# Presentation: 773878

## 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 |

- Yves Schutz

- QM2004

## 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 2007**
**Early 2008**

- *Lmax(ALICE) = 1031

-  ** Lint(ALICE) ~ 0.7 nb-1/year

- Yves Schutz

- QM2004

## 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

- ALICE PPR CERN/LHCC 2003-049

- Yves Schutz

- QM2004

## Novel aspects: 

-  Qualitatively new regime

- Hard processes contribute significantly to the total AA cross-section (**σ****hard****/****σ****tot**** = 98%****):**** **
- Bulk properties dominated by hard processes;
- Very hard probes are abundantly produced.
- Weakly interacting probes become accessible (, Z0, W±).

- Yves Schutz

- QM2004

## 3 experiments 

- JURA

- ALPES

- Yves Schutz

- QM2004

##  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.

-  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

- Yves Schutz

- QM2004

## ALICE: the dedicated HI experiment

- 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

- Yves Schutz

- QM2004

## US EMCaL (under discussion)

**Pb/Sci EMCal                        ******** x ******** = 1.4 x 2********/3**

- TPC
- TRD
- TOF
- PHOS

- RICH

- ITS

- US EMCaL (under discussion)

- Yves Schutz

- QM2004

## 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;

- Yves Schutz

- QM2004

## ALICE PID performances

- ALICE PPR CERN/LHCC 2003-049

- Yves Schutz

- QM2004

## 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

- Yves Schutz

- QM2004

## ALICE track resolution at high pt

- 10

- 100

- pt (GeV/c)

- 50

****p/p (%)

- 10

- 30

- 50

- 

- ALICE PPR CERN/LHCC 2003-049

- Yves Schutz

- QM2004

## ALICE construction status

- Yves Schutz

- QM2004

## ALICE TPC 

- ALICE TPC

- Yves Schutz

- QM2004

## ALICE Space Frame

- ALICE Space Frame

- Yves Schutz

- QM2004

## ALICE Dipole coil

- ALICE Dipole coil

- Yves Schutz

- QM2004

## ALICE pixel

- Yves Schutz

- QM2004

## CMS

-  Central tracker
-  High resolution EM calorimeter
-  Hadronic calorimeter

- Superconducting solenoid magnet 4T

-  Muon spectrometer

-  Very forward calorimeters
-  ZDC
-  CASTOR
-  TOTEM

- Yves Schutz

- QM2004

## ATLAS

- Inner detector

- Solenoid 2T

- EM calorimeter

- H calorimeter

-  detectors

- Yves Schutz

- QM2004

##        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.

- Yves Schutz

- QM2004

## 3 Experiments

- Bulk properties

- Hard processes
- Modified by the medium

- ALICE

-  CMS&ATLAS

- 3 Experiments

- PID

- T=QCD

- Qs

- Yves Schutz

- QM2004

## 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.

- Yves Schutz

- QM2004

## 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.

- Yves Schutz

- QM2004

## 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

- Yves Schutz

- QM2004

## Performance by ATLAS

- Cone algorithm R=0.4
- Et > 30 GeV

- Yves Schutz

- QM2004

## Performance by CMS

- Cone algorithm R=0.5
- Et > 30 GeV

- Energy resolution

- Et

- Yves Schutz

- QM2004

## 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%
- EtUE ~ 100 GeV

- Medium induced redistribution of jet energy occurs inside cone.

- C.A. Salgado, U.A. Wiedemann hep-ph/0310079

- Yves Schutz

- QM2004

## Exclusive jets: Redistribution of jet energy

- Jet shape: distance *R* to leading particle;
*p*T of particles for *R* < *R*max;
- Multiplicity of particles for *R* < *R*max ;
- Heating*: *kT = p  sin((particle, jet axis)) ;
- Forward backward correlation(particle, jet axis);
- Fragmentation function: F(z)=1/NjdNch/dz z=pt/pjet.

- Requires high quality tracking down to low pt .

- Yves Schutz

- QM2004

## Fragmentation functions

- z=pt/

- pjet

- pjet

- Yves Schutz

- QM2004

## Exclusive jets: Tagging

- Direct measurement of jet energy: , *, Z0

- Yves Schutz

- QM2004

## Exclusive jets: Tagging

- Direct measure of jet energy: , *,

- Z0

- Low (< 10%) background as compared to /0

- Yves Schutz

- QM2004

## Heavy flavor quenching observables

- Inclusive:
- Suppression of dilepton invariant mass spectrum (DDl+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

- Yves Schutz

- QM2004

## D quenching (D0 K-+) 

- Reduced
- Ratio D/hadrons (or D/0) enhanced and sensitive to medium properties.

- nucl-ex/0311004

- Yves Schutz

- QM2004

## c/b Quarkonia

- 1 month statistics of PbPb √sNN=5.5 TeV;

- || < 2.4

- 2.5 < < 4

- Yves Schutz

- QM2004

## 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.

- Yves Schutz

- QM2004

## Backup 

- Yves Schutz

- QM2004

## The LHC facility

- Yves Schutz

- QM2004

## The LHC facility: average L

- The LHC facility: average L

- 1

- 2

- 3

- Experiments

- * = 2 - 0.5 m
- IO  = 108 ions/bunch

- 70%

- 55%

- 50%

- Tuning time

- Yves Schutz

- QM2004

## 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 |

|  |  |
| --- | --- |
|  |  |
|  |  |
|  |  |
|  |  |
|  |  |
| ≥10 | longer |
| 30-40 |  |

-  Quantitatively new regime

- Yves Schutz

- QM2004

## 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))

- Yves Schutz

- QM2004

## 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

- Yves Schutz

- QM2004

## 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), ....

- Yves Schutz

- QM2004

## Combined PID

- Probability to be a pion

- Probability to be a kaon

- Probability to be a proton

- Yves Schutz

- QM2004

## Inclusive jets by ALICE

-  Original spectrum
-  Measured spectrum E/E = 25%
-  Original spectrum for measured energy 90 < *E*T < 110 GeV

- R=0.3
- pt > 2 GeV

- Yves Schutz

- QM2004

## Exclusive jets: Tagged jets

-  pt (GeV)

- RAA

- PbPb + 40 GeV -jet

- Yves Schutz

- QM2004

## 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+02/2)-2; 0=mQ/EQ

- Yves Schutz

- QM2004

## D0 K-+ reconstruction in ALICE

- D0 K-+ reconstruction in ALICE

- Yves Schutz

- QM2004

## Slide 48

- Yves Schutz

- QM2004

## Slide 49

- Yves Schutz

- QM2004

## ALICE TPC

**E**

**E**

- 510 cm

**E**

**E**

- 88s

- Central electrode

- Yves Schutz

- QM2004

- Yves Schutz

- QM2004

## D0 K-+ reconstruction in ALICEA. Dainese QM04

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

- Yves Schutz

- QM2004

## Slide 53

- Yves Schutz

- QM2004