e
ini ially p oduced wi h he same ela i e abundancies in Pb–Pb collisions as in pp col-
lisions, he χcand ψ(2S) mel ing would esul in a educ ion o he J/ψ yield o abou
40% [31]. In addi ion, a non-p omp J/ψ and ψ(2S) componen om he weak decay o
beau y had ons also con ibu es o he inclusi e measu emen s. Since he beau y had ons
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JHEP05(2016)179
decay ou side he QGP olume, his con ibu ion is no sensi i e o he colo -sc eening o
cha monia. Finally, a ac ion o he J/ψ and ψ(2S) supp ession can be asc ibed o cold
nuclea ma e (CNM) e ec s, also p esen in p o on-nucleus collisions [32,33]. The CNM
e ec s g oup oge he he nuclea abso p ion o he cha monia, he modi ica ion o he
pa on dis ibu ion unc ions (PDF) in he nuclei ha leads o a educ ion (shadowing) o
an enhancemen (an i-shadowing) o he c¯c pai p oduc ion, and he ene gy loss o cha m
qua ks in he nucleus.
Nume ous s udies o J/ψ p oduc ion in di e en collision sys ems a di e en ene gies
a e now a ailable. Compa isons be ween expe imen s and o heo e ical models can be
made o e wide kinema ic anges in apidi y and ans e se momen um. We al eady pub-
lished he cen ali y, ans e se momen um (p ) and apidi y (y) dependence o he J/ψ
nuclea modi ica ion ac o in Pb–Pb collisions a √sNN = 2.76 TeV [26,27]. In his pape ,
hose esul s a e ex ensi ely compa ed o a ailable heo e ical models and lowe ene gy
da a. New esul s on he J/ψ hp iand hp2
i e sus cen ali y, and on he cen ali y (p )
dependence o he J/ψ supp ession o a ious p (cen ali y) anges a e also p esen ed.
Fu he mo e, we show esul s on ψ(2S) in Pb–Pb collisions, measu ed ia he [ψ(2S)/J/ψ]
a io, as a unc ion o cen ali y.
The emainde o his pape is o ganized as ollows: he expe imen al appa a us and
he da a sample a e p esen ed in sec ions 2 and 3. Sec ion 4 gi es he de ini ion o he
obse ables used in he analysis. The analysis p ocedu e is hen desc ibed in sec ions 5
and 6. Sys ema ic unce ain ies a e discussed in sec ion 7. The J/ψ esul s a e gi en in
sec ions 8 and 9 while sec ion 10 is dedica ed o he ψ(2S) esul s. Finally, sec ion 11
p esen s ou conclusions.
2 The ALICE de ec o
The ALICE de ec o is desc ibed in de ail in [34]. A o wa d apidi y (2.5< y < 4) he
p oduc ion o qua konium s a es is s udied in he muon spec ome e ia hei µ+µ−decay
channels down o ze o p . In he ALICE e e ence ame, he posi i e zdi ec ion is along
he coun e -clockwise beam di ec ion. The muon spec ome e co e s a nega i e pseudo-
apidi y (η) ange and consequen ly a nega i e y ange. Howe e , due o he symme y o
he Pb–Pb sys em, he esul s a e p esen ed wi h a posi i e yno a ion, while keeping he
nega i e sign o η.
The muon spec ome e consis s o a en-in e ac ion-leng hs (4.1 m) hick abso be ,
which il e s he muons, in on o i e acking s a ions comp ising wo planes o ca hode
pad chambe s each. The hi d s a ion is loca ed inside a dipole magne wi h a 3 Tm
ield in eg al. The acking appa a us is comple ed by a Muon T igge sys em (MTR)
composed o ou planes o esis i e pla e chambe s downs eam om a se en-in e ac ion-
leng hs (1.2 m) hick i on wall, which abso bs seconda y had ons escaping om he on
abso be and low-momen um muons coming mainly om cha ged pion and kaon decays. A
small-angle conical abso be p o ec s he acking and igge chambe s agains seconda y
pa icles p oduced by he in e ac ion o la ge apidi y p ima y pa icles wi h he beam pipe.
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JHEP05(2016)179
Finally, a ea abso be p o ec s he igge chambe s om he backg ound gene a ed by
beam-gas in e ac ions downs eam om he spec ome e .
In addi ion, he Silicon Pixel De ec o (SPD), scin illa o a ays (V0) and Ze o Deg ee
Calo ime e s (ZDC) we e used in his analysis. The SPD consis s o wo cylind ical laye s
co e ing |η|<2.0 and |η|<1.4 o he inne and ou e ones, espec i ely, and p o ides
he coo dina es o he p ima y e ex o he collision. The V0 coun e s, wo a ays o 32
scin illa o iles each, a e loca ed on bo h sides o he nominal in e ac ion poin and co e
2.8< η < 5.1 (V0-A) and −3.7< η < −1.7 (V0-C). The ZDC a e loca ed on ei he side
o he in e ac ion poin a z≈ ±114 m and de ec spec a o nucleons a ze o deg ee wi h
espec o he LHC beam axis. The V0 and ZDC de ec o s p o ide igge ing in o ma ion
and e en cha ac e iza ion.
3 Da a sample
The da a sample analysed in his pape co esponds o Pb–Pb collisions a √sNN =
2.76 TeV. These collisions we e deli e ed by he LHC du ing 190 hou s o s able beam
ope a ions sp ead o e h ee weeks in No embe and Decembe 2011.
The Le el-0 (L0) minimum bias (MB) igge was de ined as he coincidence o signals
in V0-A and V0-C de ec o s synch onized wi h he passage o wo c ossing lead bunches.
This choice o he MB condi ion p o ides a high igge ing e iciency (>95%) o had onic
in e ac ions. To imp o e he igge pu i y, a h eshold on he ene gy deposi ed in he
neu on ZDC ejec s he con ibu ion om elec omagne ic dissocia ion p ocesses a he
Le el-1 (L1) igge le el. Beam induced backg ound is u he educed a he o line le el
by iming cu s on he signals om he V0 and he ZDC.
The cha monium analysis was ca ied ou on a da a sample, whe e in addi ion o he
MB p e equisi e, a igge condi ion o a leas one o wo econs uc ed muon candida e
acks in he MTR ( igge acks) was equi ed in each e en . The MTR logic allows o
p og amming se e al L0 igge decisions based on (i) he de ec ion o one o wo muon
igge acks, (ii) he p esence o opposi e-sign o like-sign igge ack pai s and (iii) a
lowe h eshold on he app oxima e ans e se momen um (p ig
) o he muon candida es.
The la e selec ion is pe o med by applying a cu on he maximum de ia ion o he igge
ack om an in ini e momen um ack o igina ing a he nominal in e ac ion poin . Due
o he ini e spa ial esolu ion o he igge chambe s, his does no lead o a sha p cu in
p , and he co esponding p ig
h eshold is de ined in simula ion as he p alue o which
he muon igge p obabili y is 50%. The ollowing muon-speci ic L0 igge s we e used:
•Single muon low p (p ig
= 1 GeV/c): MSL
•Opposi e-sign dimuon low p (p ig
= 1 GeV/c on each muon): MUL
•Like-sign dimuon low p (p ig
= 1 GeV/c on each muon): MLL
A da a sample o 17.3·106Pb–Pb collisions was collec ed wi h he µµ-MB igge , de ined
as he coincidence o he MB and MUL condi ions. A scaling ac o Fno m is compu ed o
each un — co esponding o a ew hou s maximum o con inuous da a aking — in o de
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JHEP05(2016)179
o no malize he numbe o µµ-MB igge s o he numbe o equi alen MB igge s. I
is de ined as he a io, in a MB da a sample, be ween he o al numbe o e en s and he
numbe o e en s ul illing he µµ-MB igge condi ion. I should be no ed ha he MB
sample used in his calcula ion was eco ded in pa allel o he µµ-MB igge s. The Fno m
alue, 30.56±0.01(s a .)±1.10(sys .), is gi en by he a e age o e all uns weigh ed by he
s a is ical unce ain ies. A small ac ion o opposi e-sign dimuons we e misiden i ied by
he igge algo i hm as like-sign pai s. Al hough o he J/ψ i amoun s o less han 1%
when conside ing he ull sample, i inc eases up o 4% a high p in pe iphe al collisions.
In his analysis, he missing ac ion o opposi e-sign dimuons was eco e ed by ex ac ing
he numbe o p oduced J/ψ and ψ(2S) om he union o he MUL and MLL da a sample
(MUL∪MLL). This is di e en om he selec ion applied in he o me pape [27], whe e
only he MUL da a sample was used. On he o he hand, he e iciency o he igge
algo i hm o de e mine he sign o he muon pai s does no impac he no maliza ion o
he collec ed da a sample o he numbe o equi alen MB e en s desc ibed abo e. This
was c oss-checked by compu ing he no maliza ion ac o o he MUL∪MLL da a sample,
esul ing in less han 1% di e ence in he ex ac ed numbe o equi alen MB e en s.
The in eg a ed luminosi y co esponding o he analysed da a sample is Lin =Nµµ-MB·
Fno m/σPb–Pb = 68.8±0.9(s a .)±2.5(sys . Fno m)+5.5
−4.5(sys . σPb–Pb)µb−1using an in-
elas ic Pb–Pb c oss sec ion σPb–Pb = 7.7±0.1+0.6
−0.5b [35].
4 De ini ion o obse ables
The cen ali y de e mina ion is based on a i o he V0 signal ampli ude dis ibu ion as
desc ibed in [36]. Va iables cha ac e izing he collision such as he a e age numbe o
pa icipan nucleons (hNpa i) and he a e age nuclea o e lap unc ion (hTAAi) o each
cen ali y class a e gi en in able 1. In his analysis a cu co esponding o he mos cen al
90% o he inelas ic nuclea c oss sec ion was applied as o hese e en s he MB igge is
ully e icien and he esidual con amina ion om elec omagne ic p ocesses is negligible.
Fo each cen ali y class i, he measu ed numbe o J/ψ (Ni
J/ψ) is no malized o he
equi alen numbe o minimum bias e en s (Ni
e en s). To ob ain Ni
e en s, one simply mul-
iplies he numbe o µµ-MB igge ed e en s by he Fno m ac o scaled by he wid h
o he cen ali y class. Co ec ions o he b anching a io o he dimuon decay channel
(BRJ/ψ→µ+µ−= 5.93 ±0.06%) and o he accep ance imes e iciency (A×i) o he
de ec o a e hen applied. The J/ψ yield (Yi
J/ψ) in a cen ali y class iis gi en by
d2Yi
J/ψ
dp dy=d2Ni
J/ψ/dp dy
BRJ/ψ→µ+µ−·Ni
e en s ·A×i(p , y).(4.1)
I is hen combined wi h he inclusi e J/ψ c oss sec ion measu ed in pp collisions a he
same ene gy o o m he nuclea modi ica ion ac o RAA de ined as
Ri
AA(p , y) = d2Yi
J/ψ/dp dy
hTAAii·d2σpp
J/ψ/dp dy.(4.2)
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JHEP05(2016)179
Cen ali y hNpa i hTAAi(mb−1) Cen ali y hNpa i hTAAi(mb−1)
0–10% 356.0±3.6 23.44±0.76 0–20% 308.1±3.7 18.91±0.61
10–20% 260.1±3.8 14.39±0.45 0–40% 232.6±3.4 12.88±0.42
20–30% 185.8±3.3 8.70±0.27 0–90% 124.4±2.2 6.27±0.21
30–40% 128.5±2.9 5.00±0.18 20–40% 157.2±3.1 6.85±0.23
40–50% 84.7±2.4 2.68±0.12 20–60% 112.8±2.6 4.42±0.16
50–60% 52.4±1.6 1.317±0.071 40–60% 68.6±2.0 1.996±0.097
60–70% 29.77±0.98 0.591±0.036 40–90% 37.9±1.2 0.985±0.051
70–80% 15.27±0.55 0.243±0.016 50–90% 26.23±0.84 0.563±0.033
80–90% 7.49±0.22 0.0983±0.0076 60–90% 17.51±0.59 0.311±0.020
Table 1. The a e age numbe o pa icipan nucleons hNpa iand he a e age alue o he nuclea
o e lap unc ion hTAAiwi h hei associa ed sys ema ic unce ain ies o he cen ali y classes,
exp essed in pe cen ages o he nuclea c oss sec ion [36], used in hese analyses.
The p and yin eg a ed J/ψ c oss sec ion is σpp
J/ψ(p <8 GeV/c, 2.5< y < 4) = 3.34 ±
0.13(s a .)±0.24(sys .)±0.12(luminosi y)+0.53
−1.07(pola iza ion)µb [37].
The ALICE measu emen s epo ed he e e e o inclusi e J/ψ yields, i.e. include
p omp J/ψ (di ec J/ψ and eed-down om ψ(2S) and χc) and non-p omp J/ψ (decay
o B-mesons). Con a y o p omp J/ψ, J/ψ om B-meson decays do no di ec ly p obe
he ho and dense medium c ea ed in he Pb–Pb collisions. Beau y had on decays occu
ou side he QGP, so he non-p omp J/ψ RAA is ins ead ela ed o he ene gy loss o he
beau y qua ks in he medium. Al hough he p omp J/ψ RAA canno be di ec ly measu ed
wi h he ALICE muon spec ome e , i can be e alua ed ia
Rp omp
AA =RAA −FB·Rnon-p omp
AA
1−FB
(4.3)
whe e FBis he ac ion o non-p omp o inclusi e J/ψ measu ed in pp collisions, and
Rnon-p omp
AA is he nuclea modi ica ion ac o o J/ψ om B-meson decays in Pb–Pb col-
lisions. The non-p omp and p omp J/ψ di e en ial c oss sec ions as a unc ion o p
and ywe e measu ed by LHCb in pp collisions a √s= 2.76 and 7 TeV [38,39] in a
kinema ic ange o e lapping wi h ha o he ALICE muon spec ome e . The e o e, one
can ex ac he p and ydependence o FB om hese da a and use i in eq. (4.3). A eli-
able de e mina ion o Rnon-p omp
AA p esen s u he complica ions. We ha e hus chosen wo
ex eme hypo heses, independen o cen ali y, co esponding o he absence o medium e -
ec s on beau y had ons (Rnon-p omp
AA = 1) o o a comple e supp ession (Rnon-p omp
AA = 0),
o e alua e conse a i e limi s on Rp omp
AA .
An excess o J/ψ compa ed o he yield expec ed assuming a smoo h e olu ion o he
J/ψ had o-p oduc ion and nuclea modi ica ion ac o was obse ed in pe iphe al Pb–Pb
collisions a e y low p [40]. This excess migh o igina e om he pho o-p oduc ion
o J/ψ. This con ibu ion is negligible in pp collisions — om LHCb measu emen a
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JHEP05(2016)179
√s= 7 TeV [41], i is O(10−3)% — bu i is enhanced by a ac o O(104) in Pb–Pb
collisions, hus eaching he o de o magni ude o he obse ed excess. The J/ψ cohe -
en pho o-p oduc ion has been measu ed in ul a-pe iphe al Pb–Pb collisions [42]. I is
cen e ed a e y low p , wi h ∼98% o hese J/ψ below 0.3 GeV/c. An incohe en pho o-
p oduc ion componen is also obse ed in ul a-pe iphe al Pb–Pb collisions. Abou 30%
o his con ibu ion has a p <0.3 GeV/c, he es being mainly loca ed in he p ange
0.3–1 GeV/c. The in luence o possible pho o-p oduc ion mechanisms on he inclusi e J/ψ
RAA p esen ed in his pape has been e alua ed by epea ing he analysis placing a low
p h eshold on he J/ψ o 0.3 GeV/c. Assuming ha he obse ed excess in pe iphe al
Pb–Pb collisions is indeed due o he pho o-p oduc ion o J/ψ, and ha he ela i e con-
ibu ion o he incohe en o e cohe en componen s is he same as he one es ima ed in
ul a-pe iphe al collisions, hen his selec ion would emo e abou 75% o he ull pho o-
p oduc ion con ibu ion. Nume ical alues o RAA wi h he low p h eshold a 0.3 GeV/c
a e gi en in he appendix A. All he igu es and alues p esen ed in he pape e e o
he inclusi e J/ψ RAA bu es ima es o he di e ence be ween he inclusi e and had onic
(wi hou J/ψ pho o-p oduc ion) J/ψ RAA, a e indica ed whe e app op ia e.
The esul s o he ψ(2S) analysis a e gi en in e ms o he a io o hei p oduc ion
c oss sec ions (o , equi alen ly, o hei p oduc ion yields), exp essed as
ψ(2S)/J/ψ =Ni
ψ(2S)
Ni
J/ψ ·(A×εi)J/ψ
(A×εi)ψ(2S)
.(4.4)
When o ming such a a io he no maliza ion ac o Ni
e en s cancels ou , as do
mos o he sys ema ic unce ain ies on A×εco ec ions. The double a io
[ψ(2S)/J/ψ]Pb–Pb /[ψ(2S)/J/ψ]pp is used in o de o di ec ly compa e he ela i e abun-
dances o ψ(2S) and J/ψ in nucleus-nucleus and pp collisions.
5 Signal ex ac ion
A e a desc ip ion o he muon selec ion p ocedu e, we p esen he e he wo me hods used
o ex ac he J/ψ and ψ(2S) signals. The i s one is di ec ly based on i s o he µ+µ−
in a ian mass dis ibu ion while he second one makes use o he e en mixing echnique
o sub ac he combina o ial backg ound.
5.1 Muon econs uc ion
The muon econs uc ion s a s wi h he exclusion o pa s o he de ec o ha show
p oblems du ing da a aking such as high ol age ips, la ge elec onic noise, pedes al
de e mina ion issues. This selec ion is pe o med on a un-by- un basis o accoun o he
ime e olu ion o he appa a us. A e pedes al sub ac ion, he adjacen well- unc ioning
pads o bo h ca hodes o each acking chambe ha ing collec ed a cha ge a e g ouped
o o m p e-clus e s. These p e-clus e s migh be he supe posi ion o se e al clus e s o
cha ges deposi ed by se e al pa icles c ossing he de ec o close o each o he s. The num-
be o clus e s o cha ges con ibu ing o he p e-clus e and hei app oxima e loca ion a e
– 7 –
JHEP05(2016)179
de e mined wi h a Maximum Likelihood - Expec a ion Maximiza ion (MLEM) algo i hm.
I assumes ha he cha ge dis ibu ion o each single clus e ollows a wo-dimensional
in eg al o he Ma hieson unc ion [43]. I he es ima ed numbe o clus e s is la ge han
3, he p e-clus e is spli in o se e al g oups o 1, 2 o 3 clus e s selec ed wi h he mini-
mum o al coupling o all he o he clus e s in o he p e-clus e . Each g oup o clus e s
is hen i ed using a sum o Ma hieson unc ions, aking he MLEM esul s as a seed, o
ex ac he p ecise loca ion o whe e he pa icles c ossed he de ec o . The o e all spa ial
esolu ion is a ound 200 (550) µm in a e age in he (non-)bending di ec ion.
The ack econs uc ion s a s om he mos downs eam s a ions, whe e he mul i-
plici y o seconda y pa icles is smalles , by o ming pai s o clus e s in he wo chambe s
o s a ion 5(4), and de i ing he pa ame e s and associa ed e o s o he esul ing muon
ack candida es. The candida es a e hen ex apola ed o he s a ion 4(5), alida ed i a
leas one compa ible clus e is ound in he s a ion and duplica e acks a e emo ed. The
p ocedu e con inues ex apola ing he acks o s a ions 3, 2 and 1, alida ing hem by he
inclusion o a leas one clus e pe s a ion. The selec ion o compa ible clus e s is based
on a 5σcu on a χ2compu ed om he clus e and ack local posi ions and e o s. I
se e al compa ible clus e s a e ound in he same chambe , he ack is duplica ed o con-
side all he possibili ies and o each o hem he ack pa ame e s and associa ed e o s
a e ecompu ed using a Kalman il e . A each o he acking s eps, he ack candida es,
whose pa ame e s indica e ha hey will exi he geome ical accep ance o he spec om-
e e in he nex s eps a e emo ed. A he end o he p ocedu e, he quali y o he ack is
imp o ed by adding/ emo ing clus e s based on a 4σcu on he local χ2and ake acks
sha ing clus e s wi h o he s in he h ee ou e mos s a ions wi h espec o he in e ac ion
poin a e emo ed. The choice o he χ2cu s is a comp omise be ween maximizing he
acking e iciency (<1–2% muon ejec ion) and minimizing he amoun o ake acks
(negligible backg ound o his analysis). Finally, muon ack candida es a e ex apola ed
o he in e ac ion e ex measu ed by he SPD aking in o accoun he ene gy loss and he
mul iple Coulomb sca e ing in he on abso be .
An accu a e measu emen o he acking chambe alignmen is essen ial o econs uc
he acks wi h enough p ecision o iden i y esonances in he µ+µ−in a ian mass spec-
um, especially he ψ(2S) o which he signal- o-backg ound a io is low. The absolu e
posi ion o he chambe s was i s measu ed using pho og amme y be o e he da a ak-
ing. Thei ela i e posi ion was hen p ecisely de e mined using a modi ied e sion o he
MILLEPEDE package [44], combining se e al samples o acks aken wi h and wi hou
magne ic ield. The small displacemen o he chambe s when swi ching on he dipole
was measu ed by he Geome y Moni o ing Sys em (an a ay o op ical senso s ixed on
he chambe s) and aken in o accoun . The esul ing alignmen p ecision is ∼100 µm,
leading o a econs uc ed J/ψ in a ian mass esolu ion o abou 70 MeV/c2, and abou
10% highe o he ψ(2S). The esolu ion is domina ed by he ene gy loss luc ua ion and
mul iple Coulomb sca e ing o he muons in he on abso be . Mo e de ails on he muon
spec ome e pe o mances a e gi en in [45].
In his analysis, he muon ack candida es also ha e o ul ill he ollowing equi e-
men s. Fi s , he econs uc ed ack mus ma ch a igge ack wi h a p ig
abo e he
– 8 –
JHEP05(2016)179
sys ema ic unce ain y on he signal ex ac ion a ies om 1% o 4%. Conce ning he
ψ(2S) analysis, in he in e als whe e he signal was ex ac ed, he sys ema ic unce ain y
is 14%, 45% and 24% o cen ali y anges 60–90%, 40–60% and 20–40% o p <3 GeV/c.
7.2 Mon e Ca lo inpu pa ame iza ion
The es ima ion o A×ε ac o s depends on he cha monium p and yshapes used as
inpu dis ibu ions in he MC simula ion. In o de o e alua e he sensi i i y o he esul s
on his choice, se e al MC simula ions we e pe o med, each one including modi ied p
and ydis ibu ions. Fo he J/ψ, he modi ica ion o he shapes was done in o de o
ake in o accoun he possible co ela ion be ween p and y(as obse ed by LHCb in pp
collisions [39]) and he co ela ion be ween p (y) and he cen ali y o he collision (as
epo ed in his pape ). A sys ema ic unce ain y o 3% is ound o A×εin eg a ed o e
p and yand is aken as co ela ed as a unc ion o he cen ali y. The p (y) dependence o
his unce ain y a ies in he ange 0–1% (3–8%). The la ge e ec seen in he ydependence
occu s a he low and high limi s, whe e he accep ance alls s eeply.
The same p ocedu e was ollowed o he ψ(2S), assuming ha he co ela ions be ween
p and yand wi h he cen ali y a e o he same magni ude as hose obse ed o he
J/ψ. A sys ema ic unce ain y o 2% is e alua ed o he [ψ(2S)/J/ψ] a io in he p <
3 GeV/c in e al.
7.3 Cen ali y dependence o he [ψ(2S)/J/ψ]A×ε
The embedding echnique was no used o he ψ(2S) MC simula ions as we ha e assumed
he same A×εdependence as a unc ion o he cen ali y o he ψ(2S) and he J/ψ. In
o de o e alua e he sys ema ic unce ain y in oduced by his assump ion, a conse a i e
±30% a ia ion o he A×εloss as a unc ion o cen ali y was applied o he ψ(2S).
This co esponds o he maximum a ia ion o he A×εloss be ween pe iphe al and
cen al collisions obse ed o he J/ψ in di e en p and yin e als. The e ec on he
(A×ε)J/ψ /(A×ε)ψ(2S) a io is 1% o lowe in all he cen ali y classes conside ed. Since
his e ec is much smalle han he sys ema ic unce ain y on he signal ex ac ion, i
is neglec ed.
7.4 T acking e iciency
The acking algo i hm, as desc ibed in sec ion 5.1, does no equi e all he chambe s o
ha e i ed o econs uc a ack. This edundancy o he acking chambe s can be used
o measu e hei indi idual e iciencies om da a, and since such e iciencies a e indepen-
den om each o he , we can combine hem o assess he o e all acking e iciency. This
e alua ion o he acking e iciency is no p ecise enough o be used o di ec ly co ec he
da a, because only he mean e iciency pe chambe can be compu ed wi h he s a is ics
a ailable in each un. Howe e , by compa ing he esul ob ained om da a wi h he same
measu emen pe o med in simula ions, we can con ol he accu acy o hese simula ions
and assess he co esponding sys ema ic unce ain y on he A×εco ec ions.
– 15 –

JHEP05(2016)179
A 9% ela i e sys ema ic unce ain y is ob ained o he J/ψ by compa ing he mea-
su ed acking e iciency in simula ions and in pe iphe al Pb–Pb collisions. This unce -
ain y is cons an and ully co ela ed as a unc ion o cen ali y. F om low o high p (y),
he sys ema ic unce ain y a ies om 9% o 7% (7% o 6% wi h a maximum o 12% a
y≃3.25). On op o ha , a small di e ence was obse ed in he cen ali y dependence o
his measu emen be ween da a and embedding simula ions. This esul s in an addi ional
1% sys ema ic unce ain y in he 0–10% cen ali y class and 0.5% in 10–20%.
Ano he sys ema ic unce ain y can a ise om co ela ed dead a eas loca ed in on o
each o he in he same s a ion, which canno be de ec ed wi h he me hod de ailed abo e.
A dedica ed s udy has shown ha his e ec in oduces a 2% sys ema ic unce ain y, ully
co ela ed as a unc ion o cen ali y and p edominan ly unco ela ed as a unc ion o
p and y.
In he [ψ(2S)/J/ψ] a io he sys ema ic unce ain y on he acking e iciency la gely
cancels ou because he ψ(2S) and J/ψ decay muons ha e simila p and ydis ibu ions
and, he e o e, c oss abou he same egions o he de ec o . Since he possible emaining
sys ema ic unce ain y is much smalle han ha on he signal ex ac ion, i is neglec ed
in his analysis.
7.5 T igge e iciency
The sys ema ic unce ain y on he J/ψ A×εco ec ions ela ed o he igge e iciency has
wo o igins: he in insic e iciency o he igge chambe s and he esponse o he igge
algo i hm. The i s pa was de e mined om he unce ain ies on he igge chambe
e iciencies measu ed om da a and applied o simula ions. P opaga ing hese e iciencies
in J/ψ simula ions esul s in a 2% sys ema ic unce ain y on he A×εco ec ions, ully
co ela ed as a unc ion o cen ali y and mainly unco ela ed as a unc ion o p and y.
The e ec o he sys ema ic unce ain y on he shape o he igge esponse as a unc ion
o he muon p was de e mined by weigh ing MC J/ψ decay muons wi h di e en igge
esponse unc ions ob ained in da a and simula ions. These unc ions we e de ined as he
ac ion, e sus p , o he single muons passing a 0.5 GeV/c p ig
h eshold ha also sa is y
he 1 GeV/c p ig
h eshold used in his analysis. The esul ing sys ema ic unce ain y
on he J/ψ A ×εco ec ion in eg a ed o e p and yis 1%. As a unc ion o p , i
amoun s o 3% o p <1 GeV/c and 1% elsewhe e. As a unc ion o y, a 1% unco ela ed
sys ema ic unce ain y was ob ained. These unce ain ies a e ully co ela ed as a unc ion
o cen ali y.
The sys ema ic unce ain y on he modi ica ion o he igge esponse as a unc ion
o cen ali y, i.e. o inc easing mul iplici y, was assessed by changing he de ec o esponse
(space size o he deposi ed cha ge) o he passage o pa icles in embedding simula ions.
The co esponding unce ain ies on he J/ψ A ×εco ec ions a e 1% in he 0–10% and
10–20% cen ali y classes, and 0.5% in 20–30% and 30–40%.
As o he case o acking e iciency, his sou ce o sys ema ic unce ain y la gely
cancels ou in he [ψ(2S)/J/ψ] a io and is neglec ed.
– 16 –
JHEP05(2016)179
7.6 Ma ching e iciency
The sys ema ic unce ain y on he ma ching e iciency be ween he acking and he igge
acks is 1%. I is gi en by he di e ences obse ed be ween da a and simula ions when
applying di e en χ2cu s on he ma ching be ween he ack econs uc ed in he acking
chambe s and he one econs uc ed in he igge chambe s. This unce ain y is ully
co ela ed as a unc ion o he cen ali y and la gely unco ela ed as a unc ion o p and y.
Also in his case, he e ec on he [ψ(2S)/J/ψ] a io is negligible.
7.7 pp e e ence
The s a is ical and sys ema ic unce ain ies on he measu emen o he J/ψ di e en ial c oss
sec ion in pp collisions a √s= 2.76 TeV a e a ailable in [37]. The s a is ical unce ain y is
combined wi h ha o he Pb–Pb measu emen when calcula ing he RAA as a unc ion o
p and y, bu is conside ed as a ully co ela ed sys ema ic unce ain y as a unc ion o he
cen ali y. The co ela ed and unco ela ed pa o he sys ema ic unce ain y on he pp
e e ence as a unc ion o p and ya e bo h ully co ela ed as a unc ion o he cen ali y.
The ψ(2S) s a is ics in he √s= 2.76 TeV pp da a sample a e oo low o be used
o he no maliza ion o he [ψ(2S)/J/ψ]Pb–Pb a io. Fo his eason, pp esul s ob ained
a highe ene gy (√s= 7 TeV) [50] we e used, hus in oducing an addi ional sou ce
o sys ema ic unce ain y. An in e pola ion p ocedu e, as he one desc ibed in [33], was
applied in o de o ex ac he [ψ(2S)/J/ψ]pp a io a √s= 2.76 TeV. The disc epancy
be ween he esul o his in e pola ion in he kinema ic ange p <3 GeV/c 2.5< y < 4
and he alue ob ained a √s= 7 TeV is 10%: his ela i e di e ence is included in he
sys ema ic unce ain y on he pp e e ence.
7.8 No maliza ion
The sys ema ic unce ain y on he no maliza ion is he one a ached o he scaling ac-
o Fno m and amoun s o 4%. This alue co esponds o one s anda d de ia ion o he
dis ibu ion o he Fno m compu ed o each un used in he analysis. This sys ema ic
unce ain y is ully co ela ed as a unc ion o he cen ali y, p and y.
7.9 O he s
Sys ema ic unce ain ies on he nuclea o e lap unc ion hTAAia e a ailable in able 1.
Ano he sys ema ic unce ain y on he de ini ion o he cen ali y classes a ises om he
V0 ampli ude cu , which co esponds o 90% o he had onic c oss sec ion [36]. A maximum
unce ain y o 5% is ob ained in he cen ali y class (80–90%) anishing wi h inc easing
cen ali y o in wide cen ali y classes.
Sys ema ic unce ain ies due o he unknown pola iza ion o he J/ψ a e no p opa-
ga ed and we assume ha J/ψ p oduc ion is unpola ized bo h in pp and in Pb–Pb col-
lisions. In pp collisions a √s= 7 TeV, J/ψ pola iza ion measu emen s a mid- apidi y
(p >10 GeV/c) and o wa d- apidi y (p >2 GeV/c) a e compa ible wi h ze o [51–53].
In Pb–Pb collisions, J/ψ mesons p oduced om ini ial pa on-pa on ha d sca e ing a e
expec ed o ha e he same pola iza ion as in pp collisions and hose p oduced om cha m
qua ks ecombina ion in he medium a e expec ed o be unpola ized.
– 17 –
JHEP05(2016)179
Sou ces Cen ali y p y[27]
p <8 GeV/c [27]p bins 0–90% [27] cen ali y bins
Signal ex ac ion 1–3 1–4 1–4 1–5 1–4
MC pa ame iza ion 3∗1–3∗0–1 0–1 3–8
T acking e iciency 0–1 and 11∗0–1 and 9–11∗9–11 and 1∗9–11 and 0–1∗8–14 and 1∗
T igge e iciency 0–1 and 2∗0–1 and 2∗2–4 and 1∗2–4 and 0–1∗2 and 1∗
Ma ching e iciency 1∗1∗1 1 1
σpp
J/ψ
s a . 4∗5–12∗6–21 6–21 7–11
sys . 8∗7∗5–6 and 6∗5–6 and 6∗5–6 and 6∗
Fno m 4∗4∗4∗4∗4∗
hTAAi3–8 3–6 3∗3–5∗3∗
Cen ali y limi s 0–5 0–3 0 0–2∗0
B.R. n/a n/a n/a 1∗n/a
Table 2. Summa y o he sys ema ic unce ain ies (in %) en e ing he J/ψ yield and/o RAA
calcula ion as a unc ion o cen ali y, p and y. Numbe s wi h an as e isk co espond o he
sys ema ic unce ain ies ully co ela ed as a unc ion o he gi en a iable.
7.10 Summa y
The sys ema ic unce ain ies ela ed o he J/ψ analysis a e summa ized in able 2.
Conce ning he ψ(2S) analysis, mos o he sys ema ic unce ain ies cancel ou in he
[ψ(2S)/J/ψ] a io and he main con ibu o s a e he signal ex ac ion (14–45%) and he
pp e e ence (10%).
8 Inclusi e J/ψ mean ans e se momen um
The p dependence o he J/ψ yields pe MB collision, de ined by eq. (4.1), was s udied
o h ee cen ali y classes (0–20%, 20–40% and 40–90%) and is displayed in igu e 5. The
s a is ical unce ain ies appea as e ical lines. The sys ema ic unce ain ies unco ela ed
as a unc ion o p a e shown as open boxes, while he ones ully co ela ed as a unc ion o
p bu unco ela ed as a unc ion o cen ali y a e shown as shaded a eas (mos ly hidden by
he poin s). The global sys ema ic unce ain y, ully co ela ed as a unc ion o cen ali y
and p , is quo ed di ec ly in he igu e. Nume ical alues o he J/ψ yields can be ound
in appendix A. The inclusi e J/ψ mean ans e se momen um was compu ed by i ing he
p dis ibu ion o inclusi e J/ψ yields wi h he unc ion
(p ) = C×p
(1 + (p /p0)2)n,(8.1)
whe e C,p0and na e ee pa ame e s. This unc ion is commonly used o ep oduce
he J/ψ p dis ibu ion in had onic collisions, see o ins ance [54–56]. Fi esul s o he
h ee cen ali y classes a e displayed as ull lines in he igu e. An excess o e his unc ion
is e ealed in he lowes p in e al (co esponding o 0 < p <500 MeV/c) o pe iph-
e al Pb–Pb collisions. I could be caused by a esidual con ibu ion om J/ψ cohe en
pho o-p oduc ion, which was measu ed in ul a-pe iphe al collisions [42]. A quan i a i e
measu emen o his con ibu ion in had onic collisions is epo ed in [40]. Thus, in he
mos pe iphe al cen ali y class (40–90%) he i was pe o med o p >500 MeV/c and
– 18 –
JHEP05(2016)179
)c (GeV/
T
p
0 1 2 3 4 5 6 7 8
-1
)c (GeV/
T
pdy/dY
2
d
5−
10
4−
10
3−
10
2−
10
= 2.76 TeV
NN
sALICE Pb-Pb
<4y, 2.5<
-
µ
+
µ → ψInclusi e J/
4%±global sys . =
0-20%
20-40%
40-90%
Figu e 5. Di e en ial yields o inclusi e J/ψ in Pb–Pb collisions a √sNN = 2.76 TeV as a unc ion
o p o h ee cen ali y classes. Solid lines co espond o he esul s om he i desc ibed in
he ex .
ex apola ed down o ze o (do ed line). In he 0–20% and 20–40% cen ali y classes, no
J/ψ excess was obse ed and i s we e pe o med down o ze o p . As a c oss-check, he
same p ocedu e as o he pe iphe al cen ali y class was es ed and he ob ained esul s
a e ully compa ible wi hin unce ain ies.
Values o he mean ans e se momen um (hp i) and mean squa ed ans e se mo-
men um (hp2
i) ob ained om he i s a e gi en in able 3as a unc ion o cen ali y. The
s a is ical (sys ema ic) unce ain y is ex ac ed by i ing he p dis ibu ion conside -
ing only he s a is ical (p -unco ela ed sys ema ic) unce ain y o he measu emen . Fo
compa isons, he hp iand hp2
i esul s om PHENIX we e ecompu ed wi h he unc ion
de ined by eq. (8.1), adjus ed in he measu ed p ange and ex apola ed o p = 8 GeV/c
o ma ch ou p ange. These esul s a e also gi en in able 3along wi h he measu emen
in pp collisions a √s= 2.76 TeV wi h upda ed unce ain ies [57].
The hp io inclusi e J/ψ measu ed in pp and Pb–Pb collisions a √sNN = 2.76 TeV is
shown in igu e 6(le side) as a unc ion o hNpa i. The e o ba s (open boxes) ep esen
he s a is ical (sys ema ic) unce ain ies. A clea downwa d end in hp iis obse ed when
going om pp o he mos cen al Pb–Pb collisions. The hp idec ease om pe iphe al
(40–90%) o cen al (0–20%) collisions is signi ican , he wo alues being sepa a ed by
mo e han 5σ. These esul s a e compa ed o he ones ob ained by PHENIX in pp, Cu–Cu
and Au–Au collisions a √sNN = 0.2 TeV. The e is no e idence o a dec easing end,
con a y o wha is obse ed in he ALICE measu emen .
In o de o compa e he e olu ion o hp2
iA–Aa di e en ene gies, one can o m he
a iable AA de ined as
AA =hp2
iA–A
hp2
ipp
.(8.2)
This a iable was measu ed o e he wide ange o ene gies and colliding sys ems co e ed
by NA50 and PHENIX expe imen s. The compa ison wi h he ALICE esul s is done in
– 19 –
JHEP05(2016)179
p ange y ange Cen ali y hp i ± s a . ±sys . hp2
i ± s a . ±sys .
( GeV/c) ( GeV/c) ( GeV2/c2)
Pb–Pb √sNN = 2.76 TeV
0–8 2.5–4 0–20% 1.92 ±0.02 ±0.03 5.17 ±0.12 ±0.16
0–8 2.5–4 20–40% 2.04 ±0.02 ±0.04 5.83 ±0.11 ±0.17
0.5–8 2.5–4 40–90% 2.22 ±0.03 ±0.04 6.72 ±0.14 ±0.20
pp √s= 2.76 TeV [57]
0–8 2.5–4 n/a 2.28 ±0.04 ±0.03 7.06 ±0.26 ±0.13
pp √s= 0.2 TeV [55]
0–7 1.2–2.2 n/a 1.61 ±0.01 ±0.012 3.60 ±0.06 ±0.07
Au–Au √sNN = 0.2 TeV [21]
0–5 1.2–2.2 0–20% 1.94 ±0.18 5.79 ±1.33
0–6 1.2–2.2 20–40% 1.87 ±0.07 4.78 ±0.34
0–6 1.2–2.2 40–60% 1.74 ±0.04 4.19 ±0.27
0–6 1.2–2.2 60–92% 1.61 ±0.05 3.87 ±0.27
Cu–Cu √sNN = 0.2 TeV [58]
0–5 1.2–2.2 0–20% 1.68 ±0.04 ±0.02 3.79 ±0.25 ±0.11
0–5 1.2–2.2 20–40% 1.69 ±0.04 ±0.02 3.71 ±0.18 ±0.08
0–5 1.2–2.2 40–60% 1.68 ±0.05 ±0.02 3.91 ±0.30 ±0.11
0–5 1.2–2.2 60–94% 1.66 ±0.10 ±0.04 4.13 ±0.64 ±0.24
Table 3. Values o hp iand hp2
ia a ious ene gies and colliding sys ems. The s a is ical and
sys ema ic unce ain ies a e quo ed sepa a ely, excep o PHENIX measu emen s in Au–Au col-
lisions whe e he quad a ic sum is gi en. I he measu emen is no a ailable o no used in he
ange 0 < p <8 GeV/c, he i unc ion is ex apola ed down o 0 and up o 8 GeV/c o compu e
hp iand hp2
i.
〉
pa
N〈
1 10 2
10
(GeV/c)〉
T
p〈
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8 <4y, 2.5<
-
µ
+
µ → ψALICE inclusi e J/
= 2.76 TeV
NN
s
Pb-Pb
= 2.76 TeVspp
|<2.2y, 1.2<|
-
µ
+
µ → ψPHENIX inclusi e J/
= 0.2 TeV
NN
s
Au-Au
= 0.2 TeV
NN
sCu-Cu
= 0.2 TeVspp
〉
pa
N〈
1 10 2
10
AA
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
<4y, 2.5<
-
µ
+
µ → ψALICE inclusi e J/
= 2.76 TeV, global sys . = 4%
NN
sPb-Pb
|<2.2y, 1.2<|
-
µ
+
µ → ψPHENIX inclusi e J/
= 0.2 TeV, global sys . = 3%
NN
s
Au-Au and Cu-Cu
<1y, 0<
-
µ
+
µ → ψNA50 inclusi e J/
= 0.017 TeV, global sys . = 3%
NN
s
Pb-Pb
T anspo model calcula ions
TM1 ALICE
TM2 ALICE RHIC SPS
Figu e 6. Mean ans e se momen um hp imeasu ed by ALICE [37,57] and PHENIX [21,55,58]
as a unc ion o he numbe o pa icipan nucleons (le ). AA measu ed by NA50 [59], PHENIX
and ALICE and compa ed o model calcula ions [13,60], as a unc ion o he numbe o pa icipan
nucleons ( igh ).
– 20 –

JHEP05(2016)179
igu e 6( igh side). A e y di e en hNpa idependence is seen, especially when compa ing
Pb–Pb collisions a he SPS and he LHC. A he SPS ene gy o √sNN = 0.017 TeV [59],
he inc ease o he J/ψ hp2
iwi h he cen ali y o he collision was a ibu ed o he C onin
e ec [61], in e p e ed as an ex a p kick due o mul iple sca e ings o he ini ial pa ons
p oducing he J/ψ. A he LHC, a clea dec ease o AA is obse ed as a unc ion o
hNpa i. This beha io could be ela ed o he onse o ecombina ion phenomena and o
he he maliza ion o cha m qua ks. Theo e ical calcula ions [13,60], based on anspo
models (desc ibed in he nex sec ion) a e able o ep oduce he AA a SPS, RHIC and
LHC ene gies. They co ela e he speci ic dependence o AA on collision cen ali y wi h
he inc eased impo ance o ecombina ion e ec s in he J/ψ p oduc ion mechanism a
he LHC.
9 Nuclea modi ica ion ac o
Some o he RAA esul s p esen ed he e we e al eady published in [27] and a e shown again
in his sec ion, whe e hey a e compa ed wi h model calcula ions and wi h esul s om
p e ious expe imen s. They include he cen ali y dependence o RAA ( igu e 7), he p
dependence o RAA o he ull cen ali y ange 0–90% and o he cen ali y class 0–20%
( igu e 9 op ow) and he apidi y dependence o RAA ( igu e 10). The new esul s shown
in his sec ion include he cen ali y dependence o RAA o h ee p in e als ( igu e 8)
and he p dependence o RAA o he cen ali y classes 20–40% and 40–90% ( igu e 9
bo om ow). These new esul s we e ob ained using a sligh ly di e en igge selec ion,
as explained in sec ion 3. The consis ency o he esul s ob ained wi h he wo selec ions
was e i ied.
9.1 Cen ali y dependence o RAA
Ou measu emen o he inclusi e J/ψ RAA a √sNN = 2.76 TeV in he ange 2.5< y < 4
and p <8 GeV/c is shown in igu e 7as a unc ion o hNpa i. S a is ical (unco ela ed
sys ema ic) unce ain ies a e ep esen ed by e ical e o ba s (open boxes). A global
co ela ed sys ema ic unce ain y a ec ing all he alues by he same amoun is quo ed
in he legend. The same con en ion is applied in he ollowing igu es, unless o he wise
speci ied. The J/ψ RAA in he cen ali y class 0–90% (co esponding o hNpa i ∼ 124,
see able 1) is R0–90%
AA = 0.58 ±0.01(s a .)±0.09(sys .), indica ing a clea J/ψ supp ession.
This supp ession is signi ican ly less p onounced han ha obse ed a lowe ene gy in
PHENIX in a simila kinema ic ange, as p e iously discussed in [26,27]. Fo hNpa i
la ge han 70, co esponding o he 50% mos cen al Pb–Pb collisions, he J/ψ RAA is
consis en wi h being cons an , wi hin unce ain ies. Such beha io was no obse ed in
hea y ion collisions a lowe ene gies (SPS, RHIC), whe e RAA is con inuously dec easing
as a unc ion o cen ali y.
The impac o non-p omp J/ψ on he inclusi e RAA analysis was s udied. The RAA
o p omp J/ψ is es ima ed (see eq. (4.3)) o be abou 7% la ge han he inclusi e J/ψ
RAA i he beau y componen is ully supp essed. In he o he ex eme case, whe e he
B-meson p oduc ion is no a ec ed by he medium and scales wi h he numbe o bina y
– 21 –
JHEP05(2016)179
〉
pa
N〈
0 50 100 150 200 250 300 350
AA
R
0
0.2
0.4
0.6
0.8
1
1.2
1.4
=0.2 TeV
NN
s=2.76 TeV, Au-Au
NN
s, Pb-Pb
-
µ
+
µ → ψInclusi e J/
15%± global sys .= c<8 GeV/
T
p<4, yALICE, 2.5<
9.2%± global sys .= c>0 GeV/
T
p|<2.2, yPHENIX, 1.2<|
〉
pa
N〈
0 50 100 150 200 250 300 350
AA
R
0
0.2
0.4
0.6
0.8
1
1.2
1.4
= 2.76 TeV
NN
s, Pb-Pb
-
µ
+
µ → ψInclusi e J/
15%± global sys .= c<8 GeV/
T
p<4, yALICE, 2.5<
SHM
TM1
TM2
CIM
Figu e 7. Inclusi e J/ψ RAA as a unc ion o he numbe o pa icipan nucleons measu ed in
Pb–Pb collisions a √sNN = 2.76 TeV [27], compa ed o he PHENIX measu emen in Au–Au
collisions a √sNN = 0.2 TeV [21] (le ) and o heo e ical models [13,60,62,63], which all include
a J/ψ egene a ion componen ( igh ). The b acke s shown in he h ee mos pe iphe al cen ali y
classes on he igh igu e quan i y he possible ange o a ia ion o he had onic J/ψ RAA o wo
ex eme hypo heses on he pho o-p oduc ion con amina ion in he inclusi e measu emen , see ex
o de ails.
collisions, i.e. Rnon-p omp
AA = 1, he RAA o p omp J/ψ would be abou 6% smalle in
cen al collisions and abou 1% smalle in pe iphe al collisions. The excess in he inclusi e
J/ψ yield obse ed a e y low p [40] also in luences he RAA in he mos pe iphe al
collisions. A la ge ac ion o his con ibu ion (abou 75% as explained in sec ion 4) can
be emo ed by selec ing J/ψ wi h a p highe han 0.3 GeV/c. Assuming ha he had onic
J/ψ RAA in he anges 0 < p <0.3 GeV/c and 0.3< p <8 GeV/c a e he same, i
becomes possible o es ima e he impac o he J/ψ pho o-p oduc ion on he inclusi e
RAA. In he cen ali y classes 60–70%, 70–80% and 80–90%, he had onic J/ψ RAA would
be abou 5%, 11% and 25% lowe , espec i ely. Ex eme hypo heses we e made o de ine
uppe and lowe limi s, ep esen ed wi h b acke s on he igu es 7,8and 9. The uppe
limi calcula ion assumes no J/ψ om pho o-p oduc ion hus he inclusi e measu emen
only con ains had onic p oduc ion. The lowe limi assumes ha i) all J/ψ p oduced wi h
ap smalle han 0.3 GeV/c o igina e om pho o-p oduc ion and ii) he e iciency o he
0.3 GeV/c p selec ion is educed om 75% o 60% (co esponding o an inc ease by a
ac o wo o he J/ψ pho o-p oduc ion abo e 0.3 GeV/c).
The compa ison wi h heo e ical models, shown on he igh -hand side o igu e 7,
helps in he in e p e a ion o he la ge di e ence obse ed be ween he PHENIX and he
ALICE esul s.
The S a is ical Had oniza ion Model (SHM) [62] assumes decon inemen and he mal
equilib a ion o he bulk o he c¯c pai s. Cha monium p oduc ion occu s a he phase
bounda y ia he s a is ical had oniza ion o cha m qua ks. The p edic ion is gi en
o wo alues o he cha m c oss sec ion dσc¯c/dy= 0.15 and 0.25 mb a o wa d
apidi y. These alues a e de i ed om he measu ed cha m c oss sec ion in pp collisions
a √s= 2.76 and 7 TeV [15] b acke ing he expec a ion o gluon shadowing in he
Pb-nucleus be ween 0.6 and 1.0. P oduc ion o non-p omp J/ψ om decays o B-mesons
is no conside ed.
– 22 –
JHEP05(2016)179
The wo anspo models om Zhao (TM1) [13] and Zhou (TM2) [60] mainly di e
in he a e equa ion con olling he J/ψ dissocia ion and egene a ion. In TM1, shadowing
is implemen ed ia a simple pa ame iza ion, leading o a 30% supp ession in he mos
cen al Pb–Pb collisions. The cha m c oss sec ion is assumed o be dσc¯c/dy≈0.5 mb a
o wa d apidi y, he ac ion o J/ψ om beau y had ons o be 10% and no b-quenching
is in oduced in he calcula ion. This model is p esen ed as a band connec ing he esul s
ob ained wi h (lowe limi ) and wi hou (uppe limi ) shadowing and is in e p e ed by he
au ho s as he unce ain y o he p edic ion. In TM2, he shadowing is gi en by he EKS98
pa ame iza ion [64]. The cha m c oss sec ion is aken in he ange dσc¯c/dy≈0.4–0.5 mb
a o wa d apidi y; he calcula ions o hese wo alues p o ide he lowe and uppe limi s
o he band displayed in he igu e. The ac ion o J/ψ om beau y had ons is assumed
o be 10% wi h a b-quenching o 0.8, inc eased o 0.4 o p abo e 5 GeV/c.
The Como e In e ac ion Model (CIM) [63] implemen s shadowing, in e ac ion wi h a
co-mo ing dense pa onic medium and ecombina ion e ec s. The shadowing is calcula ed
wi hin he Glaube -G ibo heo y making use o he gene alized Schwimme model o
mul iple sca e ing. The J/ψ dissocia ion c oss sec ion due o como e in e ac ion is aken
as σco = 0.65 mb om low-ene gy da a. Recombina ion e ec s a e included by adding a
gain e m p opo ional o σco and o he numbe o c and ¯c qua ks, hus no addi ional
pa ame e is added o he model. The cha m c oss sec ion dσc¯c/dya o wa d apidi y is
aken in he ange 0.4 o 0.6 mb, which gi es espec i ely he lowe and uppe limi s o he
calcula ion. P oduc ion o non-p omp J/ψ is no conside ed.
To ma ch ou J/ψ RAA esul s, all models abo e need o include in hei calcula ion a
sizeable J/ψ p oduc ion om decon ined c and ¯c qua ks.
A di e en es o hese models was ca ied ou by s udying he J/ψ RAA cen al-
i y dependence in p in e als. Figu e 8displays he measu emen o he inclusi e J/ψ
RAA as a unc ion o he numbe o pa icipan nucleons measu ed in Pb–Pb collisions a
√sNN = 2.76 TeV o he h ee p anges 0–2, 2–5 and 5–8 GeV/c. The unco ela ed sys-
ema ic unce ain ies shown a each poin we e sepa a ed in o unco ela ed as a unc ion
o cen ali y (open boxes) and ully co ela ed as a unc ion o cen ali y bu unco ela ed
as a unc ion o p (shaded a eas). Fo hNpa i&150, he low p J/ψ RAA is signi i-
can ly la ge han he mid and high p ones. In he mos cen al bin, he RAA alues
co esponding o he lowes and he highes p a e sepa a ed by 3.9σ. Fo hNpa i.150,
he cen ali y dependence exhibi s simila ends o he 2–5 and 5–8 GeV/c anges, while
he mos pe iphe al (hNpa i ∼ 20) RAA measu emen in he low p (0–2 GeV/c) ange
appea s o de ia e om he o he s. Howe e , he J/ψ yield excess obse ed a e y low
p may ha e a sizable e ec in he 0–2 GeV/c in e al. In he cen ali y classes 40–50%,
50–60% and 60–90%, based on he same assump ions made o he 0 < p <8 GeV/c
case, he had onic J/ψ RAA would be abou 5%, 6% and 18% lowe , espec i ely. Due
o he inc ease o he non-p omp J/ψ componen a la ge p , he di e ence be ween he
measu ed inclusi e J/ψ RAA and he p omp J/ψ RAA inc eases wi h p . I he beau y
con ibu ion is ully (no ) supp essed, RAA o p omp J/ψ is es ima ed o be 6%, 8% and
11% la ge (0–3%, 3–10% and 7–30% smalle , depending on cen ali y) o he p anges
0–2, 2–5 and 5–8 GeV/c, espec i ely.
– 23 –
JHEP05(2016)179
〉
pa
N〈
0 50 100 150 200 250 300 350
AA
R
0
0.2
0.4
0.6
0.8
1
1.2
1.4
= 2.76 TeV
NN
s<4, ALICE Pb-Pb y, 2.5<
-
µ
+
µ → ψInclusi e J/
c < 2 GeV/
T
p c < 5 GeV/
T
p2 < c < 8 GeV/
T
p5 <
7%±global sys .=
〉
pa
N〈
0 50 100 150 200 250 300 350
AA
R
0
0.2
0.4
0.6
0.8
1
1.2
1.4
= 2.76 TeV
NN
s<4, ALICE Pb-Pb y, 2.5<
-
µ
+
µ → ψInclusi e J/
c < 2 GeV/
T
p c < 8 GeV/
T
p5 < 7%±global sys .=
CIM
c < 2 GeV/
T
pc < 8 GeV/
T
p5 <
〉
pa
N〈
0 50 100 150 200 250 300 350
AA
R
0
0.2
0.4
0.6
0.8
1
1.2
1.4
= 2.76 TeV
NN
s<4, ALICE Pb-Pb y, 2.5<
-
µ
+
µ → ψInclusi e J/
c < 2 GeV/
T
p c < 8 GeV/
T
p5 < 7%±global sys .=
TM1
c < 2 GeV/
T
pc < 8 GeV/
T
p5 <
〉
pa
N〈
0 50 100 150 200 250 300 350
AA
R
0
0.2
0.4
0.6
0.8
1
1.2
1.4
= 2.76 TeV
NN
s<4, ALICE Pb-Pb y, 2.5<
-
µ
+
µ → ψInclusi e J/
c < 2 GeV/
T
p c < 8 GeV/
T
p5 < 7%±global sys .=
TM2
c < 2 GeV/
T
p c < 8 GeV/
T
p5 <
Figu e 8. Inclusi e J/ψ RAA as a unc ion o he numbe o pa icipan nucleons measu ed in
Pb–Pb collisions a √sNN = 2.76 TeV o h ee p anges (0–2, 2–5 and 5–8 GeV/c) and compa isons
o he lowes and highes p ange o he anspo and o he como e in e ac ion models [13,60,63].
The b acke s quan i y he possible ange o a ia ion o he had onic J/ψ RAA o wo ex eme
hypo heses on he pho o-p oduc ion con amina ion in he inclusi e measu emen .
Calcula ions om he anspo models and he como e in e ac ion model a e plo ed
on op o he esul s shown in igu e 8. Fo he mos pe iphe al collisions (hNpa i.100),
he models canno co ec ly ep oduce he RAA cen ali y dependence o bo h he low
and high p anges. Fo he mos cen al collisions (hNpa i&100), he RAA cen ali y
dependence o high p J/ψ is easonably ep oduced by all models. Conce ning he low
p ange in he mos cen al e en s, he measu emen is compa ible wi h he uppe side
o he heo e ical unce ain y band om he CIM and TM2 models. Fo hese models, i
co esponds o he highes alue o dσc¯c/dy, 0.6 and 0.5 mb espec i ely.
9.2 T ans e se momen um dependence o RAA
The p dependence o he inclusi e J/ψ RAA in he apidi y ange 2.5< y < 4 is shown
in igu e 9 o he ull cen ali y ange 0–90% and o h ee cen ali y classes 0–20% [27],
20–40% and 40–90%. In igu e 9 op le co ne , he inclusi e J/ψ RAA in he cen ali y class
0–90% shows a dec ease o abou 50% om low o high p . A low p , he measu emen is
close o 0.8 showing e y li le supp ession. A high p , ou RAA alue is simila o ha
o CMS [25]. They measu ed, in he di e en apidi y ange 1.6<|y|<2.4, an inclusi e
– 24 –
JHEP05(2016)179
nology o China (MSTC); Minis y o Educa ion and You h o he Czech Republic; Danish
Na u al Science Resea ch Council, he Ca lsbe g Founda ion and he Danish Na ional Re-
sea ch Founda ion; The Eu opean Resea ch Council unde he Eu opean Communi y’s
Se en h F amewo k P og amme; Helsinki Ins i u e o Physics and he Academy o Fin-
land; F ench CNRS-IN2P3, he ‘Region Pays de Loi e’, ‘Region Alsace’, ‘Region Au e gne’
and CEA, F ance; Ge man Bundesminis e ium u Bildung, Wissenscha , Fo schung und
Technologie (BMBF) and he Helmhol z Associa ion; Gene al Sec e a ia o Resea ch and
Technology, Minis y o De elopmen , G eece; Hunga ian O szagos Tudomanyos Ku a asi
Alappg ammok (OTKA) and Na ional O ice o Resea ch and Technology (NKTH); De-
pa men o A omic Ene gy and Depa men o Science and Technology o he Go e nmen
o India; Is i u o Nazionale di Fisica Nuclea e (INFN) and Cen o Fe mi — Museo S o ico
della Fisica e Cen o S udi e Rice che “En ico Fe mi”, I aly; MEXT G an -in-Aid o
Specially P omo ed Resea ch, Japan; Join Ins i u e o Nuclea Resea ch, Dubna; Na-
ional Resea ch Founda ion o Ko ea (NRF); Consejo Nacional de Cienca y Tecnologia
(CONACYT), Di eccion Gene al de Asun os del Pe sonal Academico (DGAPA), M´exico,
Ame ique La ine Fo ma ion academique — Eu opean Commission (ALFA-EC) and he
EPLANET P og am (Eu opean Pa icle Physics La in Ame ican Ne wo k); S ich ing oo
Fundamen eel Onde zoek de Ma e ie (FOM) and he Nede landse O ganisa ie oo We en-
schappelijk Onde zoek (NWO), Ne he lands; Resea ch Council o No way (NFR); Na ional
Science Cen e, Poland; Minis y o Na ional Educa ion/Ins i u e o A omic Physics and
Consiliul Na ¸ional al Ce ce ˘a ii S¸ iin ¸i ice — Execu i e Agency o Highe Educa ion Re-
sea ch De elopmen and Inno a ion Funding (CNCS-UEFISCDI) — Romania; Minis y
o Educa ion and Science o Russian Fede a ion, Russian Academy o Sciences, Russian
Fede al Agency o A omic Ene gy, Russian Fede al Agency o Science and Inno a ions
and The Russian Founda ion o Basic Resea ch; Minis y o Educa ion o Slo akia; De-
pa men o Science and Technology, Sou h A ica; Cen o de In es igaciones Ene ge icas,
Medioambien ales y Tecnologicas (CIEMAT), E-In as uc u e sha ed be ween Eu ope and
La in Ame ica (EELA), Minis e io de Econom´ıa y Compe i i idad (MINECO) o Spain,
Xun a de Galicia (Conselle ´ıa de Educaci´on), Cen o de Aplicaciones Tecnol´ogicas y De-
sa ollo Nuclea (CEADEN), Cubaene g´ıa, Cuba, and IAEA (In e na ional A omic En-
e gy Agency); Swedish Resea ch Council (VR) and Knu & Alice Wallenbe g Founda ion
(KAW); Uk aine Minis y o Educa ion and Science; Uni ed Kingdom Science and Tech-
nology Facili ies Council (STFC); The Uni ed S a es Depa men o Ene gy, he Uni ed
S a es Na ional Science Founda ion, he S a e o Texas, and he S a e o Ohio; Minis y
o Science, Educa ion and Spo s o C oa ia and Uni y h ough Knowledge Fund, C oa ia;
Council o Scien i ic and Indus ial Resea ch (CSIR), New Delhi, India.
– 31 –

JHEP05(2016)179
A Da a ables
This appendix p o ides all he nume ical alues ob ained in his analysis.
The inclusi e J/ψ di e en ial p yields in Pb–Pb in cen ali y classes a e gi en in
able 4. Tables 5 o 8p esen he inclusi e J/ψ RAA and associa ed Pb–Pb yields as a
unc ion o cen ali y o 2.5< y < 4.0 and ou p anges, p <8 GeV/c,p ≤2 GeV/c,
2< p <5 GeV/c and 5 < p <8 GeV/c. Tables 9 o 13 show he p dependence o he
inclusi e J/ψ RAA and associa ed Pb–Pb yields o he cen ali y classes 0–20%, 20–40%,
0–40%, 40–90% and 0–90%. Table 14 shows he ydependence o he inclusi e J/ψ RAA
and associa ed Pb–Pb yields o he cen ali y class 0–90% in he p ange p <8 GeV/c.
Then, he inclusi e J/ψ RAA esul s wi h a low p cu a 0.3 GeV/c a e p esen ed. The
e e ence pp c oss sec ion needed o build he RAA was ex ac ed wi h he me hod desc ibed
in [40]. The inclusi e J/ψ RAA cen ali y dependence o 2.5< y < 4 in he p anges
0.3< p <8 GeV/c and 0.3< p <2 GeV/c is shown in able 15. The inclusi e J/ψ
RAA in he p ange 0.3< p <1 GeV/c o 2.5< y < 4 in ou cen ali y classes 0–90%,
0–20%, 20–40% and 40–90% is gi en in able 16. Finally, able 17 p esen s he inclusi e
[ψ(2S)/J/ψ]Pb–Pb and [ψ(2S)/J/ψ]Pb–Pb /[ψ(2S)/J/ψ]pp a ios as a unc ion o cen ali y
o he p in e als p <3 GeV/c and 3 < p <8 GeV/c.
d2YJ/ψ/dydp ( GeV/c)−1×103
p ( GeV/c) 0–20% 20–40% 40–90%
0.0–0.5 3.253 ±0.386 ±0.446 1.366 ±0.081 ±0.165 0.257 ±0.017 ±0.031
0.5–1.0 8.012 ±0.487 ±1.087 2.571 ±0.199 ±0.310 0.346 ±0.024 ±0.042
1.0–1.5 9.909 ±0.603 ±1.149 3.494 ±0.255 ±0.388 0.533 ±0.030 ±0.061
1.5–2.0 8.193 ±0.505 ±0.907 2.907 ±0.194 ±0.320 0.493 ±0.037 ±0.053
2.0–2.5 6.342 ±0.401 ±0.701 2.371 ±0.164 ±0.260 0.441 ±0.034 ±0.049
2.5–3.0 4.759 ±0.316 ±0.542 1.997 ±0.134 ±0.227 0.270 ±0.020 ±0.029
3.0–3.5 2.735 ±0.183 ±0.290 1.313 ±0.087 ±0.151 0.222 ±0.016 ±0.023
3.5–4.0 1.876 ±0.134 ±0.201 0.874 ±0.068 ±0.092 0.174 ±0.013 ±0.018
4.0–4.5 1.075 ±0.098 ±0.109 0.483 ±0.037 ±0.048 0.108 ±0.009 ±0.011
4.5–5.0 0.731 ±0.069 ±0.073 0.339 ±0.030 ±0.033 0.076 ±0.007 ±0.007
5.0–5.5 0.453 ±0.047 ±0.045 0.263 ±0.023 ±0.026 0.042 ±0.005 ±0.004
5.5–6.0 0.345 ±0.039 ±0.046 0.132 ±0.016 ±0.014 0.028 ±0.004 ±0.003
6.0–8.0 0.099 ±0.009 ±0.010 0.068 ±0.005 ±0.007 0.012 ±0.001 ±0.001
Table 4. Inclusi e J/ψ yields (as de ined by eq. (4.1)) in p in e als o he 0–20%, 20–40% and
40–90% mos cen al Pb–Pb collisions. The apidi y ange is 2.5< y < 4. S a is ical and sys ema ic
unce ain ies a e also epo ed as d2YJ/ψ/dydp ±s a is ical unce ain y±sys ema ic unce ain y. A
global sys ema ic unce ain y o 4% a ec s all he alues. A 2%, 1% and 2% sys ema ic unce ain y,
independen o p , a ec s he cen ali y classes 0–20%, 20–40% and 40–90%, espec i ely.
– 32 –
JHEP05(2016)179
Cen ali y RAA ±(s a .)±(sys .) [27]YJ/ψ ±(s a .)±(sys .)×103
0–10% 0.557 ±0.019 ±0.024 43.095 ±1.454 ±1.049
10–20% 0.573 ±0.020 ±0.022 27.212 ±0.979 ±0.501
20–30% 0.598 ±0.022 ±0.020 17.409 ±0.638 ±0.188
30–40% 0.577 ±0.024 ±0.025 9.671 ±0.406 ±0.211
40–50% 0.609 ±0.028 ±0.030 5.413 ±0.247 ±0.041
50–60% 0.725 ±0.036 ±0.043 3.246 ±0.160 ±0.050
60–70% 0.839 ±0.041 ±0.058 1.677 ±0.083 ±0.024
70–80% 0.849 ±0.063 ±0.068 0.701 ±0.051 ±0.014
80–90% 1.094 ±0.106 ±0.104 0.362 ±0.033 ±0.008
Table 5. Inclusi e J/ψ RAA and Pb–Pb yields as a unc ion o cen ali y, o p <8 GeV/c and
2.5< y < 4.0. S a is ical and sys ema ic unce ain ies a e also epo ed. A global sys ema ic
unce ain y o 15% (12%) a ec s all he RAA (yields) alues.
Cen ali y RAA ±(s a .)±(sys .)YJ/ψ ±(s a .)±(sys .)×103
0–10% 0.732 ±0.034 ±0.041 27.932 ±1.302 ±1.282
10–20% 0.733 ±0.035 ±0.028 17.159 ±0.824 ±0.383
20–30% 0.715 ±0.038 ±0.024 10.113 ±0.541 ±0.115
30–40% 0.678 ±0.040 ±0.033 5.516 ±0.322 ±0.182
40–50% 0.641 ±0.044 ±0.032 2.789 ±0.190 ±0.064
50–60% 0.839 ±0.048 ±0.056 1.799 ±0.103 ±0.070
60–90% 1.104 ±0.064 ±0.078 0.559 ±0.032 ±0.016
Table 6. Inclusi e J/ψ RAA and Pb–Pb yields as a unc ion o cen ali y, o p <2 GeV/c and
2.5< y < 4.0. S a is ical and sys ema ic unce ain ies a e also epo ed. A global sys ema ic
unce ain y o 15% (12%) a ec s all he RAA (yields) alues.
Cen ali y RAA ±(s a .)±(sys .)YJ/ψ ±(s a .)±(sys .)×103
0–10% 0.425 ±0.019 ±0.017 15.540 ±0.681 ±0.379
10–20% 0.461 ±0.019 ±0.016 10.336 ±0.431 ±0.168
20–30% 0.529 ±0.022 ±0.018 7.164 ±0.293 ±0.106
30–40% 0.498 ±0.025 ±0.027 3.879 ±0.194 ±0.153
40–50% 0.595 ±0.030 ±0.029 2.481 ±0.126 ±0.049
50–60% 0.675 ±0.042 ±0.041 1.386 ±0.085 ±0.037
60–90% 0.722 ±0.044 ±0.050 0.350 ±0.021 ±0.009
Table 7. Inclusi e J/ψ RAA and Pb–Pb yields as a unc ion o cen ali y, o 2 < p <5 GeV/c
and 2.5< y < 4.0. S a is ical and sys ema ic unce ain ies a e also epo ed. A global sys ema ic
unce ain y o 14% (11%) a ec s all he RAA (yields) alues.
– 33 –
JHEP05(2016)179
Cen ali y RAA ±(s a .)±(sys .)YJ/ψ ±(s a .)±(sys .)×103
0–10% 0.280 ±0.021 ±0.011 1.093 ±0.081 ±0.027
10–20% 0.282 ±0.027 ±0.011 0.677 ±0.064 ±0.016
20–30% 0.410 ±0.029 ±0.013 0.594 ±0.042 ±0.006
30–40% 0.540 ±0.039 ±0.024 0.449 ±0.033 ±0.012
40–50% 0.529 ±0.053 ±0.031 0.236 ±0.024 ±0.009
50–60% 0.587 ±0.073 ±0.036 0.129 ±0.016 ±0.004
60–90% 0.644 ±0.083 ±0.047 0.033 ±0.004 ±0.001
Table 8. Inclusi e J/ψ RAA and Pb–Pb yields as a unc ion o cen ali y, o 5 < p <8 GeV/c
and 2.5< y < 4.0. S a is ical and sys ema ic unce ain ies a e also epo ed. A global sys ema ic
unce ain y o 18% (10%) a ec s all he RAA (yields) alues.
p ( GeV/c)RAA ±(s a .)±(sys .) [27] d2YJ/ψ/dydp ±(s a .)±(sys .)( GeV/c)−1×103
0–1 0.803 ±0.084 ±0.113 5.771 ±0.345 ±0.748
1–2 0.690 ±0.052 ±0.084 9.134 ±0.411 ±0.987
2–3 0.505 ±0.042 ±0.062 5.539 ±0.284 ±0.604
3–4 0.381 ±0.037 ±0.046 2.305 ±0.116 ±0.247
4–5 0.355 ±0.052 ±0.041 0.905 ±0.068 ±0.090
5–6 0.282 ±0.048 ±0.032 0.388 ±0.030 ±0.038
6–8 0.279 ±0.064 ±0.032 0.100 ±0.009 ±0.010
Table 9. Inclusi e J/ψ RAA and Pb–Pb yields as a unc ion o p o he 0–20% cen ali y class
and 2.5< y < 4.0. S a is ical and sys ema ic unce ain ies a e also epo ed. A global sys ema ic
unce ain y o 8% (4%) a ec s all he RAA (yields) alues.
p ( GeV/c)RAA ±(s a .)±(sys .) d2YJ/ψ/dydp ±(s a .)±(sys .)( GeV/c)−1×103
0–1 0.733 ±0.080 ±0.097 1.909 ±0.128 ±0.229
1–2 0.660 ±0.051 ±0.080 3.189 ±0.154 ±0.344
2–3 0.543 ±0.044 ±0.067 2.167 ±0.106 ±0.238
3–4 0.493 ±0.048 ±0.060 1.084 ±0.055 ±0.117
4–5 0.444 ±0.063 ±0.051 0.411 ±0.027 ±0.040
5–6 0.399 ±0.067 ±0.045 0.200 ±0.014 ±0.020
6–8 0.523 ±0.116 ±0.059 0.068 ±0.005 ±0.007
Table 10. Inclusi e J/ψ RAA and Pb–Pb yields as a unc ion o p o he 20–40% cen ali y class
and 2.5< y < 4.0. S a is ical and sys ema ic unce ain ies a e also epo ed. A global sys ema ic
unce ain y o 8% (4%) a ec s all he RAA (yields) alues.
– 34 –
JHEP05(2016)179
p ( GeV/c)RAA ±(s a .)±(sys .) d2YJ/ψ/dydp ±(s a .)±(sys .)( GeV/c)−1×103
0–1 0.767 ±0.074 ±0.105 3.754 ±0.163 ±0.472
1–2 0.672 ±0.046 ±0.082 6.103 ±0.212 ±0.662
2–3 0.515 ±0.038 ±0.064 3.865 ±0.134 ±0.428
3–4 0.411 ±0.038 ±0.049 1.698 ±0.063 ±0.178
4–5 0.376 ±0.051 ±0.043 0.655 ±0.033 ±0.064
5–6 0.315 ±0.050 ±0.036 0.296 ±0.016 ±0.029
6–8 0.340 ±0.075 ±0.038 0.083 ±0.005 ±0.008
Table 11. Inclusi e J/ψ RAA and Pb–Pb yields as a unc ion o p o he 0–40% cen ali y class
and 2.5< y < 4.0. S a is ical and sys ema ic unce ain ies a e also epo ed. A global sys ema ic
unce ain y o 8% (4%) a ec s all he RAA (yields) alues.
p ( GeV/c)RAA ±(s a .)±(sys .) d2YJ/ψ/dydp ±(s a .)±(sys .)( GeV/c)−1×103
0–1 0.815 ±0.081 ±0.107 0.305 ±0.015 ±0.036
1–2 0.732 ±0.059 ±0.090 0.508 ±0.028 ±0.055
2–3 0.617 ±0.053 ±0.076 0.354 ±0.020 ±0.038
3–4 0.627 ±0.062 ±0.074 0.198 ±0.010 ±0.020
4–5 0.693 ±0.097 ±0.079 0.092 ±0.006 ±0.009
5–6 0.489 ±0.087 ±0.055 0.035 ±0.003 ±0.003
6–8 0.646 ±0.150 ±0.072 0.012 ±0.001 ±0.001
Table 12. Inclusi e J/ψ RAA and Pb–Pb yields as a unc ion o p o he 40–90% cen ali y class
and 2.5< y < 4.0. S a is ical and sys ema ic unce ain ies a e also epo ed. A global sys ema ic
unce ain y o 9% (4%) a ec s all he RAA (yields) alues.
p ( GeV/c)RAA ±(s a .)±(sys .) [27] d2YJ/ψ/dydp ±(s a .)±(sys .)( GeV/c)−1×103
0–1 0.779 ±0.076 ±0.106 1.857 ±0.081 ±0.230
1–2 0.677 ±0.047 ±0.083 2.993 ±0.104 ±0.323
2–3 0.519 ±0.038 ±0.064 1.896 ±0.064 ±0.206
3–4 0.425 ±0.039 ±0.051 0.855 ±0.029 ±0.089
4–5 0.405 ±0.054 ±0.047 0.343 ±0.015 ±0.033
5–6 0.322 ±0.052 ±0.036 0.147 ±0.007 ±0.015
6–8 0.364 ±0.079 ±0.041 0.043 ±0.002 ±0.004
Table 13. Inclusi e J/ψ RAA and Pb–Pb yields as a unc ion o p o he 0–90% cen ali y class
and 2.5< y < 4.0. S a is ical and sys ema ic unce ain ies a e also epo ed. A global sys ema ic
unce ain y o 8% (4%) a ec s all he RAA (yields) alues.
– 35 –
JHEP05(2016)179
y RAA ±(s a .)±(sys .) [27] d2YJ/ψ/dydp ±(s a .)±(sys .)( GeV/c)−1×103
2.50–2.75 0.631 ±0.087 ±0.088 1.509 ±0.114 ±0.191
2.75–3.00 0.747 ±0.068 ±0.097 1.387 ±0.058 ±0.162
3.00–3.25 0.632 ±0.048 ±0.094 1.120 ±0.039 ±0.154
3.25–3.50 0.566 ±0.044 ±0.088 0.891 ±0.032 ±0.130
3.50–3.75 0.467 ±0.041 ±0.070 0.733 ±0.025 ±0.101
3.75–4.00 0.395 ±0.050 ±0.050 0.528 ±0.029 ±0.058
Table 14. Inclusi e J/ψ RAA and Pb–Pb yields as a unc ion o y o he 0–90% cen ali y class
and p <8 GeV/c. S a is ical and sys ema ic unce ain ies a e also epo ed. A global sys ema ic
unce ain y o 8% (4%) a ec s all he RAA (yields) alues.
RAA ±(s a .)±(sys .)
Cen ali y 0.3< p <8 GeV/c 0.3< p <2 GeV/c
0–10% 0.545 ±0.017 ±0.026 0.745 ±0.041 ±0.042
10–20% 0.560 ±0.018 ±0.021 0.736 ±0.036 ±0.028
20–30% 0.594 ±0.020 ±0.020 0.716 ±0.038 ±0.025
30–40% 0.570 ±0.021 ±0.025 0.671 ±0.040 ±0.032
40–50% 0.592 ±0.025 ±0.029 0.619 ±0.045 ±0.032
50–60% 0.715 ±0.033 ±0.044 0.801 ±0.049 ±0.054
60–70% 0.805 ±0.043 ±0.057 )0.959 ±0.057 ±0.067
70–80% 0.778 ±0.062 ±0.064
80–90% 0.887 ±0.097 ±0.088
Table 15. Inclusi e J/ψ RAA as a unc ion o cen ali y, o 0.3< p <8 GeV/c and 0.3< p <
2 GeV/c in he apidi y ange 2.5< y < 4.0. S a is ical and sys ema ic unce ain ies a e also
epo ed. A global sys ema ic unce ain y o 15% a ec s all he RAA alues.
Cen ali y RAA ±(s a .)±(sys .) o 0.3< p <1 GeV/c
0–90% 0.775 ±0.057 ±0.113
0–20% 0.803 ±0.066 ±0.123
20–40% 0.733 ±0.067 ±0.103
40–90% 0.688 ±0.057 ±0.098
Table 16. Inclusi e J/ψ RAA o 2.5< y < 4.0 in he cen ali y classes 0–90%, 0–20%, 20–40% and
40–90% o he lowes p ange when he 0.3 GeV/c p cu is applied. S a is ical and sys ema ic
unce ain ies a e also epo ed. A global sys ema ic unce ain y o 8%, 8%, 8% and 9% a ec he
RAA alues, espec i ely.
– 36 –

JHEP05(2016)179
p ( GeV/c) Cen ali y [ψ(2S)/J/ψ]Pb–Pb [ψ(2S)/J/ψ]Pb–Pb /[ψ(2S)/J/ψ]pp
0–3 0–20% <0.012 (95% CL) <0.65 (95% CL)
0–3 20–40% 0.017 ±0.010 ±0.004 0.86 ±0.51 ±0.23
0–3 40–60% 0.013 ±0.012 ±0.006 0.65 ±0.65 ±0.30
0–3 60–90% 0.029 ±0.012 ±0.004 1.49 ±0.62 ±0.27
3–8 0–20% <0.046 (95% CL) <1.71 (95% CL)
3–8 20–60% <0.033 (95% CL) <1.24 (95% CL)
Table 17. Inclusi e [ψ(2S)/J/ψ]Pb–Pb and [ψ(2S)/J/ψ]Pb–Pb /[ψ(2S)/J/ψ]pp a ios as a unc ion
o cen ali y o wo p in e als. S a is ical and sys ema ic unce ain ies a e epo ed when he
alue is no gi en as an uppe limi .
Open Access. This a icle is dis ibu ed unde he e ms o he C ea i e Commons
A ibu ion License (CC-BY 4.0), which pe mi s any use, dis ibu ion and ep oduc ion in
any medium, p o ided he o iginal au ho (s) and sou ce a e c edi ed.
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JHEP05(2016)179
57 Ins i u e o Suba omic Physics o U ech Uni e si y, U ech , Ne he lands
58 Ins i u e o Theo e ical and Expe imen al Physics, Moscow, Russia
59 Ins i u e o Expe imen al Physics, Slo ak Academy o Sciences, Koˇsice, Slo akia
60 Ins i u e o Physics, Academy o Sciences o he Czech Republic, P ague, Czech Republic
61 Ins i u e o Physics, Bhubaneswa , India
62 Ins i u e o Space Science (ISS), Bucha es , Romania
63 Ins i u o de Ciencias Nuclea es, Uni e sidad Nacional Au ´onoma de M´exico, Mexico Ci y, Mexico
64 Ins i u o de F´ısica, Uni e sidad Nacional Au ´onoma de M´exico, Mexico Ci y, Mexico
65 iThemba LABS, Na ional Resea ch Founda ion, Some se Wes , Sou h A ica
66 Join Ins i u e o Nuclea Resea ch (JINR), Dubna, Russia
67 Konkuk Uni e si y, Seoul, Sou h Ko ea
68 Ko ea Ins i u e o Science and Technology In o ma ion, Daejeon, Sou h Ko ea
69 KTO Ka a ay Uni e si y, Konya, Tu key
70 Labo a oi e de Physique Co pusculai e (LPC), Cle mon Uni e si ´e, Uni e si ´e Blaise Pascal,
CNRS-IN2P3, Cle mon -Fe and, F ance
71 Labo a oi e de Physique Suba omique e de Cosmologie, Uni e si ´e G enoble-Alpes, CNRS-IN2P3,
G enoble, F ance
72 Labo a o i Nazionali di F asca i, INFN, F asca i, I aly
73 Labo a o i Nazionali di Legna o, INFN, Legna o, I aly
74 Law ence Be keley Na ional Labo a o y, Be keley, Cali o nia, Uni ed S a es
75 Law ence Li e mo e Na ional Labo a o y, Li e mo e, Cali o nia, Uni ed S a es
76 Moscow Enginee ing Physics Ins i u e, Moscow, Russia
77 Na ional Cen e o Nuclea S udies, Wa saw, Poland
78 Na ional Ins i u e o Physics and Nuclea Enginee ing, Bucha es , Romania
79 Na ional Ins i u e o Science Educa ion and Resea ch, Bhubaneswa , India
80 Niels Boh Ins i u e, Uni e si y o Copenhagen, Copenhagen, Denma k
81 Nikhe , Na ionaal ins i uu oo suba omai e ysica, Ams e dam, Ne he lands
82 Nuclea Physics G oup, STFC Da esbu y Labo a o y, Da esbu y, Uni ed Kingdom
83 Nuclea Physics Ins i u e, Academy o Sciences o he Czech Republic, ˇ
Reˇz u P ahy, Czech Republic
84 Oak Ridge Na ional Labo a o y, Oak Ridge, Tennessee, Uni ed S a es
85 Pe e sbu g Nuclea Physics Ins i u e, Ga china, Russia
86 Physics Depa men , C eigh on Uni e si y, Omaha, Neb aska, Uni ed S a es
87 Physics Depa men , Panjab Uni e si y, Chandiga h, India
88 Physics Depa men , Uni e si y o A hens, A hens, G eece
89 Physics Depa men , Uni e si y o Cape Town, Cape Town, Sou h A ica
90 Physics Depa men , Uni e si y o Jammu, Jammu, India
91 Physics Depa men , Uni e si y o Rajas han, Jaipu , India
92 Physik Depa men , Technische Uni e si ¨a M¨unchen, Munich, Ge many
93 Physikalisches Ins i u , Rup ech -Ka ls-Uni e si ¨a Heidelbe g, Heidelbe g, Ge many
94 Poli ecnico di To ino, Tu in, I aly
95 Pu due Uni e si y, Wes La aye e, Indiana, Uni ed S a es
96 Pusan Na ional Uni e si y, Pusan, Sou h Ko ea
97 Resea ch Di ision and Ex eMe Ma e Ins i u e EMMI, GSI Helmhol zzen um ¨u
Schwe ionen o schung, Da ms ad , Ge many
98 Rudje Boˇsko i´c Ins i u e, Zag eb, C oa ia
99 Russian Fede al Nuclea Cen e (VNIIEF), Sa o , Russia
100 Russian Resea ch Cen e Ku cha o Ins i u e, Moscow, Russia
101 Saha Ins i u e o Nuclea Physics, Kolka a, India
102 School o Physics and As onomy, Uni e si y o Bi mingham, Bi mingham, Uni ed Kingdom
103 Secci´on F´ısica, Depa amen o de Ciencias, Pon i icia Uni e sidad Ca ´olica del Pe ´u, Lima, Pe u
104 Sezione INFN, Ba i, I aly
105 Sezione INFN, Bologna, I aly
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JHEP05(2016)179
106 Sezione INFN, Caglia i, I aly
107 Sezione INFN, Ca ania, I aly
108 Sezione INFN, Pado a, I aly
109 Sezione INFN, Rome, I aly
110 Sezione INFN, T ies e, I aly
111 Sezione INFN, Tu in, I aly
112 SSC IHEP o NRC Ku cha o ins i u e, P o ino, Russia
113 SUBATECH, Ecole des Mines de Nan es, Uni e si ´e de Nan es, CNRS-IN2P3, Nan es, F ance
114 Su ana ee Uni e si y o Technology, Nakhon Ra chasima, Thailand
115 Technical Uni e si y o Koˇsice, Koˇsice, Slo akia
116 Technical Uni e si y o Spli FESB, Spli , C oa ia
117 The Hen yk Niewodniczanski Ins i u e o Nuclea Physics, Polish Academy o Sciences, C acow,
Poland
118 The Uni e si y o Texas a Aus in, Physics Depa men , Aus in, Texas, U.S.A.
119 Uni e sidad Au ´onoma de Sinaloa, Culiac´an, Mexico
120 Uni e sidade de S˜ao Paulo (USP), S˜ao Paulo, B azil
121 Uni e sidade Es adual de Campinas (UNICAMP), Campinas, B azil
122 Uni e si y o Hous on, Hous on, Texas, Uni ed S a es
123 Uni e si y o Jy ¨askyl¨a, Jy ¨askyl¨a, Finland
124 Uni e si y o Li e pool, Li e pool, Uni ed Kingdom
125 Uni e si y o Tennessee, Knox ille, Tennessee, Uni ed S a es
126 Uni e si y o he Wi wa e s and, Johannesbu g, Sou h A ica
127 Uni e si y o Tokyo, Tokyo, Japan
128 Uni e si y o Tsukuba, Tsukuba, Japan
129 Uni e si y o Zag eb, Zag eb, C oa ia
130 Uni e si ´e de Lyon, Uni e si ´e Lyon 1, CNRS/IN2P3, IPN-Lyon, Villeu banne, F ance
131 V. Fock Ins i u e o Physics, S . Pe e sbu g S a e Uni e si y, S . Pe e sbu g, Russia
132 Va iable Ene gy Cyclo on Cen e, Kolka a, India
133 Vinˇca Ins i u e o Nuclea Sciences, Belg ade, Se bia
134 Wa saw Uni e si y o Technology, Wa saw, Poland
135 Wayne S a e Uni e si y, De oi , Michigan, Uni ed S a es
136 Wigne Resea ch Cen e o Physics, Hunga ian Academy o Sciences, Budapes , Hunga y
137 Yale Uni e si y, New Ha en, Connec icu , Uni ed S a es
138 Yonsei Uni e si y, Seoul, Sou h Ko ea
139 Zen um ¨u Technologie ans e und Telekommunika ion (ZTT), Fachhochschule Wo ms, Wo ms,
Ge many
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