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J/ψ supp ession a o wa d apidi y in Pb–Pb collisions a √sNN = 5.02 TeV
ALICE Collabo a ion
ALICE Collabo a ion. (2017). J/ψ supp ession a o wa d apidi y in Pb–Pb collisions
a √sNN = 5.02 TeV. Physics Le e s B, 766, 212-224.
h ps://doi.o g/10.1016/j.physle b.2016.12.064
2017
Physics Le e s B 766 (2017) 212–224
Con en s lis s a ailable a ScienceDi ec
Physics Le e s B
www.else ie .com/loca e/physle b
J/ψsupp ession a o wa d apidi y in Pb–Pb collisions a
√sNN =5.02 TeV
ALICE Collabo a ion
a i c l e i n o a b s a c
A icle his o y:
Recei ed 29 July 2016
Recei ed in e ised o m 5 Decembe 2016
Accep ed 26 Decembe 2016
A ailable online 10 Janua y 2017
Edi o : L. Rolandi
The inclusi e J/ψp oduc ion has been s udied in Pb–Pb and pp collisions a he cen e-o -mass ene gy
pe nucleon pai √sNN =5.02 TeV, using he ALICE de ec o a he CERN LHC. The J/ψmeson is
econs uc ed, in he cen e-o -mass apidi y in e al 2.5 <y <4and in he ans e se-momen um
ange pT<12 GeV/c, ia i s decay o a muon pai . In his Le e , we p esen esul s on he inclusi e
J/ψc oss sec ion in pp collisions a √s=5.02 TeV and on he nuclea modifica ion ac o RAA. The
la e is p esen ed as a unc ion o he cen ali y o he collision and, o cen al collisions, as a unc ion
o he ans e se momen um pTo he J/ψ. The measu ed RAA alues indica e a supp ession o he
J/ψin nuclea collisions and a e hen compa ed o ou p e ious esul s ob ained in Pb–Pb collisions
a √sNN =2.76 TeV. The a io o he RAA alues a he wo ene gies is also compu ed and compa ed
o calcula ions o s a is ical and dynamical models. The nume ical alue o he a io o cen al e en s
(0–10% cen ali y) is 1.17 ±0.04(s a )±0.20(sys ). In cen al e en s, as a unc ion o pT, a sligh
inc ease o RAA wi h collision ene gy is isible in he egion 2 <pT<6GeV/c. Theo e ical calcula ions
quali a i ely desc ibe he measu emen s, wi hin unce ain ies.
©2017 The Au ho . Published by Else ie B.V. This is an open access a icle unde he CC BY license
(h p://c ea i ecommons.o g/licenses/by/4.0/). Funded by SCOAP3.
1. In oduc ion
When hea y nuclei collide a ul a ela i is ic ene gies, a s a e o
s ongly-in e ac ing ma e is o med, cha ac e ised by high em-
pe a u e and densi y, whe e qua ks and gluons a e no confined
in o had ons (Qua k–Gluon Plasma, QGP [1]). A de ailed cha ac-
e isa ion o he QGP is he objec , since mo e han 25 yea s,
o an in ense esea ch ac i i y a he CERN/SPS [2] and a he
BNL/RHIC [3–6] and CERN/LHC [7] ion collide s. Cha monia and
bo omonia, which a e bound s a es o cha m–an icha m (cc) o
bo om–an ibo om (bb) qua ks, espec i ely [8], a e among he
mos sensi i e p obes o he cha ac e is ics o he QGP. A sup-
p ession o hei yields in nucleus–nucleus (A–A) collisions wi h
espec o expec a ions om p o on–p o on (pp) collisions was ex-
pe imen ally obse ed. Fo he J/ψmeson, he g ound ccs a e wi h
quan um numbe s JPC =1−−, a supp ession was ound a he SPS,
in Pb–Pb and In–In in e ac ions a he cen e-o -mass ene gy pe
nucleon pai √sNN =17.2GeV[9,10], RHIC, in Au–Au in e ac ions
a √sNN =200 GeV [11,12], and finally a he LHC, in Pb–Pb col-
lisions a √sNN =2.76 TeV [13,14]. Ea ly heo e ical calcula ions
p edic ed J/ψsupp ession o be induced by he sc eening o he
colou o ce in a deconfined medium and o become s onge as
he QGP empe a u e inc eases [15,16]. In a complemen a y way o
E-mail add ess: [email p o ec ed].
his s a ic app oach, J/ψsupp ession can also be seen as he esul
o dynamical in e ac ions wi h he su ounding pa ons [17–19].
The LHC esul s, in eg a ed o e ans e se momen um (pT) down
o pT=0, show a supp ession o he J/ψ, quan ified h ough he
a io be ween i s yields in Pb–Pb and hose in pp, no malised o
he numbe o nucleon–nucleon collisions in Pb–Pb (nuclea modi-
fica ion ac o , RAA). Howe e , he obse ed supp ession is smalle
han a SPS and RHIC [20,21], in spi e o he highe ini ial empe -
a u e o he QGP o med a he LHC [22]. The e ec is pa icula ly
e iden o head-on (cen al) collisions. In o de o explain hese
obse a ions, heo e ical models equi e a con ibu ion om J/ψ
egene a ion ia a ecombina ion mechanism [23,24] be ween he
c and cqua ks, du ing he deconfined phase and/o a he had o-
nisa ion o he sys em, which occu s when i s empe a u e alls
below he c i ical alue Tc∼155 MeV [25]. The s eng h o his
egene a ion e ec inc eases wi h he ini ial numbe o p oduced
ccpai s ela i e o he o al numbe o qua ks and, he e o e, in-
c eases wi h he collision ene gy, explaining he educed supp es-
sion a he LHC. Since he bulk o cha m–qua k p oduc ion occu s
a small momen a, ecombina ion should be mo e impo an o
low-pTJ/ψ, as obse ed in he LHC esul s [21].
An impo an es o he supp ession and egene a ion pic-
u e o J/ψp oduc ion a he LHC can be ob ained by compa ing
he cen ali y and pTdependence o he J/ψRAA, measu ed a
√sNN =2.76 TeV, o ha ob ained a √sNN =5.02 TeV, he highes
ene gy a ailable up o now in nuclea collisions. The supp ession
h p://dx.doi.o g/10.1016/j.physle b.2016.12.064
0370-2693/©2017 The Au ho . Published by Else ie B.V. This is an open access a icle unde he CC BY license (h p://c ea i ecommons.o g/licenses/by/4.0/). Funded by
SCOAP3.
ALICE Collabo a ion / Physics Le e s B 766 (2017) 212–224 213
e ec s ela ed o colou sc eening should become s onge when
inc easing he collision ene gy, due o he highe QGP empe a u e,
and also he ecombina ion e ec s should become s onge , due o
he expec ed inc ease o he ccp oduc ion c oss sec ion. The wo
e ec s ac in opposi e di ec ions and he compa ison o he RAA a
he di e en ene gies can p o ide insigh s in he e olu ion o he
ela i e con ibu ion o he wo p ocesses.
In his Le e , we p esen he fi s esul s on he J/ψRAA mea-
su ed by he ALICE Collabo a ion in Pb–Pb collisions a √sNN =
5.02 TeV and he in eg a ed and pTdi e en ial J/ψp oduc ion
c oss sec ion in pp collisions a he same ene gy. In bo h Pb–Pb
and pp collisions, he J/ψis econs uc ed ia i s dimuon decay
channel a o wa d apidi y, 2.5 <y <4 and o pT<12 GeV/c.
The measu emen s e e o inclusi e J/ψp oduc ion, ha includes
bo h p omp J/ψ(di ec J/ψand eed-down om highe -mass es-
onances) and non-p omp J/ψ( om decay o beau y had ons).
The nuclea modifica ion ac o is ob ained by no malising he J/ψ
yield in Pb–Pb collisions o he p oduc o he nuclea o e lap
unc ion imes he co esponding J/ψc oss sec ion measu ed in
pp, a he same ene gy and in he same kinema ic window. The
esul s on RAA a e p esen ed as a unc ion o he J/ψpTand o
he cen ali y o he collision.
2. Expe imen al appa a us and da a sample
The ALICE de ec o design and pe o mance a e ex ensi ely de-
sc ibed in [26] and [27]. The analysis p esen ed he e is based on
he de ec ion o muons in he o wa d muon spec ome e [28],
which co e s he pseudo- apidi y ange −4 <η<−2.5.1In addi-
ion, he Silicon Pixel De ec o (SPD) [29] is used o econs uc
he p ima y e ex. The V0 de ec o s [30] p o ide a minimum-
bias (MB) igge and a e used o de e mine he cen ali y o he
collision, while he T0 Che enko coun e s [31] a e used o he
luminosi y de e mina ion in pp collisions. Finally, he Ze o Deg ee
Calo ime e s (ZDC) a e used o ejec elec omagne ic Pb–Pb in e -
ac ions [32]. A b ie desc ip ion o hese de ec o s is gi en he e-
a e .
The muon spec ome e con ains a on abso be , made o ca -
bon, conc e e and s eel, placed be ween 0.9 and 5 m om he
In e ac ion Poin (IP), which fil e s ou had ons, hus dec easing
he occupancy in he downs eam acking sys em. The la e is
composed o fi e s a ions, each one consis ing o wo planes o
Ca hode Pad Chambe s (CPC). The hi d acking s a ion is placed
inside he gap o a dipole magne wi h a 3Tm field in eg al.
Two igge s a ions, each one equipped wi h wo planes o Re-
sis i e Pla e Chambe s (RPC), a e loca ed behind a 7.2 in e ac-
ion leng h i on wall, which abso bs seconda y had ons escaping
he on abso be and low-momen um muons. The muon ig-
ge sys em deli e s single-muon and dimuon igge s wi h a p o-
g ammable ans e se-momen um h eshold. Finally, h oughou
i s en i e leng h, a conical abso be a ound he beam pipe (θ<2◦)
made o ungs en, lead and s eel shields he muon spec ome e
agains seconda y pa icles p oduced by he in e ac ion o la ge-η
p ima y pa icles in he beam pipe.
The p ima y e ex is econs uc ed using hi pai s in he wo
cylind ical laye s o he SPD [26,29], which ha e a e age adii o
3.9 and 7.6 cm, and co e he pseudo- apidi y in e als |η| <2 and
|η| <1.4, espec i ely.
The wo V0 de ec o s [30], wi h 32 scin illa o iles each, a e
placed on each side o he IP, co e ing he pseudo- apidi y anges
1In he ALICE e e ence ame, he muon spec ome e co e s a nega i e η ange
and consequen ly a nega i e y ange. We ha e chosen o p esen ou esul s wi h a
posi i e yno a ion.
2.8 <η<5.1 and −3.7 <η<−1.7. The coincidence o he signals
om he wo hodoscopes defines he MB igge . Beam-induced
backg ound is educed by applying iming cu s on he signals om
he V0s and ZDCs. The la e a e posi ioned along he beam di-
ec ion a ±112.5 m om he IP. Finally, he T0 de ec o s [31],
made o wo a ays o qua z Che enko coun e s, a e placed on
bo h sides o he IP, co e ing he pseudo- apidi y in e als −3.3 <
η<−3 and 4.6 <η<4.9.
In Pb–Pb collisions, he cen ali y de e mina ion is based on
a Glaube fi o he o al V0 signal ampli ude dis ibu ion as de-
sc ibed in [33,34]. A selec ion co esponding o he mos cen al
90% o he had onic c oss sec ion was applied; o hese e en s
he MB igge is ully efficien .
Fo bo h Pb–Pb and pp da a aking, he igge condi ion used
in he analysis is a μμ-MB igge o med by he coincidence o
he MB igge and an unlike-sign (US) dimuon igge . The la -
e has a igge p obabili y o each o he wo muon candida es
ha inc eases wi h he muon pT, is 50% a 1.0 GeV/c(0.5 GeV/c)
in Pb–Pb (pp) collisions, and sa u a es a pT≈2.5GeV/c, whe e
i eaches a alue o abou 98%. Like-sign dimuon igge s we e
also collec ed, mainly o backg ound no malisa ion pu poses in
he Pb–Pb analysis.
The da a samples used in his analysis co espond o an in-
eg a ed luminosi y LPb–Pb
in ≈225 μb−1 o Pb–Pb and Lpp
in ≈
106 nb−1 o pp collisions.
3. Da a analysis
The analysis p ocedu e was e y simila o he wo da a sam-
ples desc ibed in his Le e . In he ollowing pa ag aphs, he Pb–
Pb analysis is fi s p esen ed, ollowed by he desc ip ion o he pp
one.
The J/ψcandida es we e o med by combining pai s o US
acks econs uc ed in he geome ical accep ance o he muon
spec ome e using he acking algo i hm desc ibed in [28]. The
same single-muon and dimuon selec ion c i e ia as in p e ious
analyses [21] we e applied, and acks in he acking sys em we e
equi ed o ma ch a ack segmen in he muon igge sys em
( igge ackle ).
The J/ψ aw yields we e de e mined om he in a ian mass
dis ibu ion o US dimuons using wo me hods. In he fi s one, he
US dimuon in a ian mass dis ibu ions we e fi ed wi h he sum
o a signal and a backg ound unc ion. In he second app oach,
he backg ound, es ima ed using an e en -mixing echnique and
no malised using he like-sign dimuon dis ibu ions [21], was sub-
ac ed and he esul ing spec a we e fi ed wi h he sum o a
signal unc ion and a (small) esidual backg ound componen .
Va ious shapes we e conside ed o he signal and backg ound
con ibu ions. Fo he J/ψsignal ei he an ex ended C ys all Ball
(CB2) unc ion o a pseudo-Gaussian wi h a mass-dependen wid h
we e used [35]. The non-Gaussian ails o he signal unc ions we e
fixed ei he (i) o he alues ob ained in Mon e Ca lo (MC) sim-
ula ions, whe e simula ed J/ψ →μ+μ−a e embedded in o eal
e en s o accoun o he e ec o he de ec o occupancy, o (ii)
o he alues ob ained in a high-s a is ics pp collision sample a
√s=13 TeV, collec ed unde simila de ec o condi ions. The ail
pa ame e s exhibi a dependence on he pTand apidi y o he
J/ψand a mild dependence on he cen ali y o he collision. The
small con ibu ion o he ψ(2S)signal was aken in o accoun in
he fi s, i s mass and wid h being ied o hose o he J/ψ[36].
Fo he backg ound, when he US dimuon mass spec um was fi -
ed, a a iable-wid h-Gaussian wi h a mass-dependen wid h o
he a io o a 2nd o a 3 d o de polynomial we e used. When
conside ing he US dimuon dis ibu ions a e sub ac ion o he
backg ound ob ained wi h he e en -mixing p ocedu e, a small
214 ALICE Collabo a ion / Physics Le e s B 766 (2017) 212–224
Fig. 1. (Colou online.) In a ian mass dis ibu ions o US dimuons wi h 2.5 <y <4and pT<12 GeV/c. The op (bo om) ow shows he dis ibu ion be o e (a e ) backg ound
sub ac ion wi h he e en -mixing echnique. The le panels co espond o he mos cen al e en s (0–10%) while he igh panels o a pe iphe al (70–80%) cen ali y ange.
The fi cu es shown in blue ep esen he sum o he signal and backg ound shapes, while he ed lines co espond o he J/ψsignal and he g ey ones o he backg ound.
dimuon con inuum componen is s ill p esen and was fi ed us-
ing he sum o wo exponen ials. Se e al fi ing sub- anges, wi hin
he in e al 2 <mμμ <5GeV/c2, we e used o bo h signal ex-
ac ion p ocedu es.
Fig. 1 shows examples o fi s o he US dimuon in a ian mass
dis ibu ions wi h and wi hou backg ound sub ac ion using he
e en -mixing echnique, o di e en selec ions in cen ali y. The
aw J/ψyield in each cen ali y o pTin e al was de e mined
as he a e age o he esul s ob ained wi h he wo fi ing ap-
p oaches, he a ious pa ame e isa ions o signal and backg ound
and he di e en fi ing anges, while he co esponding sys ema ic
unce ain ies we e defined as he RMS o hese esul s. A u he
con ibu ion o he sys ema ic unce ain y was es ima ed by using
a di e en se o esonance ails ob ained using in he MC simu-
la ion a di e en pa icle anspo model (GEANT4 [37] ins ead o
GEANT3 [38]). The o al numbe o J/ψ, in eg a ed o e cen ali y,
pTand y, is NJ/ψ =2.77 ±0.02(s a ) ±0.05(sys ) ·105. The sys em-
a ic unce ain y anges om 1.6% o 2.8% as a unc ion o cen ali y
and om 1.2% o 3.1% as a unc ion o pT.
The nuclea modifica ion ac o , as a unc ion o he cen ali y
class io he collision and o he J/ψ ans e se-momen um in-
e al pT, is calcula ed as
Ri
AA(pT)=
Ni
J/ψ (pT)
BRJ/ψ→μ+μ−Ni
MB Aεi(pT)Ti
AAσpp
J/ψ (pT),(1)
whe e Ni
J/ψ (pT)is he numbe o ex ac ed J/ψin a gi en cen-
ali y and pT ange, BRJ/ψ→μ+μ−=5.96 ±0.03% is he b anching
a io o he dimuon decay channel [39], Ni
MB is he numbe o
equi alen minimum-bias e en s, Aεi(pT)is he p oduc o he
de ec o accep ance imes he econs uc ion efficiency, Ti
AAis
he a e age o he nuclea o e lap unc ion, and σpp
J/ψ (pT)is he
inclusi e J/ψc oss sec ion o pp collisions a he same ene gy and
in he same kinema ic ange as he Pb–Pb da a.
The Aε alues we e de e mined om MC simula ions, wi h he
gene a ed pTand ydis ibu ions o he J/ψadjus ed on da a,
and sepa a ely uned o each cen ali y class using an i e a i e
app oach. Unpola ised J/ψp oduc ion was assumed [21]. Fo he
acking chambe s, he ime-dependen s a us o each elec onic
channel du ing he da a aking pe iod was aken in o accoun as
well as he misalignmen o he de ec ion elemen s. The efficien-
cies o he muon igge chambe s we e de e mined om da a and
we e hen applied in he simula ions. Finally, he dependence o
he efficiency on he de ec o occupancy was aken in o accoun
by embedding MC-gene a ed J/ψin o eal minimum-bias Pb–Pb
e en s.
Fo J/ψp oduced wi hin 2.5 <y <4 and pT<12 GeV/c, in
0–90% mos cen al collisions, he Aε alue is 0.136 ±0.007(sys ).
A ela i e dec ease o he efficiency by 14% was obse ed when
going om pe iphe al o cen al collisions. As a unc ion o pT,
Aεhas a minimum alue o abou 0.12 a pT≈1.5GeV/c, and
hen s eadily inc eases up o abou 0.4 a he uppe end o he
conside ed ange. The ollowing sou ces o sys ema ic unce ain y
on Aεwe e conside ed. A fi s con ibu ion o 2% due o he in-
pu MC pTand ydis ibu ions was es ima ed by (i) a ying he
inpu shapes ha we e uned on da a wi hin hei s a is ical un-
ce ain ies and (ii) aking in o accoun he e ec o possible pT−y
co ela ions by compa ing, as a unc ion o cen ali y, he Aε al-
ues wi h he co esponding esul o a 2-D accep ance calcula ion
in classes o pTand y. A second con ibu ion comes om he
acking efficiency and i was es ima ed by compa ing he single-
muon acking efficiency alues ob ained, in MC and da a, wi h
a p ocedu e ha exploi s he edundancy o he acking-chambe
in o ma ion [21]. A 3% sys ema ic unce ain y on he dimuon ack-
ing efficiency is ob ained and is app oxima ely cons an as a unc-
ion o cen ali y and kinema ics. The sys ema ic unce ain y on
he dimuon igge efficiency ep esen s he hi d con ibu ion and
i has wo o igins: he in insic efficiencies o he muon igge
chambe s and he esponse o he igge algo i hm. The fi s one
was de e mined om he unce ain ies on he igge chambe e -
ficiencies measu ed om da a and applied o simula ions and i
amoun s o 1.5%. The second one was es ima ed by compa ing he
pTdependence, a he single-muon le el, o he igge esponse
unc ion be ween da a and MC and i a ies be ween 0.2% and 4.6%
as a unc ion o pT. Combining he wo sou ces, a sys ema ic un-
ce ain y anging om 1.5% o 4.8% as a unc ion o he J/ψpTis
ob ained. Finally, he e is a 1% con ibu ion ela ed o he choice
ALICE Collabo a ion / Physics Le e s B 766 (2017) 212–224 215
Table 1
Summa y o sys ema ic unce ain ies, in pe cen age, on RAA and d2σpp
J/ψ /dydpT. Values ma ked wi h an as e isk co espond o co ela ed unce ain ies as a unc ion o pT
(second and fi h column) o cen ali y ( hi d column). The e is no co ela ion be ween he unce ain ies ela ed o he analysis o he Pb–Pb and o he pp sample. The
con en s o he “pp e e ence” ow co espond o he quad a ic sum o he con ibu ions indica ed o d2σpp
J/ψ /dydpT, excluding only he BR unce ain y which cancels ou
when o ming he RAA.
Sou ce RAA d2σpp
J/ψ /dydpT
0–90%
pT<12 GeV/c
s pT
(0–20%)
s cen ali y
(pT<8GeV/c)
pT<12 GeV/c s pT
Signal ex . 1.8 1.2–3.1 1.6–2.8 3 1.5–9.3
MC inpu 2 2 2∗2 0.7–1.5
T acking e . 3 3 3∗11
T igge e . 3.6 1.5–4.8 3.6∗1.8 1.5–1.8
Ma ching e . 1 1 1∗11
F(Lpp
in )0.5 0.5∗0.5∗(2.1) (2.1∗)
BR – – – 0.5 0.5∗
TAA3.2 3.2∗3.1–7.6
Cen ali y 0 0.1∗0–6.6
pp e e ence 5.0 3–10 2.1∗(Lpp
in )4.9∗
o he χ2cu used in defining he ma ching be ween he econ-
s uc ed acks and he igge ackle s.
The no malisa ion ac o o he numbe o equi alen MB e en s
was ob ained as Ni
MB =Fi·Nμμ-MB, whe e Nμμ-MB is he numbe
o μμ-MB igge ed e en s, and Fiis he in e se o he p oba-
bili y o ha ing a dimuon igge in a MB e en in he cen ali y
ange i. The Fi alues we e calcula ed wi h wo di e en me h-
ods, by applying he dimuon igge condi ion in he analysis on
minimum-bias e en s, o om he ela i e coun ing a e o he wo
igge s [40]. The ob ained alue, in he 0–90% cen ali y class, is
F=11.84 ±0.06, whe e he unce ain y is domina ed by a sys-
ema ic con ibu ion co esponding o he di e ence be ween he
esul s ob ained wi h he wo app oaches. As a unc ion o cen-
ali y, Fi=F·i, whe e iis he ac ion o he inelas ic c oss
sec ion o a gi en cen ali y class wi h espec o he whole 0–90%
cen ali y ange (e.g. 0.1/0.9 o 0–10% cen ali y and so on).
The alues o Ti
AAand o he a e age numbe o pa ici-
pan nucleons Ni
pa we e ob ained ia a Glaube calcula ion [33,
34,41]. The sys ema ic unce ain y is 3.2% o he 0–90% cen al-
i y ange and was ob ained by a ying wi hin unce ain ies he
densi y pa ame e s o he Pb nucleus and he nucleon–nucleon in-
elas ic c oss sec ion [34,41].
Finally, he e ec s o he unce ain y on he alue o he V0
signal ampli ude co esponding o 90% o he had onic Pb–Pb c oss
sec ion we e es ima ed by a ying such a alue by ±0.5% [33] and
edefining co espondingly he cen ali y in e als. The sys ema ic
e ec on RAA anges om 0.1% o 6.6% om cen al o pe iphe al
collisions.
The J/ψc oss-sec ion alues in pp collisions a √s=5.02 TeV,
bo h in eg a ed and pTdi e en ial, we e ob ained wi h an analysis
p ocedu e simila o he one desc ibed in he p e ious pa ag aphs
o Pb–Pb. In pa icula , he same c i e ia o single-muon and
dimuon selec ion we e adop ed.
The signal ex ac ion was hen pe o med by fi ing he spec-
a wi h he sum o a signal and a backg ound con ibu ion, using
shapes simila o hose adop ed o he Pb–Pb analysis. The back-
g ound sub ac ion ia he e en -mixing echnique was no used,
as he signal-o e -backg ound a io is la ge by a ac o ∼40, in
he pT-in eg a ed spec a, wi h espec o cen al Pb–Pb collisions,
making he influence o he backg ound es ima e much less im-
po an in he de e mina ion o he unce ain y on Npp
J/ψ . The alue
Npp
J/ψ =8649 ±123(s a )±297(sys )is ob ained, wi h he sys em-
a ic unce ain y de e mined as o he Pb–Pb analysis.
The de e mina ion o Aεpp was ca ied ou ia MC simula ions.
Since no app eciable dependence o he acking efficiency as a
unc ion o he had onic mul iplici y can be seen in pp, a pu e
MC (i.e., wi hou embedding) was used. The inpu pTand ydis-
ibu ions we e ob ained om he measu ed ones ia an i e a i e
p ocedu e, and unpola ised J/ψp oduc ion was assumed [42]. The
ob ained alue is Aεpp =0.243 ±0.007(sys ), wi h he sys ema ic
unce ain ies on he acking, igge and ma ching efficiency cal-
cula ed as in he Pb–Pb analysis. Because o he limi ed pp s a is-
ics, he sys ema ic unce ain y on he MC inpu s was no ob ained
h ough a 2-D accep ance calcula ion, as done in he Pb–Pb analy-
sis, bu i was de e mined compa ing he Aε alues ob ained using
J/ψpT(y) dis ibu ions e alua ed in a ious y(pT) in e als in pp
collisions a √s=7TeV[43].
The in eg a ed luminosi y was calcula ed as Lpp
in =(Npp
μμ-MB ·
Fpp)/σpp
e , whe e σpp
e is a e e ence- igge c oss sec ion measu ed
in a an de Mee scan, ollowing he p ocedu e de ailed in [44],
and Fpp is he a io o he e e ence- igge p obabili y o he
μμ-MB igge p obabili y. The co esponding nume ical alue is
Lpp
in =106.3 ±2.2(sys )nb−1, whe e he quo ed unce ain y e-
flec s he an de Mee scan unce ain y.
Finally, he inclusi e J/ψc oss sec ion in pp collisions a √s=
5.02 TeV was ob ained as
d2σpp
J/ψ
dydpT=
Npp
J/ψ (pT)
BRJ/ψ→μ+μ−Lpp
in Aεpp(pT)pTy.(2)
Table 1 summa ises he sys ema ic unce ain ies on he mea-
su emen o he nuclea modifica ion ac o s and d2σpp
J/ψ /dydpT.
The RAA alues p esen ed in he ollowing e e o inclusi e J/ψ
p oduc ion, i.e. include bo h p omp and non-p omp J/ψ. Since
beau y-had on decays occu ou side he QGP, he non-p omp J/ψ
RAA is ela ed o he nuclea modifica ion o he beau y-had on
pTdis ibu ions. The di e ence be ween he RAA o p omp and
inclusi e J/ψcan be es ima ed as in [21], using he ac ion FB
o non-p omp o inclusi e J/ψin pp collisions and assuming wo
ex eme cases o he Rnon-p omp
AA o non-p omp J/ψ, namely no
medium e ec s on b-qua ks (Rnon-p omp
AA =1) o hei comple e
supp ession (Rnon-p omp
AA =0). FBwas ob ained by an in e pola ion
o he LHCb measu emen s in pp collisions a √s=2.76 and 7TeV
[43,45,46]. The quan i a i e e ec on he inclusi e J/ψRAA is p o-
ided in he ollowing along wi h he esul s.
4. Resul s
The pT-di e en ial inclusi e J/ψc oss sec ion in pp collisions
a √s=5.02 TeV, in he egion 2.5 <y <4, is shown in Fig. 2.
The c oss sec ion alue, in eg a ed o e he in e al 2.5 <y <4,
pT<12 GeV/cis σpp
J/ψ =5.61 ±0.08(s a )±0.28(sys )μb. These
esul s a e used as a e e ence in he de e mina ion o he nu-
clea modifica ion ac o o Pb–Pb collisions. Bo h he di e en ial

216 ALICE Collabo a ion / Physics Le e s B 766 (2017) 212–224
Fig. 2. (Colou online.) The di e en ial c oss sec ion d2σpp
J/ψ /dydpT o inclusi e J/ψ
p oduc ion in pp collisions a
√s=5.02 TeV. The e o ba s ep esen he s a is ical
unce ain ies, he boxes a ound he poin s he unco ela ed sys ema ic unce ain-
ies. The unce ain y on he luminosi y measu emen ep esen s a co ela ed global
unce ain y.
Fig. 3. (Colou online.) The nuclea modifica ion ac o o inclusi e J/ψp oduc-
ion, as a unc ion o cen ali y, a √sNN =5.02 TeV, compa ed o published e-
sul s a
√sNN =2.76 TeV [20]. The e o ba s ep esen s a is ical unce ain ies, he
boxes a ound he poin s unco ela ed sys ema ic unce ain ies, while he cen ali y-
co ela ed global unce ain ies a e shown as a filled box a ound RAA =1. The wid hs
o he cen ali y classes used in he J/ψanalysis a
√sNN =5.02 TeV a e 2% om 0
o 12%, hen 3% up o 30% and 5% o mo e pe iphe al collisions.
and in eg a ed pp c oss sec ion alues a e consis en wi h hose
ob ained ia an in e pola ion [45,47] o he measu ed alues a
√s=2.76 and 7 TeV [48,49], which we e used o he de e -
mina ion o he nuclea modifica ion ac o in p–Pb collisions a
√sNN =5.02 TeV [40,47,50].
The nuclea modifica ion ac o o inclusi e J/ψp oduc ion in
Pb–Pb collisions a √sNN =5.02 TeV, in eg a ed o e he cen al-
i y ange 0–90%, and o he in e al 2.5 <y <4, pT<12 GeV/c
is RAA(pT<12 GeV/c) =0.65 ±0.01(s a ) ±0.05(sys ), showing a
significan supp ession o he J/ψwi h espec o pp collisions a
he same ene gy. When es ic ing he pT ange o 8 GeV/c, co -
esponding o he in e al co e ed in he √sNN =2.76 TeV esul s,
one ob ains RAA(pT<8GeV/c)=0.66 ±0.01(s a ) ±0.05(sys ).
The a io be ween he la e alue and he co esponding one
a √sNN =2.76 TeV, RAA(pT<8GeV/c)=0.58 ±0.01(s a ) ±
0.09(sys )[20], is 1.13 ±0.02(s a )±0.18(sys ). When calcula ing
he a io, he quo ed unce ain ies on he wo alues a e consid-
e ed as unco ela ed, excep o he TAAcon ibu ion.
Fig. 3 shows he cen ali y dependence o RAA a √sNN =
5.02 TeV. The esul s a e compa ed o he alues ob ained a
√sNN =2.76 TeV [20], and co espond o he same ans e se-
Fig. 4. (Colou online.) Compa ison o he cen ali y dependence (wi h 10% wid h
cen ali y classes) o he inclusi e J/ψRAA o 0.3 <pT<8GeV/cwi h heo e i-
cal models [17–19,52–55]. The model calcula ions do no include he pTcu (excep
o TM1), which was anyway ound o ha e a negligible impac , since hey only in-
clude had onic J/ψp oduc ion. The e o ba s ep esen he s a is ical unce ain ies,
he boxes a ound he da a poin s he unco ela ed sys ema ic unce ain ies, while
he cen ali y-co ela ed global unce ain y is shown as a filled box a ound RAA =1.
The b acke s shown in he h ee mos pe iphe al cen ali y in e als ep esen he
ange o a ia ion o he had onic J/ψRAA unde ex eme hypo hesis on he pho o-
p oduc ion con amina ion on he inclusi e RAA.
momen um ange, pT<8GeV/c. The cen ali y dependence, cha -
ac e ised by an inc easing supp ession wi h cen ali y up o
Npa ∼100, ollowed by an app oxima ely cons an RAA alue, is
simila a he wo ene gies. A sys ema ic di e ence by abou 15%
is isible when compa ing he wo se s o esul s, e en i he e -
ec is wi hin he o al unce ain y o he measu emen s. The RAA
o p omp J/ψwould be abou 10% highe i Rnon-p omp
AA =0 and
abou 5% (1%) smalle i Rnon-p omp
AA =1 o cen al (pe iphe al)
collisions.
An excess o e y-low pTJ/ψ, compa ed o he yield expec ed
assuming a smoo h e olu ion o he J/ψhad o-p oduc ion and nu-
clea modifica ion ac o was obse ed in pe iphe al Pb–Pb colli-
sions a √sNN =2.76 TeV [51]. This excess migh o igina e om
he pho o-p oduc ion o J/ψand could influence he RAA in pe-
iphe al collisions. To quan i y he expec ed di e ence be ween
he had onic J/ψRAA and he measu ed alues he me hod de-
sc ibed in [21] was adop ed. The had onic J/ψRAA, o 0 <pT<
8GeV/c, is es ima ed o be abou 34%, 17% and 9% smalle han
he measu ed alues in he 80–90%, 70–80% and 60–70% cen-
ali y classes, espec i ely. The a ia ion dec eases o abou 9%,
4% and 2%, espec i ely, when conside ing he RAA o J/ψwi h
0.3 <pT<8GeV/c, due o he emaining small con ibu ion o
pho o-p oduced J/ψ. Fig. 4 shows RAA as a unc ion o cen ali y,
o 0.3 <pT<8GeV/c.
Compa ing he esul s o Fig. 3 and Fig. 4, a less p onounced in-
c ease o RAA o pe iphe al e en s can indeed be seen when such
a selec ion is in oduced. The same ex eme hypo heses as in [21]
we e made o define uppe and lowe limi s, ep esen ed wi h
b acke s on Fig. 4. Thus, he selec ion o J/ψwi h pT>0.3GeV/c
makes he esul s mo e sui able o a compa ison wi h heo e ical
models ha only include had onic J/ψp oduc ion.
We s a by compa ing he esul s o a calcula ion based on
a s a is ical model app oach [52], whe e J/ψa e c ea ed, like
all o he had ons, only a chemical eeze-ou acco ding o hei
s a is ical weigh s. In his model, he nucleon–nucleon ccp o-
duc ion c oss sec ion is ex apola ed om LHCb pp measu e-
men s a √s=7TeV[56] using FONLL calcula ions [57], ob aining
dσcc/dy =0.45 mb in he y ange co e ed by he da a. Then, he
nuclea modifica ion o he pa on dis ibu ion unc ions (shadow-
ing) is accoun ed o ia he EPS09 NLO pa ame e isa ion [58].
ALICE Collabo a ion / Physics Le e s B 766 (2017) 212–224 217
Fig. 5. (Colou online.) The a io o he inclusi e J/ψRAA o 0.3 <pT<8GeV/cbe-
ween √sNN =5.02 and 2.76 TeV, compa ed o heo e ical models [17–19,52–55],
shown as a unc ion o cen ali y. The model calcula ions do no include he pT
cu (excep o TM1), which was anyway ound o ha e a negligible impac , since
hey only include had onic J/ψp oduc ion. The e o ba s ep esen he s a is i-
cal unce ain ies and he boxes a ound he da a poin s he unco ela ed sys ema ic
unce ain ies. The cen ali y-co ela ed global unce ain y is shown as a filled box
a ound =1and is ob ained as he quad a ic sum o he co esponding global un-
ce ain ies a
√sNN =2.76 and 5.02 TeV.
The co esponding 17% unce ain y on he ex apola ed dσcc/dy
plus shadowing is used when calcula ing he unce ain y bands o
his model. The esul s a e also compa ed o he calcula ions o a
anspo model (TM1) [18,54,55] based on a he mal a e equa-
ion, which includes con inuous dissocia ion and egene a ion o
he J/ψbo h in he QGP and in he had onic phase. The inclusi e
ccc oss sec ion is aken as dσcc/dy =0.57 mb, consis en wi h
FONLL calcula ions, while he J/ψp oduc ion c oss sec ion alue
in N–N collisions is dσJ/ψ /dy =3.14 μb. The esul s o his model
a e shown as a band including a a ia ion o he shadowing con-
ibu ion be ween 10% and 25% and a 5% unce ain y on he cc
c oss sec ion. The esul s a e hen compa ed o he calcula ions o
a second anspo model (TM2) [19], which implemen s a hyd o-
dynamic desc ip ion o he medium e olu ion. The inpu nucleon–
nucleon c oss sec ions o cc and J/ψa e aken as dσcc/dy =
0.82 mb, co esponding o he uppe limi o FONLL calcula ions,
and dσJ/ψ /dy =3.5μb. Also o his model he band co esponds
o he choice o ei he no shadowing, o a shadowing e ec es i-
ma ed wi h he EPS09 NLO pa ame e isa ion. Finally, he da a a e
compa ed o a ‘co-mo e ’ model [17,53], whe e he J/ψa e disso-
cia ed ia in e ac ions wi h he pa ons/had ons p oduced in he
same apidi y ange, using an e ec i e in e ac ion c oss sec ion
σco-J/ψ =0.65 mb, based on calcula ions ha desc ibed lowe en-
e gy expe imen al esul s. Regene a ion e ec s a e included, based
on dσcc/dy alues anging om 0.45 o 0.7 mb, which co espond
o he unce ain y band shown o he model. Shadowing e ec s,
calcula ed wi hin he Glaube –G ibo heo y [59], a e included and
a e consis en wi h EKS98/nDSg p edic ions [60,61]. Finally, he
con ibu ion o non-p omp p oduc ion is aken in o accoun in he
anspo models TM1 and TM2, while i is no conside ed in he
o he calcula ions.
The da a a e desc ibed by he a ious calcula ions, he la e
ha ing a he la ge unce ain ies, due o he choice o he co e-
sponding inpu pa ame e s, and in pa icula o dσcc/dy. I can
be no ed ha o mos calcula ions a be e desc ip ion is ound
when conside ing hei uppe limi . Fo anspo models his co -
esponds o a minimum con ibu ion o e en absence o nuclea
shadowing, which can be clea ly conside ed as an ex eme as-
sump ion o p ima y J/ψ, conside ing he J/ψmeasu emen s in
p–Pb collisions [47,50].
Fig. 6. (Colou online.) The pTdependence o he inclusi e J/ψRAA a √sNN =
5.02 TeV, compa ed o he co esponding esul a
√sNN =2.76 TeV [20] and o he
calcula ion o a anspo model [18,54,55] (TM1), in he cen ali y in e al 0–20%.
The pTdependence o is also shown o bo h da a and heo y. The e o ba s
ep esen s a is ical unce ain ies, he boxes a ound he poin s unco ela ed sys em-
a ic unce ain ies, while pT-co ela ed global unce ain ies a e shown as a filled box
a ound RAA =1.
A co ela ion be ween he pa ame e s o he models is p esen
when compa ing hei calcula ions o √sNN =2.76 and 5.02 TeV.
The e o e, he heo e ical unce ain ies can be educed by o m-
ing he a io =RAA(5.02 TeV)/RAA(2.76 TeV). Conce ning da a,
he unce ain ies on TAAcancel. In Fig. 5 he cen ali y de-
pendence o , calcula ed o 0.3 <pT<8GeV/c, is shown and
compa ed o models. Fo p omp J/ψ he a io would be abou
2% (1–2%) highe i beau y had ons we e ully (no ) supp essed
by he medium. The anspo model o Re . [18,54,55] (TM1)
shows a dec ease o wi h inc easing cen ali y, due o he la ge
supp ession e ec s a high ene gy, ollowed by an inc ease, e-
la ed o he e ec o egene a ion, which ac s in he opposi e
di ec ion and becomes dominan o cen al collisions. The o he
anspo model (TM2) [19] also exhibi s an inc ease o cen al
collisions, while o pe iphe al collisions he beha iou is di e -
en . In he co-mo e model [17,53], no s uc u e is isible as a
unc ion o cen ali y, and he calcula ion a ou s - alues sligh ly
below uni y, implying ha in his model he inc ease o he sup-
p ession e ec s wi h ene gy may be dominan o e he egene -
a ion e ec s o all cen ali ies. Finally, he s a is ical model [52]
shows a con inuous inc ease o wi h cen ali y, domina ed by
he inc ease in he ccc oss sec ion wi h ene gy. The unce ain y
bands shown in Fig. 5 co espond o a ia ions o abou 5% in
he ccc oss sec ion a √sNN =5.02 TeV, plus a 10% ela i e a ia-
ion o he shadowing con ibu ion be ween he wo ene gies in
he case o TM1. The da a a e, wi hin unce ain ies, compa ible
wi h he heo e ical models, and show no clea cen ali y depen-
dence. The a io o cen al collisions and 0.3 <pT<8GeV/cis
0–10% =1.17 ±0.04(s a )±0.20(sys ).
Finally, he s udy o he pTdependence o RAA has p o en o
be a sensi i e es o he p esence o a egene a ion componen
which, in calcula ions, leads o an inc ease a low pT. Fig. 6 shows,
o he cen ali y in e al 0–20%, RAA as a unc ion o ans e se
momen um, compa ed o he co esponding esul s ob ained a
√sNN =2.76 TeV, and o a heo e ical model calcula ion. The e-
gion pT<0.3GeV/cwas no excluded, because he con ibu ion
o J/ψpho o-p oduc ion is negligible wi h espec o he had onic
one o cen al e en s [51]. In he same figu e he pTdependence
o is also shown. A hin o an inc ease o RAA wi h √sNN is is-
ible in he egion 2 <pT<6GeV/c, while he - a io is consis en
218 ALICE Collabo a ion / Physics Le e s B 766 (2017) 212–224
wi h uni y elsewhe e. This ea u e is quali a i ely desc ibed by he
heo e ical model (TM1) also shown in he figu e. The p omp J/ψ
RAA is expec ed o be 7% la ge (2% smalle ) o pT<1GeV/cand
30% la ge (55% smalle ) o 10 <pT<12 GeV/cwhen he beau y
con ibu ion is ully (no ) supp essed. Assuming ha Rnon-p omp
AA
does no a y significan ly be ween he wo collision ene gies,
he a io appea s o be less sensi i e o he non-p omp J/ψ
con ibu ion. The e ec is negligible o he case o ull supp es-
sion o beau y had ons, while i a ies om no inc ease a low
ans e se momen um up o a maximum inc ease o abou 15%
o 5 <pT<6GeV/ci no supp ession is assumed. The anspo
model o Re . [18,54,55] (TM1) ai ly desc ibes he o e all shape o
he RAA pTdependence.
5. Conclusion
We epo ed he ALICE measu emen o inclusi e J/ψp oduc-
ion in pp and Pb–Pb collisions a √sNN =5.02 TeV a he LHC.
Asys ema ic di e ence by abou 15% is isible when compa ing
he RAA measu ed a √sNN =5.02 TeV o he one ob ained a
√sNN =2.76 TeV, e en i such an e ec is wi hin he o al un-
ce ain y o he measu emen s. When emo ing e y-low pTJ/ψ
(pT<0.3GeV/c), he RAA shows a less p onounced inc ease o
pe iphe al e en s, which can be asc ibed o he emo al o a la ge
ac ion o elec omagne ic J/ψp oduc ion [51]. These esul s, as
well as hose on he a io o he nuclea modifica ion ac o s
be ween √sNN =5.02 and 2.76 TeV, a e desc ibed by heo e i-
cal calcula ions, and close o hei uppe limi s. The pTdepen-
dence o RAA exhibi s an inc ease a low pT, a ea u e ha in
he model which is compa ed o he da a is ela ed o an im-
po an con ibu ion o egene a ed J/ψ. A hin o an inc ease o
RAA be ween √sNN =2.76 and 5.02 TeV is isible in he egion
2 <pT<6GeV/c, while he esul s a e consis en elsewhe e. The
esul s p esen ed in his pape confi m ha also a he highes en-
e gies eached oday a he LHC, da a on J/ψp oduc ion suppo a
pic u e whe e a combina ion o supp ession and egene a ion akes
place in he QGP, he wo mechanisms being dominan a high and
low pT, espec i ely.
Acknowledgemen s
The ALICE Collabo a ion would like o hank all i s enginee s
and echnicians o hei in aluable con ibu ions o he cons uc-
ion o he expe imen and he CERN accele a o eams o he
ou s anding pe o mance o he LHC complex. The ALICE Collab-
o a ion g a e ully acknowledges he esou ces and suppo p o-
ided by all G id cen es and he Wo ldwide LHC Compu ing
G id (WLCG) Collabo a ion. The ALICE Collabo a ion acknowledges
he ollowing unding agencies o hei suppo in building and
unning he ALICE de ec o : A. I. Alikhanyan Na ional Science
Labo a o y (Ye e an Physics Ins i u e) Founda ion (ANSL), S a e
Commi ee o Science and Wo ld Fede a ion o Scien is s (WFS),
A menia; Aus ian Academy o Sciences and Na ionals i ung ü
Fo schung, Technologie und En wicklung, Aus ia; Conselho Na-
cional de Desen ol imen o Cien ífico e Tecnológico (CNPq), Uni-
e sidade Fede al do Rio G ande do Sul (UFRGS), Financiado a de
Es udos e P oje os (Finep) and Fundação de Ampa o à Pesquisa
do Es ado de São Paulo (FAPESP), B azil; Minis y o Science and
Technology o he People’s Republic o China (MOST), Na ional
Na u al Science Founda ion o China (NSFC) and Minis y o Ed-
uca ion o China (MOE), China; Minis y o Science, Educa ion
and Spo and C oa ian Science Founda ion, C oa ia; Minis y o
Educa ion, You h and Spo s o he Czech Republic, Czech Re-
public; The Danish Council o Independen Resea ch – Na u al
Sciences, he Ca lsbe g Founda ion and Danish Na ional Resea ch
Founda ion (DNRF), Denma k; Helsinki Ins i u e o Physics (HIP),
Finland; Commissa ia à l’Éne gie A omique e aux Éne gies Al-
e na i es (CEA) and Ins i u Na ional de Physique Nucléai e e
de Physique des Pa icules (IN2P3) and Cen e Na ional de la
Reche che Scien ifique (CNRS), F ance; Bundesminis e ium ü Bil-
dung, Wissenscha , Fo schung und Technologie (BMBF) and GSI
Helmhol zzen um ü Schwe ionen o schung GmbH, Ge many;
Minis y o Educa ion, Resea ch and Religious A ai s, G eece;
Na ional Resea ch, De elopmen and Inno a ion Office, Hunga y;
Depa men o A omic Ene gy, Go e nmen o India (DAE) and
Council o Scien ific and Indus ial Resea ch (CSIR), New Delhi,
India; Indonesian Ins i u e o Science, Indonesia; Cen o Fe mi –
Museo S o ico della Fisica e Cen o S udi e Rice che En ico Fe mi
and Is i u o Nazionale di Fisica Nuclea e (INFN), I aly; Ins i u e o
Inno a i e Science and Technology, Nagasaki Ins i u e o Applied
Science (IIST), Japan Socie y o he P omo ion o Science (JSPS),
KAKENHI and Japanese Minis y o Educa ion, Cul u e, Spo s, Sci-
ence and Technology (MEXT), Japan; Consejo Nacional de Ciencia
y Tecnología (CONACYT), h ough Fondo de Coope ación In e na-
cional en Ciencia y Tecnología (FONCICYT) and Di ección Gene al
de Asun os del Pe sonal Academico (DGAPA), Mexico; Na ionaal
ins i uu oo suba omai e ysica (Nikhe ), Ne he lands; The Re-
sea ch Council o No way, No way; Commission on Science and
Technology o Sus ainable De elopmen in he Sou h (COMSATS),
Pakis an; Pon ificia Uni e sidad Ca ólica del Pe ú, Pe u; Minis y o
Science and Highe Educa ion and Na ional Science Cen e, Poland;
Ko ea Ins i u e o Science and Technology In o ma ion and Na ional
Resea ch Founda ion o Ko ea (NRF), Republic o Ko ea; Minis y o
Educa ion and Scien ific Resea ch, Ins i u e o A omic Physics and
Romanian Na ional Agency o Science, Technology and Inno a-
ion, Romania; Join Ins i u e o Nuclea Resea ch (JINR), Minis y
o Educa ion and Science o he Russian Fede a ion and Na ional
Resea ch Cen e Ku cha o Ins i u e, Russia; Minis y o Educa-
ion, Science, Resea ch and Spo o he Slo ak Republic, Slo akia;
Na ional Resea ch Founda ion o Sou h A ica, Sou h A ica; Cen-
o de Aplicaciones Tecnológicas y Desa ollo Nuclea (CEADEN),
Cubaene gía, Cuba; Minis e io de Ciencia e Inno ación and Cen o
de In es igaciones Ene gé icas, Medioambien ales y Tecnológicas
(CIEMAT), Spain; Swedish Resea ch Council (VR) and Knu & Alice
Wallenbe g Founda ion (KAW), Sweden; Eu opean O ganiza ion o
Nuclea Resea ch, Swi ze land; Na ional Science and Technology
De elopmen Agency (NSDTA), Su ana ee Uni e si y o Technol-
ogy (SUT) and Office o he Highe Educa ion Commission unde
NRU p ojec o Thailand, Thailand; Tu kish A omic Ene gy Agency
(TAEK), Tu key; Na ional Academy o Sciences o Uk aine, Uk aine;
Science and Technology Facili ies Council (STFC), Uni ed Kingdom;
Na ional Science Founda ion o he Uni ed S a es o Ame ica (NSF)
and Uni ed S a es Depa men o Ene gy, Office o Nuclea Physics
(DOE NP), Uni ed S a es o Ame ica.
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