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Inclusi e, p omp and non-p omp J/ψ p oduc ion a mid- apidi y in Pb-Pb collisions
a √sNN =2.76 TeV
ALICE Collabo a ion
ALICE Collabo a ion. (2015). Inclusi e, p omp and non-p omp J/ψ p oduc ion a
mid- apidi y in Pb-Pb collisions a √sNN =2.76 TeV. Jou nal o High Ene gy Physics,
2015(7), A icle 51. h ps://doi.o g/10.1007/JHEP07(2015)051
2015
JHEP07(2015)051
Published o SISSA by Sp inge
Recei ed:Ap il 28, 2015
Accep ed:June 17, 2015
Published:July 10, 2015
Inclusi e, p omp and non-p omp J/ψ p oduc ion a
mid- 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 ans e se momen um (pT) dependence o he nuclea modi ica ion ac o
RAA and he cen ali y dependence o he a e age ans e se momen um hpTi o inclusi e
J/ψ ha e been measu ed wi h ALICE o Pb-Pb collisions a √sNN = 2.76 TeV in he
e+e−decay channel a mid- apidi y (|y|<0.8). The hpTiis signi ican ly smalle han he
one obse ed o pp collisions a he same cen e-o -mass ene gy. Consis en ly, an inc ease
o RAA is obse ed owa ds low pT. These obse a ions migh be indica i e o a sizable
con ibu ion o cha m qua k coalescence o he J/ψ p oduc ion. Addi ionally, he ac ion
o non-p omp J/ψ om beau y had on decays, B, has been de e mined in he egion
1.5< pT<10 GeV/c in h ee cen ali y in e als. No signi ican cen ali y dependence o
Bis obse ed. Finally, he RAA o non-p omp J/ψ is discussed and compa ed wi h model
p edic ions. The nuclea modi ica ion in he egion 4.5< pT<10 GeV/c is ound o be
s onge han p edic ed by mos models.
Keywo ds: Had on-Had on Sca e ing
A Xi eP in : 1504.07151
Open Access, Copy igh CERN,
o he bene i o he ALICE Collabo a ion.
A icle unded by SCOAP3.
doi:10.1007/JHEP07(2015)051
JHEP07(2015)051
Con en s
1 In oduc ion 1
2 Da a analysis 2
2.1 Inclusi e J/ψ 3
2.2 Non-p omp J/ψ 8
3 Resul s 13
4 Conclusions 19
The ALICE collabo a ion 26
1 In oduc ion
Hea y-ion collisions a high ene gies allow he s udy o s ongly in e ac ing ma e unde
ex eme condi ions. Calcula ions based on Quan um-Ch omo-Dynamics (QCD) on he
la ice indica e ha he ho and dense medium c ea ed in hese collisions beha es like
a s ongly coupled Qua k-Gluon Plasma (QGP) [1–4]. Hea y qua ks a e an impo an
p obe o he p ope ies o his s a e o ma e , since hey a e p oduced ia ha d pa onic
collisions a a e y ea ly s age and hus expe ience he comple e e olu ion o he sys em.
Qua konium s a es, i.e. bound s a es o a hea y qua k and an i-qua k such as he J/ψ meson
(c¯c s a e) a e o pa icula in e es . I was p edic ed ha he J/ψ o ma ion is supp essed
in a QGP due o he sc eening o he c¯c po en ial in he p esence o ee colou cha ges [5].
Expe imen ally, a supp ession o he inclusi e J/ψ yield in hea y-ion collisions ela i e o
he co esponding yield in pp, scaled by he numbe o bina y nucleon-nucleon collisions, has
been obse ed a he Supe P o on Synch o on (SPS) [6–8] and he Rela i is ic Hea y Ion
Collide (RHIC) [9,10]. The le el o supp ession was ound o be simila a SPS and RHIC,
despi e he signi ican ly di e en collision ene gy. Mo e ecen ly, he nuclea modi ica ion
o J/ψ was also measu ed o Pb-Pb collisions a he LHC [11–13]. While a high ans e se
momen um (pT>4 GeV/c) he supp ession ac o is a he same le el as he one obse ed
a RHIC in he low pT egion, a signi ican educ ion o he supp ession is measu ed
owa ds lowe pT. This has been in e p e ed as he e ec o an addi ional con ibu ion
o J/ψ p oduc ion a low pT, due o he combina ion o co ela ed o unco ela ed c and
¯c qua ks [14,15]. This con ibu ion becomes sizable a LHC ene gies, since he numbe
o c¯c pai s is much highe han a lowe ene gies. Assuming ha a decon ined phase is
p oduced and ha all he J/ψ a e dissocia ed, his p ocess happens a he chemical eeze-
ou s age o he i eball e olu ion. This is he app oach ollowed wi hin he s a is ical
had oniza ion models desc ibed in e s. [16,17]. Al e na i ely, J/ψ could be gene a ed ia
coalescence h oughou he ull e olu ion o he QGP phase, i hei su i al p obabili y in
– 1 –
JHEP07(2015)051
his en i onmen is la ge enough. This scena io has been implemen ed in se e al pa onic
anspo models [18,19]. I was ound ha bo h app oaches can p o ide a desc ip ion o
he measu ed nuclea modi ica ion ac o s [12] and o he ellip ic low o inclusi e J/ψ [20].
The p oduc ion o open beau y had ons is expec ed o be sensi i e o he densi y o he
medium c ea ed in hea y-ion collisions due o he ene gy loss expe ienced by he pa en
pa on (a beau y qua k) which had onizes in o he beau y had on. This ene gy loss is
expec ed o occu ia medium-induced gluon adia ion [21,22] and elas ic collisional ene gy
loss p ocesses [23–25] and i depends on he QCD Casimi coupling ac o o he pa on
(la ge o gluons han o qua ks) and on he pa on mass [26–29]. O he mechanisms,
such as in-medium had on o ma ion and dissocia ion, can be en isaged as pa icula ly
ele an o hea y- la ou had ons due o hei small o ma ion imes [30–32].
Inclusi e J/ψ p oduc ion is he sum o se e al con ibu ions. In addi ion o he di-
ec ly p oduced J/ψ, he decays o hea ie cha monium s a es, such as he χcand ψ(2S),
also con ibu e o he inclusi e J/ψ yield. These wo sou ces (di ec and cha monium de-
cays) a e de ined as p omp J/ψ, whe e he con ibu ion om cha monium decays is abou
35% as measu ed in pp collisions [33]. Since hea ie cha monia a e less s ongly bound
han he J/ψ hey should be mo e easily dissol ed in a decon ined medium [34]. The J/ψ
supp ession measu ed a he SPS is indeed compa ible wi h he assump ion ha only he
exci ed s a es a e dissol ed and no he di ec ly p oduced J/ψ [6,7]. On op o he p omp
J/ψ p oduc ion, he e is an addi ional non-p omp con ibu ion o he inclusi e J/ψ a
high cen e-o -mass ene gies, coming om he decay o beau y had ons. Since hese decays
p oceed ia weak in e ac ions, he esul ing J/ψ will o igina e om a decay e ex ha is
displaced om he main in e ac ion e ex. Thei measu emen p o ides a di ec de e -
mina ion o he nuclea modi ica ion o beau y had ons. By sub ac ing he non-p omp
con ibu ion om he inclusi e J/ψ yield one can also p o ide an unbiased in o ma ion
on medium modi ica ion o p omp cha monia. The non-p omp J/ψ con ibu ion a mid-
apidi y has al eady been measu ed in pp collisions a √s= 7 TeV by ATLAS [35], CMS [36]
and ALICE [37]. Fo Pb-Pb collisions a √sNN = 2.76 TeV CMS has also published p omp
and non-p omp J/ψ p oduc ion esul s a mid- apidi y o pT>6.5 GeV/c [13].
In his pape we p esen a di e en ial measu emen o he inclusi e J/ψ p oduc ion a
mid- apidi y in Pb-Pb collisions a √sNN = 2.76 TeV. The pTdependence o he nuclea
modi ica ion ac o and he cen ali y dependence o he a e age ans e se momen um o
J/ψ ha e been ob ained, ex ending he se o esul s p esen ed in [12]. A measu emen o
he p omp and non-p omp con ibu ions o he inclusi e J/ψ p oduc ion is also p esen ed.
The nuclea modi ica ion ac o o non-p omp J/ψ is de e mined down o pT= 1.5 GeV/c
and compa ed o model p edic ions.
2 Da a analysis
A de ailed desc ip ion o he ALICE de ec o can be ound in [38]. Fo he analysis p e-
sen ed he e he de ec o s o he cen al ba el ha e been used, in pa icula he Inne
T acking Sys em (ITS) and he Time P ojec ion Chambe (TPC). These de ec o s a e
loca ed inside a la ge solenoidal magne wi h a ield s eng h o 0.5 T. They allow he
– 2 –
JHEP07(2015)051
measu emen o J/ψ mesons ia he dielec on decay channel in he cen al apidi y egion
down o ze o pT. The ITS [39] consis s o six laye s o silicon de ec o s su ounding he
beam pipe a adial posi ions be ween 3.9 cm and 43.0 cm. I s wo inne mos laye s a e
composed o Silicon Pixel De ec o s (SPD), which p o ide he spa ial esolu ion o sepa a e
on a s a is ical basis he non-p omp J/ψ. The ac i e olume o he TPC [40] co e s he
ange along he beam di ec ion −250 < z < 250 cm ela i e o he In e ac ion Poin (IP)
and ex ends in adial di ec ion om 85 cm o 247 cm. I is he main acking de ice in he
cen al ba el and is in addi ion used o pa icle iden i ica ion ia he measu emen o he
speci ic ioniza ion (dE/dx) in he de ec o gas.
T igge ing and e en cha ac e iza ion is pe o med ia o wa d de ec o s, he V0 [41]
and wo Ze o Deg ee Calo ime e s (ZDC) [42]. The V0 de ec o s consis o wo scin illa o
a ays posi ioned a z=−90 cm and z= +340 cm and co e he pseudo- apidi y anges
−3.7≤η≤ −1.7 and 2.8≤η≤5.1. The ZDCs, each one consis ing o wo qua z ibe
sampling calo ime e s, a e placed a a dis ance o 114 m ela i e o he IP in bo h di ec ions
along he beam axis and a e used o de ec spec a o nucleons.
The esul s p esen ed in his a icle a e based on da a samples collec ed du ing he
Pb-Pb da a aking pe iods o he LHC in he yea s 2010 and 2011. In he case o he
2011 da a sample he Minimum Bias (MB) Le el-0 (L0) igge condi ion was de ined by
he coincidence o signals in bo h V0 de ec o s along wi h a alid bunch c ossing igge .
Fo he 2010 da a sample, in addi ion, he de ec ion o a leas wo hi s in he ITS was
equi ed. Bo h MB igge de ini ions lead o igge e iciencies la ge han 95% o in-
elas ic Pb-Pb collisions. Elec omagne ic in e ac ions we e ejec ed by he Le el-1 (L1)
igge , which equi ed a minimum ene gy deposi ion in he ZDC by spec a o neu ons.
The beam-induced backg ound was u he educed du ing he o line analysis by selec ing
e en s acco ding o he ela i e iming o signals in V0 and ZDC. The o line cen ali y
selec ion is done using he sum o he wo V0 signal ampli udes. By i ing he co e-
sponding dis ibu ion wi h he esul s o Glaube model simula ions, he a e age numbe
o pa icipan s hNpa iand he a e age nuclea o e lap unc ion hTAAi=hNcolli/σinel
NN o a
gi en cen ali y class can be de e mined as desc ibed in [43]. He e, hNcolliis he a e age
numbe o bina y nucleon-nucleon collisions and σinel
NN he inelas ic nucleon-nucleon c oss
sec ion. The nume ical alues o hNpa i,hNcolli, and hTAAia e abula ed in [12].
The 2010 da a sample consis s o 1.5×107e en s, aken wi h he co esponding MB
igge . The 2011 e en sample was en iched wi h cen al and semi-cen al Pb-Pb collisions
by using h esholds on he V0 mul iplici y a he L0 igge . F om he la e da a se we
analyzed 1.9×107cen al (0–10% o he cen ali y dis ibu ion) and 1.7×107semi-cen al
(10–50%) e en s. The summed 2010 and 2011 da a samples co espond o an in eg a ed
luminosi y o Lin = 26.4±0.3(s a .)+2.1
−1.7(sys .) µb−1[12].
2.1 Inclusi e J/ψ
J/ψ candida es a e econs uc ed by combining opposi e-sign (OS) pai s o elec-
on/posi on candida es and calcula ing hei in a ian mass mee. These candida es a e
selec ed om acks econs uc ed in he ITS and he TPC by employing he se o quali y
c i e ia desc ibed in [12,44]. In o de o ejec he backg ound om pho on con e sions
– 3 –

JHEP07(2015)051
in he de ec o ma e ial, acks a e equi ed o ha e a hi in one o he SPD laye s. In
addi ion, a leas 70 ou o a maximum o 159 space poin s econs uc ed in he TPC mus
be assigned o a gi en ack, which also needs o ul ill a quali y c i e ion o he ack i
(χ2/nd < 4). The acks a e equi ed o be in he ange |η|<0.8, whe e he acking and
pa icle iden i ica ion pe o mance o he TPC is op imal, and o ha e pT>0.85 GeV/c o
imp o e he signal- o-backg ound a io in he J/ψ mass egion.
Elec on candida es a e selec ed by equi ing ha he dE/dxmeasu emen in he TPC
lies wi hin a band [−1σ, +3σ] a ound he momen um-dependen pa ame e iza ion o he
expec ed signal, whe e σis he phase space dependen dE/dx esolu ion (de ails can be
ound in [45]). The selec ion is asymme ic in o de o minimize he con ibu ion om
pions. To u he supp ess he had on con amina ion, acks ha a e compa ible wi hin
±4σwi h he p o on expec a ion a e ejec ed. A side e ec o his cu is ha acks below
pT= 1 GeV/c a e e ec i ely emo ed.
Measu emen o he inclusi e J/ψ yield. The J/ψ signal coun s NJ/ψ a e ob ained
om he numbe o en ies in he backg ound sub ac ed in a ian mass dis ibu ions in
he ange 2.92 < mee <3.16 GeV/c2. The unco ela ed backg ound is e alua ed wi h a
mixed e en (ME) echnique. In o de o achie e a good desc ip ion o he backg ound
only elec ons and posi ons om e en s wi h simila p ope ies in e ms o cen ali y,
p ima y e ex posi ion, and e en plane angle a e combined. The ME dis ibu ions a e
scaled o he same e en (SE) dis ibu ions in he mass anges 1.5< mee <2.5 GeV/c2
and 3.2< mee <4.2 GeV/c2, so ha he J/ψ signal egion is excluded. The no maliza ion
a ea con ains he ψ(2S) signal, bu i s con ibu ion is negligible and can he e o e be
sa ely igno ed. Also, con ibu ions om he ail o he J/ψ signal shape o his mass
in e al a e below he pe cen le el and will hus no signi ican ly a ec he no maliza ion.
Figu e 1shows a compa ison o he SE and ME in a ian mass dis ibu ions o he 0–40%
mos cen al Pb-Pb collisions o elec on-posi on pai s a mid- apidi y (|y|<0.8) in
wo pTin e als: 0–2.5 GeV/c and 2.5–6 GeV/c. The ag eemen be ween he SE and
ME dis ibu ions ou side he signal egion is e y good and allows signal ex ac ion wi h
signi icances la ge han eigh .
The J/ψ yield pe MB e en in a gi en pTin e al, YJ/ψ, is ob ained as
YJ/ψ(pT) = NJ/ψ(pT)
BRee Ne s hA×i(pT).(2.1)
He e BRee is he b anching a io o he decay J/ψ →e+e−,Ne s he numbe o e en s,
and hA×i he phase space dependen p oduc o accep ance Aand econs uc ion e i-
ciency . The la e is calcula ed om Mon e Ca lo (MC) simula ions as he a io be ween
he numbe o econs uc ed and gene a ed MC J/ψ, which a e assumed o be unpola -
ized. In pp collisions a √s= 7 TeV he J/ψ pola iza ion has been measu ed and was
ound o be compa ible wi h ze o a mid- apidi y (pT>10 GeV/c) and o wa d apidi y
(pT>2 GeV/c) [46–48]. In hea y-ion collisions no measu emen exis s, bu J/ψ mesons
p oduced om he ecombina ion o cha m qua ks in he medium a e expec ed o be un-
– 4 –
JHEP07(2015)051
Figu e 1. The in a ian mass dis ibu ions o inclusi e J/ψ a mid- apidi y (|y|<0.8) o
Pb-Pb collisions (0–40% mos cen al) a √sNN = 2.76 TeV. The le panels show he in e al
0< pT<2.5 GeV/c and he igh ones 2.5< pT<6 GeV/c. The uppe panels display he opposi e
sign dis ibu ions oge he wi h he esul o he mixed e en p ocedu e. In he lowe panels he
backg ound sub ac ed dis ibu ions a e shown and compa ed o he simula ed line shape. Also,
he signal- o-backg ound a io S/B and he signi icance o he signal a e gi en.
pola ized.1The MC e en s used o he calcula ion o hA×ia e cons uc ed by adding
o backg ound e en s, gene a ed wi h he HIJING model [49], J/ψ mesons decaying in o
e+e−pai s, whose phase space dis ibu ion is ob ained om ex apola ions o o he mea-
su emen s [50], aking in o accoun shadowing e ec s as pa ame e ized in EKS98 [51]. The
dielec on decay is simula ed wi h he E Gen [52] package, using he PHOTOS model [53]
o desc ibe he in luence o inal s a e adia ion. This choice, oge he wi h he simula ion
o b emss ahlung in he de ec o ma e ial, is manda o y o a p ope desc ip ion o he
low mass ail in he measu ed J/ψ mass dis ibu ion and ensu es ha he ac ion o he
signal ou side o he mee in eg a ion window is p ope ly accoun ed o in he co ec ion
hA×i. The p opaga ion o he simula ed pa icles is done by GEANT3 [54] and a ull
simula ion o he de ec o esponse is pe o med. The same econs uc ion p ocedu e and
cu s a e applied o MC e en s and o eal da a. The quali y o he simula ion is illus a ed
by he good ag eemen o he backg ound-sub ac ed in a ian mass dis ibu ions wi h he
1The impac o he pola iza ion on he accep ance was s udied o ex eme pola iza ion scena ios in [44].
– 5 –
JHEP07(2015)051
MC simula ion o he J/ψ signal shape, a e no malizing i o he same in eg al as he
measu ed signal (see igu e 1).
The analysis has been pe o med in wo sligh ly di e en cen ali y in e als (0–40%
and 0–50%), whe e he la ge one is used o he ex ac ion o non-p omp J/ψ which
equi es a highe s a is ics han he inclusi e measu emen . Also, he pTin e als ha e
been op imized o he di e en analyses. I was checked ha he esul s o inclusi e J/ψ
ob ained wi h he wo cen ali y binnings a e in good ag eemen .
De e mina ion o he pp e e ence o RAA.F om he co ec ed J/ψ yield YJ/ψ(pT)
he nuclea modi ica ion ac o RAA(pT) is calcula ed as
RAA(pT) = YJ/ψ(pT)
hTAAiσpp
J/ψ(pT).(2.2)
Since no di e en ial J/ψ measu emen a mid- apidi y a low pTis a ailable o pp collisions
a √s= 2.76 TeV [55], he e e ence needed o he cons uc ion o RAA is based on an
in e pola ion o he mid- apidi y measu emen s by PHENIX a √s= 0.2 TeV [56], CDF
a √s= 1.96 TeV [57], and ALICE a √s= 7 TeV [55]. The in e pola ed pTdis ibu ion
is ob ained by i ing he ollowing pa ame e iza ion o he a ailable da a se s [50]
1
dσ/dy
d2σ
dzTdy=czT
(1 + a2z2
T)n.(2.3)
He e, zTis de ined as pT/hpTi,a= Γ(3/2) Γ(n−3/2)/Γ(n−1), and c= 2(n−1) a,
whe e nis he only ee i pa ame e . The alue o hpTi(calcula ed in he pT ange
0–10 GeV/c) a √s= 2.76 TeV, which is needed o ansla e his pa ame e iza ion in o
dσ/dpT, is de e mined by in e pola ing be ween he exis ing hpTimeasu emen s o pp
and p¯p collisions [55–57]. This in e pola ion is done using a ious unc ional o ms o he
√sdependence o de e mine he sys ema ic unce ain y. Fo he absolu e no maliza ion
o he pa ame ized spec um, he same in e pola ed alue dσ/dy= 4.25 ±0.28(s a .) ±
0.43(sys .) µb as in [12] is used.
The main sou ces o sys ema ic unce ain ies o he pTdependen RAA o inclusi e J/ψ
a e he signal econs uc ion p ocedu e, he MC inpu kinema ics, he unce ain ies on he
in e pola ed pp e e ence and on he nuclea o e lap unc ion. The co esponding alues
a e summa ized in able 1. While he i s wo componen s a e unco ela ed be ween
he pTin e als ( ype II), he unce ain y due o he nuclea o e lap unc ion is ully
co ela ed ( ype I). The pp e e ence on he o he hand in oduces bo h unco ela ed and
co ela ed con ibu ions. To de e mine he unce ain y ela ed o he signal econs uc ion,
he no maliza ion ange o he ME backg ound and he size and posi ions o he mee bins
ha e been a ied. All ack and elec on selec ion c i e ia, such as he elec on inclusion
cu and he SPD hi equi emen , ha e been elaxed and/o igh ened in o de o es he
s abili y o he esul , as was pe o med in [12]. The alue o he sys ema ic unce ain y
is de e mined as he s anda d de ia ion o he dis ibu ion o all esul s ob ained wi h
he lis ed a ia ions. The e alua ion o he unce ain ies associa ed wi h he MC inpu
kinema ics is also desc ibed in [12], while he unce ain y o he pp e e ence is es ima ed
– 6 –
JHEP07(2015)051
Figu e 2. The a e age ans e se momen um hpTio e+e−pai s, measu ed o he pT ange 0–
10 GeV/c, as a unc ion o he in a ian mass mee in cen ali y selec ed Pb-Pb collisions a √sNN =
2.76 TeV. The shown unce ain ies a e s a is ical only. The backg ound hpTidis ibu ions and he
o al i esul s a e also shown supe imposed o he da a poin s.
om he di e ences be ween he c oss-sec ion alues ob ained wi h he i ing p ocedu e
based on eq. (2.3) and he measu ed alues used o he i a he a ious ene gies.
De e mina ion o hpTiand hp2
Ti.Since he collec ed Pb-Pb s a is ics would allow he
ex ac ion o he J/ψ yield in a ew pTin e als only, he a e age ans e se momen um
hpTiis de e mined by a i o he dis ibu ion o he hpTio e+e−pai s as a unc ion o
mee. When building such a dis ibu ion, he indi idual e+e−pai s a e weigh ed by he
in e se o hei accep ance imes e iciency (A×)−1, assuming ha hey come om he
decay o a J/ψ. The esul ing hpTidis ibu ions a e i ed by he exp ession
hpTimeas =1
S(mee) + B(mee)S(mee)hpTiJ/ψ +B(mee)hpTiBkg.(2.4)
Bo h ac o s Sand Bdepend on mee and co espond o he dis ibu ion o he J/ψ signal
and o he backg ound. Fo S he same backg ound sub ac ed signal dis ibu ion S(mee)
is used as o he ex ac ion o he yield (see lowe panels o igu e 1), while he backg ound
Bis gene a ed om he ME sample, as B(mee) = cBBME(mee). The no maliza ion ac o
is de e mined by i ing cBBME(mee) o he co esponding mee dis ibu ion o e+e−pai s in
he egions 1.5< mee <2.5 GeV/c2and 3.2< mee <4.2 GeV/c2, hus excluding he signal
egion. Fo he sum S(mee)+B(mee) in he denomina o o eq. (2.4), he measu ed OS pai
mee dis ibu ion is used. The hpTiBkg, de ined as he hpTio he combina o ial backg ound
pai s, is also calcula ed om he ME sample. This analysis is pe o med in h ee di e en
cen ali y in e als: 0–10%, 10–40%, and 40–90%. Figu e 2shows he measu ed hpTio
he e+e−pai s in he pT ange 0–10 GeV/c oge he wi h he esul s o he i p ocedu e.
In addi ion, wi h an equi alen me hod, he mean squa e ans e se momen um hp2
Tiis
also calcula ed o he same cen ali y in e als.
The sys ema ic unce ain ies o he hpTimeasu emen o inclusi e J/ψ a e mainly
de e mined by he signal ex ac ion, he s abili y o ack and elec on selec ion c i e ia
and he i p ocedu e (see able 2). While he i s wo componen s a e no co ela ed
be ween he di e en cen ali y in e als ( ype II), he sys ema ic unce ain y in insic o
he i p ocedu e can a ec he da a poin s in a co ela ed way ( ype I). The unce ain ies
– 7 –
JHEP07(2015)051
Figu e 4. The a e age ans e se momen um hpTio inclusi e J/ψ measu ed a mid- apidi y
(|y|<0.8) in cen ali y selec ed Pb-Pb collisions ( illed ci cles) and pp collisions (open ci cles) a
√sNN = 2.76 TeV as a unc ion o he numbe o pa icipan s hNpa i. The unco ela ed sys ema ic
unce ain ies ( ype II) a e depic ed by he open boxes. Le panel: a compa ison o esul s ob ained
by he PHENIX collabo a ion o Au-Au and Cu-Cu collisions a √sNN = 0.2 TeV [9,72] (open
and illed diamonds) and by he NA50 collabo a ion o Pb-Pb collisions a √sNN = 17.3 GeV [73]
(c osses). The hpTi alues a e calcula ed o NA50 and PHENIX in he pTin e al 0–5 GeV/c, while
o ALICE he pTin e al is 0–10 GeV/c. Righ panel: hpTiis compa ed o heo y p edic ions by
Zhou e al. [74] and Zhao e al. [75,76] o he pTin e al 0–10 GeV/c.
Cen ali y hpTi(GeV/c)hp2
Ti(GeV 2/c2)
0–10% 2.23 ±0.10 ±0.08 5.50 ±0.58 ±0.25
10–40% 2.01 ±0.12 ±0.08 4.97 ±0.65 ±0.34
40–90% 2.02 ±0.19 ±0.29 5.15 ±1.05 ±1.23
pp 2.54 ±0.02 ±0.01 9.07 ±0.15 ±0.07
Table 4. The nume ical alues o hpTiand hp2
Ticalcula ed in he ange 0 < pT<10 GeV/c o
he h ee analyzed cen ali y in e als in Pb-Pb collisions ( he i s unce ain y is he s a is ical
and he second is he unco ela ed sys ema ic ( ype II), he co ela ed unce ain y has a alue o
2%, see able 2). The alues o pp collisions ob ained by he in e pola ion p ocedu e a e gi en as
a e e ence.
J/ψ spec al unc ions, h oughou he e olu ion o a he mally expanding i eball. I also
inco po a es nuclea shadowing by educing he inpu cha m c oss sec ion by a ac o o
up o 1/3, wi h a cen ali y dependence as es ima ed in [78]. The e is a ai ag eemen
be ween ou hpTi esul s and he model calcula ion, while he AA is no desc ibed by his
p edic ion. Ou hpTiand AA esul s a e also compa ed wi h he calcula ions by Zhou
e al. [74]. These calcula ions a e also based on a anspo app oach and inco po a e
dissocia ion and egene a ion o J/ψ and hea ie cha monia, as well as nuclea shadowing
– 14 –

JHEP07(2015)051
Figu e 5. The a io AA =hp2
TiAA/hp2
Tipp in he pTin e al 0–10 GeV/c o inclusi e J/ψ mea-
su ed a mid- apidi y (|y|<0.8) in cen ali y selec ed Pb-Pb collisions ( illed ci cles) a √sNN =
2.76 TeV as a unc ion o he numbe o pa icipan s hNpa i. The unco ela ed sys ema ic unce -
ain ies ( ype II) a e depic ed by he open boxes, while co ela ed unce ain y ( ype I) is shown as
he illed box a uni y. Le panel: a compa ison o esul s ob ained by he PHENIX collabo a ion
o Au-Au and Cu-Cu collisions a √sNN = 0.2 TeV [9,72] ( illed diamonds) and by he NA50
collabo a ion o Pb-Pb collisions a √sNN = 17.3 GeV [73] (c osses). The PHENIX and NA50
AA alues a e calcula ed in he pTin e al 0–5 GeV/c. Righ panel: AA is compa ed o heo y
p edic ions by Zhou e al. [74] and Zhao e al. [75,76] o he pTin e al 0–10 GeV/c.
acco ding o EKS98 [51]. While he mos cen al da a poin is ma ched by he p edic ion,
i does no desc ibe he e olu ion o AA owa ds pe iphe al collisions. I mus be no ed
ha ou esul s om Pb-Pb collisions a o wa d apidi y [79] exhibi a con inuous dec ease
o hpTiand AA om pe iphe al owa ds cen al e en s and a e hus close o he heo y
p edic ions, while he beha iou o mid- apidi y Pb-Pb esul s is mo e compa ible wi h a
la hNpa idependence.
The RAA o inclusi e J/ψ in h ee pTin e als is shown in igu e 6along wi h he
esul s by he CMS collabo a ion o he in e al 6.5< pT<30 GeV/c [13], bo h in 0–40%
mos cen al Pb-Pb collisions. The co esponding nume ical alues a e 0.82 ±0.11(s a .) ±
0.10(sys .) o he in e al 0 < pT<2.5 GeV/c and 0.58 ±0.06(s a .) ±0.08(sys .) o
2.5< pT<6 GeV/c, whe e he sys ema ic unce ain ies quo ed he e a e he unco ela ed
( ype II) ones, as lis ed in able 1. The da a poin o 4.5< pT<10 GeV/c co esponds
o he RAA alue gi en in able 5(cen ali y ange 0–50%). Table 5also con ains he RAA
alues o p omp J/ψ, which a e nume ically iden ical o he ones o inclusi e J/ψ. The
inclusi e RAA alues below pT= 6 GeV/c a e signi ican ly highe han hose measu ed a
highe pT, co esponding o a dec ease o RAA wi h inc easing pT, while he high pTda a
poin is close o he CMS measu emen . This pTdependence is simila o he one obse ed
a o wa d apidi y [12], and is in clea con as o he pTdependence measu ed a lowe
– 15 –
JHEP07(2015)051
Figu e 6. The nuclea modi ica ion ac o RAA o inclusi e J/ψ, measu ed a mid- apidi y
(|y|<0.8) in Pb-Pb collisions (0–40% mos cen al) a √sNN = 2.76 TeV, as a unc ion o ans e se
momen um pT. The illed symbols a e placed a he measu ed pT o he gi en in e al. Since o
he da a poin in 4.5< pT<10 GeV/c (open symbol, 0–50% mos cen al) hpTiis no a ailable due
o he limi ed s a is ics, i is plo ed a he cen e o he pTin e al. The unco ela ed sys ema ic
unce ain ies ( ype II) a e depic ed by he open boxes, while he co ela ed unce ain ies ( ype I)
a e shown as he illed boxes a uni y. The da a a e compa ed o co esponding esul s by PHENIX
o Au-Au collisions (0–40% mos cen al) a √sNN = 0.2 TeV [9], by CMS o Pb-Pb collisions
(0–40% mos cen al) a √sNN = 2.76 TeV [13], and o p edic ions by he model o Zhou e al. [74]
and Zhao e al. [75,76].
cen e-o -mass ene gies by he PHENIX collabo a ion o √sNN = 0.2 TeV [9]. Figu e 6
also shows he model p edic ions by Zhou e al. [74]. The alue o he p edic ed RAA is
sys ema ically below he measu emen and exhibi s a pTdependence simila o he one in
he da a. The p edic ion by Zhao e al. [75,76] is close o ou esul . In bo h models,
he ise o RAA owa ds pT= 0 is due o he dominan con ibu ion om J/ψ egene a ion
ia coalescence.
The ac ion o non-p omp J/ψ in he pT ange 1.5–10 GeV/c is shown as a unc ion
o he numbe o pa icipan s o he cen ali y in e als 40–90% (hNpa i= 38), 10–40%
(hNpa i= 192), and 0–10% (hNpa i= 356) in he le panel o igu e 7. Wi hin unce ain-
ies, no cen ali y dependence is obse ed. The pTdependence o B(cen ali y: 0–50%)
is shown in he igh panel o igu e 7and compa ed wi h he measu emen s by CMS in
he cen ali y in e al 0–100% and pT>6.5 GeV/c ( o he nume ical alues see able 5).
Ou esul s a low ans e se momen a ex end he CMS measu emen s in Pb-Pb collisions
owa ds lowe pT. Also shown a e esul s a mid- apidi y in pp a √s= 7 TeV (ALICE [37],
ATLAS [35] and CMS [70]) and in p¯p collisions a √s= 1.96 TeV (CDF [57]). Conside ing
he ALICE and CMS esul s in Pb-Pb collisions oge he , a simila pTdependence as in pp
– 16 –
JHEP07(2015)051
Figu e 7. The ac ion o J/ψ om beau y had on decays Ba mid- apidi y measu ed in he
pTin e al 1.5< pT<10 GeV/c o cen ali y selec ed Pb-Pb collisions a √sNN = 2.76 TeV (le ).
The pTdependence o Ba mid- apidi y o Pb-Pb (√sNN = 2.76 TeV, |yJ/ψ|<0.8) and pp (√s=
7 TeV, |yJ/ψ|<0.9) [37] collisions is compa ed wi h measu emen s by CDF (|yJ/ψ|<0.6) [57],
ATLAS (|yJ/ψ|<0.75) [35], and CMS (|yJ/ψ|<0.9) [13,70] ( igh ).
pT(GeV/c) B(%) RAA(inclusi e J/ψ)RAA(p omp J/ψ)RAA(non-p omp J/ψ)
0.0–1.5 – 0.89±0.20±0.21 – –
1.5–4.5 10.7±4.8±2.5 0.76±0.09±0.08 0.76±0.10±0.08 0.73±0.34±0.20
4.5–10.0 17.0±6.1±2.2 0.38±0.07±0.06 0.38±0.07±0.06 0.37±0.15±0.09
Table 5. The nume ical alues on he ac ion o J/ψ om beau y had on decays Ba mid-
apidi y and he nuclea modi ica ion ac o s RAA o inclusi e, p omp and non-p omp J/ψ o
Pb-Pb collisions a √s= 2.76 TeV. These esul s co espond o he cen ali y in e al 0–50%. The
i s unce ain y is s a is ical and he second unco ela ed sys ema ic ( ype II).
is obse ed. Howe e , his simila i y could be coinciden al, being due o a compensa ion o
he medium e ec s on he p omp componen (J/ψ dissocia ion and ecombina ion) and
on he non-p omp pa (b-qua k ene gy loss).
In igu e 8 he nuclea modi ica ion ac o o non-p omp J/ψ o 1.5< pT<
4.5 GeV/c and 4.5< pT<10 GeV/c is shown oge he wi h he esul by CMS o
6.5< pT<30 GeV/c [13] and wi h heo e ical model p edic ions [30,31,59–61,80–85].
One should no e ha he cen ali y anges a e no he same o ALICE (0–50%) and CMS
(0–20% and 20–100%). Howe e , he esul s ob ained by CMS o hese wo cen ali y bins
a e compa ible wi h each o he , and also compa ible wi h ou measu emen in he high
pTin e al (4.5< pT<10 GeV/c). The model by Upho e al. [61] ollows a pa onic
anspo app oach based on he Bol zmann equa ion, which allows in e ac ions among all
pa ons. I does no include adia i e p ocesses o hea y qua ks. The calcula ion has been
– 17 –
JHEP07(2015)051
Figu e 8. The nuclea modi ica ion ac o RAA a mid- apidi y (|y|<0.8) o non-p omp
J/ψ in Pb-Pb collisions a √sNN = 2.76 TeV as a unc ion o ans e se momen um pT. The
ALICE measu emen co esponds o he 0–50% cen ali y ange and o he pTin e als 1.5<
pT<4.5 GeV/c and 4.5< pT<10 GeV/c. The unco ela ed sys ema ic unce ain ies ( ype II) a e
depic ed by he open boxes, while he co ela ed unce ain ies ( ype I) a e shown as illed boxes
a uni y. Resul s by CMS o highe pTin he cen ali y ange 0–20% and 20–100% [13] a e also
shown ( he wo poin s ha e been sligh ly displaced ho izon ally o be e isibili y). The da a
a e compa ed o heo e ical p edic ions a mid- apidi y (see ex o de ails). In he igh panel,
he ALICE esul in he pTin e al 4.5< pT<10 GeV/c is compa ed o heo e ical p edic ions
in eg a ed o e he same pT ange.
pe o med o a ixed impac pa ame e b= 5 m. In he model o Albe ico e al. [59,60] he
p opaga ion o he hea y qua ks in he medium is desc ibed by he ela i is ic Lange in
equa ion. The p edic ed pTdependence o RAA is s ongly in luenced by he choice o
anspo coe icien s. Two alues a e conside ed, ei he as p o ided by a pe u ba i e
calcula ion (ha d he mal loop app oach) o ex ac ed om la ice-QCD simula ions. The
calcula ions ha e been p o ided o he cen ali y ange 0–50%. A anspo app oach,
which is based on a s ong-coupling scheme, is employed in he model o He e al. [80]. The
anspo is implemen ed using non-pe u ba i e in e ac ions o hea y qua ks and mesons
h ough he QGP, had oniza ion and had onic phases o a nuclea collision. In pa icu-
la , he elas ic hea y-qua k sca e ing in he QGP is e alua ed wi hin a he modynamic
T-ma ix app oach, by gene a ing esonances close o he c i ical empe a u e ha can in
u n ecombine in o B mesons, ollowed by had onic di usion using e ec i e had onic sca -
e ing ampli udes. The hyd odynamic e olu ion o he sys em is quan i a i ely cons ained
by he measu ed ans e se momen um dis ibu ions and ellip ic low o ligh had ons. Ra-
dia i e p ocesses, which should imp o e he desc ip ion a high pT, a e no included in his
app oach. The calcula ions ha e been pe o med in he cen ali y ange 0–50%. The model
o Vi e e al. [30,31] assumes he exis ence o open hea y la ou bound-s a e solu ions
in he QGP in he icini y o he c i ical empe a u e. A desc ip ion o beau y qua k
quenching is combined wi h B meson inelas ic b eakup p ocesses. Fu he mo e, modi ied
– 18 –
JHEP07(2015)051
beau y pa on dis ibu ion unc ions and beau y agmen a ion unc ions in a co-mo ing
plasma a e implemen ed in his calcula ion. The p edic ion is shown o a ixed cen ali y,
co esponding o hNpa i= 200, a alue e y close o he a e age numbe o pa icipan s in
he cen ali y ange 0–50%. In he model, a sizable ac ion o he supp ession is asc ibed o
he inelas ic b eak-up p ocesses (collisional dissocia ion), as can be deduced om igu e 8
by compa ing he ull model p edic ion wi h and wi hou he con ibu ion o his speci ic
p ocess. The model o Djo dje ic [81], shown in igu e 8 o he cen ali y ange 0–50%,
uses a o malism ha akes in o accoun ini e size dynamical QCD medium wi h ini e
magne ic mass e ec s and unning coupling. In he WHDG model [82] (cen ali y ange
0–50%) he ene gy loss is compu ed using pe u ba i e QCD and conside ing bo h elas ic
and inelas ic pa onic collisions and pa h leng h luc ua ions. The app oach o Aichelin
e al. [83,84] includes a con ibu ion o adia i e gluon emission in he in e ac ion o hea y
qua ks wi h ligh qua ks, which a e conside ed as dynamical sca e ing cen e s. In his
model he ela i e con ibu ion o he ene gy loss by adia i e p ocesses, as compa ed o
collisional ones, is in luenced by in oducing a ini e gluon mass. The esul s o he model
shown in igu e 8, which a e ob ained o he cen ali y ange 0–50%, co espond o ei he
a pu e collisional scena io o a combina ion o collisional and adia i e ene gy loss. Finally,
in he model o Ho owi z and Gyulassy [85], also applied o he cen ali y in e al 0–50%,
he s ing inspi ed AdS/CFT g a i y-gauge heo y co espondence [86,87] is applied o he
case o hea y qua k ene gy loss. In he igh hand inse o igu e 8, he ALICE RAA alue,
in eg a ed o e he ange 4.5< pT<10 GeV/c, is compa ed o heo e ical p edic ions com-
pu ed in he same pT ange. Mos o he models p edic a la ge alue o RAA han obse ed
in he measu emen . Howe e , mo e p ecise da a a e needed o disc imina e among he
di e en models. The nex LHC un will p o ide inc eased s a is ics o his measu emen .
4 Conclusions
A s udy o J/ψ p oduc ion a mid- apidi y in Pb-Pb collisions a √sNN = 2.76 TeV has
been p esen ed. A educ ion o he inclusi e J/ψ hpTiis obse ed in Pb-Pb collisions in
compa ison o pp. The a io AA =hp2
TiAA/hp2
Tipp is ound o be signi ican ly below uni y,
co esponding o a medium-induced change in he shape o he pTspec a. The nuclea
modi ica ion ac o RAA depends on pT. I is a ound 0.8 o pT<2.5 GeV/c and eaches,
a highe pT, almos he same le el o supp ession as obse ed a RHIC ene gies a low pT.
These obse a ions migh be indica i e o a sizable con ibu ion o cha m qua k coalescence
o he J/ψ p oduc ion a low pT. T anspo models including his addi ional componen
a e able o quali a i ely desc ibe he ea u es seen in he da a.
The ac ion o J/ψ om beau y had on decays is de e mined as a unc ion o cen ali y
and pT. No signi ican cen ali y dependence is obse ed. By combining his measu emen
wi h he inclusi e J/ψ esul s he RAA o non-p omp J/ψ is ob ained in he egion 1.5<
pT<10 GeV/c, hus ex ending he co e age o CMS o he low pT egion. The nuclea
modi ica ion in he egion 4.5< pT<10 GeV/c is ound o be s onge han p edic ed by
mos o he models.
– 19 –

JHEP07(2015)051
Acknowledgmen 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 Collabo 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 ac-
knowledges he ollowing unding agencies o hei suppo in building and unning he AL-
ICE de ec o : S a e Commi ee o Science, Wo ld Fede a ion o Scien is s (WFS) and Swiss
Fonds Kidagan, A menia, Conselho Nacional de Desen ol imen o Cien ´ı ico e Tecnol´ogico
(CNPq), Financiado a de Es udos e P oje os (FINEP), Funda¸c˜ao de Ampa o `a Pesquisa do
Es ado de S˜ao Paulo (FAPESP); Na ional Na u al Science Founda ion o China (NSFC),
he Chinese Minis y o Educa ion (CMOE) and he Minis y o Science and Technology 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 Resea 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 Finland; 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 Technol-
ogy, Minis y o De elopmen , G eece; Hunga ian O szagos Tudomanyos Ku a asi Alapp-
g ammok (OTKA) and Na ional O ice o Resea ch and Technology (NKTH); Depa 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 o-
mo 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 enschappelijk 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 ˇa ii S¸ iin i ice – Execu i e Agency o Highe Educa ion Resea ch De elop-
men 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 Foun-
da ion o Basic Resea ch; Minis y o Educa ion o Slo akia; Depa men o Science and
Technology, Sou h A ica; Cen o de In es igaciones Ene ge icas, Medioambien ales y Tec-
nologicas (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 (Con-
selle ´ıa de Educaci´on), Cen o de Aplicaciones Tecnol´ogicas y Desa ollo Nuclea (CEA-
DEN), Cubaene g´ıa, Cuba, and IAEA (In e na ional A omic Ene gy Agency); Swedish
– 20 –
JHEP07(2015)051
Resea ch Council (VR) and Knu & Alice Wallenbe g Founda ion (KAW); Uk aine Min-
is y o Educa ion and Science; Uni ed Kingdom Science and Technology 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
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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– 23 –
JHEP07(2015)051
15 Commissa ia `a l’Ene gie A omique, IRFU, Saclay, F ance
16 COMSATS Ins i u e o In o ma ion Technology (CIIT), Islamabad, Pakis an
17 Depa amen o de F´ısica de Pa ´ıculas and IGFAE, Uni e sidad de San iago de Compos ela,
San iago de Compos ela, Spain
18 Depa men o Physics and Technology, Uni e si y o Be gen, Be gen, No way
19 Depa men o Physics, Aliga h Muslim Uni e si y, Aliga h, India
20 Depa men o Physics, Ohio S a e Uni e si y, Columbus, Ohio, Uni ed S a es
21 Depa men o Physics, Sejong Uni e si y, Seoul, Sou h Ko ea
22 Depa men o Physics, Uni e si y o Oslo, Oslo, No way
23 Dipa imen o di Ele o ecnica ed Ele onica del Poli ecnico, Ba i, I aly
24 Dipa imen o di Fisica dell’Uni e si `a ’La Sapienza’ and Sezione INFN Rome, I aly
25 Dipa imen o di Fisica dell’Uni e si `a and Sezione INFN, Caglia i, I aly
26 Dipa imen o di Fisica dell’Uni e si `a and Sezione INFN, T ies e, I aly
27 Dipa imen o di Fisica dell’Uni e si `a and Sezione INFN, Tu in, I aly
28 Dipa imen o di Fisica e As onomia dell’Uni e si `a and Sezione INFN, Bologna, I aly
29 Dipa imen o di Fisica e As onomia dell’Uni e si `a and Sezione INFN, Ca ania, I aly
30 Dipa imen o di Fisica e As onomia dell’Uni e si `a and Sezione INFN, Pado a, I aly
31 Dipa imen o di Fisica ‘E.R. Caianiello’ dell’Uni e si `a and G uppo Collega o INFN, Sale no, I aly
32 Dipa imen o di Scienze e Inno azione Tecnologica dell’Uni e si `a del Piemon e O ien ale and
G uppo Collega o INFN, Alessand ia, I aly
33 Dipa imen o In e a eneo di Fisica ‘M. Me lin’ and Sezione INFN, Ba i, I aly
34 Di ision o Expe imen al High Ene gy Physics, Uni e si y o Lund, Lund, Sweden
35 Ebe ha d Ka ls Uni e si ¨a T¨ubingen, T¨ubingen, Ge many
36 Eu opean O ganiza ion o Nuclea Resea ch (CERN), Gene a, Swi ze land
37 Excellence Clus e Uni e se, Technische Uni e si ¨a M¨unchen, Munich, Ge many
38 Facul y o Enginee ing, Be gen Uni e si y College, Be gen, No way
39 Facul y o Ma hema ics, Physics and In o ma ics, Comenius Uni e si y, B a isla a, Slo akia
40 Facul y o Nuclea Sciences and Physical Enginee ing, Czech Technical Uni e si y in P ague,
P ague, Czech Republic
41 Facul y o Science, P.J. ˇ
Sa ´a ik Uni e si y, Koˇsice, Slo akia
42 Facul y o Technology, Buske ud and Ves old Uni e si y College, Ves old, No way
43 F ank u Ins i u e o Ad anced S udies, Johann Wol gang Goe he-Uni e si ¨a F ank u ,
F ank u , Ge many
44 Gangneung-Wonju Na ional Uni e si y, Gangneung, Sou h Ko ea
45 Gauha i Uni e si y, Depa men o Physics, Guwaha i, India
46 Helsinki Ins i u e o Physics (HIP), Helsinki, Finland
47 Hi oshima Uni e si y, Hi oshima, Japan
48 Indian Ins i u e o Technology Bombay (IIT), Mumbai, India
49 Indian Ins i u e o Technology Indo e, Indo e (IITI), India
50 Inha Uni e si y, Incheon, Sou h Ko ea
51 Ins i u de Physique Nucl´eai e d’O say (IPNO), Uni e si ´e Pa is-Sud, CNRS-IN2P3, O say, F ance
52 Ins i u ¨u In o ma ik, Johann Wol gang Goe he-Uni e si ¨a F ank u , F ank u , Ge many
53 Ins i u ¨u Ke nphysik, Johann Wol gang Goe he-Uni e si ¨a F ank u , F ank u , Ge many
54 Ins i u ¨u Ke nphysik, Wes ¨alische Wilhelms-Uni e si ¨a M¨uns e , M¨uns e , Ge many
55 Ins i u Plu idisciplinai e Hube Cu ien (IPHC), Uni e si ´e de S asbou g, CNRS-IN2P3,
S asbou g, F ance
56 Ins i u e o Nuclea Resea ch, Academy o Sciences, Moscow, Russia
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
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JHEP07(2015)051
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 ional Ins i u e o Suba omic Physics, 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
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
– 31 –
JHEP07(2015)051
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, USA
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
– 32 –