N. Topilskaya, A.Kurepin – INR, Moscow Transverse momentum dependence of charmonium production in heavy ion collisions. 3rd INT. WORKSHOP ON HIGH-PT PHYSICS AT LHC TOKAJ, HUNGARY March, 16-19, 2008 Tokaj, 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 T c ) – 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) )  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/  Be Al Cu in vacuum Ag W Pb J/  suppression is generally considered as one of the most direct signatures of QGP formation (Matsui-Satz 1986)

Fit to the mass spectrum

J/ψ suppression from p-A to Pb-Pb collisions Projectile Target J/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 NA60 : is anomalous suppression present also in lighter In-In nuclear systems ? Scaling variable- L, Npart, ε ?

NA60 experimental setup MUON FILTER BEAM TRACKER TARGET BOX VERTEX TELESCOPE Dipole field 2.5 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 Iron wall Hadron 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 < N Part < 100 Large systematic errors Nuclear absorption The ratio Measured / Expected is normalized to the standard analysis E ZDC (TeV)

Сomparison J/  results vesus N part 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  2.3 L = 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 σ co = 0.65 mb (Capella-Ferreiro) EPJ C42(2005) 419 J/  NColl 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/  /  DY Nuclear Absorption Regeneration QGP+hadronic suppression Suppression + Regeneration In-In 158 GeV Number of participants fixed thermalization time centrality 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 N part ~ 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) 209 F. 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 Study and T dependence on centrality NA60 In-In

J/  transverse momentum distribution NA50 and NA38 Fitting : (L) = pp + α gN L Simultanious fit with an energy dependent  p T 2  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

J/  transverse momentum distribution versus L Fitting : (L) = pp + α gN L pp = 1.08 ± 0.02 GeV 2 /c 2 χ 2 = 0.85  α gN = ± 0.002 GeV 2 /c 2 fm -1 The observed dependence could simply result from parton initial state multiple scattering

J/  transverse momentum distribution in p-A 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

 p T 2  increases linearly with L in both p-A, In-In and Pb-Pb However, the scaling of  p T 2  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/  p T distributions do not scale with L J/  transverse momentum distribution in p-A and A-A NA60 p-A and In-In and NA50 Pb-Pb - at 158 GeV and in the same kinematical domain versus L

NA50 and NA38 Teff rescalculated to 158 GeV vs energy density In NA38 and NA50 T J/ 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 = (  1.04)  fm 3 Tslope(cent Pb-Pb)=(8.87  2.07) fm 3 R(slopes)=2.27 +/- 0.54

Сomparison T( J/ψ) at 158 GeV Fitting functions Fitting functions: dN/dM T ~ M T 2 K 1 (M T /T) – NA50 dN/dM T ~ M T exp(-M T /T) – NA60 – gives slightly lower temperature ~ 7 MeV No scaling with L for p-A and A-A

J/ψ suppression versus p T. F=(J/  DY>4.2  acc vs p T in 5 E T bins NA50 Pb-Pb 2000 Et bins in GeV >100 F pT 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 E T.

R cp = (J/ψ i (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 p T for p-A, S-U and Pb-Pb S-U Pb-Pb 2000 Et bins GeV – 125 p-A Cronin effect- enhancement at p T >2 GeV/c Rcp  ~A α

0-1.5%1.5-5 %5-10%10-16% 16-23%23-33%33-47%47-57% p T (GeV/c) R AA Nuclear modification factor R AA =N AA /(N pp * ) NA60 In-In Enhancement (Cronin effect) at p T > 2 GeV/c J/  p T distribution for pp was calculated in the form 1/p T dN/dp T ~ M T K 1 (M T /T) – systematic error 11%

p T (GeV/c) R CP 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 p T, growing with centrality- as in R AA NA60 and in R cp NA50. R cp vs p T. R cp = (J/ψ i (p T )/N coll i )/(J/ψ 1 (p T )/N coll 1 )

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 The suppression in Pb-Pb and In-In is significant mainly at low p T where it strongly increases with centrality. For central events the R cp suppression exists over the whole p T range in Pb-Pb and In-In. In p-A, S-U, peripheral Pb-Pb events and in R AA In-In the enhancement for p T > 2 GeV (Cronin effect) is seen. Summary for SPS data

J/  in PHENIX J/   e + e – identified in RICH and EMCal –|y| < 0.35 –P e > 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

Satz Rap p Capella J/ ,  ’,  c All models for y=0 nucl-ex/ Yan, Zhuang, Xu nucl-th/ PHENIX Au-Au data Without regenerationWith regeneration Models for mid-rapidity Au-Au data Suppression R AA vs N part at RHIC.

(dN/dy) AuAu (dN/dy) pp x R AA = Cold Nuclear Matter (CNM) effects Nuclear absorption Gluons shadowing Evaluated from J/ψ production in d+Au collisions. A.Adare et al. (PHENIX) arXiv: Au+Au: A. Adare et al. (PHENIX) PRL (2007) Cu+Cu: A. Adare et al. (PHENIX) arXiv: 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 R AA vs N part at RHIC.

J /ψ suppression (SPS and RHIC) J/ψ yield vs N part, normalized on N coll. Unexpected good scaling. Coherent interpretation- problem for theory. Work start - : Karsch, Kharzeev and Satz., PRL637(2006)75

arXiv: [nucl-ex] J/  was measured from p T =0GeV/c to beyond p T =5GeV/c. PHENIX invariant cross sections of J/ 

For low p T suppression grows with centrality. J/ψ suppression R AA vs p T at PHENIX. nucl-ex/ Au-Au arXiv: [nucl-ex] Cu-Cu

Comparison SPS (NA60) and RHIC (PHENIX) data The same suppression at low p T. Larger values of at RHIC

P Suppression R AA in Au-Au (PHENIX) vs p T. J/ψ up to only 5 GeV Central events The same R AA for  0,  at all p T and J/  (up to 4 GeV/c). R AA for  is higher. R AA for direct  <1 for high p T.

PHENIX and STAR Cu-Cu data J/ψ suppression R AA at RHIC. Data consistent with no suppression at high p T : R AA (p T > 5 GeV/c) = 0.9 ± 0.2 At low-p T R AA : 0.5—0.6 (PHENIX) R AA increase from low p T to high p T Most models expect a decrease R AA at high p T : X. Zhao and R. Rapp, hep-ph/ H. Liu, K. Rajagopal and U.A. Wiedemann, PRL 98, (2007) and hep-ph/  But some models predict an increase R AA at high p T : K.Karch and R.Petronzio, 193( ; 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 p T, growing with centrality Need information at high p T. Conclusions

Hope- measurement at LHC with high values of energy density and transverse momentum p T. Need- high statistic pp, p-A and A-A data at the same conditions. Work for theory.