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
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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
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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
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5. Nonperturbative phenomena
QCD Phase Diagram
Nonperturbative phenomena 
hep-ph/020516
Lattice QCD
PLB478(2000)447
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6. Space Time Evolution of the Collisions
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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!
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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
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9. From R.J.Cashmore,IOP Bham
Bat 40
ATLAS
CMS
ALICE
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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
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11. PT Resolution
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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
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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
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14. First ALICE trigger board (LTU)
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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
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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)
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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
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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)
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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
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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).
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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
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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
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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
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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
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26. Heavy Quarks D0 K-p+ reconstruction in ALICE
PbPb: pT>1 GeV/c
pp: pT>0 GeV/c
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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 !
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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
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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
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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
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31. ALICE Setup
HMPID
TRD
TPC
PMD
MUON SPEC.
ITS
TOF
PHOS
FMD
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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
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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
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34. Number of Participants
Participants Npart
Spectators
pA:
Npart=n+1
AA:
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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
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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
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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
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40. Elliptic flow as a function of centrality
Non-flow considerable for central and peripheral events
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STAR Nucl. Phys. A698 (2002) 193

41. 1+2 Experiments T=LQCD Qs 1 2 10 100 pt (GeV/c) Hard processes1 2 10
100
pt (GeV/c)
Hard processes
Modified by the medium
Bulk properties
ALICE
PID
CMS&ATLAS
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42. High pt RHIC Results RAA clearly different between mesons and baryons
Importance of PID at high pt
p+p baseline measurement!
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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
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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
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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
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46. Parton Energy Loss
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47. UK HEP Forum

48. UK HEP Forum

49. Permanent closure of L3 door in RB26 (05/03/04)
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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
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51. ALICE Pb-Pb central event
Nch(-0.5<<0.5)=8000
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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
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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
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