1 / 42

“Trends in heavy ion physics research” Dubna May 22-24, 2008

Hot and dense matter: from RHIC to LHC. “Trends in heavy ion physics research” Dubna May 22-24, 2008. Itzhak Tserruya. Hot and dense matter: from RHIC to RHIC and LHC. “Trends in heavy ion physics research” Dubna May 22-24, 2008. Itzhak Tserruya. Outline. Introduction

hamlet
Download Presentation

“Trends in heavy ion physics research” Dubna May 22-24, 2008

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Hot and dense matter: from RHIC to LHC “Trends in heavy ion physics research”Dubna May 22-24, 2008 Itzhak Tserruya JINR, May 22, 2008

  2. Hot and dense matter: from RHIC to RHIC and LHC “Trends in heavy ion physics research”Dubna May 22-24, 2008 Itzhak Tserruya JINR, May 22, 2008

  3. Outline • Introduction • Highlights from RHIC • Flow • Charmonium • Low-mass dileptons • Thermal radiation • High pT suppression • Summary JINR, May 22, 2008

  4. Introduction JINR, May 22, 2008

  5. Eight years of RHIC operation • RHIC’s main goals • Nuclear collisions • To provide definitive experimental evidence for/against Quark Gluon Plasma (QGP) • and study its properties under the much better conditions offered by RHIC • Large√s  Access to reliable pQCD probes • Polarized p+p collisions • Accelerator complex • Impressive machine performance: • Routine operation at 2-4 x design luminosity (Au+Au) • Extraordinary variety of operational modes • Collided four different species: Au+Au, d+Au, Cu+Cu, p+p • 4 Energies: 20 GeV (Au+Au, Cu+Cu), 62 GeV (Au+Au,Cu+Cu, p+p) , 130 GeV (Au+Au), 200 GeV (Au+Au, Cu+Cu, d+Au, p+p)

  6. PHENIX Run History JINR, May 22, 2008

  7. Eight years of RHIC operation • RHIC’s main goals • Nuclear collisions • To provide definitive experimental evidence for/against Quark Gluon Plasma (QGP) • and study its properties under the much better conditions offered by RHIC • Large√s  Access to reliable pQCD probes • Polarized p+p collisions • Accelerator complex • Impressive machine performance: • Routine operation at 2-4 x design luminosity (Au+Au) • Extraordinary variety of operational modes • Collided four different species: Au+Au, d+Au, Cu+Cu, p+p • 4 Energies: 20 GeV (Au+Au, Cu+Cu), 62 GeV (Au+Au,Cu+Cu, p+p) , 130 GeV (Au+Au), 200 GeV (Au+Au, Cu+Cu, d+Au, p+p) • Two small detectors, two large detectors • Complementary capabilities. Worked !

  8. STAR RHIC and Its Experiments JINR, May 22, 2008

  9. Eight years of RHIC operation • RHIC’s main goals • Nuclear collisions • To provide definitive experimental evidence for/against Quark Gluon Plasma (QGP) • and study its properties under the much better conditions offered by RHIC • Large√s  Access to reliable pQCD probes • Polarized p+p collisions • Accelerator complex • Impressive machine performance: • Routine operation at 2-4 x design luminosity (Au+Au) • Extraordinary variety of operational modes • Collided four different species: Au+Au, d+Au, Cu+Cu, p+p • 4 Energies: 20 GeV (Au+Au, Cu+Cu), 62 GeV (Au+Au,Cu+Cu, p+p) , 130 GeV (Au+Au), 200 GeV (Au+Au, Cu+Cu, d+Au, p+p) • Two small detectors, two large detectors • Complementary capabilities. Worked ! • Science • Unexpected results, major discoveries • More than 170 papers in refereed literature, among them ~100 PRL • Future: RHIC and LHC • Key science questions identified • Accelerator and experiment upgrade program underway to perform that science • LHC to open a new energy frontier (increase by a factor of ~30!)

  10. Non-central Collisions z x y Geometry of Heavy Ion Collisions Reaction plane • N_participants: number of incoming nucleons in the overlap region • N_binary: number of inelastic nucleon-nucleon collisions • Centrality of the collision expressed as percentile of the total cross section. N_participants: N_collisions: Centrality JINR, May 22, 2008

  11. Flow (second major discovery at RHIC) JINR, May 22, 2008

  12. Reaction plane Flow: Evidence of Pressure and Collective Effects Origin:In non-central collisions, the pressure converts the initial spatial asymmetry (almond shape of overlap region) into azimuthal anisotropy of particle emission Collective effect Absent in pp collisions The flow is quantified by v2 (elliptic flow parameter) determined from the azimuthal distribution of particles with respect to the reaction plane ψR 2v2 JINR, May 22, 2008

  13. Every particle flows • Mass hierarchy • Large v2 of heavier particles: f, X, W, d. • Even open charm flows (measured through single electrons) • Strong interactions at early stage  early thermalization. JINR, May 22, 2008

  14. ~ The “Flow” Is Perfect The mass hierarchy disappears if one uses the transverse kinetic energy: • as expected from “perfect fluid” hydrodynamics. baryons mesons JINR, May 22, 2008

  15. The “Flow” knows quarks • Scaling the flow parameters by the valence quark content nq resolves the meson-baryon separation baryons mesons All this makes the case for sQGP with early thermalization of partonic matter made of constituent quarks and behaving like a perfect fluid JINR, May 22, 2008

  16. How Perfect is “Perfect” ? But there is a (conjectured) quantum limit:“A Viscosity Bound Conjecture”, P. Kovtun, D.T. Son, A.O. Starinets, hep-th/0405231 • First hydrodynamic calculations for RHIC matter have all assumed zero viscosity h = 0 “perfect fluid” • Where do “ordinary” fluids sit wrt this limit? • RHIC “fluid” mightbe at ~1 on this scale (!) T=1012 K

  17. PRELIMINARY minimum-bias Rapp & van Hees, PRC 71, 034907 (2005) Run-7 Run-4 Open charm flows! Elliptic flow of heavy flavor via non-photonic electrons Do bottom quarks flow too, or just charm? ANS: VTX in Run-11 Does thermalized charm contribute to J/ via recombination ? i.e. does J/ flow too? ANS: Run-9 + Run-7! JINR, May 22, 2008

  18. J/ψ (the deconfinement probe?) JINR, May 22, 2008

  19. T=0 confinement T≠0 color screening Screening length hadron size Physics motivation • ccbarpredominantlyproduced by gluon fusion in the initial parton collisions  probe the created medium : • ccbar (quarkonia) suppressed by color screening  deconfinement • open charm (or beauty) energyloss  energydensity • Anomalous J/ suppressionseenat CERN SPS by NA50 • At RHIC energy(10x√sNN ) expect much higher suppression NA50 : Pb + Pb √sNN ~ 17 GeV nuclear absorption σabs = 4.18 ± 0.35 mb JINR, May 22, 2008

  20. First surprise: RHIC vs SPS comparison • RHIC @ |y|<0.35 : • √s = 200 GeV • CNM = shadowing + nuclear absorptionσabsfrom 0 to 3 mb (Vogt, nucl-th/0507027) • SPS @ 0<y<1 : • √s ~ 17 GeV • CNM = normal nuclear absorptionσabs= 4.18 ± 0.35mb Very similar suppression at RHIC and SPS contrary to expectations.- JINR, May 22, 2008

  21. Second surprise: Rapidity dependence Stronger suppression at forward rapidity compared to mid-rapidity JINR, May 22, 2008

  22. |y| < 0.35 J/Au+Au: suppression vs CNM Effects Cold nuclear matter (CNM) effects derived from d+Au data (run 3): CNM = Shadowing(EKS) + Breakup = 2.8 mb +1.7 -1.4 • More forward suppression beyond CNM than at mid-rapidity • Large errors - need higher statistics d+Au data (Run 8) J/ RAuAu 200 GeV (Run4) 1.2 < |y| < 2.2 arXiv:0711.3917

  23. Satz, J.Phys.G32:R25,2006 χc ’ J/ J/ at RHIC: present status • Suppression compensated by Recombination ? • Models with only cold nuclear matter effects don’t quite have • enough suppression • 2) Models with color screening (or comovers) have too much suppression • 3) Models with color screening (or comovers) AND recombination are • in reasonable agreement with the data OR • Sequential dissociation? • Dissociation temperature Td : F. Karsch et al. (Nucl. Phys. A698(2002) 199c; hep-lat/0106019)

  24. J/: outlook • J/ from regeneration should inherit the large charm-quark elliptic flow • First J/ flow measurement by PHENIX: • v2 = –10 ± 10 ± 2 ± 3 % • FVTX: • 4x less ,K decays • M: 170100 MeV • Vertex detectors (VTX,FVTX) & forward calorimeter (NCC) will give: • ’ with reduced combinatoric background + sharper mass resolution • precise open-charm measurements to constrain regeneration picture LHC ?

  25. Low-mass dileptons (the chiral symmetry restoration probe) JINR, May 22, 2008

  26. Origin of mass Constituent quark masses generated by spontaneous chiral symmetry breaking Origin of mass: 95% of the (visible) mass is due to the spontaneous breaking of the chiral symmetry. X • Many models link the hadron masses to the quark condensate. • At high T or density Current quark masses generated by spontaneous symmetry breaking (Higgs field)

  27. No enhancement in pp nor in pA Pioneering CERES results at CERN SPS Strong enhancement of low-mass e+e- pairs in A-A collisions (wrt to expected yield from known sources) Final CERES result (from 2000 Pb run): Enhancement factor (0.2 <m < 1.1 GeV/c2 ): 2.58 ± 0.32 (stat) ± 0.41 (syst)± 0.77 (decays) JINR, May 22, 2008

  28. CERES Pb+Au NA60 In+In CERES and NA60 • Interpretation: thermal radiation from HG: • +-  * e+e- • Subtract the hadronic cocktail w/o the  * Both NA60 and CERES attribute excess to in-medium broadening of  spectral shape (Rapp and Wambach)as opposed todropping  meson mass (Brown et al) JINR, May 22, 2008

  29. Low-mass dielectrons at RHIC arXiv:0706.3034 All pairs Combinatorial BG Signal PHENIX • Significant enhancement of low-mass pairs • Different origin from SPS? • Limited by poor S/B ratio ( 1/200 at m=0.4 GeV/c2) JINR, May 22, 2008

  30. 2 side covers with frame 6 active panels window support 2 vertical panels Hadron Blind Detector novel concept for e ID →Dalitz rejection • Windowless Cherenkov detector • 50 cm CF4radiator • CsI reflective photocathode • Triple GEM with pad readout HV panels frame

  31. Thermal Radiation (the thermometer) JINR, May 22, 2008

  32. Thermal Photons • High energy density matter is formed at RHIC • If the matter is thermailzed, it should emit “thermal radiation” • The thermal photon spectrum provides a direct measurement of the temperature of the matter • Thermal photons are predicted to be the dominant source of direct photon for 1<pT<3 GeV/c at RHIC energies. • Higher pT: pQCD photon • Lower pT: from hadronic phase • Measurement is difficult since the expected signal is only 1/10 of photons from hadron decays S.Turbide et al PRC 69 014903 JINR, May 22, 2008

  33. Alternative approach: virtual photons ( low-mass e+e- pairs) • Any source ofreal emitsvirtual *with very low mass • If the Q2 (=m2) of virtual photon is sufficiently small, the source strength is the same • The ratio of real photons and virtual photons can be calculated by QED • The real photon yield can be measured from the virtual photon yield, which is observed as low mass e+e- pairs • Excess of low-mass dileptons (wrt hadronic sources) is assigned to direct photons The idea of measuring direct photon via low mass lepton pair is not new one: J.H.Cobb, et al, PL 78B, 519 (1978)

  34. exp + TAA scaled pp Fit to pp NLO pQCD (W. Vogelsang) Tinit via low mass, high pTdileptons M < 0.3 GeV/c2 pT = 1-5 GeV/c pp Au+Au min bias Fit with exponential + TAA scaled p+p fit: T = 221 ± 23 ± 18 MeV (central) JINR, May 22, 2008 arXiv: 0804.4168

  35. High pT suppression (first major discovery at RHIC) JINR, May 22, 2008

  36. RAA RAA = 1 RAA < 1 Nuclear modification factor • Zero hypothesis: scale pp to AA with the number of nn collisions Ncoll: • d2NAA/dpTd(b) = Ncoll d2Npp /dpTd = pp TAA(b) ? • Quantify “effect” with nuclear modification factor: Ncoll /σinel pp • If no “effect”: • RAA < 1 at low pT (soft physics regime) • RAA = 1 at high-pT (hard scattering dominates) • If “jet quenching”: • RAA < 1 at high-pT JINR, May 22, 2008

  37. p-p AuAu Run4 0-10% central Ncoll =975 ± 94.0 η=0 Central Au-Au collisions yield significantly suppressed relative to scaled pp yield 0pT spectra at √sNN = 200 GeV 70-80% peripheral Ncoll =12.3 ± 4.0 Excellent agreement between measured π0’s in p-p and measured π0’s in Au-Au peripheralcollisions scaled by the number of collisions over ~ 5 decades JINR, May 22, 2008

  38. Control: Photons shine, Pions don’t • Direct photons are not affected by hot/dense medium • Rather: shine through consistent with pQCD

  39. Quantitative Analysis of Energy Loss JINR, May 22, 2008

  40. Jet correlations in Au+Au • Away side jet strongly modified in Au+Au compared to p+p collisions • Low/intermediate pT: • -broad away-side • -maxima at Δφ= π +/- 1 rad • High pT • -away-side shape like p+p • -but suppressed yield • Current conjecture: • Head region -> jet modification (dominant at high pT) • Shoulder region -> medium response (dominant at intermediate pT)

  41. Fluid Effects on Jets ? • Mach cone? • Jets travel faster than the speed of sound in the medium. • While depositing energy via gluon radiation. • QCD “sonic boom” (?) • To be expected in a dense fluid which is strongly-coupled JINR, May 22, 2008

  42. Summary and Outlook • RHIC has so far been very successful . Much is left to do to further characterize the properties of the “perfect fluid” • LHC is behind the corner. • It will offer an unparalleled increase in √s. Will this still create a strongly coupled perfect fluid? Or will we approach the ideal QGP of free gas of quarks and gluons as originally sought? • Active pursuit via • Dedicated experiment (ALICE) • Targeted studies (CMS, ATLAS) 62.4 GeV Au+Au • Onset of heavy flavor energy loss? • Emergence of opacity • Onset of RHIC’s perfect fluid • Energy Scans: where is the critical point? • Low-mass dileptons • Photon + Jets • Ambitious upgrade program underway • RHIC  RHIC II x40 luminosity increase • Detectors and DAQ upgrades

More Related