Quark Gluon Plasma
Y. Akiba (RIKEN Nishina Center)
Qukars to Universe in Computational Science
December 14, 2012

QCD Phase Transition• The colliding nuclei at high energies would melt protons and neutrons
into a collection of quarks and gluons
εSB (T) =π230(N bosons + 7 /8 N fermions )T 4

Quark Gluon Plasma
JHEP11(2010) 77

HadronTc ~ 160 MeV; ε ~ 1 GeV/fm3
This is the only phase transition that occurred in the early universe that can berecreated in the lab23

RHIC at BNLApprox 500 tracks result
from a Au+Au ion collisionp+p at √s=510 GeV max
Au+Au at √s=200 GeV max
Started at Year 2000
collided various beams
pp, dAu, CuCu, CuAu
AuAu, UULHC at CERN
p+p at √s=7, 8 TeV
Pb+Pb at √s=2.76 TeV
heavy ion running: 4 physics weeks/year
First Pb+Pb in 2010

CMSATLAS
ALICE
Oct 518, 2012

Hot QCD MatterProbe of Nuclear Collisions
Timetime

γπ φp K

γπKπfreeze-out

Hadron Gas

quark-gluon plasma
hard parton scattering
Probe the earlystage from variousprobes
AuSpaceAu6Probing QGP
Jet/High pt particle
 Energy loss
Thermal radiation
Temperature
Low mass dilepton
Chiral restoration
Heavy Quark
Eloss and flow

Elliptic flow v2
 eta/sHigher order flow
V3, v4, v5….
 eta/sInitial condition
Quarkonia
Debye screening• Systematic study with different condition (T, µ) with various probe isrequired to quantitatively understand properties of QGP• Both RHIC and LHC is needed to provide large leverage in conditions
7and dynamic range of hard probes (pT, mass, etc).

RHIC’s Two Major Discoveries
PHENIX PRL88,022301(2002)

High pT suppression
Energy loss of quark/gluon
Very dense matter

STAR PRL86,402 (2001)

Strong Elliptic flow
Agree with ideal hydrodynamics
Low viscosity/entropy (η/s)

Dense and low viscosity fluid is formed in nuclear collisions at RHIC
These results are confirmed by LHC at higher energy

Initial temperature via photons
PHENIX PRL104, 132391 (2010)• Large enhancementof direct photons at
low pT at RHIC
• Consistent withthermal radiation
with initial
temperature of 300600 MeV
RHIC Tinit

9High pT hadron suppression
No energy loss ofscattered partonp+pp+p

Au+Au

Scattered parton suffered
energy loss in QGP

Au+Au
Scaled by Ncoll
Energy LosstimeStrong suppression of high pT pi0
2002 data.

Nuclear Modification factor
Au-Au at 200 GeV PRL91 072301
Peripheral collisoin

N+N baseline

Central collision

R AA =

YieldAuAu / 〈Nbinary 〉 AuAu
Yieldpp

Suppression/enhancement
factor relative to binarycollisions

A facor of five
suppression at 10 GeV/c
Scattered paron suffer alarge energy loss in QGPRAA of various particles• A factor of ~5 suppression of π0 to ~20 GeV/c• Same suppression for pi0 and eta• Ncoll scaling for direct γ

LHC extends RAA to ~100 GeV/c

Rise to RAA ~ 0.5 at pT~30-40 GeV/c and stay constant (?)

Energy loss at RHIC and LHC
PHENIX arXiv:1208.2254

ALICE PLB696,301(2011)

LHC central
RHIC centralperipheral

Fractional energy loss deduced from RAA• RAA increase at high pT at RHIC and LHC• RAA(LHC)<RAA(RHIC) at the same pT, indicating stronger energy loss
• Fractional energy loss deduced from RAA is higher at LHC
 Started to see difference in medium property at RHIC and LHC
14

Jet energy loss is directly seenJet Energy asymmetry• A large jet ET asymmetry  direct evidence ofJet energy loss in QGP

Jet measurements at LHC
CMS QM2012

Jet RAAATLAS QM2012

γ-Jet asymmetry

CMS QM2012

Jet fragmentation• LHC demonstrated that direct jet measurement in heavy ion
collision is possible.
• Rich data on reconstructed jets at LHC from ATLAS and CMS– RAA, v2, Jet-Jet, γ-Jet, Z/W-jet, Jet fragmentation, etc
17Elliptic Flow
Non Central collisionHigh density matter

Reaction Plane

Beam view of the reaction

strongly-coupledsmall η/s

Reaction Plane

Weakly-coupledlarge η/s

In non-central collisions, high density
matter with elliptic shape is formed
Expansion towards reaction plane Elliptic Flow

Comparison with viscous hydro• Behavior of the fluid is
P. Romatschke and U. Romatschke、PRL99,172301(2007)
governed by the sheer
viscosity (η) to entropy
density (s) ratio η/s• Recent theoreticalwork with non-zero
viscosity suggests thatvery small η/s ~ 0.1 isrequired to explain
RHIC v2 data
• Matter formed at RHIC
is almost perfect fluid.

(Almost) perfect liquid

4π×η/sv2 data from RHIC indicates that the high density matter
formed at RHIC has very small η/s.
The value, η/s ~ 0.1, is 1/10 of all known matter, and it isclose to the lower bound 1/4π conjectured by AdS/CFTmodelHeN2H 2O

Quark Gluon Plasma
201012 0C

Elliptic Flow at LHC：similar to RHIC

V2 measured by ALICE = v2 measuread by STAR
 eta/s of QGP at LHC is also very small
Is there difference in eta/s?

Triangular flow ｖ３
Elliptic flow v2 is the 2nd order Fourier component of azimuthal distribution
There are higher order componets v3, v4, v5….
Odd order componets v3, v5, etc relative to reaction plane is zero due to symmetry

Event-by-Event Fluctuation of initialgeometry cause ｖ３ and higher odd
order components.
Initial geometry 3rd order component
ε3 causes 3rd order flow v3

V3 is a good probe of initial condition

v3 disentangles initial state and η/s
PRL107,252301

v2 described by Glauber and CGC

v3 described only by Glauber

Theory calculation:
Alver et al.
PRC82,034913

Theory calculation:
Alver et al.
PRC82,034913

Lappi, Venugopalan, PRC74, 054905
Drescher, Nara, PRC76, 041903

favored Glauber

Glauber initial state η/s = 1/4π


Two models
Stefan Bathe for PHENIX, QM2011

MC-KLNCGC initial state η/s = 2/4π


23

Higher Order Flow and eta/s
Higher order flows v3, v4, etc are sensitive toviscosity η/s Finite η/s makes the final state smoother reduce higher vn

initialfinal•B. Schenke, S. Jeon, C. Gale,
Phys. Rev. C82, 014903(2010); Phys.Rev.Lett.106,042301 (2011)•B.Schenke, P.Tribedy,
R.Venugopalan, Phys.Rev.Lett.
108, 252301 (2012)

The Big Bang vs the Little Bangs
The UniverseHIC

lumpy initialenergy density

hadronization

kinetic
freeze-out

distributions andcorrelations of
produced particles

QGP phasequark andgluon degrees
of freedom

Credit: NASAWMAP
P. Sorensen – NSAC Subcommittee 201225

What we conclude from fluid dynamics• Recent data & recent analyses yield tight constraints
Slide by Wiedermann

LHC

H. Song et al. PRL 106 (2011) 192301
Z. Qiu et al., Phys.Lett.B 707 (2012) 151RHIC

Beam Energy Scan : Search for critical point0) Turn-off of sQGP signatures
1) Search for the signals ofphase boundary2) Search for the QCD criticalpoint
BES Phase-I

27

What I didn’t covered• Hadron spectra and yield• Heavy quark probe– Energy loss– Flow

• Quarkonia (J/Psi, Upsilon)• Low mass lepton pairs• Direct photon v2• Chiral magnetic effect• Fluctuations• and more…

Computation for QGP physics
Quantitative study of QGP property requires comparison of thedata and precise theory calculations• Relativistic Hydrodynamics– Full 3D with viscosity– event-by-event calculation to take into account fluctuations of theinitial condition• QGP properties from Lattice QCD–––––––Tc
Critical Point
EOS
eta/s
Heavy quark potential at finite Tc
conductivity in QGP
EM emission rateSummaryΤ

Temperature

LHC

Quark Gluon
PlasmaRHIC

Baryon DensityµΒ• New phase of matter, QGP, isdiscovered at RHIC and isconfirmed at LHC• QGP is characterized by– Near perfect fluidity– Strong energy loss of parton• This is the only “Phasetransition” of quantum fieldrealized at laboratory• Quantitative study of its
properties at RHIC and LHC30