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HEAVY ION COLLISIONS AT HIGH ENERGY

qcd Matter created at the lhc Barbara Erazmus cnrs /IN2P3 France Crete center for theoretical physics May 28, 2013. HEAVY ION COLLISIONS AT HIGH ENERGY. Extreme states of matter QCD phase diagram Deconfinement Chiral symmetry restoration

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HEAVY ION COLLISIONS AT HIGH ENERGY

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  1. qcd Matter created at the lhcBarbara Erazmuscnrs/IN2P3 FranceCrete center for theoretical physics May 28, 2013

  2. HEAVY ION COLLISIONS AT HIGH ENERGY Extreme states of matter QCD phase diagram Deconfinement Chiral symmetry restoration Universal character of wave functions of large nuclei Dense gluonic system Saturation Color glass condensate

  3. HERA demonstrated that the gluon distribution in a proton rises very fast with decreasing x at fixed Q RHIC LHC In this range saturation of the rapidly growing gluon distribution at saturation scale Qs

  4. ALICE | DIS | 22 Avril 2013 | B. Erazmus

  5. L3 Magnet T0/VZEROTrigger/Centrality ACORDE Cosmictrigger EMCAL γ, π0, jets HMPID PID (RICH) @ highpT TRD Electron ID (TR) TOF PID PMD γmultiplicity TPC Tracking, PID (dE/dx) ITS Low pTtracking PID +Vertexing MUON μ-pairs FMD Charged multiplicity PHOS γ, π0, jets ALarge Ion Collider Experiment Dipole ALICE | SIPB | 21 March 2013 | B. Erazmus Not shown: ZDC (at ±114m)

  6. ALICE – dedicated heavy-ion experiment at the LHC TPC ITS TOF TRD HMPID vertexing • particle identification (practically all known techniques) • extremely low-mass tracker ~ 10% of X0 • excellent vertexing capability • efficient low-momentum tracking down to ~ 100 MeV/c

  7. LHC Heavy-Ion running • Two heavy-ion runs at the LHC so far: • in 2010 – commissioning and the first data taking • in 2011 – already above nominal instant luminosity! • p–Pb run just finished at the beginning of this year • Followed by Long Shutdown–1 (LS1)

  8. GLOBAL EVENT PROPERTIES State and dynamical evolution of the bulk matter characterized by soft particles (below a few GeV/c) multiplicity distributions (initial energy density) spectra, yields (hadronization process) flow (collective transport phenomena) correlations (space-time evolution)

  9. MULTIPLICITY DISTRIBUTIONS ALICEPRL105(2010) ALICEPRL106(2011) ALICE | DIS | 22 Avril 2013 |

  10. Initial Density and Temperature from Bjorken formulaSEE CMS PRL 109 (2012) (2.6 times RHIC) (+30% RHIC) • Lattice QCD predictions : Tc 155 MeV – 175 MeV • The conditions of the formation of a quark gluon plasma • are reached in the early stages of the collisions

  11. IDENTIFIEDPT SPECTRA • Comparisonwith hydromodels:radial flow andkinetic freeze-out temperatureTkin 1/N 1/(2πp )d2N/(dp dy)(GeV/c)-2 106 105 Largeradial flow in mostcentral events: <βT>=0.65 ±0.02 (~10%higherw.r.t. RHIC) increases with centrality ALICE, Pb-Pb s = 2.76TeV NN ALICECollaboration,Phys.Rev.Lett.109,252301(2012)+arXiv:1303.0737 STAR,Au-Au s = 200 GeV NN PHENIX,Au-Au s = 200 GeV NN 103 T π+ +π- (×100) 10 Tkin =95± 10 MeV (sameasRHIC within errors) - K+ + K (×10) p + p (×1) VISH2+1 10-1 T HKM Krakow EPOS 10-3 0-5%Centralcollisions ev • modelcomparisons: • VISH2+1(viscoushydro) • HKM(hydro+UrQMD) • Kraków(viscouscorr., lower the effectiveTch) • EPOS(hydro+UrQMD) 1.5 π+ +π- 1 Data/Model 1.5 K++K- 1 p +p 1.5 1 ALICE PRL 109 (2012) 0 1 2 3 4 5 p (GeV/c) T

  12. IDENTIFIEDPT SPECTRA Comparisonwith hydromodels:radial flow andkinetic freeze-out temperatureTkin • Largeradial flow in top central events: <βT>=0.65 ±0.02 (~10%higherw.r.t. RHIC) increases with centrality 1/N 1/(2πp )d2N/(dp dy)(GeV/c)-2 105 104 ALICE, Pb-Pb s = 2.76TeV ALICECollaboration,Phys.Rev.Lett.109,252301(2012)+arXiv:1303.0737 NN STAR,Au-Au s = 200 GeV NN PHENIX,Au-Au s = 200 GeV NN 102 T π+ +π- (×100) Tkin =95 ± 10MeV (sameasRHIC within errors) 1 - K+ + K (×10) VISH2+1 p + p (×1) 10-2 T HKM Krakow EPOS • modelcomparisons: • VISH2+1(viscoushydro) • HKM(hydro+UrQMD) • Kraków(viscouscorr., lower the effectiveTch) • EPOS(hydro+UrQMD) 10-4 20-30%Centralcollisions ev 1.5 π+ +π- 1 Data/Model 1.5 K++K- 1 p +p 1.5 ALICE arXiv: 1303.0737 1 0 1 2 3 4 5 p (GeV/c) T

  13. IDENTIFIEDPT SPECTRA • Comparisonwith hydromodels:radial flow andkinetic freeze-out temperatureTkin 1/N 1/(2πp )d2N/(dp dy)(GeV/c)-2 -2 ) c 106 (GeV/ 105 ALICE, Pb-Pb NN= 2.76TeV s STAR,Au-Au s = 200 GeV NN ) PHENIX,Au-Au s = 200 GeV y 3 NN d 10 T p /(d π+ +π- (×100) N 10 2 d K+ + K- (×10) ) VISH2+1 T 10-1 p + p (×1) p HKM π 1/(2 10-3 0-5%Centralcollisions Krakow EPOS ev N 1/ 1.5 π+ +π- 1 Data/Model 1.5 K++K- 1 1.5 p +p 1 0 1 2 T 104 ALICE, Pb-Pb s = 2.76TeV ALICECollaboration,Phys.Rev.Lett.109,252301(2012)+arXiv:1303.0737 NN Largeradial flow in top central events: <βT>=0.65 ±0.02 (~10%higherw.r.t. RHIC) increases with centrality STAR,Au-Au s = 200 GeV NN 102 PHENIX,Au-Au s = 200 GeV NN T 1 π+ +π- (×100) 10-2 K+ + K- (×10) Tkin =95 ± 10MeV (sameasRHIC within errors) VISH2+1 p + p (×1) T 10-4 HKM Krakow 70-80%Centralcollisions 10-6 1.5 ev • modelcomparisons: • VISH2+1(viscoushydro) • HKM(hydro+UrQMD) • Kraków(viscouscorr., lower the effectiveTch) • EPOS(hydro+UrQMD) π+ +π- 1 Data/Model 1.5 K++K- 1 ➡moreperipheralevents aremorechallenging for the models p +p 1.5 1 ALICE arXiv: 1303.0737 0 1 2 3 4 5 p (GeV/c) T

  14. Matterat CHEMICAL freeze-out well described by statistical models (fromJ. Cleymans etal,hep-ph/0511094)

  15. Annihilationinbaryon-antibaryoncorrelations Deviation ofproton yieldsfrom thermal modelsexpectations annihilation shouldbe taken into accountwhile determiningyields Steinheimer, Aichelin,Bleicher; arXiv:1203.5302 Werneret al.;Phys.Rev.C85(2012)064907Karpenko, Sinyukov, Werner; arXiv:1204.5351 (...)switching BB-annihilation one suppresses baryon yields, in the same time increases pion yield, thus lowering p/πratio to the value 0.052, which is quite close to the onemeasuredbyALICE(...) →annihilation must be seen in baryon-antibaryon correlations

  16. Baryonfemtoscopy C(⃗q)=∫S(⃗r)∣Ψ(⃗q,⃗r)∣2d4 r measuredcorrelation cross-section emissionfunction(radius) increaseof(anti)correlation = decrease of theradius or increase oftheinteraction cross-section expectedshape ofthesignal(MC) Quark Matter2012 MaciejSzymański

  17. ppcorrelationfunctions Shape dominatedbyCoulombandStrongFSI Significantannihilation(from strongFSI) expectedand measured Quark Matter 2012

  18. y2 ANISOTROPIC ELLIPTIC FLOW Spatial deformation y3 y4 Azimuthal (φ) pressure gradients Anisotropic particle density φ Z y x PressureΔpx >Δpy Y X

  19. ELLIPTIC FLOW COEFFICIENTS ALICE PLB 719 (2013)

  20. ELLIPTIC FLOW COEFFICIENTS Hydro model using Glauber initial conditions for different values of the viscosity Schenke, Jeon, Gale Phys.Lett. B7012 (2011) Further constraints on viscosity and initial conditions provided by measurements ofhigher harmonics very sensitive to properties of the medium ALICE PRL 107

  21. HARD PROBES at high mass and high pTheavy quarks, quarkonia, photons, jets… Created at early stages of the collisions Production and propagation in medium provides information about parton energy loss

  22. REFERENCE COLLISIONS proton-proton

  23. J/ψSUPPRESSION RHIC SPS ‘anomalous’suppression LHC suppression / regeneration ALICE PRL 109 (2013)

  24. J/y elliptic flow arXiv: 1303.5880 J/y produced by recombination of thermalized c-quarks should have non-zero elliptic flow – measurements give a hint for non-zero v2 – qualitative agreement with transport models, including regeneration – complementary to indications obtained from J/yRAA studies

  25. D mesons RAA Average D-meson RAA: – pT < 8 GeV/c hint of slightly less suppression than for light hadrons – pT > 8 GeV/cboth (all) very similar no indication of colour charge dependence ALICE | DIS | 22 Avril 2013 | B. Erazmus

  26. D MESONS v2 Non-zero D meson v2 observed Comparable to that of light hadrons Simultaneous description of RAA and v2 c-quark transport coefficient in medium ALICE | DIS | 22 Avril 2013 | B. Erazmus

  27. Ds MESONS RAA Strong suppression (~ 4–5 ) at pT above 8 GeV/c Uncertainty will improve with future pp and Pb–Pb data taking

  28. REFERENCE COLLISIONS p - Pb Reference for Pb-Pb collisions ? Cold nuclear matter ? Unexpected collective effects ?

  29. Cold nuclear matter effects vs. jet quenching in Pb-Pb… Phys. Rev. Lett. 110, 082302 (2013) Compatible with unity above 2-3 GeV/c Jet quenching in Pb-Pb collisions is a final state effect <=> QGP opaque to energetic partons 30

  30. The Ridge 2 < pT,trig < 4 GeV/c1 < pT,assoc < 2 GeV/c20% highest multiplicity (zoomed) Near-side jet(Dj ~ 0, Dh ~ 0) 1/Ntrig d2Nassoc/dDhdDj Away-side jet(Dj ~ p, elongated in Dh) Near-side ridge(Dj ~ 0, elongated in Dh) Dh Dj (rad) • The near-side long-range ridge observed by CMS in pp and p-Pb seen by ALICE in p-Pb[JHEP 09 (2010) 091, PLB718 (2013) 795]

  31. Interpretation Flow? viscous hydro (arXiv:1112.0915) Saturation? Color glass condensate (arXiv:1302.7018) Band: Calculation Points: ALICE data arXiv:1112.0915 Ridge Yields per Dh arXiv:1302.7018 0-20% 20-40% 40-60%

  32. CONCLUSIONS Hot and dense matter created at the LHC behaves as a liquid with low viscosity well described by hydrodynamical approaches New precise hard probes allow to study the QGP Recent measurements of proton-lead collisions reveal surprising (collective ?) behaviour

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