1. qcd Matter created at the lhc Barbara Erazmus cnrs/IN2P3 France Crete center for theoretical physics May 28, 2013

2. HEAVY ION COLLISIONS AT HIGH ENERGY
Extreme states of matter
QCD phase diagram
Deconfinement
Chiral symmetry restoration
Universal character of wave functions of large nuclei
Dense gluonic system
Saturation
Color glass condensate

3. HERA demonstrated that the gluon distribution
in a proton rises very fast with decreasing x at fixed Q
RHIC
LHC
In this range
saturation of the rapidly growing gluon distribution at saturation scale Qs

4. ALICE | DIS | 22 Avril 2013 | B. Erazmus

6. A Large Ion Collider Experiment
T0/VZERO Trigger/Centrality
L3 Magnet
EMCAL
γ, π0, jets
ACORDE
Cosmic trigger
TRD
Electron ID (TR)
HMPID
PID high pT
TOF
PID
PMD
γ multiplicity
FMD
Charged
multiplicity
ITS
Low pT tracking
PID + Vertexing
Dipole
TPC
Tracking, PID (dE/dx)
MUON
μ-pairs
PHOS
γ, π0, jets
ALICE | SIPB | 21 March 2013 | B. Erazmus
Not shown: ZDC (at ±114m)

7. ALICE – dedicated heavy-ion experiment at the LHC
ITS
TPC
TOF
vertexing
TRD
HMPID
particle identification (practically all known techniques)
extremely low-mass tracker ~ 10% of X0
excellent vertexing capability
efficient low-momentum tracking down to ~ 100 MeV/c

8. integrated luminosity
LHC Heavy-Ion running
Two heavy-ion runs at the LHC so far:
in 2010 – commissioning and the first data taking
in 2011 – already above nominal instant luminosity!
p–Pb run just finished at the beginning of this year
Followed by Long Shutdown–1 (LS1)
year
system
energy √sNN
TeV
integrated luminosity
2010
Pb – Pb
2.76
~ 10 mb-1
2011
~ 0.1 nb-1
2013
p – Pb
5.02
~ 30 nb-1

9. GLOBAL EVENT PROPERTIES
State and dynamical evolution of the bulk matter characterized by
soft particles (below a few GeV/c)
multiplicity distributions (initial energy density)
spectra, yields (hadronization process)
flow (collective transport phenomena)
correlations (space-time evolution)

10. MULTIPLICITY DISTRIBUTIONS
ALICE PRL 105 (2010)
ALICE PRL 106 (2011)
ALICE | DIS | 22 Avril 2013 |

11. Initial Density and Temperature from Bjorken formula SEE CMS PRL 109 (2012)
(2.6 times RHIC)
(+30% RHIC)
Lattice QCD predictions : Tc MeV – 175 MeV
The conditions of the formation of a quark gluon plasma
are reached in the early stages of the collisions

12. Large radial flow in most central events:
IDENTIFIED PT SPECTRA
Data/Model
1/N 1/(2πp ) d2N/(dp dy ) (GeV/c)-2 T ev
10-3
Krakow
EPOS
10-1 10
103
106
105
0-5% Central collisions
π+ + π- (× 100)
K+ + K (× 10)
p + p (× 1) -
= 2.76 TeV NN
ALICE, Pb-Pb s
STAR, Au-Au s = 200 GeV
PHENIX, Au-Au s = 200 GeV
VISH2+1
HKM 1
1.5
π+ + π-
K+ + K-
p + p 2 3 4 5 •
ALICE Collaboration, Phys. Rev. Lett. 109, (2012) + arXiv:
Comparison with hydro models: radial flow and kinetic freeze-out temperature Tkin
Large radial flow in most central events:
<βT> = 0.65 ± 0.02 (~10% higher w.r.t. RHIC) increases with centrality
Tkin = 95 ± 10 MeV
(same as RHIC within errors)
model comparisons:
VISH2+1 (viscous hydro)
HKM (hydro+UrQMD)
Kraków (viscous corr., lower the effective Tch)
EPOS (hydro+UrQMD)
ALICE PRL 109 (2012)
p (GeV/c) T

13. Large radial flow in top central events:
IDENTIFIED PT SPECTRA
Comparison with hydro models: radial flow and kinetic freeze-out temperature Tkin •
Data/Model
1/N 1/(2πp ) d2N/(dp dy ) (GeV/c)-2 T ev
10-4
10-2
HKM 1
102
105
104
20-30% Central collisions
π+ + π- (× 100)
K+ + K (× 10) -
p + p (× 1)
ALICE, Pb-Pb s = 2.76 TeV NN
= 200 GeV
STAR, Au-Au s
PHENIX, Au-Au s = 200 GeV
VISH2+1
Krakow
EPOS
1.5
π+ + π-
K+ + K-
p + p 2 3 4 5
p (GeV/c)
ALICE Collaboration, Phys. Rev. Lett. 109, (2012) + arXiv:
Large radial flow in top central events:
<βT> = 0.65 ± 0.02 (~10% higher w.r.t. RHIC) increases with centrality
Tkin = 95 ± 10 MeV
(same as RHIC within errors)
model comparisons:
VISH2+1 (viscous hydro)
HKM (hydro+UrQMD)
Kraków (viscous corr., lower the effective Tch)
EPOS (hydro+UrQMD)
ALICE arXiv:

14. Large radial flow in top central events:
IDENTIFIED PT SPECTRA -2
c 106 )
(GeV/ 105 ALICE, Pb-Pb NN = 2.76 TeV
STAR, Au-Au s = 200 GeV s
) PHENIX, Au-Au s = 200 GeV NN
d 10
y 3 NN T p
/(d π+ + π- (× 100)
N 10 2
d K+ + K - (× 10)
) VISH2+1
T p + p (× 1)
p HKM π
1/( % Central collisions
Krakow
EPOS ev N
1/ 1.5 π+ + π- 1
Data/Model 1.5 K+ + K-
1.5 p + p
0 1 2
Data/Model
1/N 1/(2πp ) d2N/(dp dy ) (GeV/c)-2
p (GeV/c)
10-6
1.5
10-4
10-2
102
104
70-80% Central collisions
π+ + π- (× 100)
K+ + K - (× 10)
p + p (× 1)
ALICE, Pb-Pb s = 2.76 TeV
PHENIX, Au-Au s = 200 GeV
VISH2+1
HKM
π+ + π-
K+ + K- 3
4 5
p + p •
ALICE Collaboration, Phys. Rev. Lett. 109, (2012) + arXiv:
Comparison with hydro models: radial flow and kinetic freeze-out temperature Tkin
Large radial flow in top central events:
<βT> = 0.65 ± 0.02 (~10% higher w.r.t. RHIC) increases with centrality
Tkin = 95 ± 10 MeV
(same as RHIC within errors)
model comparisons:
VISH2+1 (viscous hydro)
HKM (hydro+UrQMD)
Kraków (viscous corr., lower the effective Tch)
EPOS (hydro+UrQMD)
➡ more peripheral events are more challenging for the models
ALICE arXiv:

15. Matter at CHEMICAL freeze-out
well described by statistical models
(from J. Cleymans et al, hep-ph/ )

16. Annihilation in baryon-antibaryon correlations
Deviation of proton yields from thermal models expectations
annihilation should be taken into account while determining yields
Steinheimer, Aichelin, Bleicher; arXiv:
Werner et al.; Phys.Rev. C85 (2012) Karpenko, Sinyukov, Werner;
arXiv:
(...)switching BB-annihilation one suppresses baryon yields, in the same time increases pion yield, thus lowering p/π ratio to the value , which is quite close to the one measured by ALICE(...)
→ annihilation must be seen in baryon-antibaryon correlations

17. C (⃗q)=∫ S (⃗r )∣Ψ (⃗q , ⃗r )∣2 d 4 r
Baryon femtoscopy
C (⃗q)=∫ S (⃗r )∣Ψ (⃗q , ⃗r )∣2 d 4 r
measured correlation
emission function (radius)
cross-section
increase of (anti)correlation =
decrease of the radius or
increase of the interaction cross-section
expected shape of the signal (MC)
Maciej Szymański
Quark Matter 2012

18. pp correlation functions
Shape dominated by Coulomb and Strong FSI
Significant annihilation (from strong FSI) expected and measured
Quark Matter 2012

19. ANISOTROPIC ELLIPTIC FLOW
Spatial deformation
Azimuthal (φ) pressure gradients
Anisotropic particle density Z φ y2 y3 y4 y x
Pressure Δpx > Δpy Y X

20. ELLIPTIC FLOW COEFFICIENTS
ALICE PLB 719 (2013)

21. ELLIPTIC FLOW COEFFICIENTS
Hydro model using Glauber initial conditions for different values of the viscosity Schenke, Jeon, Gale Phys.Lett. B7012 (2011) Further constraints on viscosity and initial conditions provided by measurements of higher harmonics very sensitive to properties of the medium ALICE PRL 107

22. Created at early stages of the collisions
HARD PROBES at high mass and high pT heavy quarks, quarkonia, photons, jets…
Created at early stages of the collisions
Production and propagation in medium provides information about parton energy loss

23. REFERENCE COLLISIONS
proton-proton

24. J/ψ SUPPRESSION RHIC SPS LHC ALICE PRL 109 (2013)
‘anomalous’ suppression
LHC
suppression / regeneration
ALICE PRL 109 (2013)

25. J/y elliptic flow arXiv: 1303.5880
J/y produced by recombination of thermalized c-quarks should have
non-zero elliptic flow
– measurements give a hint for non-zero v2
– qualitative agreement with transport models, including regeneration
– complementary to indications obtained from J/y RAA studies

26. D mesons RAA Average D-meson RAA:
– pT < 8 GeV/c hint of slightly less
suppression than for light hadrons
– pT > 8 GeV/c both (all) very similar
no indication of colour charge dependence
ALICE | DIS | 22 Avril 2013 | B. Erazmus

27. D MESONS v2 Non-zero D meson v2 observed
Comparable to that of light hadrons
Simultaneous description of RAA and v2
c-quark transport coefficient in medium
ALICE | DIS | 22 Avril 2013 | B. Erazmus

28. Ds MESONS RAA Strong suppression (~ 4–5 ) at pT above 8 GeV/c
Uncertainty will improve with
future pp and Pb–Pb data taking

29. Reference for Pb-Pb collisions ? Cold nuclear matter ?
REFERENCE COLLISIONS
p - Pb
Reference for Pb-Pb collisions ?
Cold nuclear matter ?
Unexpected collective effects ?

30. Cold nuclear matter effects vs. jet quenching in Pb-Pb…
Phys. Rev. Lett. 110, (2013)
Compatible with unity above 2-3 GeV/c
Jet quenching in Pb-Pb collisions is a final state effect <=> QGP opaque to energetic partons
3030

31. The Ridge
2 < pT,trig < 4 GeV/c 1 < pT,assoc < 2 GeV/c 20% highest multiplicity
(zoomed)
Near-side jet (Dj ~ 0, Dh ~ 0)
1/Ntrig d2Nassoc/dDhdDj
Away-side jet (Dj ~ p, elongated in Dh)
Near-side ridge (Dj ~ 0, elongated in Dh) Dh
Dj (rad)
The near-side long-range ridge observed by CMS in pp and p-Pb seen by ALICE in p-Pb [JHEP 09 (2010) 091, PLB718 (2013) 795]

32. viscous hydro (arXiv:1112.0915)
Interpretation
Flow?
viscous hydro (arXiv: )
Saturation?
Color glass condensate (arXiv: )
Band: Calculation
Points: ALICE data
arXiv:
Ridge Yields per Dh
arXiv:
0-20% % %

39. CONCLUSIONS
Hot and dense matter created at the LHC behaves as a liquid
with low viscosity well described by hydrodynamical approaches
New precise hard probes allow to study the QGP
Recent measurements of proton-lead collisions reveal
surprising (collective ?) behaviour