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Transverse momentum dependence of charmonium production in heavy ion collisions. N. Topilskaya, A.Kurepin – INR, Moscow . 3rd INT. WORKSHOP ON HIGH-PT PHYSICS AT LHC TOKAJ, HUNGARY March, 16-19, 2008 Tokaj , Hungary. Charmonium.

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slide1

Transverse momentum dependence of charmonium production in heavy ion collisions.

N. Topilskaya, A.Kurepin – INR, Moscow

3rd INT. WORKSHOP ON HIGH-PT PHYSICS AT LHCTOKAJ, HUNGARY March, 16-19, 2008Tokaj, Hungary

slide2

Charmonium

  • 33 years ago:discovery of J/ψ, 21 years ago: Matsui & Satz
  • colour screening in deconfined matter →J/ψ suppression
  • →possible signature of QGP formation
  • Experimental and theoretical progress since then → situation is much more complicated
    • cold nuclear matter / initial state effects
      • “normal” absorption in cold matter
      • (anti)shadowing
      • saturation, color glass condensate
    • suppression via comovers
    • feed down from cc, y’
    • sequential screening (first: cc, y’, J/y only well above Tc)
    • regeneration via statistical hadronization or charm coalescence
      • important for “large” charm yield, i.e. RHIC and LHC

Tokaj, N.Topilskaya, March 16-19, 2008

slide3

NA50 experimental setup

The J/ is detected via its decay into muon pairs

Dimuon spectrometer: Centrality detectors: EM calorimeter (1.1< lab<2.3)

2.92 < ylab< 3.92 ZDC calorimeter (lab> 6.3)

cos CS < 0.5 Multiplicity detector (1.9<lab<4.2)

Pb-Pb 158 GeV/c p – A 400 GeV/c 2000 year

Data period Subtargets Number of J/ Target Number of J/

1995 7 50000 Be 38000

1996 7 190000 Al 48000

1998 1 49000 Cu 45000

2000 1 in vacuum 129000 Ag 41000

W 49000

Pb 69000

J/y suppression is generally considered as one of the most direct signatures of QGP formation (Matsui-Satz 1986)

slide5

Light systems and peripheral Pb-Pb collisions:J/ψ is absorpted by nuclear matter . The scaling variable -L (length of nuclear matter crossed by the J/ψ)

  •  (J/ψ) ~ exp( -abs L)
  • Central Pb-Pb collisions:the L scaling is broken - anomalous suppression

J/ψ suppression from p-A to Pb-Pb collisions

J/ψ production has been extensively studied inp-A, S-UandPb-Pbcollisions by the NA38 and NA50 experiments at the CERN SPS

Projectile

J/y

Target

J/y normal nuclear absorption curve

NA60 : is anomalous suppression present also in lighter In-In

nuclear systems ?Scaling variable- L, Npart, ε ?

slide6

MWPC’s

m

~ 1m

Muon Spectrometer

Iron

wall

Hadron absorber

Toroidal Magnet

Target area

m

beam

Trigger Hodoscopes

Dipole field2.5 T

ZDC

TARGET

BOX

MUON FILTER

Matching in coordinate and in momentum space

BEAM

BEAMTRACKER

VERTEX

TELESCOPE

IC



not to scale

  • Origin of muons can be accurately determined
  • Improved dimuon mass resolution

allows studies vs.

collision centrality

ZDC

NA60 experimental setup

High granularity and radiation-hard silicon tracking telescope in the vertex region before the absorber

slide7

Comparison of J//DY results

An “anomalous suppression” is presented already in In-In

The normal absorption curve is based on NA50 results. Its uncertainty (~ 8%) at 158 GeV is dominated by the (model dependent) extrapolation from the 400 and 450 GeV

p-A data.

need p-A measurements at 158 GeV

slide8

Direct J/ in In-In

Data are compared with a theoretical J/ distribution, obtained within the Glauber model, taking into account the nuclear absorption.

The ratio Measured / Expected is normalized to thestandard analysis

Nuclear

absorption

Anomalous suppression begins in the range 80 < NPart < 100

Large systematic errors

EZDC(TeV)

slide9

Сomparison J/resultsvesus Npart

NA50: Npart ftom Et (left) and from Ezdc (right, as in NA60)

J/ysuppression inIn-Inis in agreement withPb-Pb

S-Uhas different behaviour

slide10

(J/)/DY = 29.2  2.3

L = 3.4 fm

Сomparison of J//DY

Preliminary NA60 results on p-A at 158 GeV show that rescaling from 400 and 450 GeV to 158 GeV is correct.

Results on abs will appear soon HP08- crucial to confirm (or modify) the anomalous suppression pattern

slide11

Preliminary!

’ suppression(NA38, NA50, NA60)

abs=8±1 mb

abs~20 mb

Small statistics in NA60 In-In for’ (~300)

The most peripheral point (Npart~60)– normal nuclearabsorption

slide12

Suppression by produced hadrons (“comovers”)

The model takes into account nuclear absorption and comovers interaction with σco = 0.65 mb (Capella-Ferreiro) EPJ C42(2005) 419

In-In 158 GeV

J/y / NColl

nuclear absorption

comover + nuclear absorption

(E. Ferreiro, private communication)

Pb-Pb 158 GeV

NA60 In-In 158 GeV

slide13

QGP + hadrons + regeneration + in-medium effects

The model simultaneously takes into account dissociation and regeneration processes in both QGP and hadron gas (Grandchamp, Rapp, Brown EPJ C43 (2005) 91)

In-In 158 GeV

fixed thermalization time

centrality dependent thermalization time

BmmsJ/y/sDY

Nuclear Absorption

Suppression + Regeneration

QGP+hadronic suppression

Regeneration

Number of participants

Pb-Pb 158 GeV

centrality dependent thermalization time

fixed thermalization time

NA60 In-In 158 GeV

slide14

Suppression due to a percolation phase transition

Model based on percolation (Digal-Fortunato-Satz)

Eur.Phys.J.C32 (2004) 547.

Prediction: sharp onset (due to the disappearance of the cc meson) at Npart ~ 125 for Pb-Pb and

~ 140 for In-In

Pb-Pb 158 GeV

NA60 In-In 158 GeV

The dashed line includes the smearing due to the resolution

slide15

Maximal hadronicabsorption

  • Comparison J/ production
  • with calculations
    • nuclear absorption---
    • maximal possible __
    • absorption in a hadron
    • gas(T = 180 MeV)

L. Maiani et al.,

Nucl.Phys. A748(2005) 209

F. Becattini et al.,Phys. Lett. B632(2006) 233

l –transverse size of fire-ball

  • Pb-Pb and In-In (in lower order)showextra suppression
slide16

Comparison of experimental SPS data.

p-A:

J/ and - normal nuclear absorption

S-U:

J/ - normal nuclear absorption

 - anomalous suppression

Pb-Pb:

J/ - onset of anomalous suppression

- anomalous suppression ~ S-U

In-In:

J/ - onset of anomalous suppression

- anomalous suppression < S-U

Open question: S-U vs In-In ? Theoretical description?

slide17

J/transverse momentum distribution

Study <pT2> and T dependence on centrality

NA60 In-In

slide18

J/transverse momentum distribution

NA50 and NA38

Fitting: <pT2>(L) = <pT2>pp + αgN L

Simultanious fit with an energy dependent pT2pp and

a common slope:

gN= 0.081±0.002 (GeV/c)2/fm-1

Then model dependent

extrapolation of all

data to 158 GeV

slide19

J/transverse momentum distribution

<pT2> versus L

Fitting: <pT2>(L) = <pT2>pp + αgN L

<pT2>pp= 1.08 ± 0.02 GeV2/c2

χ2= 0.85

 αgN = 0.083 ± 0.002 GeV2/c2fm-1

The observed dependence could simply

result from parton initial state multiple

scattering

slide20

J/transverse momentum distribution in p-A

<pT2> versus L

NA60 p-A at 158 GeV/c-

the same energy and kinematical domain as

Pb-Pb and In-In

New 158 GeV/c data show that at SPS gN

depends on

theenergy of the collision

slide21

J/transverse momentum distribution in p-A and A-A

<pT2> versus L

NA60p-A and In-In and

NA50 Pb-Pb - at 158 GeV

and in the same kinematical

domain

  • pT2 increases linearly with L in both p-A, In-In and Pb-Pb
  • However, the scaling of pT2 with L is broken moving from p-A to A-A
  • On one hand comparing p-A and peripheral In-In the suppression scales with L
  • On the other hand the J/ pT distributions do not scale with L
slide22

NA50 and NA38 Teff rescalculated to

158 GeV vs energy density

T(=0) =( 182)2 MeV

Tslope = ( 20.16  1.04)  10-3 fm3

Tslope(cent Pb-Pb)=(8.87  2.07) 10-3 fm3

R(slopes)=2.27 +/- 0.54

InNA38 and NA50 TJ/ ψ grows linearly with the energy density and with L.

Model dependent recalculation 400 and 200 GeV data to 158 GeV- scaling.

For the most central Pb-Pb collisions more flat behaviour could be seen.

slide23

СomparisonT(J/ψ) at 158 GeV

Fitting functions:

dN/dMT ~ MT2K1(MT/T) – NA50

dN/dMT ~ MT exp(-MT/T) – NA60 –

gives slightly lower temperature ~ 7 MeV

Fitting functions

No scaling with L for p-A and A-A

slide24

J/ψ suppression versus pT.

F=(J//DY>4.2 )acc vs pT in 5 ET bins

F

NA50 Pb-Pb 2000

F

Et bins in GeV

1. 5 - 20

2. 20 - 40

3. 40 - 70

4. 70 - 100

5. >100

pT

slide25

J/ψ suppression versus ET.

F=(J//DY>4.2 )acc vs ET in 11 pT bins

5 Et bins

NA50 Pb-Pb 2000

log scale

Clear centrality dependence for low pt.

Much weaker dependence for high pt.

slide26

Rcp = (J/ψi(pT)/DYi>4.2)/(J/ψ1(pT)/DY1>4.2)

Pb-Pb NA50

5 Et bins

The ratios to the most peripheral E 1 bin.

The suppression vs the most peripheral events is significant mainly at low pT where it strongly increases with centrality. For central events the suppression exists over the whole pT range.

slide27

Suppression vs pT for p-A, S-U and Pb-Pb

Rcp

p-A

S-U

~Aα

Cronin effect- enhancement at pT>2 GeV/c

Pb-Pb 2000

Rcp

Et bins GeV

5 - 40

40 - 80

80 – 125

slide28

RAA

0-1.5%

1.5-5 %

5-10%

10-16%

16-23%

23-33%

33-47%

47-57%

pT (GeV/c)

NA60 In-In

Nuclear modification factor RAA=NAA/(Npp*<Ncoll>)

J/ pT distribution for pp was calculated in the form 1/pT dN/dpT ~ MTK1(MT/T) – systematic error 11%

Enhancement (Cronin effect) at pT > 2 GeV/c

slide29

1.5-5%

5-10%

10-16%

0-1.5%

RCP

23-33%

16-23%

33-47%

pT (GeV/c)

Rcp vs pT.

NA60 In-In

Rcp = (J/ψi(pT)/Ncolli)/(J/ψ1(pT)/Ncoll1)

The ratios to the peripheral i=1 (47-57%)bin.

Large suppression at low pT, growing with centrality- as in RAA NA60

and in Rcp NA50.

slide30

Summary for SPS data

  • The J/y shows an anomalous suppression discovered in Pb-Pb
  • and existing already in In-In
  • None of the available models properly describes the observed suppression pattern simultaneously in Pb-Pb and In-In
  • The transverse momentum dependence for p-A and A-A at 158 GeV
  • shows no L scaling in <pT2>

The suppression in Pb-Pb and In-In is significant mainly at low

pT where it strongly increases with centrality.

For central events the Rcp suppression exists over the whole

pT range in Pb-Pb and In-In.

In p-A, S-U, peripheral Pb-Pb events and in RAA In-In the

enhancement for pT> 2 GeV (Cronin effect) is seen.

slide31

J/ in PHENIX

J/  e+e–

identified in RICH and EMCal

  • |y| < 0.35
  • Pe > 0.2 GeV/c
  •  = 

J/μ+μ–

identified in 2 fwd spectrometers

South :

    • -2.2 < y < -1.2

North :

    • 1.2 < y < 2.4
  • P > 2 GeV/c
  •  = 2 

Event centrality and vertex given by

BBC in 3<||<3.9 (+ZDC)

Centrality is calculated to Npart (Ncoll) using Glauber model

slide32

Yan, Zhuang, Xu

nucl-th/0608010

All models for y=0

nucl-ex/0611020

nucl-ex/0611020

J/,’,c

Satz

Capella

Rapp

Suppression RAA vs Npart at RHIC.

PHENIX Au-Au data

Models for mid-rapidity Au-Au data

Without regeneration

With regeneration

slide33

(dN/dy)AuAu

(dN/dy)pp x<Ncol>

RAA=

Suppression RAA vs Npart at RHIC.

Au+Au: A. Adare et al. (PHENIX) PRL 98 232301 (2007)

Cu+Cu: A. Adare et al. (PHENIX) arXiv:0801.0220

  • Cold Nuclear Matter (CNM) effects
    • Nuclear absorption
    • Gluons shadowing
  • Evaluated from J/ψ production
  • in d+Au collisions.
  • A.Adare et al. (PHENIX) arXiv:0711.3917

Au+Au

(|y|<0.35)

Cu+Cu

(|y|<0.35)

  • J/y suppression at mid-rapidity
  • at RHIC is compatible to
  • CNM effects except most central Au+Au collisions.
  • Stronger suppression at forward
  • rapidity than CNM effects.

Cu+Cu

(1.2<|y|<2.2)

Au+Au

(1.2<|y|<2.2)

slide34

J/ψ suppression (SPS and RHIC)

J/ψ yield vs Npart,

normalized on Ncoll.

Unexpected good scaling.

Coherent interpretation-

problem for theory.

Work start - : Karsch, Kharzeev and Satz., PRL637(2006)75

slide35

arXiv:0801.0220 [nucl-ex]

PHENIX invariant cross sections of J/y

J/y was measured from pT=0GeV/c to beyond pT =5GeV/c.

slide36

arXiv:0801.0220 [nucl-ex]

J/ψ suppression RAA vs pT at PHENIX.

Au-Au

Cu-Cu

nucl-ex/0611020

For low pT suppression grows with centrality.

slide37

Comparison SPS (NA60) and RHIC (PHENIX) data

The same suppression at

low pT.

Larger values of <pT2> at

RHIC

slide38

Suppression RAA in Au-Au (PHENIX) vs pT.

P

J/ψ up to only 5 GeV

Central events

The same RAA for

0,  at all pT

and J/ (up to 4 GeV/c).

RAA for  is higher.

RAA for direct  <1 for

high pT.

slide39

J/ψ suppression RAA at RHIC.

PHENIX and STAR Cu-Cu data

  • Data consistent with no suppression at

high pT: RAA(pT > 5 GeV/c) = 0.9 ± 0.2

  • At low-pT RAA: 0.5—0.6 (PHENIX)
  • RAA increase from low pT to high pT
  • Most models expect a decrease RAA at

high pT:

X. Zhao and R. Rapp, hep-ph/07122407

H. Liu, K. Rajagopal and U.A. Wiedemann,

PRL 98, 182301(2007) and hep-ph/0607062

  •  But some models predict an increase RAA
  • at high pT:
  • K.Karch and R.Petronzio, 193(1987105;
  • J.P.Blaizot and J.Y.Ollitrault, PRL (1987)499
slide40

Conclusions

  • At SPS energiesthe J/y shows an anomalous suppression discovered in Pb-Pb and existing already in In-In
  • None of the available models properly describes the observed suppression pattern simultaneously in Pb-Pb and In-In
  • The  shows an anomalous suppression for S-U, In-In
  • and Pb-Pb
  • At RHIC energies the J/suppression is of the same order as at SPS
  • None of the theoretical model could describe all the data
  • The transverse momentum dependence of J/ψ suppression shows
  • suppression mainly ay low pT, growing with centrality
  • Need information at high pT.
slide41

Hope- measurement at LHC with high values of energy density

and transverse momentum pT.

Need- high statistic pp, p-A and A-A data at the same conditions.

Work for theory.

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