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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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N. Topilskaya, A.Kurepin – INR, Moscow


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    1. 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

    2. 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

    3. 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)

    4. Fit to the mass spectrum

    5. 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 ?

    6. 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

    7. 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

    8. 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)

    9. 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

    10. (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

    11. 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

    12. 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

    13. 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

    14. 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

    15. 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

    16. 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?

    17. J/transverse momentum distribution Study <pT2> and T dependence on centrality NA60 In-In

    18. 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

    19. 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

    20. 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

    21. 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

    22. 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.

    23. 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

    24. 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

    25. 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.

    26. 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.

    27. 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

    28. 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

    29. 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.

    30. 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.

    31. 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

    32. 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

    33. (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)

    34. 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

    35. 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.

    36. 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.

    37. Comparison SPS (NA60) and RHIC (PHENIX) data The same suppression at low pT. Larger values of <pT2> at RHIC

    38. 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.

    39. 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

    40. 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.

    41. 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.