charmonium suppression in pb-pb collisions from...

Hyunchul Kim Quarkonium 2013, IHEP

Charmonium suppression in Pb-Pb collisions from CMS

Hyunchul Kim 金铉哲 (Korea University)

for the CMS Collaboration

The 9th International Workshop on Heavy Quarkonium

IHEP, Beijing, China, Apr 23rd, 2013

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Contents •  Motivation of the study •  CMS detector(Muon reconstruction mechanism) •  Results (until Quark Matter 2012)

–  Charmonia •  prompt J/ψ •  non-prompt J/ψ •  ψ(2S)

•  Summary

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https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsHIN

–  Bottomonia – ϒ(1S, 2S, 3S) : Byungsik Hong’s talk (Next session, 3rd talk)


Theoretical motivation

3 E. Scomparin, CERN seminar (06/11/2012)

Perturbative vacuum Hot-dense matter

Agnes Mocsy: Potential Models for Quarkonia 5

Fig. 5. The QGP thermometer.

In principle, a state is dissociated when no peak struc-ture is seen, but the widths shown in spectral functionsfrom current potential model calculations are not physi-cal. Broadening of states as the temperature increases isnot included in any of these models. At which T the peakstructure disappears then? In [27] we argue that no needto reach Ebin = 0 to dissociate, but when Ebin < T a stateis weakly bound and thermal fluctuations can destroy it.Let us quantify this statement.

Due to the uncertainty in the potential we cannot de-termine the binding energy exactly, but we can never-theless set an upper limit for it [27]: We can determineEbin with the most confining potential that is still withinthe allowed ranges by lattice data on free energies. Forthe most confining potential the distance where deviationfrom T = 0 potential starts is pushed to large distancesso it coincides with the distance where screening sets in[12]. From Ebin we can then estimate, following [28], thequarkonium dissociation rate due to thermal activation,obtaining this way the thermal width of a state Γ (T ).At temperatures where the width, that is the inverse ofthe decay time, is greater than the binding energy, that isthe inverse of the binding time, the state will likely to bedissociated. In other words, a state would melt before itbinds. For example, already close to Tc the J/ψ would meltbefore it would have time to bind. To quantify the dissoci-ation condition we have set a more conservative conditionfor dissociation: 2Ebin(T ) < Γ (T ). The result for differ-ent charmonium and bottomonium states is shown in thethermometer of figure 5. Note, that all these numbers areto be though of as upper limits.

In summary, potential models utilizing a set of poten-tials between the lower and upper limit constrained bylattice free energy lattice data yield agreement with lat-tice data on correlators in all quarkonium channels. Dueto this indistinguishability of potentials by the data the

precise quarkonium properties cannot be determined thisway, but the upper limit can be estimated. The decreasein binding energies with increasing temperature, observedin all the potential models on the market, can yield sig-nificant broadening, not accounted for in the currentlyshown spectral functions from these models. The upperlimit estimated using the confining potential predicts thatall bound states melt by 1.3Tc, except the Upsilon, whichsurvives until 2Tc. The large threshold enhancement abovefree propagation seen in the spectral functions even at hightemperatures, again observed in all the potential modelson the market, compensates for melting of states (yieldingflat correlators), and indicates that correlation betweenquark and antiquark persists. Lattice results are thus con-sistent with quarkonium melting.

And What’s Next?

Implications of the QGP thermometer of figure 5 for heavyion collisions should be considered by phenomenologicalstudies. This can have consequences for the understandingof the RAAmeasurements, since now the Jψ should meltat SPS and RHIC energies as well. The thermometer alsosuggests that the Υ will be suppressed at the LHC, andthat centrality dependence of this can reveal whether thishappens already at RHIC. So measurements of the Υ canbe an interesting probe of matter at RHIC as well as atthe LHC.

The exact determination of quarkonium properties thefuture is in the effective field theories from QCD at finiteT. First works on this already appeared [14] and both realand imaginary parts of the potential have been derivedin certain limits. In these works there is indication thatmost likely charmonium states dissolve in QGP due ther-mal effects, such as activation to octet states, screening,Landau-damping.

The correlations of heavy-quark pairs that is embeddedin the threshold enhancement should be taken seriouslyand its consequences, such as possible non-statistical re-combination taken into account in dynamic models thatattempt the interpretation of experimental data [24].

All of the above discussion is for an isotropic medium.Recently, the effect of anisotropic plasma has been con-sidered [29]. Accordingly, quarkonium might be strongerbound in an anisotropic medium, especially if it is alignedalong the anisotropy of the medium (beam direction).Qualitative consequences of these are considered in an up-coming publication [30]. Also, all of the above discussionrefers to quarkonium at rest. Finite momentum calcula-tions are under investigation. It is expected that a movingquarkonium dissociates faster.

Acknowledgment

I thank Peter Petreczky for collaboration on performingthis work and for carefully reading this manuscript. I amgrateful to the Organizers of Hard Probes 2008 for inviting

Mocsy, EPJ C 61 (2009) 705

T>T d

T<

T d

cc

ccc clight quark Td

Debye screening length

From Matsui & Satz PLB 178 (1986) 416

is melted cc

•  Heavy quarks produced in the initial hard-scattering process

•  Melting of quarkonia caused by Debye screening •  Use sequential melting of the quarkonia states as the

thermometer of the hot and dense matter


Experimental motivation •  Puzzles from SPS and RHIC

–  Similar J/ψ suppression at SPS(< 20 GeV) and RHIC(200 GeV) –  Suppression does not increase with local energy density RAA(forward) < RAA(mid)

– Possible answers •  regeneration? •  cold nuclear matter effects?

•  LHC can give the hint –  higher energy([email protected] TeV, [email protected] TeV) –  higher luminosity(peak instant luminosity : 0.5 Hz/µb@PbPb) –  more charm (possible to regenerate) –  more bottom → a new probe : ϒ

4

PHENIX, PRL 98 (2007) 232301 PRC 84 (2011) 054912 SPS from Scomparin @ QM06

Npart

RAA : Nuclear Modification Factor RAA>1:regeneration, RAA<1:suppression


Summary of Pb-Pb collision from LHC •  Pb-Pb collision

–  2.76 TeV per nucleon pair –  ~1 month per year in 2010, 2011 –  Integrated luminosity

•  2010 : 7.28 µb-1 •  2011 : 157.6 µb-1 recorded

•  pp [email protected] TeV per nucleon –  For comparison with Pb-Pb [email protected] TeV per nucleon pair –  Equivalent statistics compared to the integrated luminosity of the

2010 HI run

5

X20


CMS detector

6

Superconducting solenoid : 3.8 T Muon chambers Barrel : 250 DT, 480 RPC Endcaps : 468 CSC, 432 RPC

Silicon Trackers Pixel (100*150 µm) ~ 16m2, 66M channels Microstrips (80*180 µm) ~ 200m2, 9.6M channels


CMS muon reconstruction mechanism

•  Global muons reconstructed with information from inner tracker and muon stations

•  Apply with additional further muon ID quality cut (χ2, # of hits)

Superconducting Solenoid

inner tracker

muon station

Endcap Barrel

7


Acceptance and Efficiency •  Because of the magnetic field

and energy loss (2~3 GeV) in the iron yoke, Global muons need minimum pµ to reach the muon stations (3~5 GeV, depending on η)

•  Limits J/ψ acceptance –  mid-rapidity: pT, J/ψ>6.5 GeV/c –  forward: pT, J/ψ>3 GeV/c

8 µη

-2 -1.5 -1 -0.5 0 0.5 1 1.5 2

Effi

cien

cyµ

Sing

le

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Trigger Efficiency

- 0.002 + 0.0022011 MC PYTHIA+EvtGen: 0.860

- 0.004 + 0.0042011 Data: 0.915

CMS Preliminary = 2.76 TeVNNsPbPb

6.5 GeV/c≥ ψJ/T

p

(GeV/c)µ

Tp

0 2 4 6 8 10 12 14 16 18 20

Effi

cien

cyµ

Sing

le

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Trigger Efficiency

- 0.002 + 0.0022011 MC PYTHIA+EvtGen: 0.860

- 0.004 + 0.0042011 Data: 0.915


6.5 GeV/c≥ ψJ/T

p

•  Efficiencies are evaluated with MC

•  Crosschecked with tag-and-probe method in data and MC


Prompt, non-prompt J/ψ signal extraction

Inclusive J/ψ

Prompt J/ψ

Direct J/ψ Feed-down from ψ’ and χc

Non-Prompt J/ψ from B decays

•  Reconstruct µ+µ− vertex •  Separation of prompt and

non-prompt J/ψ –  by 2D simultaneous fit of µ+µ− mass

and pseudo-proper decay length

�J/� = LxymJ/�

pT

B Lxy

J/ψ µ− µ+

9 CMS-PAS HIN-12-014

pp 7TeV


Prompt J/ψ RAA : centrality dependence

•  With more statistics binning is more finer •  Suppressed by factor 5 in most central collision

10

partN0 50 100 150 200 250 300 350 400

AAR

0

0.2

0.4

0.6

0.8

1

1.2

1.4 CMS Preliminary = 2.76 TeVNNsPbPb

|y| < 2.4 < 30 GeV/c

T6.5 < p

ψPrompt J/

partN0 50 100 150 200 250 300 350 400

AAR

0

0.2

0.4

0.6

0.8

1

1.2

1.4

ψPrompt J/

= 2.76 TeVNNsCMS PbPb

|y| < 2.4 < 30 GeV/c

T6.5 < p

2010 2011 CMS-PAS HIN-12-014 JHEP 1205 (2012) 063


Prompt J/ψ RAA : y & pT dependence

11

•  No strong dependence on pT and rapidity (GeV/c)

Tp

0 5 10 15 20 25 30AA

R0

0.2

0.4

0.6

0.8

1

1.2


Cent. 0-100%|y| < 2.4

ψPrompt J/

|y|0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

AAR

0

0.2

0.4

0.6

0.8

1

1.2


Cent. 0-100% < 30 GeV/c

T6.5 < p

ψPrompt J/

CMS-PAS HIN-12-014


Prompt J/ψ RAA : y & pT dependence on centrality

partN0 50 100 150 200 250 300 350 400

AAR

0

0.2

0.4

0.6

0.8

1

1.2

1.4

|y|<1.21.2<|y|<1.61.6<|y|<2.4


ψPrompt J/

<30 GeV/cT

6.5<p

partN0 50 100 150 200 250 300 350 400

AAR

0

0.2

0.4

0.6

0.8

1

1.2

1.4

<30 GeV/cT

6.5<p<6.5 GeV/c

T3<p


ψPrompt J/

1.6<|y|<2.4

•  No strong dependence on rapidity at higher pT region

•  At forward rapidity region, there might be suppression of lower pT J/ψ

Rapidity dependence pT dependence

12

CMS-PAS HIN-12-014


Prompt J/ψ RAA : theory comparison

(GeV/c)T

p0 5 10 15 20 25 30

AAR

0

0.2

0.4

0.6

0.8

1

1.2


Cent. 0-100%|y| < 2.4

Rishi,Vitev: 0-100%f max

CNM E-loss + coll dissoc, T

f minCNM E-loss + coll dissoc, T

ψPrompt J/

partN0 50 100 150 200 250 300 350 400

AAR

0

0.2

0.4

0.6

0.8

1

1.2

1.4

ψPrompt J/

R. Rapp & X. Zhao (V=U)ψPrompt J/

ShadowingCroninFormation time


|y| < 2.4 < 30 GeV/c

T6.5 < p

•  In the high-pT region, no need for regeneration to describe data •  Treatment of quarkonia energy loss similarly as open flavor energy loss,

without color-octet included, is not supported by data

NPA 859 (2011) 114 + private communication arXiv:1203.0329 + private communication

13


partN0 50 100 150 200 250 300 350 400

AAR

0

0.2

0.4

0.6

0.8

1

1.2

1.4

ψNon-prompt J/

= 2.76 TeVNNsCMS PbPb

|y| < 2.4 < 30 GeV/c

T6.5 < p

0-20%20-100%

non-prompt J/ψ RAA : centrality dependence

partN0 50 100 150 200 250 300 350 400

AAR

0

0.2

0.4

0.6

0.8

1

1.2


|y| < 2.4 < 30 GeV/c

T6.5 < p

ψNon-prompt J/

•  With more statistics we observed the centrality dependent suppression of non-prompt J/ψ.

•  Directly measuring the b-quark energy loss in the medium

2011 Suppressed by

factor 2.5

14

CMS-PAS HIN-12-014 JHEP 1205 (2012) 063

2010


non-prompt J/ψ RAA : y and pT dependence

(GeV/c)T

p0 5 10 15 20 25 30

AAR

0

0.2

0.4

0.6

0.8

1

1.2


Cent. 0-100%|y| < 2.4

ψNon-prompt J/

|y|0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

AAR

0

0.2

0.4

0.6

0.8

1

1.2


Cent. 0-100% < 30 GeV/c

T6.5 < p

ψNon-prompt J/

•  non-prompt J/ψ is less suppressed in mid-rapidity region than in forward region

•  non-prompt J/ψ in lower pT is slightly less suppressed than in higher pT


15

CMS-PAS HIN-12-014


non-prompt J/ψ RAA : y & pT dependence on centrality

partN0 50 100 150 200 250 300 350 400

AAR

0

0.2

0.4

0.6

0.8

1

1.2

1.4

|y|<1.21.2<|y|<1.61.6<|y|<2.4


ψNon-prompt J/

<30 GeV/cT

6.5<p

partN0 50 100 150 200 250 300 350 400

AAR

0

0.2

0.4

0.6

0.8

1

1.2

1.4

<30 GeV/cT

6.5<p<6.5 GeV/c

T3<p


ψNon-prompt J/

1.6<|y|<2.4


•  All rapidity bins at high pT region show centrality dependent suppression •  In the forward region, low pT J/ψ has strong centrality dependence and less

suppressed than high pT J/ψ

16

CMS-PAS HIN-12-014


non-prompt J/ψ RAA : theory comparison

(GeV/c)T

p0 5 10 15 20 25 30

AAR

0

0.2

0.4

0.6

0.8

1

1.2

1.4

WHDG: 0-80%, y~0Rad+Coll E loss

Vitev: 0-10%, y~0Rad E loss+CNMRad E loss+CNM+Dissoc

Buzatti: 0-100%, y~0CUJET preliminary

He,Fries,Rapp: 0-100%,y~0HF transport


|<2.4η | b-quarks: 0-100%)) -µ+µ(ψ(via secondary J/

Vitev: J. Phys.G35 (2008) 104011 + private communications Horowitz: arXiv:1108.5876 + private communications Buzzatti, Gyulassy: arXiv: 1207.6020+ private communications He, Fries, Rapp: PRC86(2012)014903+ private communications 17

•  For theory comparison, need to shift non-prompt J/ψ pT to higher pT side : J/ψ pT < B pT

•  Within large uncertainties, data is described with various theoretical scenarios.

•  Model involving only radiative energy loss and cold nuclear matter effects clearly fails to describe the data


b-quark RAA compared with other particles

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partN0 50 100 150 200 250 300 350 400

AAR

0

0.2

0.4

0.6

0.8

1

1.2

1.4 CMS = 2.76 TeVNNsPbPb

b-quarks

)-µ+µ(ψvia secondary J/<30 GeV/c),|y|<2.4

T6.5<p

ALICE: c-quarks*+, D+, D0average D

<12 GeV/c, |y|<0.5T

6<p

In central collisions RAA

charm < RAAbottom

ALICE : arXiv:1203.2160 CMS : CMS-PAS HIN-12-014 b-quark is suppressed distinctly

CMS Highlights from Gunther Roland@QM12


ψ(2S) in pp & PbPb at √sNN = 2.76 TeV

19

PAS CMS-HIN-12-007 Low-pT, forward region (pT>3 GeV/c and 1.6<|y|<2.4)

)2 (GeV/cµµm2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2

)2Ev

ents

/ ( 0

.04

GeV

/c

310


-1bµ = 150 intL

0-20%, 1.6 < |y| < 2.4 < 30 GeV/c

T3 < p

112±: 3510 ψJ/N 0.020±: 0.105 (2S)ψR

2 1) MeV/c± = (50 σ

datatotal fitbackground

Rψ(2S) = Nψ(2S) /NJ/ψ limited by pp statistics Rψ(2S)

PbPb ~ 5 × Rψ(2S) pp

PbPb 2011 pp

PbPb fit


)2 (GeV/cµµm2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2

)2Ev

ents

/ ( 0

.04

GeV

/c

210

310


-1bµ = 150 intL

0-20%, |y| < 1.6 < 30 GeV/c

T6.5 < p

65±: 3211 ψJ/N 0.008±: 0.024 (2S)ψR

2 1) MeV/c± = (29 σ

datatotal fitbackground

ψ(2S) in pp & PbPb at √sNN = 2.76 TeV

20

High-pT, mid-rapidity region (pT>6.5 GeV/c and |y|<1.6) PAS CMS-HIN-12-007

Rψ(2S) PbPb ~ 0.5 × Rψ(2S)

pp Rψ(2S) = Nψ(2S) /NJ/ψ

PbPb fit

PbPb 2011 pp


ψ (2S) results

partN0 50 100 150 200 250 300 350 400

pp]ψ

J/⁄(2

S)

ψ[⁄ Pb

Pb]

ψJ/⁄

(2S)

ψ[

0

1

2

3

4

5

6

7

8

9

10 = 2.76 TeVNNsPbPb

< 30 GeV/c, 1.6 < |y| < 2.4T

3 < p

pp uncertainty (global)

CMS Preliminary

partN0 50 100 150 200 250 300 350 400

0

0.2

0.4

0.6

0.8

1

1.2

1.4 = 2.76 TeVNNsPbPb

< 30 GeV/c, |y| < 1.6T

6.5 < p

pp uncertainty (global)

CMS Preliminary

N (2S)/NJ/ |PbPb

N (2S)/NJ/ |pp = RAA( (2S)RAA(J/ )

R0�100%AA ( (2S)) = 0.11±0.03(stat)±0.02(syst)±0.02(pp)

R0�100%AA ( (2S)) = 1.54±0.32(stat)±0.22(syst)±0.76(pp)

AA AA AA AA

limited by pp statistics from 2011 pp data

Low-pT, forward region

High-pT, mid-rapidity region

21

CMS-PAS HIN-12-007


Summary •  CMS measured the suppression of prompt J/ψ from

2.76 TeV PbPb collisions. •  Also the suppression of non-prompt J/ψ is measured

and this indicates the suppression of the bottom quark in heavy-ion collisions

•  In Low-pT, forward region, the enhancement of ψ(2S) relative to prompt J/ψ is observed, but need to more statistics in pp collisions.

•  With new 5.02 TeV pPb collision data and enhanced 2.76 TeV pp data, CMS is doing the charmonia analysis.

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Thank you for your attention 谢谢


BACK UP

23


Acceptable region for single muon

24

JHEP 1205 (2012) 063

•  Choose the region which the single muon efficiency is larger than 0.1

•  Upper than white line


b fraction of J/ψ production

25

(GeV/c)T

p0 5 10 15 20 25 30

b fra

ctio

n

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1 = 2.76 TeV (|y|<2.4)NNsCMS PbPb = 2.76 TeV (1.6<|y|<2.4)NNsCMS PbPb

= 2.76 TeV (|y|<2.4)sCMS pp = 2.76 TeV (1.6<|y|<2.4)sCMS pp = 7 TeV (1.6 < |y| < 2.4)sCMS pp = 7 TeV (1.2 < |y| < 1.6)sCMS pp = 7 TeV (|y| < 1.2)sCMS pp = 1.96 TeV (|y|<0.6)s pCDF p


Summary of 2013 pPb & pp collision •  proton-Pb ion collisions (2013. Jan. ~ Feb)

–  Beam Energy : 5.02 TeV/nucleon (proton : 4 TeV, Pb ion : 1.58 TeV) –  Asymmetry collision, boosted to Pb ion backward direction –  Beam configuration

–  Pbp(B1:p,B2:Pb ion) collision : Jan. 20th ~ 30th

•  acceptance : - 2.4 ~ + 1.46 •  Integrated luminosity : 18.4 nb-1

–  pPb(B1:Pb ion,B2:p) collision : Feb. 2nd ~ 10th •  Change beam direction requested by ALICE •  acceptance : - 1.46 ~ + 2.4 •  Integrated luminosity : 12.5 nb-1

•  proton-proton collisions (Feb. 11th ~ 14th) –  For the reference to pPb, PbPb data –  Beam energy : 2.76 TeV/proton –  Integrated luminosity : 5.41 pb-1

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- η CMS + η Beam 2(B2) Beam 1(B1)

charmonium suppression in pb-pb collisions from...

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