1. Heavy Ion Program in ALICE
A. Mastroserio
Bari University & INFN
On behalf of the ALICE collaboration
Outline
LHC
Multiplicity, particle ratios
high pt probes
Summary and ALICE start up configuration
04/04/2019
A. Mastroserio - XLIIIth Rencontres de Moriond

2. A. Mastroserio - XLIIIth Rencontres de Moriond
LHC
~8.5 km
LHC
SPS
CERN
ALICE
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A. Mastroserio - XLIIIth Rencontres de Moriond

3. A. Mastroserio - XLIIIth Rencontres de Moriond
ALICE Setup
ALICE Setup
ITS
HMPID
TRD
TPC
MUON ARM
TOF
PHOS
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A. Mastroserio - XLIIIth Rencontres de Moriond

4. Physics topics of ALICE
Event characterization
Multiplicity, centrality
Bulk properties of the hot and dense medium (dynamics of hadronization)
hadron ratios, hadronic resonances
Chiral symmetry restoration
Short lived resonance masses
Space-time fireball description and fireball expansion dynamics
Momentum correlations (HBT), Radial and anisotropic flow
Heavy quark production
Charmonium and bottonium (Debye screening, recombination(?))
Partonic energy loss in QGP
Jet reconstruction, Jet quenching, high pt spectra, inclusive high pTsuppression, open charm (Mass/color dependence of E loss)
Fluctuation phenomena
Event-by-Event analysis
………..
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A. Mastroserio - XLIIIth Rencontres de Moriond

5. Multiplicity and hadronic yields
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6. A. Mastroserio - XLIIIth Rencontres de Moriond
HI Day 1 measurement
dNch/dy = 2900
Eskola hep-ph/050649
dNch/dy = 1200
ln(√s) extrapolation
ε(RHIC) ~ 15 GeV/fm3
ε(LHC) ~ x RHIC
dNch/dy ~
ALICE performances tested up to dNch/dη = 8000!
04/04/2019
A. Mastroserio - XLIIIth Rencontres de Moriond

7. A. Mastroserio - XLIIIth Rencontres de Moriond
ALICE performances
ALICE PPR Vol II
J. Phys. G: Nucl. Part. Phys. 32 (2006) 1295–2040
dNch/dy = 6000
Efficiency (%)
pt/pt
pt/pt
pt/pt ~ 3 % at 100 GeV/c
Photon tagging also feasible: direct , π0, η (PHOS)
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A. Mastroserio - XLIIIth Rencontres de Moriond

8. A. Mastroserio - XLIIIth Rencontres de Moriond
Hadronic ratios
Statistical models assume a chemical freeze out stage: hadron abundances are fixed.
Chemical equilibrium model: depends on two parameters (T, μB) and it is able to describe succesfully hadron yields from SPS to RHIC energies. It predicts a chemical freeze out at LHC energies:
A.Andronic, P.Braun-Munzinger, J. Stachel: arXiv: v1 [nucl-th]
rate of strange (especially multi-strange) hadrons is expected to strongly increase with respect to the equilibrium yields
A.Andronic, P. Braun-Munzinger, J. Stachel. Nucl. Phys. A 772: , 2006
Non-equilibrium scenario: the strangeness phase space is oversaturated (S>1 in the partition function). Tch temperature depends on S and it is lower than the chemical equilibrium prediction. arXiv: v1 [nucl-th].
3 < S < > < Tch (Mev) < EPJ C49 (2007)
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9. ALICE particle ID performances
Unique capability to identify and reconstruct particles
- “stable particles” through dE/dx (TPC+ITS) + TOF + Cherenkov (HMPID)
π, k, p : – 5 GeV/c -> 50 GeV/c (relativistic rise)
Invariant mass reconstruction already done for many resonances and strange weak decaying hadrons (K0s, , , ) L
Pt limits for 107 central Pb-Pb events (1-year data taking)
resolution
~ 1.2 MeV
f (1020)  K+K-
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10. A. Mastroserio - XLIIIth Rencontres de Moriond
High PT probes
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11. A. Mastroserio - XLIIIth Rencontres de Moriond
High PT probes
What if QGP is formed:
Partons propagate in a hot and dense medium before fragmenting in the vacuum
E loss medium > E lossvacuum and depends on the the length of the traversed medium
High pT hadrons are suppressed
“Jet quenching” -> q [medium dependent]
QGP probes: inclusive hadron yields at high pT, Jet Structure
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12. Inclusive hadron yields
Factor 5 suppression @RHIC:
RAA ~ constant at pT > 5 GeV/c
Possible LHC scenario:
- light flavour RAA
- constant ~0.1 at 10< pT (GeV/c) < 20 (gluon dominance)
- slow rise up to 0.2 at 20 < pT (GeV/c)< 100
[arXiv: v1 [hep-ph] and arXiv: v1 [hep-ph]
- slow rise to up to pT < 400 GeV/c
[arXiv: v1 [hep-ph] ]
Heavy flavour / light flavour RAA :
- D quenching vs h quenching probes color charge
dependence (ΔEQ < ΔE g)
- B quenching vs D quenching probes parton mass
dependence of parton E loss
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13. A. Mastroserio - XLIIIth Rencontres de Moriond
Jet physics in HI
Jet in QCD: cascades of consecutive emissions of partons initiated by partons from an initial hard scattering
What if QGP is formed:
The initial energy of fast partons is degraded in the medium
Broadening of the parton shower along the fast parton direction
Modified jet structure and fragmentation functions
N. Borghini & U. Wiedemann
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14. Jet Reconstruction: RAA(x)
e-by-e jet reconstruction feasible
A. QM08
GeV2/fm
[AQM]
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15. A. Mastroserio - XLIIIth Rencontres de Moriond
Summary
ALICE is a versatile experiment which will study the QGP formation in different physics domains (statisical thermodynamics, hydrodynamics, pQCD,etc.)
Only few topics of the ALICE Heavy Ion Physics programme have been shown!
first 105 events: global event properties
multiplicity, rapidity density
elliptic flow
first 106 events: source characteristics
particle spectra, resonances
flow analysis
interferometry
first 107 events: high-pt, heavy flavours
jet quenching, heavy-flavour energy loss
first 108 events: heavy quark production
J/Ψ, 
-> initial conditions
-> chemical equilibrium
-> Parton E loss in the medium
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16. ALICE start up configuration
complete – fully installed & commissioned
ITS, TPC, TOF, HMPID, MUON SPECTROM., PMD, V0, T0, FMD, ZDC, ACORDE
partially completed
TRD (25%) to be completed by 2009
PHOS (60%) to be completed by 2010
HLT (30%) to be completed by 2009
EMCAL (0%) to be completed by 2010/11
at start-up full hadron and muon capabilities
partial electron and photon capabilities
….looking forward to “detect” this!
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17. A. Mastroserio - XLIIIth Rencontres de Moriond
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18. A. Mastroserio - XLIIIth Rencontres de Moriond
Bkp slides
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19. A. Mastroserio - XLIIIth Rencontres de Moriond
QGP in lQCD
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20. HI collisions from SPS to LHC
Central collisions
SPS
RHIC
LHC
sNN (GeV) 17
200
5500
Bj nom(GeV/fm3)
2.9 5
15 (?)
QGP(fm/c)
<1
1.5-4
4-10 (?)
0(fm/c) 1
0.5
< 0.2 (?)
hard/tot
~ 50%
~ 98%
Phase transition
(lattice QCD):
Tcr ~ 170 MeV
εcr~ 1 GeV/fm3
New scenario:
Hard processes dominate AA cross section
QGP at LHC > RHIC : parton dynamics dominate the fireball expansion
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21. A. Mastroserio - XLIIIth Rencontres de Moriond
Alice ID
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Hadron ratios
Non equilibrium
Chemical equilibrium
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23. Strangeness production in HI
- No initial net strangeness
strange particle are a direct
consequence of the collision
dynamics
Strangeness production mechanism is in the QGP phase:
gg-> s sbar
(no hadron mass thresholds to be overcome! )
arXiv: v1 [nucl-ex] 17 May 2007
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24. A. Mastroserio - XLIIIth Rencontres de Moriond
1 year data taking
>107
Jets
Background ~ R2
— no pT cut
— pT >1 GeV/c
— pT >2 GeV/c
ETjet
100 GeV
150 GeV
50 GeV
30 GeV R
E(R), charged [GeV]
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25. A. Mastroserio - XLIIIth Rencontres de Moriond
LHC rates and HQ σ
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A. Mastroserio - XLIIIth Rencontres de Moriond