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E. Scapparone (INFN – Bologna, Italy) o n behalf of the ALICE Collaboration MIAMI 2012

Recent results from ALICE. E. Scapparone (INFN – Bologna, Italy) o n behalf of the ALICE Collaboration MIAMI 2012 Fort Lauderdale, Dec. 17, 2012. The ALICE Collaboration. ~ 1300 members from both NP and HEP communities 35 Countries

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E. Scapparone (INFN – Bologna, Italy) o n behalf of the ALICE Collaboration MIAMI 2012

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  1. Recent results from ALICE E. Scapparone (INFN – Bologna, Italy) on behalf of the ALICE Collaboration MIAMI 2012 Fort Lauderdale, Dec. 17, 2012

  2. The ALICE Collaboration ~ 1300members from both NP and HEP communities 35 Countries 132 Institutes~ 160 MCHF capital cost (+ ‘free’ magnet)

  3. THE ALICE DETECTOR V0 scintillators h: -1.7– -3.7, 2.8–5.1 Muon Spectrometer -2.5 > h> -4 PID: SPD, TPC (dE/dX) TOF (Time of Flight)TRD (e/p) HMPID (Cherenkov) Centrality: V0 ZDC Tracking @ |h| < 1:ITS TPC TRD Collaboration: > 1000 Members>100 Institutes > 30 countries Detector: Length: 26 meters Height: 16 meters Weight: 10,000 tons

  4. ALICE performance TPC ITS TOF TRD ALICE performance 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

  5. Warning:this is not an exhaustive presentation on All ALICE results, but just a talk focusing on few selected ALICE results…

  6. A taste of pp results at √s=2.76 Tevand √s=7 TeV J/y: the 4 LHC experiments ATLAS J/y yield as a function of charged-multiplicity in ppcollisions at √s=7 TeV CMS ALICE e+e- ALICE mm The charged particle multiplicities measured in high-multiplicity pp collisions at LHC energies ~ same order as those measured in heavy-ion collisions at lower energies. Are their production rates in high multiplicityppcollisions already exhibiting any effect like J/ψ suppression? LHCb Phys.Lett.B704 (2011) 442 Phys.Lett. B712 (2012) 165 Hard partonic scattering shows a different trend J/Y accompanied by high hadronic activity. MPI for heavy quarks ?

  7. First measurement of J/ypolarization at LHC (Phys. Rev. Lett. 108 (2012) 082001) M.Butenschoen, A.Kniehl, arXiv:1201.3862 • Long standing puzzle with Tevatron results • First result at the LHC: almost no polarization for the J/ • Crucial input for tuning NRQCD parameters

  8. Heavy ions ! 2010 run : L ~ 7 mb -1 2011 run : L ~ 100 mb -1

  9. Phys. Lett. B 696 (2011) 328 Global properties PRL 105, 252301 (2010) Energy density ~ 3 x RHIC ~ 10 GeV/fm3 Volume ~ 2 x RHIC (R3 ~ 300 fm3) At LHC the fireball is hotter, larger and lasts more Photon T = 304±51 MeV ~ 1.4 x TRHIC Lifetime: +20% wrt RHIC(~ 10 fm/c) Phys. Lett. B 696 (2011) 328

  10. Radial Flow • pressure P in center • drives expansion flow • velocity b=v0/c • depends on f(P, t, EoS,) • momentum p = g m v0 => • particles of different mass have • characteristic& different • momentum spectra v0 p- v0 S. Das at QM2012 v0 Isotropic radial flow p Hydro Calculation v0 K WhataboutRadial Flow @ LHC ? p P = 0 PbPb P >> 0 v0 RHIC pp v0 Very significant changes in slope compared to RHIC, most dramatically for protons Very strong radial flow, b≈ 0.65 (2/3 of c!) even larger than predicted by most recent hydro Radial flow pushes spectra depending on mass

  11. Comparing to models Fit to the data with Blast-Wave model Schnedermann et al., PRC 48, 2462 (1993) 〈βT〉 = 0.65 ±0.02 Comparison with models: VISH2+1: viscous hydrodynamics Shen et al., PRC 84, 044903 (2011) p,K ok up to 1.5 GeV/c, missing p  lack of hadron phase ? HKM: hydro + UrQMD(hadron particle Cascade), Karpenkoet al., arXiv:1204.5351 improved p description (hadron cascade increases radial flow) Krakow: viscous corrections, lower effective Tch,Bozek, PRC 85, 034901 (2012) Model vs data comparison suggests a hydrodynamic interpretation of the transverse momentum spectra at the LHC. arXiv: 1208.1272, accepted by PRL

  12. z y x Azimuthalasimmetries py Py Px • Fourier expansion of azimuthal distribution: • Flow: Correlation between coordinate and momentum space => azimuthal asymmetry of interaction regiontransported to the p T • measure the strength of collective phenomena • Large mean free path • particles stream out isotropically, no memory of the asymmetry • extreme: ideal gas (infinite mean free path) • Small mean free path • larger density gradient -> larger pressure gradient -> larger momentum • extreme: ideal liquid (zero mean free path, hydrodynamic limit)

  13. v2 Measurements at the LHC semi-central central PRL 105, 252302 (2010), > 250 citations (INSPIRE) • Collective behavior observed in Pb-Pb collisions at LHC (+30% wrtv2RHIC)ideal fluid behavior (extremely low viscosity h» 0 ) • v2 as a function of pTnot dramatically different • wrt RHIC (few variations for identified hadrons, • predicted by hydro models - see C. Shen et al • arXiv:1105.3226) •  v2 increase with s from hadron <pT> increase • Testing hydrodynamicalevolution

  14. Hydrodynamic model predictions Hydro not ok for baryons at 10-20% centrality Viscous hydrodynamic model calculations reproduce the main features of v2 at low transverse momentum: • mass dependence is better modelled for peripheral collisions; • for central collisions overestimate baryon flow; • Adding hadronicrescattering phase (VISHNU) improves the agreement with data Heinz, Shen, Song, AIP Conf. Proc. 1441, 766 (2012)

  15. NCQ scaling goodbye…. STAR, S.Shu at QM2012 PHENIX Phys. Rev. C85064914(2012) NCQ scaling at RHIC holds in 0-10% Centrality bin: deviations start at ~1GeV/c NCQ scaling holds quite well at any centralities at low energies.. STAR, Phys. Rev. C 77 (2008) 54901 Particles Data/fit NCQ scaling: partonicdof dominant; No scaling: hadronicdof dominant Alice: stronger NCQ violation. Stronger radial flow or Jet quenching/rescattering, more important than coalescence ?

  16. Fluctuations  v3 ….(+ 3 v3 cos(3(j-y))) Sensitive to h/s  “ideal” shape of participants’ overlap is ~ elliptic; no odd harmonics expected participants’ plane coincides with event plane • but fluctuations in the initial position of the partecipant nucleons give: - plane  event plane - v3 (“triangular”) harmonic appears [B Alver & G Roland, PRC81 (2010) 054905]  and indeed, v3  0 ! arXiv:1205.5761v2 ALICE: PRL 107 (2011) 032301 Similar v2 trend, mass ordering; fluctuations discriminate & constrain models:largesensitivity to viscosity v3has weaker centrality dependence than v2when calculated wrt participants plane, v3 vanishes (as expected, if due to fluctuations…). Progress in precision measurements ofh/s

  17. J/Yin ALICE: the forward region 2.5 < y < 4 Colour screening @ work 1.2 < y < 2.2 c c c c • Less suppression wrt RHIC; • ALICE data flatter at high centralities: almost no centrality dependence • for Npart > 100; • Evidence for c quark coalescence ? σ(cc)LHC ≈ 10 × σ(cc)RHIC

  18. J/Yin ALICE: the pT dependence Predicted by coalescence model • Nice agreement with CMS data; • Higher suppression at high pT Doesshadowing depends on the interaction centrality ? Still uncertainties from shadowing  run p-Pb coming soon

  19. ψ’ should have a similar suppression at LHC energies wrt J/ψ (ψ’ melts at smaller T wrtJ/ψ) Tc ~ 160-170 MeV TAlice ~ 300 Mev l ~ 0.15 fm > 0.29 fm (J/Y) > 0.56 fm(ψ’ ) ALICE not confirming CMS data (though at different rapidity)

  20. Hints for J/Yand D v2≠ 0 ..hints for a strong coupling c - medium

  21. First pA Collision, Sep. 13th, 2012

  22. p-Pb pilot run, Sep 2012 Compatible with 1 above 2-3 GeV/c → binary scaling is preserved, no (or small) initial state effects No sign ( or weak) Cronin effect arXiv:1210.3615v1, arXiv:1210.4520v1 - Data favour models including shadowing - Saturation models predict too steep h dependence pT spectrum not reproduced by HIJING or DPMJET. Both saturation models and models with shadowing can reproduce data

  23. Hard Processes to Probe the Medium (Rutherford experiment...) • Nucleus-nucleus collisions • ►hard initial scattering • ►scattered partons probe traversed hot and dense medium • ► ‘jet tomography’ Medium modification quantified via nuclear modification factor RAA Initial parton-partonscattering with large momentum transfer: ►calculable in pQCD Particle jets follow direction of partons

  24. Strong suppression for hadrons…. RAA(pT) for charged particles produced in 0-5% centrality range @ LHC: minimum for pT ~ 6-7 GeV/c then slow increase at high pTinterpreted as due to loss of energy of parton propagating through medium. A deeper inspection: selected hadrons in the medium: heavy quarks

  25. Jet particle composition Near side: compatible with Pythia Bulk: p/p increase; overall baryon enhancement

  26. Energy loss in a dense medium proceedsmostlythrough gluon radiation: • Gluon radiation higher for light quark than for heavy quark: 1) • ( dead cone: for q < MQ/EQ) q smaller for light quarks • Gluonradiationstrongerfor gluons wrt quarks (higher colour charge); • Cr= 3 • Cr= 3/4 • Cr= 1/2 L • ..and heavyhadrons originate mostly from quark jets L path in the medium ^ <DE> as· Cr· q · L 2 DEg > DEq> DEc > DEb  Summary: smallerDE expected for heavy quarks

  27. RAA for heavy flavours ALICE: JHEP 09 (2012) 112 Hint for smaller D0,D+,D- suppression for pt < 8 GeV/c ?

  28. New: DS ! Lesssuppression (s quark @ work) ?

  29. The future: upgrade planning ►Strong detector/physics efforts in view of the LHC upgrade ►Upgrade experiment to be able to run with 50 kHz Pb-Pb collision rates, several nb-1 per run (2 MHz proton-proton) • ►Various new detectors being proposed • (stregthen ALICE uniqueness at LHC) • ITS: B/D separation, heavy baryons, • low-mass dielectrons • MFT: b-tagging for low pt J/psi and • low-mass di-muons at forward y • VHMPID: New high momentum PID • capabilities • FOCAL: Low-x physics with identified g/p0

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