Andry Rakotozafindrabe LLR – École Polytechnique J/ production in Cu+Cu and Au+Au collisions at √sNN = 200 GeV measured by PHENIX at RHIC Andry Rakotozafindrabe LLR – École Polytechnique 42nd Rencontres de Moriond QCD session – Italy (March 2007)

Physics motivation – the starting point What are the properties of the hot and dense matter produced in relativistic heavy ion collisions ? c and b are produced in the initial parton collisions, so they can be used to probe the created medium : open charm (or beauty) energy loss  energy density Topic already covered this morning by Alan Dion , (quarkonia) suppressed by color screening  deconfinement At lower energy, NA50 (CERN) experiment measured an anomalous J/ suppression in Pb+Pb collisions, in excess of the normal suppression expected from the nuclear absorption. NA50 Collaboration, Eur. Phys. J. C39 (2005) 335 At lower energy, NA60 (CERN) recent results in In+In At RHIC energy ? 10x √sNN 2-3x gluon density 23/03/2007 Andry Rakotozafindrabe – LLR

Screening the J/ in a QGP Production ~ 60% direct production J/ ~ 30% via χc J/ + x ~ 10% via ’ J/ + x Temperature of dissociation Td for χc and ’: Td ~ 1.1 Tc for J/ : Td ~ 1.5 to 2 Tc Sequential dissociation as the temperature (or energy density) increases : Satz, J.Phys.G32:R25,2006 ’ χc J/ Energy density (τ0 = 1fm) vs the max. √s for SPS, RHIC and LHC 23/03/2007 Andry Rakotozafindrabe – LLR

Physics motivation – a few complications J/ or  + feed-down b, ’, c J/ + x quarkonia production g+g fusion dominant at RHIC energies Final state “Normal” nuclear absorption Absorption by (hadronic ?) comovers ? Color screening ? In-medium formation (recombination) ? Flow ? Sensitive to: Initial state Modification of the parton distribution functions (shadowing, CGC) pT broadening (Cronin effect) Parton energy loss in the initial state ? 23/03/2007 Andry Rakotozafindrabe – LLR

J/ in PHENIX : capsule history Run Species √s [GeV ] Ldt # J/ # J/ Reference |y|<0.35 1.2<|y|<2.2 01 Au+Au 130 1 b-1 02 Au+Au 200 24 b-1 13 PRC69, 014901 (2004) p+p 200 0.15 pb-1 46 65 PRL92, 051802 (2004) 03 d+Au 200 2.74 nb-1 364 1186 PRL96, 012304 (2006) p+p 200 0.35 pb-1 130 448 04 Au+Au 200 241 b-1 1000 4449 nucl-ex/0611020 Au+Au 62 9 b-1 05 Cu+Cu 200 3 nb-1 2300 9000 coming soon Cu+Cu 62 0.19 nb-1 146 Cu+Cu 22.5 2.7 b-1 p+p 200 3.8 pb-1 1500 8005 hep- ex/0611020 06 p+p 200 10.7 pb-1 p+p 62 0.1 pb-1 23/03/2007 Andry Rakotozafindrabe – LLR

Andry Rakotozafindrabe – LLR PHENIX detector J/  e+e– |y| < 0.35 Pe > 0.2 GeV/c  =  Tracking, momentum measurement with drift chambers, pixel pad chambers e ID with EmCAL + RICH J/µ+µ– 1.2< |y| < 2.2 Pµ > 2 GeV/c  = 2 Tracking, momentum measurement with cathode strip chambers µ ID with penetration depth / momentum match Centrality measurement, vertex position Beam-beam counters (charged particle production) Zero-degree calorimeters (spectator neutrons) 23/03/2007 Andry Rakotozafindrabe – LLR

Production baseline : (Run5) p+pJ/ @ √s = 200 GeV energy rapidity Cross section vs : pT hep-ex/0611020 Cross section vs rapidity better constraints on available J/ production mechanisms Total cross section in p+p Bll.pp(J/ ) = 178 ± 3(stat) ± 53(sys) ± 18(norm) nb in agreement with COM Cross section vs pT Forward rapidity <pT2> = 3.59 ± 0.06 ± 0.16 Central rapidity p+pJ/ measurement used as a reference for A+BJ/ : 23/03/2007 Andry Rakotozafindrabe – LLR

Heavy ion results @ √s = 200 GeV Au+Au final results : nucl-ex/0611020 Cu+Cu preliminary results (QM05) but forthcoming final results (article in preparation) with increased statistics in the dielectron channel (a factor ~2) significant improvement of systematic errors better precision measurement than the present Au+Au results for Npart<~100 1 RAA Bar: uncorrelated error Bracket : correlated error 23/03/2007 Andry Rakotozafindrabe – LLR

RHIC : beyond cold nuclear matter effects Available d+Au data qCNM : Weak shadowing and weak nuclear absorption (σabs ~ 1mb favored) derived from model Vogt PRC71, 054902 (2005) Au+Au data : even compared to the « worst » σabs~ 2mb case shown here suppression beyond cold effects for Npart>100 at y~1.7 Npart>200 at y~0 Need to improve the knowledge of CNM effects at RHIC Bar: uncorrelated error Bracket : correlated error nucl-ex/0611020 RHIC CNM effects : σ abs = 0, 1, 2 mb @ y=0, y=2 Cold nuclear matter predictions from Vogt, nucl-th/0507027 (shadowing + σabs) 23/03/2007 Andry Rakotozafindrabe – LLR

RHIC : different amount of suppression at different rapidities nucl-ex/0611020 RAA vs Npart : Stronger suppression at forward rapidity than at central rapidity Ratio forward/central ~0.6 for Npart>100 CGC (initial state effect) ? models predicts less heavy quark production at forward rapidity than at mid rapidity K. L. Tuchin J.Phys. G30 (2004) S1167 ratio RAA (1.2<|y|<2.2) /RAA (|y|<0.35) 1 RAA Bar: uncorrelated error Bracket : correlated error 23/03/2007 Andry Rakotozafindrabe – LLR

Andry Rakotozafindrabe – LLR RHIC vs SPS SPS @ 0<y<1 : √s ~ 17 GeV CNM = normal nuclear absorption σabs = 4.18 ± 0.35 mb Maximum ε ~ 3 GeV/fm3 (τ0 = 1) Compare to RHIC @ |y|<0.35 : x10 √s CNM = shadowing + nuclear absorption σabs from 0 to 2mb (Vogt, nucl-th/0507027) Maximum ε ~ 5 GeV/fm3 (τ0 = 1), higher than at SPS Same pattern of J/ suppression for the same rapidity! Suppression beyond CNM larger at RHIC NA50 at SPS (0<y<1) PHENIX at RHIC (|y|<0.35) PHENIX at RHIC (1.2<|y|<2.2) Bar: uncorrelated error Bracket : correlated error Global error = 12% is not shown 23/03/2007 Andry Rakotozafindrabe – LLR

RHIC vs SPS (II) : extrapolating suppression models Suppression models in agreement with NA50 data extrapolated at RHIC energies Opposite suppression behaviour vs rapidity Unmatched suppression pattern at central rapidity Recombination at work at RHIC ? Dissociation by thermal gluons (R. Rapp et al., nucl-th/0608033 Nu Xu et al., Phys.Rev.Lett. 97 (2006) 232301) Dissociation by comovers (Capella et al., hep-ph/0610313) 23/03/2007 Andry Rakotozafindrabe – LLR

Recombination at RHIC ? Suppression+recombination predictions compared to data RAA vs Npart R. Rapp et al. PRL 92, 212301 (2004) Thews Eur. Phys. J C43, 97 (2005) Nu Xu et al. Phys.Rev.Lett. 97 (2006) 232301 Bratkovskaya et al. PRC 69, 054903 (2004) A. Andronic et al. nucl-th/0611023 Better matching with the data but regeneration goes as the (single) charm density which is poorly known at RHIC What about the other variables ? 23/03/2007 Andry Rakotozafindrabe – LLR

Recombination at RHIC ? Suppression+recombination predictions compared to data RAA vs Npart Yield vs rapidity RMS 1.32±0.06 RMS 1.30±0.05 Recombination predicts a narrower rapidity distribution with an increasing Npart Data shows a slight decrease of the RMS with increasing centrality Thews & Mangano, PRC73 (2006) 014904c No recombination All recombination RMS 1.40±0.04 RMS 1.43±0.04 nucl-ex/0611020 23/03/2007 Andry Rakotozafindrabe – LLR

Recombination at RHIC ? Suppression+recombination predictions compared to data RAA vs Npart Yield vs rapidity <pT2> vs Ncoll No recombination Recombination predicts a narrower pT distribution with an increasing centrality, thus leading to a lower <pT²> Data shows a rather flat dependence of <pT²> with centrality With recombination Thews, Eur.Phys.J. C43 (2005) 97, Phys.Rev. C73 (2006) 014904 (and private communication). 23/03/2007 Andry Rakotozafindrabe – LLR

Ending where it began: revisiting the sequential dissociation (I) Karsch, Kharzeev & Satz, PLB 637 (2006) 75 : Sequential melting  overall J/ survival probability (measured/expected): S = 0.6 S direct J/  + 0.4 S J/←’, χc Recent lattice QCD results : direct J/ melting at 10-30 GeV/fm3  S ~ 0.6 at RHIC RAA/CNM vs. Bjorken energy density dET/dy : PHENIX, PRC 71, 034908 (2005) Bar: uncorrelated error Bracket : correlated error PHENIX Global error = 12% + 7% Box : uncertainty from CNM effects εBj.τ0 Sequential dissociation of ψ’ and χc only does not seem to be consistent with the data 23/03/2007 Andry Rakotozafindrabe – LLR

Refinement : 3D hydro + sequential dissociation (II) Gunji et al., hep-ph/0703061 : Charmonia initial spatial distribution = from collisions in the Glauber model + free streaming in a full (3D+1) hydro J/ survival probability ( RAA/CNM with CNM = shadowing + nuclear absorption σabs = 1mb ) S = (1 – fFD) S direct J/  + fFD S J/←’, χc 3 free parameters : feed-down fFD , melting temperatures TJ/ and T’,χc + (3D+1) hydro : same setup as the one used to reproduce charged dN/dη measured at RHIC Assuming thermalization for τ°≥°0.6°fm, initial energy density distribution in the transverse plane, EOS of the medium (T<Tc and T>Tc), … 23/03/2007 Andry Rakotozafindrabe – LLR

Refinement : 3D hydro + sequential dissociation (II) Gunji et al., hep-ph/0703061 : Charmonia J/ survival probability ( RAA/CNM with CNM = shadowing + nuclear absorption σabs = 1mb ) S = (1 – fFD) S direct J/  + fFD S J/←’, χc 3 free parameters : Feed-down fFD , melting temperatures TJ/ and T’,χc + (3D+1) hydro  best fit with : TJ/ = 2.12 Tc T’,χc = 1.34 Tc fFD = 0.25 ± 0.10 due to uncertainty on σabs (1 ± 1mb) Better matching with the data 23/03/2007 Andry Rakotozafindrabe – LLR

Andry Rakotozafindrabe – LLR Summary (I) PHENIX final results on J/dileptons at forward and mid-rapidity in p+p, Au+Au, and preliminary results in Cu+Cu : Improved baseline Run 5 p+p with x10 more statistics than Run 3 Suppression pattern Beyond cold nuclear effects for Npart > 200 More suppression at forward than at central rapidity Ratio forward/central ~0.6 for Npart>100 May be accounted for by CGC models Suppression models (comover) predicts the opposite behaviour Similar to SPS suppression in the same rapidity region? despite a higher energy density reached Understandable as recombinations that partially compensate the J/ suppression ? Still open question (test vs <pT²> dependance and rapidity distribution) 23/03/2007 Andry Rakotozafindrabe – LLR

Andry Rakotozafindrabe – LLR Summary (II) Alternate explanations ? Sequential dissociation with feed-down assumed to be ~40% and direct J/ not melting at present energy densities is not consistent with data (3D+1) hydro + sequential dissociation in agreement with mid-rapidity data if direct J/ is melting (at T = 2.12 Tc) and if feed-down is assumed to be (25 ± 10)% Feed-down not measured at RHIC energies At lower energies, large deviations between experiments Need to improve knowledge on cold nuclear effects at RHIC Stay tuned : forthcoming final results for Cu+Cu ! Improved precision for the measurements in the range Npart <~ 100 23/03/2007 Andry Rakotozafindrabe – LLR

Andry Rakotozafindrabe – LLR Back-up 23/03/2007 Andry Rakotozafindrabe – LLR

Andry Rakotozafindrabe – LLR Hint of things to come Final results for Cu+Cu What about the forward vs central suppression at lower Npart ? … Improved reference p+p : x3 higher statistics from run 6 Future measurements in ’ ? Future measurements in χc Planning Au+Au (1 nb-1 vs 0.24 nb-1 in run 4 ) with high luminosity during Run 7 Later runs : d+Au with higher luminosity (28 nb-1 vs 2.7 nb-1 in run 3) ? Run 6 200GeV p+p Invariant Mass (GeV/c2) A. Bickley, Hard Probes 06 (c - J/) Mass (GeV/c2) PHENIX Run 5 200GeV p+p Work under progress 23/03/2007 Andry Rakotozafindrabe – LLR

Upsilon measurement PHENIX QM05 Dimuon mass spectrum for the two muon arms added together. y~1.7 ~10 counts PHENIX : 1st Upsilons at RHIC from ~3pb-1 collected during the 2005 p+p run. y=0 ~50 cnts STAR QM06 STAR Preliminary p+p 200 GeV e+e- Minv Background Subtracted 23/03/2007 Andry Rakotozafindrabe – LLR

STAR results and near future M. Cosentino, QWG06 STAR Preliminary STAR – J/ Run4 AuAu STAR – J/ Run5 pp Dataset Au+Au@200 GeV : No trigger due to high background Just a faint signal For efficient J/y trigger, full barrel ToF is needed (just patch in Run5) p+p@200GeV (Run5): trigger commissioning (~1.7M events) Run 6: expect 500-1000 (work in progress) Upsilon 23/03/2007 Andry Rakotozafindrabe – LLR

Andry Rakotozafindrabe – LLR J/ production Production ~ 60% direct production J/ ~ 30% via χc J/ + x ~ 10% via ’ J/ + x Large deviations between experiments : χc feed-down fraction vs √s Not measured at RHIC energies 23/03/2007 Andry Rakotozafindrabe – LLR

Invariant yield vs tranverse momentum 23/03/2007 Andry Rakotozafindrabe – LLR

Andry Rakotozafindrabe – LLR <pT2> vs Npart A closer look at <pT2> vs Npart hep-ex/0611020 nucl-ex/0611020 23/03/2007 Andry Rakotozafindrabe – LLR

Cold nuclear effects : d+AuJ/ Vogt, PRC71, 054902 (2005), Kopeliovich, NP A696, 669 (2001) Phys. Rev. Lett. 96 (2006), 012304 Low x2 ~ 0.003 (shadowing region) Cold nuclear effects : d+AuJ/ gluons in Pb / gluons in p Anti Shadowing Shadowing x Nucl. Phys. A696 (2001) 729-746 Available d+Au data  CNM : Weak shadowing (modification of gluon distribution) and weak nuclear absorption (σabs ~ 1mb favored) derived from model Vogt PRC71, 054902 (2005) Data driven parametrizations of CNM Karsch, Kharzeev & Satz, PLB 637 (2006) 75 Granier de Cassagnac, hep-ph/0701222 xd xAu J/ South y < 0 rapidity y y < -1.2 : large xAu ~ 0.090 xd xAu J/ North y > 0 y > 1.2 : low xAu ~ 0.003 y ~ 0 : intermediate xAu ~ 0.020 23/03/2007 Andry Rakotozafindrabe – LLR

RHIC : beyond cold nuclear effects (II) ? Comparison to a data driven parametrization of CNM (Granier de Cassagnac, hep-ph/0701222) in the same centrality classes CNM : RAA(y, b) = Σcollisions[RdA(-y,b1i).RdA(+y,b2i)]/Ncoll Essentially the same conclusions as the previous slide But stat+syst error that comes from d+Au data are visible Need a higher luminosity d+Au sample 23/03/2007 Andry Rakotozafindrabe – LLR

J/ production in d+Au vs centrality High x2 ~ 0.09 Small centrality dependence Model with absorption + shadowing ( black lines* ): shadowing EKS98 σabs = 0 to 3 mb σabs = 1 mb good agreement σabs = 3 mb is an upper limit weak shadowing and weak nuclear absorption Low x2 ~ 0.003 *Colored lines: FGS shadowing for 3 mb 23/03/2007 Andry Rakotozafindrabe – LLR

SPS vs RHIC (III) : RAA/CNM vs Npart NA50 at SPS (0<y<1) PHENIX at RHIC (|y|<0.35) PHENIX at RHIC (1.2<|y|<2.2) SPS @ 0<y<1 : CNM = normal nuclear absorption σabs = 4.18 ± 0.35 mb Compare to RHIC @ |y|<0.35 : CNM = shadowing + nuclear absorption σabs=1 mb (Vogt, nucl-th/0507027) Additionnal syst. error from uncertainity on CNM Need to improve knowledge on cold nuclear effects at RHIC Suppression beyond CNM larger at RHIC Bar: uncorrelated error Bracket : correlated error Global errors (12% and 7%) are not shown here. Box : uncertainty from CNM effect 23/03/2007 Andry Rakotozafindrabe – LLR

100% Recombination (shape only) Recombination at RHIC ? RAA vs y 0mb 3mb 100% Recombination (shape only) R. Vogt nucl-th/0507027 (EKS) R. L. Thews, M. L. Mangano Phys.Rev. C73 (2006) 014904 23/03/2007 Andry Rakotozafindrabe – LLR

Andry Rakotozafindrabe – LLR Charm flow S. Sakai QM06 M. Djordjevic et al., Phys.Lett.B632 (2006) 81 dNg/dy=1000 c and b quark pT distributions at mid-rapidity before fragmentation : b contribution is dominant at high pT Significant flow observed for heavy flavor electrons Main source is D meson (1) Consistent with c-quark thermalization (2) large cross section is needed in AMPT ~10 mb (3) Resonance state of D & B in sQGP Charm quark strongly coupled to the matter [Phys.Lett. B595 202-208 ] [PRC72,024906] [PRC73,034913] 23/03/2007 Andry Rakotozafindrabe – LLR

Computing the J/ yield Invariant yield : i : i-th bin (centrality for e.g.) : number of ‘s reconstructed : probability for a thrown and embeded into real data to be found (considering reconstruction and trigger efficiency) : total number of events : BBC trigger efficiency for events with a : BBC trigger efficiency for minimum bias events For Au+Au or Cu+Cu collision : ~ 23/03/2007 Andry Rakotozafindrabe – LLR

Collision geometry and centrality (eg : Cu+Cu) Participants (charged particles) QBBC Spectators (neutrons) EZDC For a given b, Glauber model (Woods-Saxon function) predicts: Npart (No. participants) Ncoll (No. binary collisions) 10 fm b 0 fm 0 Npart 104 0 Ncoll 198 BBC charge N+S distribution for min.bias Cu+Cu √s = 200 GeV data 80-88% 70-80% etc Monte-Carlo Glauber model Probability for a given Npart Each participant contributes to a Negative Binomial distribution of hits Fit BBC charge distribution 23/03/2007 Andry Rakotozafindrabe – LLR

tsecondaries formation Energy density Longitudinally expanding plasma : dET/dη measurement at mid-rapidity by PHENIX EMCal Which τ0 ? pR2 t0 ~ 1 fm/c tcross ~ 0.13 fm/c tsecondaries formation ~ 0.35 fm/c ttherm ~ 0.6 - 1 fm/c 23/03/2007 Andry Rakotozafindrabe – LLR