N. Topilskaya, A.Kurepin – INR, Moscow

Transverse momentum dependence of charmonium production in heavy

ion collisions.

3rd INT. WORKSHOP ON HIGH-PT PHYSICS

AT LHCTOKAJ, HUNGARY

March, 16-19, 2008Tokaj, Hungary

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

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 c, ’– sequential screening (first: c, ’, J/ only well above Tc)– regeneration via statistical hadronization or charm coalescence

● important for “large” charm yield, i.e. RHIC and LHC

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

Fit to the mass spectrumFit to the mass spectrum

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

Projectile

Target

J/

J/ψ production has been extensively studied in p-A, S-U and Pb-Pb collisions by the NA38 and NA50 experiments at the CERN SPS

J/ normal nuclear

absorption curve

• 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

4.18 0.35mbJabs

NA60 : is anomalous suppression present also in lighter In-In nuclear systems ? Scaling variable- L, Npart, ε ?

NA60 experimental setup

MUON FILTER

BEAMTRACKER

TARGETBOX

VERTEX TELESCOPE

Dipole field2.5 T

BEAM

IC

not to scale

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

Matching in coordinate and in momentum space

ZDC allows studies vs. collision centrality

beam

~ 1m Muon Spectrometer

MWPC’s

Trigger Hodoscopes

Toroidal Magnet

IronwallHadron absorber

ZDC

Target area

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

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

Comparison of J//DY results

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

Direct J/ in In-In

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

Anomalous suppression begins in the range 80 < NPart < 100

Large systematic errors

Nuclearabsorption

The ratio Measured / Expected is normalized to the standard analysis

EZDC(TeV)

Сomparison J/ results vesus Npart

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

J/ suppression in In-In is in agreement with Pb-Pb S-U has different behaviour

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

(J/)/DY = 29.2 2.3L = 3.4 fm

’ suppression (NA38, NA50, NA60)

Small statistics in NA60 In-In for ’ (~300) The most peripheral point (Npart~60) – normal nuclear absorption

Preliminary!

abs=8±1 mb

abs~20 mb

Suppression by produced hadrons (“comovers”)

In-In 158 GeV

The model takes into account nuclear absorption and comovers interaction

with σco = 0.65 mb (Capella-Ferreiro) EPJ C42(2005) 419

J/

NC

oll

nuclear absorption

comover + nuclear absorption

Pb-Pb 158 GeV

(E. Ferreiro, private communication)

NA60 In-In 158 GeV

QGP + hadrons + regeneration + in-medium effects

Pb-Pb 158 GeV

B

J/

/D

Y

Nuclear Absorption

Regeneration

QGP+hadronic suppression

Suppression + Regeneration

In-In 158 GeV

Number of participants

fixed thermalization timecentrality dependent thermalization time

The model simultaneously takes into account dissociation and regeneration processes in

both QGP and hadron gas (Grandchamp, Rapp, Brown EPJ C43 (2005) 91)

centrality dependent thermalization time

fixed thermalization time

NA60 In-In 158 GeV

The dashed line includes the smearing due to the resolution

Suppression due to a percolation phase transition

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

~ 140 for In-In

Model based on percolation (Digal-Fortunato-Satz)

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

Pb-Pb 158 GeV

NA60 In-In 158 GeV

• Comparison J/ production with calculations

• nuclear absorption ---• maximal possible __ absorption in a hadron gas (T = 180 MeV)

• Pb-Pb and In-In (in lower order) show extra suppression

L. Maiani et al.,Nucl.Phys. A748(2005) 209F. Becattini et al.,Phys. Lett. B632(2006) 233

Maximal hadronic absorption

l –transverse size of fire-ball

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?

J/transverse momentum distribution J/transverse momentum distribution

Study <pT2> and T

dependence on centrality

NA60 In-In

J/transverse momentum distribution J/transverse momentum distribution

NA50 and NA38Fitting : <pT

2>(L) = <pT2>pp + αgN L

Simultanious fit with an energy dependent pT

2pp and a common slope:gN= 0.081±0.002 (GeV/c)2/fm-1

Then model dependent extrapolation of alldata to 158 GeV

J/ transverse momentum distributionJ/ transverse momentum distribution

<pT

2> versus L

Fitting : <pT

2>(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

J/ transverse momentum distribution in p-AJ/ transverse momentum distribution in p-A

<pT

2> 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 the energy of the collision

• 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

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

NA60 p-A and In-In andNA50 Pb-Pb - at 158 GeV and in the same kinematical domain

<pT

2> versus L

NA50 and NA38 Teff rescalculated to 158 GeV vs energy density

In NA38 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.

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

Сomparison T( J/ψ) at 158 GeVСomparison T( J/ψ) at 158 GeV

Fitting functions

Fitting functions: dN/dMT ~ MT

2K1(MT/T) – NA50dN/dMT ~ MT exp(-MT/T) – NA60 – gives slightly lower temperature ~ 7 MeV

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

J/ψ suppression versus pT.

F=(J/DY>4.2

acc vs p

T in 5 E

T bins

NA50 Pb-Pb 2000

Et bins in GeV

1. 5 - 202. 20 - 403. 40 - 704. 70 - 1005. >100

F

pT

F

F=(J/DY>4.2

acc vs E

T in 11 p

T bins

NA50 Pb-Pb 2000 log scale

5 Et bins

Clear centrality dependence for low pt.

Much weaker dependence for high pt.

J/ψ suppression versus ET.

Rcp = (J/ψi(p

T)/DY

i>4.2)/(J/ψ

1(p

T)/DY

1>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 p

T where it strongly

increases with centrality. For central events the suppression exists over the whole p

T range.

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

S-U

Pb-Pb 2000

Et bins GeV

5 - 40 40 - 80 80 – 125

p-A

Cronin effect- enhancement at p

T>2 GeV/c

Rcp

Rcp

~Aα

0-1.5% 1.5-5 % 5-10% 10-16%

16-23% 23-33% 33-47% 47-57%

pT (GeV/c)

RA

A

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

NA60 In-In

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

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

pT (GeV/c)

RC

P

0-1.5% 1.5-5% 5-10% 10-16%

16-23% 23-33% 33-47%

NA60 In-In

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

Large suppression at low pT, growing with centrality- as in RAA NA60and in Rcp NA50.

Rcp vs pT.

Rcp = (J/ψi(pT)/Ncoll i)/(J/ψ1(pT)/Ncoll1)

• The J/ 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 <pT

2> 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.

Summary for SPS dataSummary for SPS data

J/ in PHENIXJ/ e+e–

identified in RICH and EMCal– |y| < 0.35 – Pe > 0.2 GeV/c– =

J/μ+μ– identified in 2 fwd

spectrometersSouth :

• -2.2 < y < -1.2North :

• 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

Satz

Rapp

Capella

J/,’,c

All models for y=0

nucl-ex/0611020

nucl-ex/0611020

Yan, Zhuang, Xunucl-th/0608010

PHENIX Au-Au data

Without regeneration With regeneration

Models for mid-rapidity Au-Au data

Suppression RAA vs Npart at RHIC.

(dN/dy)AuAu

(dN/dy)pp x<Ncol> RAA =

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: A. Adare et al. (PHENIX) PRL 98 232301 (2007)Cu+Cu: A. Adare et al. (PHENIX) arXiv:0801.0220

Au+Au (|y|<0.35)

Au+Au (1.2<|y|<2.2)

Cu+Cu (|y|<0.35)

Cu+Cu (1.2<|y|<2.2)

•J/ 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.

Suppression RAA vs Npart at RHIC.

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

arXiv:0801.0220 [nucl-ex]

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

PHENIX invariant cross sections of J/

For low pT suppression grows with centrality.

J/ψ suppression RAA vs pT at PHENIX.

nucl-ex/0611020

Au-AuarXiv:0801.0220 [nucl-ex]

Cu-Cu

Comparison SPS (NA60) and RHIC (PHENIX) data

The same suppression atlow pT.

Larger values of <pT2> at

RHIC

P

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

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.

PHENIX and STAR Cu-Cu data

J/ψ suppression RAA at RHIC.

• 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

• At SPS energies the J/ 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.

ConclusionsConclusions

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.