Heavy-Ion%20Physics%20@%20LHC

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Heavy-Ion Physics _at_ 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 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

• Program
• Detectors
• Observables

2
The LHC facility

• Running conditions
• other collision systems pA, lighter ions (Sn,
  Kr, Ar, O) energies (pp _at_ 5.5 TeV).

vsNN (TeV) L0 (cm-2s-1) ltLgt/L0 () Run time (s/year) sgeom (b)
14.0 1034 107 0.07
Collision system
pp
PbPb
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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Novel aspects
Qualitatively new regime

• Probe initial partonic state in a novel Bjorken-x
  range (10-3-10-5)
• nuclear shadowing,
• high-density saturated gluon distribution.
• Larger saturation scale (QS0.2A1/6vsd 2.7 GeV)
  particle production dominated by the staturation
  region.

ALICE PPR CERN/LHCC 2003-049
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Novel aspects
Qualitatively new regime

• Hard processes contribute significantly to the
  total AA cross-section (shard/stot 98)
• Bulk properties dominated by hard processes
• Very hard probes are abundantly produced.
• Weakly interacting probes become accessible (g,
  Z0, W).

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3 experiments
JURA
ALPES
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HI experiments

• 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/dh 1500
dNch/dh 2500
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ALICE the dedicated HI experiment
Cosmic rays trigger

• Forward detectors
• PMD
• FMD, T0, V0, ZDC

• Specialized detectors
• HMPID
• PHOS

• Central tracking system
• ITS
• TPC
• TRD
• TOF

• MUON Spectrometer
• absorbers
• tracking stations
• trigger chambers
• dipole

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US EMCaL (under discussion)
RICH
Pb/Sci EMCal Dh x Df 1.4
x 2p/3
TPC TRD TOF PHOS
ITS
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ALICE the dedicated HI experiment

• Measure flavor content and phase-space
  distribution event-by-event
• Most (2p 1.8 units h) 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 (lt 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 performances
ALICE PPR CERN/LHCC 2003-049
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ALICE tracking efficiency
ALICE PPR CERN/LHCC 2003-049
e
TPC only
1.2
100
0.8
Dp/p lt 1
0.4
0
1
3
5
pt (GeV/c)
12
ALICE track resolution at high pt
ALICE PPR CERN/LHCC 2003-049
Dp/p ()
50
30
9
10
100
pt (GeV/c)
50
10
13
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 pixel
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CMS

• Very forward calorimeters
• ZDC
• CASTOR
• TOTEM

• Central tracker
• High resolution EM calorimeter
• Hadronic calorimeter

Superconducting solenoid magnet 4T

• Muon spectrometer

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ATLAS
m detectors
EM calorimeter
Solenoid 2T
Inner detector
H calorimeter
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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 (EMHadronic) 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 (gt 1 GeV/c) probes for HI physics.

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3 Experiments
Qs
TLQCD
Hard processes Modified by the medium
Bulk properties
ALICE
PID
CMSATLAS
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QGP probes hard processes modified by the medium

• Q LQCD, T, Qs ? Dt, Dr 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 conium bonium 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
  (shadowingCronin).
• Measurement of suppression pattern of leading
  partons remains experimentally the most
  straightforward observable for jet-tomography
  analysis.

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Jets reconstruction

• Jets are produced copiously.
• Jets are distinguishable from the HI underlying
  event.

pt (GeV)
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100
200
2
100/event
1/event
100K/year
HI event
100 GeV jet
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Performance by ATLAS
Cone algorithm R0.4 Et gt 30 GeV
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Performance by CMS
Cone algorithm R0.5 Et gt 30 GeV
Energy resolution
Et
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Jet quenching

• Excellent jet reconstruction but challenging to
  measure medium modification of its shape
• Et100 GeV (reduced average jet energy fraction
  inside R)
• Radiated energy 20
• R0.3 DE/E3
• EtUE 100 GeV

Medium induced redistribution of jet energy
occurs inside cone.
C.A. Salgado, U.A. Wiedemann hep-ph/0310079
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Exclusive jets Redistribution of jet energy

• Jet shape distance R to leading particle
• pT of particles for R lt Rmax
• Multiplicity of particles for R lt Rmax
• Heating kT p ? sin(?(particle, jet axis))
• Forward backward correlation ??(particle, jet
  axis)
• Fragmentation function F(z)1/Nj?dNch/dz
  zpt/pjet.

Requires high quality tracking down to low pt .
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Fragmentation functions
pjet
zpt/
pjet
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Exclusive jets Tagging

• Direct measurement of jet energy g, g, Z0

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Exclusive jets Tagging
Z0

• Direct measure of jet energy g, g,

Low (lt 10) background as compared to g/p0
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Heavy flavor quenching observables

• Inclusive
• Suppression of dilepton invariant mass spectrum
  (DD?ll-, BB ?ll- , B ?D ?l)l-
• Suppression of lepton spectra
• Exclusive jet tagging
• High- pT lepton (B?Dl?) displaced vertex
• Hadronic decay (ex. D0 ?K-p) displaced vertex

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D quenching (D0 ?K-p)
nucl-ex/0311004

• Reduced
• Ratio D/hadrons (or D/p0) enhanced and sensitive
  to medium properties.

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c/b Quarkonia

• 1 month statistics of PbPb vsNN5.5 TeV

h lt 2.4
2.5 lth lt 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
  12 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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The LHC facility average L
b 2 - 0.5 m IO 108 ions/bunch
70
1
Tuning time
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Experiments
2
3
50
Time (h)
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Novel aspects
Quantitatively new regime
SPS RHIC LHC
vsNN (GeV) 17 200
dNch/dy 500 850
t0QGP (fm/c) 1 0.2
T/Tc 1.1 1.9
e (GeV/fm3) 3 5
tQGP (fm/c) 2 2-4
tf (fm/c) 10 20-30
Vf(fm3) few 103 few 104








few 105 bigger

5500 X 28



0.1 faster




3.0-4.2 hotter






10 longer
30-40 longer


1500-8000 ?





15-60 denser
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Novel aspects
Qualitatively new regime

• Thermodynamics of the QGP phase ? Thermodynamics
  of massless 3-flavor QCD.
• Parton dynamics (tQGP/t0gt50-100) dominate the
  fireball expansion and the collective features of
  the hadronic final state.

as(T)4p/(18log(5T/Tc))
mu md ms mu md mu md ms ? mu,d HQ
suppressed exp(-mc,b,t/T)
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Scientific objectives of HI physics
RHIC CBM

• 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.

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 _at_ 14 TeV, Llt 5.1030
  cm-2s-1 )
• PbPb _at_ L 1027 cm-2s-1 rare observables
• Year 3
• p(d, a)Pb _at_ 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 _at_ L 1027 -1029 cm-2s-1 energy density
  dependencies
• Options for later
• pp _at_ 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
R0.3 pt gt 2 GeV

• Original spectrum
• Measured spectrum DE/E 25
• Original spectrum for measured energy 90 lt ET lt
  110 GeV

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Exclusive jets Tagged jets
PbPb 40 GeV g-jet
RAA
pt (GeV)
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Heavy quarks jets A. Dainese QM04

• Initially produced Qs experience the full
  collision history
• Short time scale for production t?1/mQ
• Production suppressed at larger times mQT
• Long time scale for decay tdecaytQGP
• 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?02/?2)-2 ?0mQ/EQ

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D0 ?K-p reconstruction in ALICE
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ALICE TPC
E
E
E
E
88ms
510 cm
Central electrode
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D0 ?K-p reconstruction in ALICEA. Dainese QM04

• Invariant-mass analysis of fully-reconstructed
  topologies originating from displaced secondary
  vertices

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