Presentation is loading. Please wait.

Presentation is loading. Please wait.

University of Birmingham

Similar presentations

Presentation on theme: "University of Birmingham"— Presentation transcript:

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

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

3 Collision Systems pp PbPb 14.0 1031 107 April 2007 5.5 1027 106
Year √sNN (TeV) L0 (cm-2s-1) Run time (s/year) Collision system pp PbPb 14.0 1031 107 April 2007 5.5 1027 106 2007/2008 Other collision systems and energies: pA, lighter ions (Sn, Kr, Ar, O) 5.5 TeV UK HEP Forum

4 The study of Quantum Chromodynamics: A-A collisions:
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 UK HEP Forum

5 Nonperturbative phenomena
QCD Phase Diagram Nonperturbative phenomena hep-ph/020516 Lattice QCD PLB478(2000)447 UK HEP Forum

6 Space Time Evolution of the Collisions
UK HEP Forum

7 ALICE Physics Goals Use a variety of experimental techniques!
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 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 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! 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 UK HEP Forum

9 From R.J.Cashmore,IOP Bham
Bat 40 ATLAS CMS ALICE UK HEP Forum From R.J.Cashmore,IOP Bham

10 ALICE Detector Acceptance
Alice acceptance Muon arm: 2.4<h<4 PMD 2.3<h<3.5 FMD: -5.4<h<-1.6, 1.6<h<3 UK HEP Forum

11 PT Resolution UK HEP Forum

12 ALICE PID p, K, p identified in large acceptance (2p * 1.8 units h) via a combination of dE/dx in Si and TPC and TOF from ~100 MeV to 2 (p/K) (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 p/K p (GeV/c) p(GeV/c) TRD e /p PHOS g /p0 TPC+ITS (dE/dx) K/p e /p HMPID (RICH) TOF UK HEP Forum

13 ALICE Trigger (Birmingham)
Triggering on: collision centrality high pT muons high pT 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=1027 cm-2 s-1 60 % pile-up probability p-p collisions: 200 kHz interaction rate L=3x1030 cm-2 s-1 100 % pile-up probability TPC drift time  90 s UK HEP Forum

14 First ALICE trigger board (LTU)
UK HEP Forum

15 Medium characteristics
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 UK HEP Forum

16 We can extrapolate from RHIC data:
Multiplicity What multiplicity do we expect? dNch/dh ~ 2500 We can extrapolate from RHIC data: Aka funkcia ? Pozri odvolavku ! Partial answer is in PPR: Left: charged particle rapidity density per participant pair as a function of center mass energy for AA and pp collisions. Experimanetal data for pp are overlaid by the solid line. The dashed line is a fit 0.68 ln(sqrt(s)/0.68) to all nuclear data. The dotted curve is *(ln(s))**2. The long dashed curve is is saturation model ALICE design: dN/dy=8000 (from K.Kajantie, K.Eskola) UK HEP Forum

17 Transverse mass spectra
NA57 Transverse mass spectra NA57 Pb-Pb at s=17GeV Transverse mass spectra Freeze out temperature Transverse flow 5% most central events UK HEP Forum

18 Hadron Ratios Degree of chemical equlibrium: Constraint on timescales of flavour production mechanism

19 L Detection One year of ALICE running
(107 events)  Ls up to pt = 12 GeV/c Topological signature, not reliant on identification of daughters % % of rec. Ls vs pt S/B  1 5.5 L/event pt (GeV/c) Entries L Yield Reconstructed pt spectrum M(pp) (GeV/c2) UK HEP Forum pt (GeV/c)

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

21 J. Adams et al., Phys. Rev. Lett. 91, 072304 (2003).
High pT Suppression AA coll RAB = d2N/dpTdh TABd2spp/dpTdh pp coll STAR results: Number of coll d-Au, Cronin effect Au-Au, jet quenching High pt particles suppressed in Au-Au relative to pp, d-Au. J. Adams et al., Phys. Rev. Lett. 91, (2003). UK HEP Forum

22 Di-jets Missing jet Mini-jets in Au+Au at RHIC (STAR)
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 Missing jet UK HEP Forum

23 Jets Reconstruction in ALICE
Jets are produced copiously. Jets are distinguishable from the HI underlying event. pt (GeV) 2 20 100 200 100/event 1/event 100K/year + HI event 100 GeV jet UK HEP Forum

24 Heavy Quarks Initially produced quarks experience the full collision history: Short time scale for production: t1/mQ Production suppressed at larger times: mQ»T Long time scale for decay tdecay»tQGP 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 UK HEP Forum

25 Heavy Quarks D0 K-p+ reconstruction in ALICE
cuts depend on D0 pt D0  K-p+ ct =  0.8 mm BR: (3.83  0.09) % Affected by main vertex resolution in p+p case UK HEP Forum

26 Heavy Quarks D0 K-p+ reconstruction in ALICE
PbPb: pT>1 GeV/c pp: pT>0 GeV/c UK HEP Forum

27 Heavy Quarkonia J/Y and  via Dielectrons
Mass resolution for : 100 MeV (B = 0.4T) : Mass resolution of upsilon – we can see upsilon family Acceptance down to pt = 0 GeV/c ! 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 UK HEP Forum

29 ALICE Features for pp Excellent particle identification (TOF and HMPID) pt cut-off Magnetic field (but this could be lowered) Material thickness (hard to change) ATLAS and CMS have better -coverage UK HEP Forum

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


32 Low pt Physics Examples Resonances: K*
Decay channel K* K+p- Invariant mass distribution for 550 events Entries STAR Preliminary Au+Au minimum bias pT  0.2 GeV/c |y|  0.5 Statistical error only STAR data shows clear K* on background Other resonances (r,w,f0... ) are being extracted UK HEP Forum

33 HBT Event-by-Event p+p+ HBT
Single event Raw correlation function Uncorrected for Coulomb R = 8 fm, l = 0.5 Tracking with ITS+TPC, B = 0.2T C(Qinv) Qinv (GeV) d6N d3N d3N C(p1,p2)= d3p1 d3p2 d3p1d3p2 Resolution for B=0.2T UK HEP Forum

34 Number of Participants
Participants Npart Spectators pA: Npart=n+1 AA: UK HEP Forum

35 UK HEP Forum

36 Charged Particle Multiplicity
130 GeV AuAu 200 GeV AuAu dN/d 0-6%cent Ntot = 4100 ±210 Ntot = 4960 ±250 25-35%cent 45-55%cent UK HEP Forum

37 EMCAL => trigger and g-jet, + improve resolution on Ejet
Proposed EMCAL |h|<0.7 Df ~ 120o g-jet with PHOS+EMCAL + TPC jet g Collision axis TPC PHOS+EMCAL 2% 8% h UK HEP Forum

38 Elliptic flow scaled with n(quarks) STAR Preliminary dN(pT,b,y,)=A(1 + 2v1(pT,b,y) cos() + 2v2(pT,b,y)cos(2  ) +…)  - the angle relative to reaction plane v1=0 at y=0 by symmetry v2 – information about the information about the equation of state UK HEP Forum

39 Why is elliptic flow interesting?
Raimond Snellings coordinate space 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 Momentum space py px UK HEP Forum

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

41 1+2 Experiments T=LQCD Qs 1 2 10 100 pt (GeV/c) Hard processes
1 2 10 100 pt (GeV/c) Hard processes Modified by the medium Bulk properties ALICE PID CMS&ATLAS UK HEP Forum

42 High pt RHIC Results RAA clearly different between mesons and baryons
Importance of PID at high pt p+p baseline measurement! UK HEP Forum

43 Heavy Quarks Open Charm via Hadronic Decays
Pb+Pb: pt > 1 GeV/c dN/dpt Significance p+p: pt > 0 GeV/c ! Significance = dN/dpt Significance 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 Pb+Pb 84 37 Significance for107(109)evts 50 % 11 % S/B 20000 13000 Signal for107(109)evts pp (14TeV) Pb-Pb (5.5TeV) System (s) Invariant mass spectrum of decay products. Note that alice can measure do down to one gev in pbpb and almost to 0 in pp sminv = 12 MeV (B = 0.4T) PbPb:pT>1 GeV;pp: pT>0 UK HEP Forum

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

46 Parton Energy Loss UK HEP Forum

47 UK HEP Forum

48 UK HEP Forum

49 Permanent closure of L3 door in RB26 (05/03/04)
UK HEP Forum

50 c/b Quarkonia via dimuons Mm+m- (GeV)
1 month statistics of PbPb √sNN=5.5 TeV; Events/100 MeV 103 J/ Y 5 10 15 102 dN/dh=8000 Mm+m- (GeV) Events/25 MeV 104 J/ Y 2 3 4 9 10 11 105 dN/dh=5000 |h| < 2.4 2.5 <h < 4 UK HEP Forum

51 ALICE Pb-Pb central event
Nch(-0.5<<0.5)=8000 UK HEP Forum

52 The LHC facility Running conditions:
+ other collision systems: pA, lighter ions (Sn, Kr, Ar, O) & energies 5.5 TeV). Collision system pp PbPb √sNN (TeV) L0 (cm-2s-1) <L>/L0 (%) Run time (s/year) sgeom (b) 14.0 1034* 107 0.07 April 2007 5.5 1027 70-50 106 * * 7.7 End 2007 Early 2008 *Lmax(ALICE) = 1031 ** Lint(ALICE) ~ 0.7 nb-1/year 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’ = 106 effective s, ~like at SPS) 2 - 3 years Pb-Pb L ~ 1027 cm-2s-1 1 year p - Pb ‘like’ (p, d or a ) L ~ 1029 cm-2s-1 1 year light ions (e.g. Ar-Ar) L ~ few to 1029 cm-2s plus, for ALICE (limited by pileup in TPC): reg. pp run at Ös = 14 TeV L ~ and < 3x1030 cm-2s-1 Later: different options depending on Physics results Heavy Ion running part of LHC initial program, early pilot run expected by end of 2007 Few words about the trigger which is built by birmingham group UK HEP Forum

Download ppt "University of Birmingham"

Similar presentations

Ads by Google