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Recent Results from ALICE

Recent Results from ALICE. E. Vercellin Dipartimento di Fisica dell’Università di Torino and INFN Torino. Summary. ALICE motivations, layout, data taking ALICE (Pb-Pb) results: a selection Global observables Anisotropic flow High- p T particles and Jets Heavy Flavors Quarkonia

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Recent Results from ALICE

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  1. Recent Results from ALICE E. Vercellin Dipartimento di Fisica dell’Università di Torino and INFN Torino

  2. Summary • ALICE motivations, layout, data taking • ALICE (Pb-Pb) results: a selection • Global observables • Anisotropic flow • High-pT particles and Jets • Heavy Flavors • Quarkonia • Conclusions and perspectives Based mainly on “fresh” results presented at the Quark Matter conference, held in August 2012

  3. motivations, detector layout and data taking

  4. Heavy Ion Collisions Create QGP by colliding ultra-relativistic heavy ions pre-equilibration  QGP  hadronisation  freeze out Accellerators: AGS, SPS, RHIC, LHC SNN (GeV) = 5.4 19 200 2360 (5200)

  5. Observables Jets Open charm, beauty 9

  6. Diversi esperimenti, ciascuno mirato allo studio di diverse osservabili

  7. LHC compared to SPS and RHIC • The LHC is the ideal place to study the QGP: • hotter - bigger -longer lived • ~ 104particles per event: Event by eventphysics

  8. New or more important at LHC • Vanishing net baryon density (B 0) • Stronger thermal radiation (photons, dileptons) • Longer QGP lifetime • Parton dynamics has an impact on fireball expansion • High density (saturated) p.d.f. at small x (10-5) • impact on particle production • Hard processes:jets and jet quenching • 30 (310-3) partons with Et>10 GeV (100 GeV)in centr. Pb-Pb • Heavy quarkonia: • Y family experimentally accessible, e high enough for melting? • Heavy flavors abundant production • 100 c-cbar and few b-bbar in central Pb-Pb •  J/Y enhancement ?

  9. RHIC LHC Y production X 2000 R. Vogt, hep-ph/0205330 Hard Probes, heavy quarks and quarkonia @ LHC Pion Production

  10. ALICE physics goal • Global observables: • Multiplicities,  distributions • Degrees of freedom as a function of T: • hadron ratios and spectra, dilepton continuum, direct photons • Early state manifestation of collective effects: • elliptic flow • Energy loss of partons in quark gluon plasma: • jet quenching, high pt spectra, open charm and open beauty • Study deconfinement: • charmonium and bottonium spectroscopy • Study chiral symmetry restoration: • neutral to charged ratios, resonance decays • Detect fluctuation phenomena - critical behavior: • event-by-event particle composition, spectra • Measure the geometry of the emitting source: • HBT, impact parameter via zero-degree energy flow

  11. .. all the above measurements in a high-multiplicity environment!

  12. Central Barrel 2 p tracking & PID • |h| < 1 ALICE detector ACORDE (cosmics) VZERO scint. (centrality) h: -1.7– -3.7, 2.8–5.1 T0 (timing) ZDC (centrality) FMD (Nch -3.4<h<5) PMD (Ng, Nch) Muon Spectrometer -2.5 > h> -4 Collaboration: ̴1200Members132Institutes 36 countries Detector: Length: 26 meters Height: 16 meters Weight: 10,000 tons

  13. (charged particles) ALICE Acceptance • central barrel -0.9 < h < 0.9 • 2 p tracking, PID (dE/dx, TOF, TRD) • single arm RICH (HMPID) • single arm PHOS • jet calorimeter EMCal • forward muon arm 2.4 < h < 4 • absorber, 3 Tm dipole magnet10 tracking + 4 trigger chambers • multiplicity -5.4 < h < 3 • including photon counting in PMD • trigger & timingdets • 6 Zero Degree Calorimeters • T0: ring of quartz window PMT's • V0: ring of scint. Paddles µ arm

  14. Particle identification in ALICE

  15. TPC ITS TOF TRD ALICE: main features and performance HMPID vertexing • particle identification (practically all known techniques) • excellent vertexing capability • efficient tracking – down to ~ 100 MeV/c • particle detection over a large rapidity range • quarkonia detection down to pT=0 Central Barrel  Forward det.  Muon Arm & C.B. 

  16. EMCal Neutral mesons Photon conversion PHOS

  17. Identification of strange particles

  18. D+→ Kpp Charmonium and D mesons • J/y m+m- , -2.5<h<-4.0, pt≥ 0 σJ/Ψ = (75 ± 3)MeV/c2 • J/ye+e- , -0.9<h<0.9, pt≥ 0

  19. Two heavy-ion runs at the LHC so far: • in 2010 – commissioning and the first data taking • in 2011 – (energy scaled) above nominal luminosity! • pp data taken at different c.m. energies in 2009-2012: • 0.9, 2.36, 2.76, 7 and 8 TeV • reference for HI data and genuine pp physics • p-Pb run foreseen in Jan-Feb 2013 (pilot run Sept. 2012) ALICE Data Taking

  20. A couple of heavy-ion-specific aspects CENTRALITY determinations and coulomb interaction

  21. VZERO, SPD and ZDCs VZERO

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