1. M.Poghosyan1 The ALICE experiment at LHC Martin Poghosyan For the ALICE Collaboration SILAFAE 2010 Valparaíso, Chile Dec. 6 - 12, 2010 Pb-Pb (Nov. 2010) pp (Nov. 2009)

2. SILAFAE2010M.Poghosyan2 ~1000 members from ~30 countries

3. SILAFAE2010M.Poghosyan3 PUEBLA, Autonomous Univ. of Puebla CULIACAN, Universidad Autonoma de Sinaloa MEXICO D.F., Universidad Nacional Autonoma de Mexico; Inst. de Fisica MEXICO D.F., Universidad Nacional Autonoma de Mexico; Inst. de Ciencias Nucleares MEXICO D.F., Merida, Centro de Investigacion y de Estudios Avanzados del IPN CINVESTAV HABANA, Centre de Aplicaciones Tecnologicas y Desarrollo Nuclear ~ 70 members from four Latin American Countries LIMA, Pontificia Universidad Catolica del Peru CAMPINAS, Universidade Estadual de Campinas UniCamp SAO PAULO, Universidade de Sao Paulo, Instituto de Fisica CAMPINAS, Universidade Estadual de Campinas UniCamp SAO PAULO, Universidade de Sao Paulo, Instituto de Fisica Hardware  V0 (MB trigger)  ACORDE (CR trigger)  EMCAL  UPGRADES: VHMIPD, AD Analysis  Jets/ Event Structure  Cosmic Ray Physics  Diffractive Physics  Strangeness Software  Unfolding  Event Display www  Official web page  Indico

4. ITS, TPC, TOF, HMPID, MUON, V0, T0, FMD, PMD, ZDC (100%) TRD (7/18) EMCAL (4/12) PHOS (3/5) Detector configuration A Large Ion Collider Experiment High granularity (dN/dy~8000) Minimized material Good PlD Good acceptance for p t down to 100 MeV/c SILAFAE2010M.Poghosyan4

5. ITS, TPC, TOF, HMPID, MUON, V0, T0, FMD, PMD, ZDC (100%) TRD (7/18) EMCAL (4/12) PHOS (3/5) Detector configuration A Large Ion Collider Experiment High granularity (dN/dy~8000) Minimized material Good PlD Good acceptance for p t down to 100 MeV/c SILAFAE2010M.Poghosyan5 BeamEnergy# of Events pp900 GeV~ 8 M MB pp2.36 TeV~ 40 k MB pp7 TeV~ 800 M MB ~ 50 M muons ~ 20 M high N ch PbPb2.76 TeV/Nfew 10 7 MB

6. SPD1 SPD2 Fiducial window = ΔθΔφ = 25mdar×80 mrad  Two innermost layers of the ITS  Radii of 3.9/7.6 cm (|η| < 2.0/1.4)  ~8 M channels  Trigger & Tracking  ~80% active  Fast aligned/calibrated and used to estimate the o position of the interaction point o number of primary tracks ( |η| 50 MeV/c) Charged particle multiplicity measurement with Silicon Pixel Detector z y x SILAFAE2010M.Poghosyan6

7. Multiplicity distribution SILAFAE2010M.Poghosyan7 K. Aamodt et al., EPJ C68 (2010) 345

8. How to go from Inel>0 to Inel, NSD ?  The Inel>0 sample is an accurate measurement but  One has to correct for diffractive processes for going from Inel>0 to Inel or NSD. Mainly normalization problem: densities of particles in diff. processes are rather small at mid-rapidity, but their cross-sections are not negligible.  What is the definition of diffraction? Theory: coherence, quantum numbers, …. Pomeron exchange Experiment: rapidity gap  How much do we really rely on gap measurements with "Swiss cheese” detectors? no data at lower energies for comparison useless for analytical models SILAFAE2010M.Poghosyan8

9. Inel. and NSD for ALICE at 0.9 and 2.36 TeV Data samples are selected as follows: SPD or V0A or V0C for Inel at 900 GeV (at least one charged particle in 8 units of pseudorapidity) V0A and V0C for NSD at 900 GeV At 2.36 TeV V0 was not in. MC (efficiency/process-type/…): PYTHIA and PHOJET SD and NSD are mixed using SD and Inel cross-sections from UA5 and E710 at 900 GeV 0.153 ± 0.023 (UA5) at 1.8 TeV 0.159 ± 0.024 (E710) – practically no extrapolation needed for 2.36 TeV SILAFAE2010M.Poghosyan9 K. Aamodt et al., EPJ C68 (2010) 89

10. Measuring SD and DD with ALICE Strategy: Identify diffractive process based on the kinematics of produced particles in 9 units of pseudorapidity. ALICE Work in progress ALICE Work in progress ALICE Work in progress ALICE Work in progress ALICE Work in progress ALICE Work in progress SILAFAE201010M.Poghosyan Understanding of diffraction dissociation of hadrons is important for understanding hh, hA and AA collisions. Diffractive intermediate states have a small influence on hA and AA total cross-section (at current energies they are close to a black limit) but they have a strong impact on hh interaction cross-section and on inclusive spectra in hh, hA and AA collisions.

11. PLC 20J. Schukraft 11 p-Nucleus absorption cross section Full tracking requires much more Alignment Proper transport through detector Proper material budget description SILAFAE2010M.Poghosyan11

12. Spectrum seems to get harder towards mid-rapidity (jets become oriented in the tr. plane?) Transverse momentum distribution at 900 GeV ITS+TPC tracking SILAFAE2010M.Poghosyan12 K. Aamodt et al., Phys. Lett. B693 (2010) 53

13. Inclusive spectra as a function of √s SILAFAE2010M.Poghosyan13

14. Number of cut Pomerons ~ s Δ p t 2 ~ Number of cut Pomerons Number of charged particles ~ Number of cut Pomerons as a function of N ch SILAFAE2010M.Poghosyan14

15. PLC 20J. Schukraft No vertex cut ! Particle Identification SILAFAE2010M.Poghosyan15

16. Identified particle spectra SILAFAE2010M.Poghosyan16

17. SILAFAE2010 V0 reconstruction M.Poghosyan17

18. SILAFAE2010 Strangeness at 900 GeV M.Poghosyan18

19. SILAFAE2010  →     →   →     →  Strangeness at 7 TeV M.Poghosyan19

20. Charm at 7 TeV SILAFAE2010 J/  →    , y = 2.5 - 4 1 J/  → e + e - |y| < 1 M.Poghosyan20

21. SILAFAE2010 Antiproton/proton ratio at mid-rapidity α P = 1.2, α ω = 0.44; C ≈ 5 = ½ln s C = 5.7 ± 1.1 D = -0.15 ± 0.45 α Odd = 0.84 ± 0.36 If one requires D>0: D = 5*10 -9 ± 3.8 M.Poghosyan21 K. Aamodt et al., Phys Rev Lett 105 (2010)

22. SILAFAE2010M.Poghosyan22 Bose–Einstein correlations (HBT) identical pions unlike-sign pions pair momentum multiplicity K. Aamodt et al., Phys. Rev. D82 (2010) 052001

23. SILAFAE2010M.Poghosyan23 Source radius at √s = 900 GeV Source radius vs Multiplicity Using different baselines - Radius increases with N ch, comparable to ISR, RHIC, Tevatron - rather constant vs flat baseline results to k T dependent radius dependence usually interpreted as sign of ‘flow’ in heavy ions K. Aamodt et al., Phys. Rev. D82 (2010) 052001

24. SILAFAE2010M.Poghosyan24 Charged particle multiplicity density at mid-rapidity in central Pb-Pb collisions dN ch /dη ~ 1600 ± 76 (syst) at √s NN = 2760 GeV Measured value is mainly on high side of expectations growth with √s stripper in AA than in pp K. Aamodt et al., arXiv:1011.3916

25. SILAFAE2010M.Poghosyan25 Multiplicity vs centrality in Pb-Pb at √s NN = 2760 GeV submitted to arXive on 7 December

26. SILAFAE2010M.Poghosyan26 (after tuning) Multiplicity vs centrality & models

27. SILAFAE2010M.Poghosyan27 Factor: 2.1 Factor: 4.1 Factor: 2.4 Comparison with the average from RHIC experiments (done by PHENIX) What is the physics behind this?

28. SILAFAE2010M.Poghosyan28 dN/dη depends on A 4/3 or A 1.1 ? A 4/3 - Gribov-Glauber without enhanced diagramsA 1.1 - Gribov-Glauber with enhanced diagrams A. Capella, A. Kaidalov, J. Tran Thanh Van, arXiv:hep-ph/9903244 (note, published before the RHIC era!)

29. SILAFAE2010M.Poghosyan29 dN/dη depends on A 4/3 or A 1.1 ? A 4/3 - Gribov-Glauber without enhanced diagramsA 1.1 - Gribov-Glauber with enhanced diagrams A. Capella, A. Kaidalov, J. Tran Thanh Van, arXiv:hep-ph/9903244 (note, published before the RHIC era!) In fact, this dependence is a consequence of having large- mass diffractive intermediate states. Thermalisation and QGP formation strongly depend on the strength of the interactions between Pomerons. In fact, this dependence is a consequence of having large- mass diffractive intermediate states. Thermalisation and QGP formation strongly depend on the strength of the interactions between Pomerons.

30. 30 v 2 vs pt and centrality practically no change with energy +30% RHIC ALICE 30% increase from RHIC for p t integrated v 2 (because of increase of ) v 2 as a function of p t v 2 as a function of centrality SILAFAE2010M.Poghosyan K. Aamodt et al., arXiv:1011.3914

31. R AA = 1 for (very) hard QCD processes in absence of nuclear modifications Suppression of charged particle production at large p t SILAFAE201031M.Poghosyan K. Aamodt et al., arXiv:1012.1004

32. Suppression of charged particle production at large p t Suppression of high p t particles ( ~ leading jet fragments) Minimum R AA ~ 1.5 – 2 x smaller than at RHIC Rising with p t ! (ambiguous at RHIC !) accuracy limited by pp reference SILAFAE201032M.Poghosyan R AA = 1 for (very) hard QCD processes in absence of nuclear modifications K. Aamodt et al., arXiv:1012.1004

33. SILAFAE2010M.Poghosyan33 Strangeness in Pb-Pb

34. SILAFAE2010M.Poghosyan34 Charm in Pb-Pb

35. SILAFAE2010 ALICE is in a good shape Performance of track and vertex reconstruction and particle identification close to design value for both pp and PbPb Physics analysis well underway. Already some important results during one year of data taking: Conclusions M.Poghosyan EEEEEEEEEEEEEEEEEE€ 35 Published results pp N ch multiplicity & distributions 900 GeV: EPJ C65 (2010) 111 900 GeV, 2.36 TeV: EPJ C68 (2010) 89 7 TeV: EPJ C68 (2010) 345 Momentum distributions(900 GeV) Phys. Lett. B693 (2010) 53 Bose Einstein correlations (900 GeV) Phys. Rev. D82 (2010) 052001 pbar/p ratio (900 GeV & 7 TeV) Phys Rev Lett 105 (2010) Pb-Pb Multiplicity in central collisions arXiv:1011.3916 v 2 arXiv:1011.3914 RAA arXiv:1012.1004 Multiplicity vs centrality submitted to arXive on 7 december Many ongoing analysis…