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J/  production in Cu+Cu and Au+Au collisions at √s NN = 200 GeV measured by PHENIX at RHIC

J/  production in Cu+Cu and Au+Au collisions at √s NN = 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.

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J/  production in Cu+Cu and Au+Au collisions at √s NN = 200 GeV measured by PHENIX at RHIC

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  1. 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)

  2. 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 Andry Rakotozafindrabe – LLR

  3. Sequential dissociation as the temperature (or energy density) increases : 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 Satz, J.Phys.G32:R25,2006 Screening the J/ in a QGP χc ’ J/ • Energy density (τ0 = 1fm)vs the max. √s for SPS, RHIC and LHC Andry Rakotozafindrabe – LLR

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

  5. Run Species √s[GeV ] Ldt # J/ # J/ Reference |y|<0.351.2<|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 1186PRL96, 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 8005hep-ex/0611020 06 p+p 200 10.7 pb-1 p+p 62 0.1 pb-1 J/ in PHENIX : capsule history Andry Rakotozafindrabe – LLR

  6. 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) Andry Rakotozafindrabe – LLR

  7. Cross section vs : energy rapidity pT Production baseline : (Run5) p+pJ/ @ √s = 200 GeV 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/ : Andry Rakotozafindrabe – LLR

  8. RAA 1 Bar: uncorrelated error Bracket : correlated error 0 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 Andry Rakotozafindrabe – LLR

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

  10. RAA 1 Bar: uncorrelated error Bracket : correlated error 0 1 ratioRAA (1.2<|y|<2.2)/RAA (|y|<0.35) 0 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 Andry Rakotozafindrabe – LLR

  11. NA50 at SPS (0<y<1) PHENIX at RHIC (|y|<0.35) PHENIX at RHIC (1.2<|y|<2.2) RHIC vs SPS • SPS @ 0<y<1 : • √s ~ 17 GeV • CNM = normal nuclear absorptionσabs= 4.18 ± 0.35 mb • Maximum ε ~ 3 GeV/fm3 (τ0 = 1) • Compare to RHIC @ |y|<0.35 : • x10 √s • CNM = shadowing + nuclear absorptionσabs 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 Bar: uncorrelated error Bracket : correlated error Global error = 12% is not shown Andry Rakotozafindrabe – LLR

  12. 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) Andry Rakotozafindrabe – LLR

  13. 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 Recombination at RHIC ? • Suppression+recombination predictions compared to data • RAA vs Npart Better matching with the data but regeneration goes as the (single) charm density which is poorly known at RHIC What about the other variables ? Andry Rakotozafindrabe – LLR

  14. No recombination All recombination 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 RMS 1.40±0.04 RMS 1.43±0.04 nucl-ex/0611020 Andry Rakotozafindrabe – LLR

  15. 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). Andry Rakotozafindrabe – LLR

  16. Bar: uncorrelated error Bracket : correlated error PHENIX Global error = 12% + 7% Box : uncertainty from CNM effects dET/dy : PHENIX, PRC 71, 034908 (2005) εBj.τ0 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 Sequential dissociation of ψ’ and χc only does not seem to be consistent with the data Andry Rakotozafindrabe – LLR

  17. 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 absorptionσabs = 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), … Andry Rakotozafindrabe – LLR

  18. Refinement :3D hydro + sequential dissociation (II) Gunji et al., hep-ph/0703061 : • Charmonia • J/ survival probability ( RAA/CNM with CNM = shadowing + nuclear absorptionσabs = 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 Andry Rakotozafindrabe – LLR

  19. 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 • Ratioforward/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) Andry Rakotozafindrabe – LLR

  20. 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 Andry Rakotozafindrabe – LLR

  21. Back-up Andry Rakotozafindrabe – LLR

  22. A. Bickley, Hard Probes 06 Run 6 200GeV p+p PHENIX Run 5 200GeV p+p Invariant Mass (GeV/c2) (c - J/) Mass (GeV/c2) (c - J/) Mass (GeV/c2) 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) ? Work under progress Andry Rakotozafindrabe – LLR

  23. 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 Andry Rakotozafindrabe – LLR

  24. 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 Andry Rakotozafindrabe – LLR

  25. 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 Andry Rakotozafindrabe – LLR

  26. Invariant yield vs tranverse momentum Andry Rakotozafindrabe – LLR

  27. hep-ex/0611020 nucl-ex/0611020 hep-ex/0611020 nucl-ex/0611020 <pT2> vs Npart • A closer look at <pT2> vs Npart Andry Rakotozafindrabe – LLR

  28. Phys. Rev. Lett. 96 (2006), 012304 Low x2 ~ 0.003 (shadowing region) Anti Shadowing Shadowing Vogt, PRC71, 054902 (2005), Kopeliovich, NP A696, 669 (2001) rapidity y xAu xd J/ South y < 0 xAu xd J/ North y > 0 y < -1.2 : large xAu ~ 0.090 y > 1.2 : low xAu ~ 0.003 Cold nuclear effects : d+AuJ/ • Available d+Au data  CNM : • Weak shadowing (modification of gluon distribution) and weak nuclear absorption (σabs ~ 1mbfavored) 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 gluons in Pb / gluons in p x Nucl. Phys. A696 (2001) 729-746 y ~ 0 : intermediate xAu ~ 0.020 Andry Rakotozafindrabe – LLR

  29. 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 Andry Rakotozafindrabe – LLR

  30. 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 Andry Rakotozafindrabe – LLR

  31. 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 absorptionσabs= 4.18 ± 0.35 mb • Compare to RHIC @ |y|<0.35 : • CNM = shadowing + nuclear absorptionσabs=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 Andry Rakotozafindrabe – LLR

  32. 0mb 3mb Recombination at RHIC ? RAA vs y 100% Recombination(shape only) R. Vogt nucl-th/0507027 (EKS) R. L. Thews, M. L. Mangano Phys.Rev. C73 (2006) 014904 Andry Rakotozafindrabe – LLR

  33. dNg/dy=1000 Charm flow S. Sakai QM06 M. Djordjevic et al., Phys.Lett.B632 (2006) 81 • 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 c and b quark pT distributions at mid-rapidity before fragmentation : b contribution is dominant at high pT [Phys.Lett. B595 202-208] [PRC72,024906] [PRC73,034913] Andry Rakotozafindrabe – LLR

  34. For Au+Au or Cu+Cu collision : ~ Computing the J/ yield Invariant yield : : 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 i : i-th bin (centrality for e.g.) Andry Rakotozafindrabe – LLR

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

  36. pR2 t0 ~ 1 fm/c tsecondaries formation ~ 0.35 fm/c tcross ~ 0.13 fm/c ttherm ~ 0.6 - 1 fm/c Energy density • Longitudinally expanding plasma : • dET/dηmeasurement at mid-rapidity by PHENIX EMCal • Which τ0 ? Andry Rakotozafindrabe – LLR

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