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Results from ALICE

Results from ALICE. Ken Oyama - University of Heidelberg - ALICE Collaboration. Large Hadron Collider at CERN. LHC 7 TeV c - 10 km/h Tevatron 0.98 TeV c - 495 km/h RHIC 250 GeV c - 7602 km/h. SPS. ALICE. ALICE Setup. 16 x 26 meters 10,000 tons 18 detectors 20 y to built.

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Results from ALICE

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  1. Results from ALICE Ken Oyama - University of Heidelberg - ALICE Collaboration K. Oyama, Heavy Ion Cafe

  2. Large Hadron Collider at CERN LHC7TeVc- 10 km/h Tevatron 0.98TeVc- 495 km/h RHIC250GeVc- 7602 km/h SPS ALICE K. Oyama, Heavy Ion Cafe

  3. ALICE Setup 16 x 26 meters 10,000 tons 18 detectors 20y to built K. Oyama, Heavy Ion Cafe

  4. Main Trigger Devices V0C 8 cm < r < 76 cm V0A 8 cm < r < 100 cm SPD Interaction point 90 cm (3 nsec) 340 cm (11 nsec) K. Oyama, Heavy Ion Cafe Scintillator paddles placed at 90 cm or 340 cm away from the interaction point (V0-C and V0-A) 32 channels PMT readout for each SPD (Silicon Pixel Vertex detector)

  5. Trigger and Operation K. Oyama, Heavy Ion Cafe • Synchronous operation with LHC at 25 ns periodic beam clock • Typical minimum bias trigger: • p+p: V0A | V0C | SPD • At least one charged particle in of 8 • Pb+Pb: two out of V0A, V0C, SPD • Always gated with 25 ns beamclock, according to fill scheme • Backgrounds • after glow = long-lived radiation • may become problem at50 ns bunch spacing(number of bunches will increasefrom ~300 to ~3000) • beam-gas (vacuum is very good) • in Pb+Pb, electro-magnetic events ( few 10 b or more of cross section)

  6. Charged Particle Identifications TPC ITS TOF K. Oyama, Heavy Ion Cafe PID using ITS, TPC, TOF TPC dE/dx separates p from K up to 1.1 GeV TOF: separates K frompi up to ~ 1.5 GeV

  7. ALICE Status 2x 2x 2x 4 3/5 PHOS 10/18 TRD 18/18 TOF 7/7 HMPID 10/10 EMCAL 5 3 2x 6 2 7 1 2x 8 0 9 17 10 16 15 11 14 12 13 4 0 3 1 2 ALICE 2009 / 2010 Setup EMCAL TOF HMPID TRD ITS TPC L3 Magnet All systems fully operational PHOS K. Oyama, Heavy Ion Cafe

  8. LHC&ALICE Performed Excellent K. Oyama, Heavy Ion Cafe • 2010 p+p 851 DAQ hours in 7 months • increased L. step by step up to 2x1032 [cm-2s-1] • more bunches (up to 368 with 4 x 150 ns trains) • squeezing beams • sustained running efficiency 80% • Pb+Pb 223 DAQ hours in 1 month • 2.5 GB/s sustained data rate

  9. First Pb+Pb Collisions in ALICE! K. Oyama, Heavy Ion Cafe

  10. A First Candidate K. Oyama, Heavy Ion Cafe

  11. ALICE Physics Publications K. Oyama, Heavy Ion Cafe • p+p 0.9, 2.36, and 7 TeV, • pT spectra of charged particles at 900 GeV[Physics Letters B 693 (2010) 53] • Two-pion Bose-Einstein correlations at 900 GeV[Phys. Rev. D 82, 052001 (2010)] • Midrapidity Antiproton-to-Proton Ratio at 0.9 and 7 TeV [PhysRev Lett Vol.105, No.7, (2010) ] • Charged-particle multiplicity at 7 TeV[Eur. Phys. J. C (2010) 68: 345] • Charged-particle multiplicity at 0.9 and 2.36 TeV[Eur. Phys. J. C (2010) 68: 89] • First p+p by ALICE, and charged particle dN/detaat 900 GeV[Eur. Phys. J. C (2010) 65: 111-125] • Pb+Pb 2.76 TeV • Charged-particle multiplicity density at mid-rapidity [Phys. Rev. Lett. 105, 252301 (2010)] • Elliptic flow of charged particles [Phys. Rev. Lett. 105, 252302 (2010)] • Suppression of Charged Particle Production at Large pT[Phys. Lett. B 696 (2011) 30-39] • Centrality dependence of the charged particle multiplicity density at mid-rapidity [arXiv:1012.1657v1 [nucl-ex]] • Two-pion Bose-Einstein correlations [Phys.Lett.B696:328-337,2011]

  12. p+p Data: Some Terminology Drawing by TorbjörnSjöstrand, MCnet school, 2008. p p P p M K. Oyama, Heavy Ion Cafe • Events are categorized to different types which have characteristic differences in rapidity space distribution • Elastic • Single-diffractive (SD) • Double-diffractive (DD) • Non-diffractive (ND) • Not easy to split all of them • Detector dependent • ALICE compared two classes • INEL: inelastic … sum of all inelastic (ND+SD+DD) • Essentially all events triggered by either SPD or V0A or V0C • NSD: non-single-diffractive … ND and DD only, suppressed SD • Essentially it is required that BOTH V0A and V0C have particles

  13. Comparing p+p and Pb+Pb Participants scaling Binary collision scaling peripheral b = large central b = small Each nucleon collides “all” nucleons of the other nuclei Number of collisions max : >1000 in Pb+Pb depends on nucleon density AND N+N cross section Number of participants max : 2A depends on nucleon density K. Oyama, Heavy Ion Cafe • Pb+Pb is considered as “super-position” of p+p events? • If so, scaling factor may exist at given impact parameter

  14. Centrality peripheral (large b) arXiv:1012.1657v1 [nucl-ex] most central (small b) K. Oyama, Heavy Ion Cafe • Impact parameter is not directly measured • centrality as “fractional “ cross section • experiment oriented • Glauber model (Wood-Saxon density distribution) is used to fit the data • Nuclear modification factor (definition) • This is calculated for each centrality class using Glauber model

  15. p+p Charged Multiplicity K. Oyama, Heavy Ion Cafe • using Pixel at 1.4 • Larger than often used models • Basis of everything from now • One of the important global property constrains phenomenological models

  16. Multiplicity Distribution in p+p 7 TeV K. Oyama, Heavy Ion Cafe Higher multiplicity events are much more enhanced compare to PHOJET etc (factpor 10 at Nch=60)

  17. Pb+Pb Charged Multiplicity M.C. shadowing saturation K. Oyama, Heavy Ion Cafe • First fast measurement immediately after the first collisions • 160076 (syst.) • growth with faster in AA than pp • Expected energy density of a created matter (naively) • … x3 of RHIC assuming the same (lower limit?)

  18. Centrality Dependence K. Oyama, Heavy Ion Cafe • Normalized to nuclear overlap volume • The shape of dependence is almost exactly the same as the one of lower energy (RHIC 0.2 TeV) • No model well describe the trend • Important constraint for models

  19. Spectra at 0.9 TeVp+p K. Oyama, Heavy Ion Cafe • Harder spectra at high Nchevents • Basic data for all following analysis and input for models • no model so far reproduce well especially at high- • establishing soft-production at LHC

  20. Proton-antiProton Ratio K. Oyama, Heavy Ion Cafe At central rapidity ratio very close to 1 at 7 TeV

  21. Elliptic Flow of Charged Particles 30 % larger observedcompare to RHIC Harder shape strong partonic pressuregradients? • Spatial non-uniformity  phase space • Fourier components of particle spectrum • : elliptic flow … maximum at  evidence of the thermalized liquid like system K. Oyama, Heavy Ion Cafe

  22. Elliptic Flow Results K. Oyama, Heavy Ion Cafe • dependence  no essential change from RHIC • consistent to hydro prediction • Integrated v.s. centrality • 30 % larger than RHIC results • increases with

  23. pp Pb Shoulders PHENIX PRL 98, 232302 (2007) PbPbcentral ALICE performance v2 flow to be subtracted K. Oyama, Heavy Ion Cafe • Discovery at RHIC • correlation peak not at but • Positions and shape don’t depend on or collision system (centrality, Npart) • Similar not “yet” seen in ALICE but same situation as PHENIX before flow subtraction

  24. Ridge STAR PRC 80 (2009) 64912 K. Oyama, Heavy Ion Cafe • direction correlationobserved at RHIC • At intermediate pT (1~4 GeV/c) and up to • CMS found too, even in p+p • Striking effect. Possible explanations is unclear • CGC initial state (color flux tubes)?

  25. ALICE’s Case PbPb peripheral PbPb central K. Oyama, Heavy Ion Cafe • Indeed, the ridge is seen in central Pb+Pb collisions • but not in 80-90% perhiperal

  26. Initial State Fluctuations? single ev 1000 evavg K. Oyama, Heavy Ion Cafe • Takahashi et al Phys Rev Lett 103, 242301 (2009) • Broken symmetry initial tate • No parton to medium coupling is required • Both shoulder and ridge like structures are reproduced • Unclear yet if it fits with thte rest

  27. Femtoscopy Results for 0.9 TeVp+p Phys. Rev. D82, 052001 (2010) K. Oyama, Heavy Ion Cafe • System size grow with multiplicity (), same trends as world’s trend however to be careful • acceptance, analysis methods are very different • at large , mini-jet effect is a large systematic (treated in ALICE) • No (pair momentum) dependence in p+p but in Pb+Pb

  28. Dependence at 7 TeVp+p Seen? K. Oyama, Heavy Ion Cafe Much higher statistics Under collaboration review No large dependence dependence significant in

  29. Femtoscopy Results for 7 TeV Phys. Rev. D82, 052001 (2010) K. Oyama, Heavy Ion Cafe • HBT Quantum correlation • Flow and jets as underlying effect • scaling • ALICE p+p grow linearly toohowever with different slope • p+p (high mult) is probably qualitatively different from Au+Au peripheral • Statistics much higher • System size grow with multiplicity • same trends as world’s trend • p+p A+A (peripheral) !

  30. Dependence in Pb+Pb K. Oyama, Heavy Ion Cafe Strong dependence As expected are all seen

  31. Femtoscopyfor Pb+Pb arXiv:1012.4035; PLB696:328 K. Oyama, Heavy Ion Cafe Clear increase of system size Much longer QGP in a significantly longer volume Scaling is being tested carefully in ALICE

  32. ‘near’ side pTt ALICE preliminary ‘away’ side UE Trigger Particle (Di-)Jet Fragmentations and leading K. Oyama, Heavy Ion Cafe • Leading particle ~ jet thrust • Near side (intra-jet) “Single” jet properties • Away side (inter-jet): Di-jet, hard scattering properties () • … avg. transverse momentum of jet fragments relative to jet axis • Independent of trigger particle pT • Independent of collision energy

  33. jT Measurement K. Oyama, Heavy Ion Cafe • … average transverse momentum of fragmentation products relative to jet axis • Independent of trigger • Independent of collision energy • p+p 0.9 TeV MeV/c • p+p 7 TeV MeV/c

  34. Extracting Partonic K. Oyama, Heavy Ion Cafe • Width of away side peak and of pair • (mean jet acoplanarity) • increases with collision energy

  35. Jet quenching in Leading Particles peripheral central central peripheral K. Oyama, Heavy Ion Cafe • Suppression of high particles observed in Pb+Pb of ALICE • Strong dependence • stronger than that was observed at RHIC (but similar trend up to 10 GeV/c) • Up to 50 GeV/c to be measured with current statistics • Accuracy is still limited by p+preference (needs reference run)

  36. Calorimeter and Conversion (p+p) p+p 7 TeV p+p 0.9 TeV K. Oyama, Heavy Ion Cafe • Different methods: • (EMcal/PHOS) and (Tracker) • Hiroshima U. for PHOS • Tsukuba for EMCal and its extension (DCAL) • Fair agreement among different methods, Pb+Pb and will come soon

  37. Open Charm in p+p K. Oyama, Heavy Ion Cafe • 1/7 of total p+p statistics • reach will go up to 20 GeV/c • Finalizing for publication

  38. p+p   K. Oyama, Heavy Ion Cafe No absolute normalization yet Compared to an extrapolation based on measurement of CDF (fit using vs. dependence)[J. Phys. G 32 (2006) 1295]

  39. p+p   (cont.) K. Oyama, Heavy Ion Cafe Data to be published soon

  40. Measurements in p+p K. Oyama, Heavy Ion Cafe • Few 1000 in and • Final review for publication • Latest Vernierscan result to be used • Constrain production models

  41. Pb+Pb Needs More Data  Expected result of data collection of 2x108Pb+Pb (20 times of 2010 data)  needs trigger by TRD and/or EMCal K. Oyama, Heavy Ion Cafe • J/Psi for Pb+Pb already visible • Only small fraction of data analyzed yet • ~1000 expected • OK for few slices up to 3 to 4 GeV/c

  42. Summary and Future Plan K. Oyama, Heavy Ion Cafe • ALICE at LHC has started and successfully took first p+p and Pb+Pb data • Already at p+p, many questions came up • Some basic comparisons already done and already many things (re-) discovered (strong jet quenching, much larger size, etc) • Plenty of new analysis will come soon! • ALICE Plan in Future • Another 7 TeV run: if everything goes well, already next week • LHC luminosity goes up to 1033 [cm-2s-1] (factor 5 more of 2010) • ATLAS/CMS collect 5 /fb(too see < pb stuff)  discovery year? • ALICE collects 2 /pb data accumulation (factor 30 or more of 2010) • Short reference p+p run for Pb+Pb • Pb+Pb with much higher luminosity (few kHz which is factor 10 more) • 2012 we might have p+Pb run

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