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 Conclusions and perspectives 2 Based mainly on “fresh” results presented at the Quark Matter conference, held in August 2012

MOTIVATIONS, DETECTOR LAYOUT AND DATA TAKING 3

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7 Heavy Ion Collisions pre-equilibration  QGP  hadronisation  freeze out Accellerators: AGS, SPS, RHIC, LHC Create QGP by colliding ultra-relativistic heavy ions  S NN (GeV) = (5200)

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9 Observables Jets Open charm, beauty

10 Diversi esperimenti, ciascuno mirato allo studio di diverse osservabili

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LHC compared to SPS and RHIC SPSRHICLHC √s NN (GeV) dN ch /dy  0 QGP (fm/c) T/T c  (GeV/fm 3 )  QGP (fm/c) ≤22-4≥10  f (fm/c) ~ V f (fm 3 )few 10 3 few 10 4 Few 10 5 The LHC is the ideal place to study the QGP: hotter - bigger -longer lived ~ 10 4 particles per event: Event by event physics

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  ) partons with E t >10 GeV (100 GeV) in centr. Pb-Pb Heavy quarkonia:  Y family experimentally accessible,  high enough for melting? Heavy flavors abundant production  100 c-c bar and few b-b bar in central Pb-Pb  J/  enhancement ?

Hard Probes, heavy quarks and LHC Y production RHICLHC R. Vogt, hep-ph/ X 2000 Pion Production

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

.. all the above measurements in a high-multiplicity environment! 17

ALICE detector Detector: Length: 26 meters Height: 16 meters Weight: 10,000 tons Collaboration: ̴ 1200 Members 132 Institutes 36 countries ACORDE (cosmics) VZERO scint. (centrality)  -1.7– -3.7, 2.8–5.1 T0 (timing) ZDC (centrality) FMD (N ch -3.4<  <5) PMD (N , N ch ) Central Barrel 2  tracking & PID  < 1 Muon Spectrometer -2.5 >  > -4 18

ALICE Acceptance central barrel -0.9 <  < 0.9 – 2  tracking, PID (dE/dx, TOF, TRD) – single arm RICH (HMPID) – single arm PHOS – jet calorimeter EMCal forward muon arm 2.4 <  < 4 – absorber, 3 Tm dipole magnet 10 tracking + 4 trigger chambers multiplicity -5.4 <  < 3 – including photon counting in PMD trigger & timing dets – 6 Zero Degree Calorimeters – T0: ring of quartz window PMT's – V0: ring of scint. Paddles (charged particles) µ arm

20 Particle identification in ALICE

ALICE: main features and performance 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 p T =0 vertexing HMPID ITS TPC TRD TOF Central Barrel  Forward det.  Muon Arm & C.B.  21

22 Photon conversion EMCal PHOS Neutral mesons

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Identification of strange particles

Charmonium and D mesons σ J/Ψ = (75 ± 3) MeV/c 2 D + → 

ALICE Data Taking 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 : 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) yearsystemenergy √s NN TeV integrated luminosity 2010Pb – Pb2.76 ~ 10  b Pb – Pb2.76 ~ 0.1 nb p – Pb5.02 ~ 30 nb -1 26

CENTRALITY DETERMINATIONS AND COULOMB INTERACTION A couple of heavy-ion-specific aspects 27

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VZERO, SPD and ZDCs 29 VZERO

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