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Roman Lietava, University of Birmingham UK HEP Forum 1 ALICE Experiment Physics motivation Detectors Observables and Physics Performance Summary Roman.

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Presentation on theme: "Roman Lietava, University of Birmingham UK HEP Forum 1 ALICE Experiment Physics motivation Detectors Observables and Physics Performance Summary Roman."— Presentation transcript:

1 Roman Lietava, University of Birmingham UK HEP Forum 1 ALICE Experiment Physics motivation Detectors Observables and Physics Performance Summary Roman Lietava University of Birmingham

2 Roman Lietava, University of Birmingham UK HEP Forum 2 937 members (63% from CERN MS) 77 Institutions, 29 Countries ALICE Collaboration ALICE UK: 6 members University of Birmingham

3 Roman Lietava, University of Birmingham UK HEP Forum 3 Collision Systems Collision system pp PbPb 10 7 Run time (s/year) L 0 (cm -2 s -1 ) s NN (TeV) 10 31 14.0 10 6 10 27 5.5 Other collision systems and energies: pA, lighter ions (Sn, Kr, Ar, O) pp @ 5.5 TeV Year April 2007 2007/2008

4 Roman Lietava, University of Birmingham UK HEP Forum 4 Physics Motivation The study of Quantum Chromodynamics: A-A collisions: - physics of many particles interacting strongly, QCD phase transition p-p and p-A collisions: - benchmark for AA collisions - specific aspects Ultra peripheral AA collisions – physics Cosmic ray physics

5 Roman Lietava, University of Birmingham UK HEP Forum 5 QCD Phase Diagram Lattice QCD Nonperturbative phenomena hep-ph/020516 PLB478(2000)447

6 Roman Lietava, University of Birmingham UK HEP Forum 6 Space Time Evolution of the Collisions

7 Roman Lietava, University of Birmingham UK HEP Forum 7 ALICE Physics Goals Deconfinement: charmonium and bottomonium spectroscopy Chiral symmetry restoration: neutral to charged ratios, res. decays Fluctuation phenomena - critical behaviour: event-by-event particle comp. and spectra Geometry of the emitting source: HBT, impact parameter via zero-degree energy flow pp collisions in a new energy domain Degrees of freedom as a function of T hadron ratios and spectra, dilepton continuum, direct photons Global observables: Multiplicities, distributions 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 Large acceptance Good tracking capabilities Selective triggering Excellent granularity Wide momentum coverage P.I.D. of hadrons and leptons Good sec. vertex reconstr. Photon Detection Use a variety of experimental techniques!

8 Roman Lietava, University of Birmingham UK HEP Forum 8 Alice Detector Tracking (B=0.2-0.5 T): - Inner Tracking System (ITS) – pixels,drift,strips - Time Projection Chamber (TPC) - Transition Radiation Detector (TRD) PID: - TPC - TRD - Time Of Flight (TOF) - High Momentum PID (HMPID) Muons: dimuon arm Calorimetry: - PHOton Spectrometer (PHOS) - Electromagnetic Calorimeter (EMCAL) - under discussion

9 Roman Lietava, University of Birmingham UK HEP Forum 9 Bat 40ALICE ATLAS CMS From R.J.Cashmore,IOP Bham

10 Roman Lietava, University of Birmingham UK HEP Forum 10 ALICE Detector Acceptance Muon arm: 2.4< <4 PMD 2.3< <3.5 FMD: -5.4< <-1.6, 1.6< <3

11 Roman Lietava, University of Birmingham UK HEP Forum 11 P T Resolution

12 Roman Lietava, University of Birmingham UK HEP Forum 12 ALICE PID, K, p identified in large acceptance (2 * 1.8 units ) via a combination of dE/dx in Si and TPC and TOF from ~100 MeV to 2 (p/K) - 3.5 (K/p) GeV/c Electrons identified from 100 MeV/c to 100 GeV/c (with varying efficiency) combining Si+TPC+TOF with a dedicated TRD In small acceptance HMPID extends PID to ~5 GeV Photons measured with high resolution in PHOS, counting in PMD, and in EMC /K 0 1 2 3 4 5 p (GeV/c) 1 10 100 p(GeV/c) TRD e / PHOS / TPC+ITS (dE/dx) /K K/p e / HMPID (RICH) TOF

13 Roman Lietava, University of Birmingham UK HEP Forum 13 ALICE Trigger (Birmingham) Triggering on: collision centrality high p T muons high p T electrons jets ALICE trigger features: Global trigger selection Past-Future protection Different trigger rates for group of detectors Dynamic suppression of common triggers Rates and pile-up: Pb-Pb collisions: 8 kHz interaction rate L=10 27 cm -2 s -1 60 % pile-up probability p-p collisions: 200 kHz interaction rate L=3x10 30 cm -2 s -1 100 % pile-up probability TPC drift time 90 s

14 Roman Lietava, University of Birmingham UK HEP Forum 14 First ALICE trigger board (LTU)

15 Roman Lietava, University of Birmingham UK HEP Forum 15 Observables Medium characteristics Particle multiplicities Particle spectra Particle ratios Flow Particle correlation Fluctuations Hard probes Jets Heavy quark and quarkonium production Direct photons and dileptons

16 Roman Lietava, University of Birmingham UK HEP Forum 16 Multiplicity (from K.Kajantie, K.Eskola) dN ch /d ~ 2500 We can extrapolate from RHIC data: What multiplicity do we expect? ALICE design: dN/dy=8000

17 Roman Lietava, University of Birmingham UK HEP Forum 17 Transverse mass spectra 5% most central events NA57 Pb-Pb at s=17GeV Transverse mass spectra Freeze out temperature Transverse flowNA57

18 Roman Lietava, University of Birmingham 18 Hadron Ratios Degree of chemical equlibrium: Constraint on timescales of flavour production mechanism

19 Roman Lietava, University of Birmingham UK HEP Forum 19 Detection One year of ALICE running (10 7 events) s up to p t = 12 GeV/c Topological signature, not reliant on identification of daughters S/B 1 5.5 /event S/B 1 5.5 /event % of rec. s vs p t Reconstructed p t spectrum Reconstructed p t spectrum M(p ) (GeV/c 2 ) Entries % p t (GeV/c) Yield

20 Roman Lietava, University of Birmingham UK HEP Forum 20 Hard Processes Modified by the Medium Jet quenching: –energy degradation of leading hadrons, p t dependence; –modification of genuine jet observables; –energy imbalance in dijet events Open charm/beauty production conium & bonium bound states production Final state (medium) interaction versus initial state (Cronin,shadowing) interaction p-p and p-A measurement are mandatory

21 Roman Lietava, University of Birmingham UK HEP Forum 21 High p T Suppression High p t particles suppressed in Au-Au relative to pp, d-Au. R AB = d 2 N/dp T d T AB d 2 pp /dp T d STAR results: d-Au, Cronin effect Au-Au, jet quenching AA coll pp coll Number of coll J. Adams et al., Phys. Rev. Lett. 91, 072304 (2003).

22 Roman Lietava, University of Birmingham UK HEP Forum 22 Di-jets In central Au-Au events,although trigger jet is clearly visible, away-side jet is not visible, as predicted from strong absorption in a high colour charge density volume, e.g. that produced in a QGP Mini-jets in Au+Au at RHIC (STAR) Missing jet

23 Roman Lietava, University of Birmingham UK HEP Forum 23 Jets Reconstruction in ALICE Jets are produced copiously. Jets are distinguishable from the HI underlying event. p t (GeV) 2 20100200 100/event1/event100K/year 100 GeV jet + HI event

24 Roman Lietava, University of Birmingham UK HEP Forum 24 Heavy Quarks Initially produced quarks experience the full collision history: –Short time scale for production: 1/m Q –Production suppressed at larger times: m Q »T –Long time scale for decay decay » QGP The large masses of c and b quarks make them qualitatively different probes ( massless partons) Observables: Total production rate transverse momentum distribution correlation between quark and antiquark

25 Roman Lietava, University of Birmingham UK HEP Forum 25 Heavy Quarks D 0 K - + reconstruction in ALICE Affected by main vertex resolution in p+p case Affected by main vertex resolution in p+p case D 0 K - c = 123.7 0.8 m BR: (3.83 0.09) % D 0 K - c = 123.7 0.8 m BR: (3.83 0.09) % cuts depend on D 0 p t

26 Roman Lietava, University of Birmingham UK HEP Forum 26 Heavy Quarks D 0 K - + reconstruction in ALICE PbPb: p T >1 GeV/c pp: p T >0 GeV/c

27 Roman Lietava, University of Birmingham UK HEP Forum 27 Heavy Quarkonia J/ and via Dielectrons Mass resolution for 100 MeV (B = 0.4T) Mass resolution for 100 MeV (B = 0.4T) : : J/ : Acceptance down to p t = 0 GeV/c !

28 Roman Lietava, University of Birmingham UK HEP Forum 28 Motivation for pp Study First insight in pp collisions in new energy domain ( s 14 TeV), study of evolution of soft hadronic physics Contribution to knowledge of underlying minimum bias (background) pp events to complement other LHC physics programmes (Higgs search, B physics, etc.) Provide pp data as a reference for study of other collision systems (p-A, A-A) Low multiplicity data to commission and calibrate various components of ALICE

29 Roman Lietava, University of Birmingham UK HEP Forum 29 ALICE Features for pp Excellent particle identification (TOF and HMPID) p t cut-off Magnetic field (but this could be lowered) Material thickness (hard to change) ATLAS and CMS have better -coverage

30 Roman Lietava, University of Birmingham UK HEP Forum 30 Permanent closure of L3 door in RB26 (05/03/04) Summary ALICE experiment is getting ready: - the detectors are being built - -the software is getting ready... and so does the number of people involved - - the understanding of the physics potential grows …

31 Roman Lietava, University of Birmingham UK HEP Forum 31 ALICE Setup ITS TPC TRD TOF PHOS HMPID MUON SPEC. PMD FMD

32 Roman Lietava, University of Birmingham UK HEP Forum 32 Low p t Physics Examples Resonances: K* Decay channel K* K + - Invariant mass distribution for 550 events Entries Au+Au minimum bias p T 0.2 GeV/c |y| 0.5 Statistical error only STAR Preliminary STAR data shows clear K* on background Other resonances ( f 0... ) are being extracted

33 Roman Lietava, University of Birmingham UK HEP Forum 33 HBT Event-by-Event + + HBT Single event Raw correlation function –Uncorrected for Coulomb –R = 8 fm, = 0.5 –Tracking with ITS+TPC, B = 0.2T Q inv (GeV) C(Q inv ) Resolution for B=0.2T d6Nd6N d3p1d3p2d3p1d3p2 C(p 1,p 2 )= d 3 N d 3 p 1 d 3 p 2

34 Roman Lietava, University of Birmingham UK HEP Forum 34 Number of Participants pA: AA: Participants Npart Spectators Npart= +1

35 Roman Lietava, University of Birmingham UK HEP Forum 35

36 Roman Lietava, University of Birmingham UK HEP Forum 36 Charged Particle Multiplicity 130 GeV AuAu 200 GeV AuAu 25-35%cent 0-6%cent 45-55%cent N tot = 4100 ±210 N tot = 4960 ±250 dN/d

37 Roman Lietava, University of Birmingham UK HEP Forum 37 EMCAL => trigger and -jet, + improve resolution on E jet 2% 8% jet Collision axis TPC PHOS+EMCAL Proposed EMCAL | |<0.7 ~ 120 o -jet with PHOS+EMCAL + TPC

38 Roman Lietava, University of Birmingham UK HEP Forum 38 Elliptic flow dN(p T,b,y, )=A(1 + 2v 1 (p T,b,y) cos( ) + 2v 2 (p T,b,y)cos(2 ) +…) - the angle relative to reaction plane STAR Preliminary scaled with n(quarks) v 1 =0 at y=0 by symmetry v 2 – information about the information about the equation of state

39 Roman Lietava, University of Birmingham UK HEP Forum 39 Why is elliptic flow interesting? Coordinate space configuration anisotropic (almond shape) however, initial momentum distribution isotropic (spherically symmetric) Only interactions among constituents generate a pressure gradient, which transforms the initial coordinate space anisotropy into a momentum space anisotropy (no analogy in pp) Multiple interactions lead to thermalization -> limiting behavior ideal hydrodynamic flow y x pypy pxpx coordinate space Momentum space Raimond Snellings

40 Roman Lietava, University of Birmingham UK HEP Forum 40 Elliptic flow as a function of centrality STAR Nucl. Phys. A698 (2002) 193 Non-flow considerable for central and peripheral events

41 Roman Lietava, University of Birmingham UK HEP Forum 41 01210100 p t (GeV/c) Bulk properties Hard processes Modified by the medium ALICE CMS&ATLAS 1+2 Experiments PID T= QCD QsQs

42 Roman Lietava, University of Birmingham UK HEP Forum 42 High p t RHIC Results R AA clearly different between mesons and baryons Importance of PID at high p t p+p baseline measurement!

43 Roman Lietava, University of Birmingham UK HEP Forum 43 Heavy Quarks Open Charm via Hadronic Decays Pb+Pb: dN/dp t Significance p t > 1 GeV/c p+p: p t > 0 GeV/c ! dN/dp t Significance Significance =

44 Roman Lietava, University of Birmingham UK HEP Forum 44 Heavy Quarks Open Charm via Hadronic Decays Input to simulation –cc: PYTHIA, tuned to NLO calculations, with CTEQ4L and nuclear shadowing EKS98 –Background: HIJING Reconstruction effects included PID with TOF 8437 Significance for10 7 (10 9 )evts 50 %11 % S/B 2000013000 Signal for10 7 (10 9 )evts pp (14TeV) Pb-Pb (5.5TeV) System ( s) Pb+Pb minv = 12 MeV (B = 0.4T) PbPb:p T >1 GeV;pp: p T >0

45 Roman Lietava, University of Birmingham UK HEP Forum 45 Parton Energy Loss - Reduction of single inclusive high p t particles Parton specific (stronger for gluons than quarks) Flavour specific (stronger for light quarks) Measure identified hadrons (, K, p,, etc.) + partons (charm, beauty) at high p t –Suppression of mini-jets same-side / away-side correlations –Change of fragmentation function for hard jets (p t >> 10 GeV/c) Transverse and longitudinal fragmentation function of jets Jet broadening reduction of jet energy, dijets, -jet pairs - p+p and p+A measurements crucial

46 Roman Lietava, University of Birmingham UK HEP Forum 46 Parton Energy Loss

47 Roman Lietava, University of Birmingham UK HEP Forum 47

48 Roman Lietava, University of Birmingham UK HEP Forum 48

49 Roman Lietava, University of Birmingham UK HEP Forum 49 Permanent closure of L3 door in RB26 (05/03/04)

50 Roman Lietava, University of Birmingham UK HEP Forum 50 c/b Quarkonia 1 month statistics of PbPb s NN =5.5 TeV; Events/100 MeV 10 3 J/ Y 51015 10 2 dN/d=8000 M + - (GeV) Events/25 MeV 10 4 J/ Y 234 9 10 11 0 10 5 10 4 dN/d=5000 | | < 2.4 2.5 < < 4 via dimuons

51 Roman Lietava, University of Birmingham UK HEP Forum 51 ALICE Pb-Pb central event N ch (-0.5< <0.5)=8000

52 Roman Lietava, University of Birmingham UK HEP Forum 52 The LHC facility Running conditions: + other collision systems: pA, lighter ions (Sn, Kr, Ar, O) & energies (pp @ 5.5 TeV). Collision system pp PbPb s NN (TeV) L 0 (cm -2 s -1 ) /L 0 (%) Run time (s/year) geom (b) 14.010 34 * 10 7 0.07 5.510 27 70-5010 6 * * 7.7 April 2007 End 2007 Early 2008 *L max (ALICE) = 10 31 ** L int (ALICE) ~ 0.7 nb -1 /year

53 Roman Lietava, University of Birmingham UK HEP Forum 53 Experimental Conditions @ LHC pp commissioning start April 2007 wish list of the HI community for the LHC Initial few years (1HI year = 10 6 effective s, ~like at SPS) –2 - 3 years Pb-Pb L ~ 10 27 cm -2 s -1 –1 year p - Pb like (p, d or ) L ~ 10 29 cm -2 s -1 –1 year light ions (e.g. Ar-Ar) L ~ few 10 27 to 10 29 cm -2 s -1 plus, for ALICE (limited by pileup in TPC): – reg. pp run at s = 14 TeV L ~ 10 29 and < 3x10 30 cm -2 s -1 Later: different options depending on Physics results Heavy Ion running part of LHC initial program, early pilot run expected by end of 2007


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