heavy-ion physics @ lhc
DESCRIPTION
Heavy-Ion Physics @ LHC. ~1100 participants: 26 experimental contributions QM04 6 oral : P. Glaessel, V. Manzari, A. Vestbo, H. Takai, B. Wyslouch, S. Blyth. 20 posters : Spectra 23, HBT 1, High p T 17, 20, 21, Flavor 18, 19, 23, Instr. 1, 2, 7, 8, 10, 12, 14, 15, 16, 17, 22, 30. Program - PowerPoint PPT PresentationTRANSCRIPT
QM2004 Yves Schutz 1
Heavy-Ion Physics @ LHC
Program Detectors Observables
~1100 participants:
26 experimental contributions QM04 6 oral: P. Glaessel, V. Manzari, A. Vestbo, H. Takai, B. Wyslouch, S. Blyth. 20 posters: Spectra 23, HBT 1, High pT 17, 20, 21, Flavor 18, 19, 23, Instr. 1, 2, 7, 8, 10, 12, 14, 15, 16, 17, 22, 30.
1000 ALICE 60 CMS 25 ATLAS
QM2004 Yves Schutz 2
The LHC facility
Running conditions:
+ other collision systems: pA, lighter ions (Sn, Kr, Ar, O) & energies (pp @ 5.5 TeV).
Collision system
pp
PbPb
√sNN
(TeV)
L0
(cm-2s-1)
<L>/L0
(%)
Run time(s/year)
geom
(b)
14.0 1034* 107 0.07
5.5 1027 70-50 106 * * 7.7
April 2007
End 2007Early 2008 *Lmax(ALICE) = 1031 ** Lint(ALICE) ~ 0.7 nb-1/year
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Novel aspects:
Probe initial partonic state in a novel Bjorken-x range (10-3-10-5): nuclear shadowing, high-density saturated
gluon distribution. Larger saturation scale
(QS=0.2A1/6√s= 2.7 GeV): particle production dominated by the staturation region.
Qualitatively new regime
J/ψ
ALICE PPR CERN/LHCC 2003-049
10-6 10-4 10-2 100
x
108
106
104
102
100
M2 (
GeV
2)
10 GeV
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Novel aspects: Qualitatively new regime
Hard processes contribute significantly to the total AA cross-section (σhard/σtot = 98%): Bulk properties
dominated by hard processes;
Very hard probes are abundantly produced.
Weakly interacting probes become accessible (, Z0, W±).
LHC
RHIC
SPS
(h+
+h-)/20
17 GeV
200 GeV
5500 GeV=√s
LO p+p y=0
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3 experiments
JURA
ALPES
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hep-ph0104010
5
√s (GeV)10 102 103 102 103 104
1.0
5.0
10.0
15.0
Nch
/(0
.5N
part)
dN
ch/d|
<1
2
5
103
Which particle multiplicity to expect at LHC ?
ALICE optimized for dNch/dY = 4000, checked up to 8000 (reality factor 2).
CMS & ATLAS (checked up to 7000) will provide good performances over the expected range.
dNch/d ~ 1500
HI experiments
dNch/d ~ 2500
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ALICE: the dedicated HI experiment
Solenoid magnet 0.5 T
Central tracking system:• ITS •TPC• TRD• TOF
MUON Spectrometer:• absorbers• tracking stations• trigger chambers• dipole
Specialized detectors:• HMPID• PHOS
Forward detectors:• PMD• FMD, T0, V0, ZDC
Cosmic rays trigger
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Pb/Sci EMCal x = 1.4 x 2/3
TPC
TRD
TOF
PHOS
RICH
ITS
US EMCaL (under discussion)
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ALICE: the dedicated HI experiment
Measure flavor content and phase-space distribution event-by-event: Most (2 * 1.8 units ) of the hadrons (dE/dx + ToF),
leptons (dE/dx, transition radiation, magnetic analysis) and photons (high resolution EM calorimetry);
Track and identify from very low (< 100 MeV/c; soft processes) up to very high pt (~100 GeV/c; hard
processes); Identify short lived particles (hyperons, D/B meson)
through secondary vertex detection; Jet identification;
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ALICE PID performancesALICE PPR CERN/LHCC 2003-049
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ALICE tracking efficiency
p/p < 1%
100%
pt (GeV/c)1 3 5
0
0.4
0.8
1.2
ALICE PPR CERN/LHCC 2003-049
TPC only
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ALICE track resolution at high pt
10 100pt (GeV/c)50
p/p
(%
)
10
30
50
ALICE PPR CERN/LHCC 2003-049
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ALICE construction status
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ALICE TPC
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ALICE Space Frame
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ALICE Dipole coil
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ALICE pixel40K channels200+150 m
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CMS
• Central tracker• High resolution EM calorimeter• Hadronic calorimeter
Superconducting solenoid magnet 4T
• Muon spectrometer
• Very forward calorimeters• ZDC• CASTOR• TOTEM
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ATLAS
Inner detector
Solenoid 2TEM calorimeter
H calorimeter
detectors
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CMS & ATLAS Experiments designed for high pt physics in
pp collisions: Precise tracking systems in a large solenoid
magnetic field; Hermetic calorimeters (EM+Hadronic)
systems with fine grain segmentation; Large acceptance muon spectrometers; Accurate measurement of high energy
leptons, photons and hadronic jets. Provide adequate performances for selected
high pt (> 1 GeV/c) probes for HI physics.
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0 1 2 10 100
pt (GeV/c)
Bulk propertiesHard processes
Modified by the medium
ALICE
CMS&ATLAS
3 Experiments
PID
T=QCD Qs
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QGP probes: hard processes modified by the medium
Q » QCD, T, Qs , r ~ 1/Q
Jet quenching: Energy degradation of leading hadrons, pt
dependence; Modification of genuine jet observables; Mass dependence of energy loss (light and heavy
quarks). Dissolution of c’onium & b’onium bound
states.
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Leading hadron quenching
Nuclear modification factor pattern very different at LHC: Final state interactions
(radiative & collisional energy loss) dominate over nuclear effects (shadowing+Cronin).
Measurement of suppression pattern of leading partons remains experimentally the most straightforward observable for jet-tomography analysis. 0 20 40 60 80 100
pt (GeV)
0.05
0.1
0.5
1
RAA
A+A √sNN = 200, 5500 GeV
Vitev&Gyulassy QM02
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Jets reconstruction Jets are produced copiously.
Jets are distinguishable from the HI underlying event.
pt (GeV)2 20 100 200
100/event 1/event 100K/year
100 GeV jet + HI event
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Performance by ATLAS
50 150 250 3500
40
80
%
Efficiency
Fake jets
Et
Cone algorithm R=0.4Et > 30 GeV
50 150 250 350Et
0
20
10
Energy resolutionPbPb
pp
E/E (%)
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50 150 250 3500
40
80
%
Et
0
20
10
E/E (%)
200 3000 1000
Performance by CMS
Cone algorithm R=0.5Et > 30 GeV
Energy resolution
Et
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Jet quenching Excellent jet reconstruction…
but challenging to measure medium modification of its shape…
Et=100 GeV (reduced average jet energy fraction inside R): Radiated energy ~20% R=0.3 E/E=3% Et
UE ~ 100 GeV
RMedium induced redistribution of jet energy occurs inside cone.
C.A. Salgado, U.A. Wiedemann hep-ph/0310079
vacuum
medium
Et = 50 GeV
Et = 100 GeV
0.200
0.4 0.6 0.8 1
0.2
R=√(2+2)
0.4
0.6
0.810
0.20.4
0.6
0.8
1
(R
)
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Exclusive jets: Redistribution of jet energy
Jet shape: distance R to leading particle; pT of particles for R < Rmax;
Multiplicity of particles for R < Rmax ;
Heating: kT = p sin((particle, jet axis)) ;
Forward backward correlation(particle, jet axis);
Fragmentation function: F(z)=1/NjdNch/dz z=pt/pjet.
Requires high quality tracking down to low pt .
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Fragmentation functions
0 0.5 1z
10-4
10-2
1vacuummedium
0 0.5 1z
1/N
jetsdN
c/dz
10-1
10
103
reconstructed
input
pjet
z
kt
z=pt/pjetpjet
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Exclusive jets: Tagging
Direct measurement of jet energy: , *, Z0
40500Z0 (μ+ μ-)-jet
50104*(μ+ μ-)- jet
50106-jet
pt
(GeV)
Statistics(evts/month)
Channel
50600
1006103
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Exclusive jets: Tagging
Direct measure of jet energy: , *, Z0
Low (< 10%) background as compared to /0
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Heavy flavor quenching observables
Inclusive: Suppression of dilepton invariant mass
spectrum (DDl+l-, BB l+l- , B D+ l+)l-
Suppression of lepton spectra Exclusive jet tagging:
High- pT lepton (B→Dl) & displaced vertex
Hadronic decay (ex. D0 K-+) & displaced vertex
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D quenching (D0 K-+) Reduced
Ratio D/hadrons (or D/0) enhanced and sensitive to medium properties.
nucl-ex/0311004
tpp
tAA
collAA dpdN
dpdN
NR
/
/1
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c/b Quarkonia 1 month statistics of PbPb √sNN=5.5 TeV;
Even
ts/1
00 M
eV
103
J/Y
5 10 15
102
dN/d=8000
M+- (GeV)
Even
ts/2
5 M
eV
104
J/Y
2 3 4 9 10 11 0
105
104
dN/d=5000
|| < 2.4 2.5 < < 4
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Looking forward For a timely completion of LHC and
experiments construction in April 2007; Accelerators and experiments are today in the
production phase. For an exciting decade of novel HI physics
in continuation of the SPS and complementary to RHIC; Detailed physics program, complementary
between 1+2 experiments, takes shape (see PPRs, Yellow reports…).
The 2004 challenge: demonstrate world-wide distributed Monte-Carlo production and data analysis.
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Backup
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The LHC facility
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Time (h)
The LHC facility: average L
1
23
Experiments
* = 2 - 0.5 mIO = 108 ions/bunch
70%
55%
50%
Tuning time
0.2
0.4
0.6
0.8
1<L>/L0
0 5 10 15 200ALICE PPR CERN/LHCC 2003-049
QM2004 Yves Schutz 39
Novel aspects:
SPS RHIC LHC
√sNN (GeV) 17 200
dNch/dy 500 850
0QGP (fm/c) 1 0.2
T/Tc 1.1 1.9
(GeV/fm3) 3 5
QGP (fm/c) ≤2 2-4
f (fm/c) ~10 20-30
Vf(fm3) few 103 few 104 few 105 bigger
5500 X 28
1500-8000 ?
0.1 faster
3.0-4.2 hotter
15-60 denser
≥10longer
30-40
Quantitatively new regime
QM2004 Yves Schutz 40
Novel aspects: Qualitatively new regime
mu= md = ms
mu = md
mu = md ; ms mu,d
HQ suppressed exp(-mc,b,t/T)
Thermodynamics of the QGP phase Thermodynamics of massless 3-flavor QCD.
Parton dynamics (QGP/0>50-100) dominate the fireball expansion and the collective features of the hadronic final state.
s(T)=4/(18log(5T/Tc))
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Scientific objectives of HI physics
Study the QCD phase transition and the physics of the QGP state: How to apply and extend the SM to a complex
and dynamically evolving system of finite size; Understand how collective phenomena and
macroscopic properties emerge from the microscopic laws of elementary particle physics;
Answer these questions in the sector of strong interaction by studying matter under conditions of extreme temperature and density.
RHIC + CBM
LHC
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Heavy-ion running scenario Year 1
pp: detector commissioning & physics data PbPb physics pilot run: global event-properties, observables
with large cross-section Year 2 (in addition to pp @ 14 TeV, L< 5.1030 cm-2s-1 )
PbPb @ L~ 1027 cm-2s-1: rare observables Year 3
p(d, )Pb @ L~ 1029 cm-2s-1 : Nuclear modification of structure function
Year 4 (as year 2) : Lint = 0.5-0.7 nb-1/year Year 5
ArAr @ L~ 1027 -1029 cm-2s-1 : energy density dependencies Options for later
pp @ 5.5 TeV, pA (A scan to map A dependence), AA (A scan to map energy-density dependence), PbPb (energy-excitation function down towards RHIC), ….
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Combined PID
Probability to be a pion
Probability to be a kaon
Probability to be a proton
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Inclusive jets by ALICE
● Original spectrum● Measured spectrum E/E = 25%● Original spectrum for measured energy 90 < ET < 110 GeV
R=0.3
pt > 2 GeV
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Exclusive jets: Tagged jets
pt (GeV)
RAA
PbPb + 40 GeV -jet
1
0 10 20 30 400
2
3
4
Tagging
0 10 20 30 40
No Tagging
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Heavy quarks jets A. Dainese QM04
Initially produced Qs experience the full collision history: Short time scale for production: 1/mQ
Production suppressed at larger times: mQ»T
Long time scale for decay decay»QGP
The large masses of c and b quarks make them qualitatively different probes ( massless partons)
Radiative energy loss suppressed as compared to q, g: (1+0
2/2)-2; 0=mQ/EQ
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D0 K-+ reconstruction in ALICE
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ALICE TPC
EE
510 cm
EE
88s
Central electrode
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D0 K-+ reconstruction in ALICEA. Dainese QM04
Invariant-mass analysis of fully-reconstructed topologies originating from displaced secondary vertices
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Cone angle (°)0 20 40
0
0.1
0.2
C.A. Salgado, U.A. Wiedemann
E/E