1. Heavy Ion Physics: the ALICE program
Preliminary version
Heavy Ion Physics: the ALICE program
Raimond Snellings
1. Physics motivation and the focus of our group
2. The NIKHEF hardware contribution to ALICE
3. Current status and our ambitions at NIKHEF

2. QCD at extreme conditions
Lattice QCD predicts a phase transition to a quark gluon plasma at energy densities of about 1 GeV/fm3 and at a temperature of about 170 MeV
The quark gluon plasma is a state of matter expected to have existed in the early universe about 1 microsecond after the Big Bang
Heavy-ion collisions provide experimental access to the properties of QCD matter at extreme temperature and density (the equation of state at the QGP phase transition and in the QGP phase)
Spontaneous chiral symmetry restoration
The origin of our mass
deconfinement
The building blocks of QCD, quarks and gluons, become quasi free
9/19/2018
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3. The focus of our group
The properties of the QCD Equation of State above Tc
dp/de calculable in lattice QCD
observables: collective motion of low transverse momentum particles as function of mass
The color density of hot and dense QCD matter
Induced soft gluon radiation by partons traversing the medium
observables: medium modifications of jets and heavy particle production
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4. Heavy ion physics needs a reference…
QGP properties are calculable from first principles in lattice QCD
However currently our observables are not completely calculable from first principles (i.e. contributions from “cold” hadronic matter)
A reference measurement is needed and can be provided by elementary collisions (p+p and p+A)
p+A certainly not before 2010
Or by collision geometry
Centrality dependence
Azimuthal dependence
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5. Non central A-A collisions
Non central collisions break the azimuthal symmetry!
Observables, like the collective motion and the medium modification of jets, become azimuthally dependent.
These are currently studied at STAR by our group
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6. Azimuthal dependence of particle yield (elliptic flow)
Phys.Rev.Lett.86: ,2001 e-Print Archive: nucl-ex/ TOPCITE = 100+ Cited 265 times
Strong elliptic flow observed at RHIC
Agreement with hydrodynamic model calculations for non-peripheral collisions
Mass dependence shows sensitivity to the EoS, heavy mass particles are particularly sensitive
Day 1 measurement
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7. Big impact!
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8. Parton energy loss in hot and dense matter
Radiated gluons decohere due to multiple interactions with the medium
This energy loss depends on the path length and gluon density at the early phase
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9. High-pt azimuthal correlations
Clear back to back azimuthal correlation in p+p and d+Au collisions
Disappearance of the back to back correlation in central Au+Au collisions
Color density more than 50 times larger than in cold nuclear matter!
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10. “Jets” versus the reaction plane
Energy loss dependence on path length!
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11. The analysis of elliptic flow and jet correlations are closely connected
Elliptic flow and jets, both sources of azimuthal correlations between the particles
Azimuthal correlations due to jets need to be understood in order to study flow
Azimuthal correlations due to flow need to be understood to study jets
At large transverse momenta largest contribution to azimuthal correlations still due to elliptic flow
After flow correction jet like signature clearly visible
Sophisticated analysis of multiparticle correlations allow to disentangle the flow component from the jets
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12. The QGP observables we study versus the reaction plane in ALICE
Collective motion of low pt particles versus the reaction plane (elliptic flow)
Test of quark gluon plasma Equation of State properties, dp/de (calculable in lattice QCD)
Order of the phase transition
Open charm particularly interesting: test if heavy masses participate in the hydrodynamic behavior
Jet correlations versus the reaction plane
Detailed test of medium induced parton energy loss, jet quenching mechanism (length and gluon density dependence)
Open charm particularly interesting: detailed test of jet quenching mechanism (dead cone effect)
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13. Why heavy-ions at the LHC?
SPS(17)
RHIC(200)
LHC(5500)
dNch/dy
400
700
e[GeV/fm3]
(t0 = 1 fm/c)
≈ 2.5 ≈
≈ 15 – 40
Vf [fm3]
≈ 103
≈ 7*103
≈ 2*104
tQGP [fm/c]
≤ 1
1.5 – 4
4 – 10 t0
≥ 1
≈ 0.5
≤ 0.2
Larger, longer lived QGP phase
Observables get largest contribution from the QGP phase
Higher energies provide access to abundant hard probes (high-pt jets, charm, ..)
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14. Calculated elliptic flow and the QGP properties at the LHC
(black line) QGP contribution to the observable, increases with colliding energy
(red dots) total observed signal: QGP + hadron phase
At the LHC about 80% of the integrated flow signal generated in the QGP phase!
Hirano, private communication
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15. The best suited detector at the LHC for heavy-ions: ALICE
Ideally suited for these correlation with the reaction plane measurements
Full azimuthal coverage
Particle reconstruction and identification from 100 MeV/c to tens of GeV/c
The key detectors are the TPC and the ITS (with the NIKHEF SSD contribution)
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16. The Alice ITS FE module Support and cooling Endcap ADC SSD DAQ
Strong contribution to outer layers (SSD)
project leader SSD (6 labs)
Main vertex 15 µm in central PbPb
Vertex charm, strange decays 50 µm
Δp/p (pT>1 GeV, with TPC) 14%->3%
Particle ID (dE/dx)
FE module
Support and cooling
Endcap
ADC
SSD
DAQ
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17. NIKHEF ALICE hardware activities (SSD)
Design of SSD support (with Turin)
Design ladder frames (with St. Petersburg)
Design of SSD cooling system (with CERN)
Design of front-end modules (with Kharkov and Strasbourg)
Design ladder cabling (with Kharkov)
Design SSD cabling (industrial production)
Design and production of front-end module test equipment
Design and production of EndCap electronics
Design and production of read-out modules
Ladder assembly (with Nantes)
Final SSD assembly
Bottom line: ITS project on schedule and NIKHEF SSD contribution will finish on time (2006)
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18. ALICE group: current manpower
Utrecht and NIKHEF Amsterdam
Amsterdam manpower:
Staff physicist: 3
PhD students: 2
Amsterdam infrastructure:
Fraction of mechanical and electronics workshop
Ladder assembly room
Utrecht manpower:
Staff physicist: 4
Post-doc: 1
PhD students: 5
Students: 2
Utrecht infrastructure:
Fraction of the faculty mechanical and electronics workshop
mechanical and electronic workshop of the SAP department (4 fte)
Assembly room
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19. ALICE group: current physics activities
Have strong role in STAR EMC analysis
1 fte staff, 1 post-doc, 3 PhD's (until 2009) and 2 students
Had a leading role in correlation analysis with the reaction plane in STAR
Effort is scaled down to 1 PhD (until 2007) and 0.2 fte staff
Have a coordinating role in correlation analysis with the reaction plane in ALICE (Physics Performance Report)
Effort 4 fte staff and 2 PhD
Will increase further with 3 PhD’s and 1 post-doc
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20. Summary NIKHEF ALICE hardware effort on track for timely delivery!
NIKHEF had and has a big impact in STAR physics program
Important preparation for the ALICE physics program
NIKHEF has a strong effort in physics analysis in ALICE,
observables identified which test the initial gluon density of the created system and the QCD Langrangian at the phase transition and in the quark gluon plasma phase
observables have in common correlations with the reaction plane
observables like elliptic flow and first jet correlations with the reaction plane are day one physics with big impact
observables like charm flow and charm energy loss provide more detailed constrains and are a longer term effort
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21. Extra
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22. ALICE: neutral Kaon flow
E. Simili
Full simulations, using charged particle tracks from ITS and TPC to determine reaction plane and calculate neutral Kaon elliptic flow
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23. Flow in non-central collisions: elliptic flow
Different flow in and out of the reaction plane: the main component elliptic flow
Unambiguous signature of collective motion
The driving force of elliptic flow dominates at “early” times (self quenching)
Largest contribution comes from QGP phase
Large magnitude of elliptic flow signature of hydrodynamic behavior (local thermalization -> LQCD)
P.F. Kolb and U. Heinz, in Quark Gluon Plasma, nucl-th/
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