Download - Richard Seto UCR CSULA – 11/17/2010
Strings and Things: The Discovery of the strongly interacting Quark Gluon Plasma at the Relativistic Heavy Ion Collider
Richard SetoUCR
CSULA – 11/17/2010
What happens if you cook the nucleus? Why ask the question?
Large scale QCD system we have NO IDEA what it is really like
Properties (dynamical – lattice can calculate static only)
viscosity thermal conductivity ???
innovations in both experiments and theory Strings hydro models (3d viscous relativistic) initial state – new non-perturbative QCD methods
Fermi asked the question
RHIC
From Fermi notes on Thermodynamics
4
The Phase diagram (water)
Pressure
Tem
pera
ture
Gas
Liquid
Solid
Phase Transition: Tc = 273K
TC
The Phase Diagram (Nuclear Matter)
Phase Transition: Tc = 190 MeV = 1012K e ~ 0.6 GeV/fm3
Tc
6
Tem
pera
ture
Baryon Density
Collide Au + Au ions for maximum volumes = 200 GeV/nucleon pair, p+p and d+A to compare
BNL-RHIC Facility
STAR
In the last few days: LHC
7
What does an Au+Au Collisions at 200 GeV Center of mass look like?
trans
vers
e m
omen
tum
pt
time
Relativistic Heavy Ion Collisions Lorenz contracted pancakes Pre-equilibrium < ~1fm/c ?? QGP and hydrodynamic
expansion ~ few fm/c ??
Stages of the Collision
Tc ~ 190 MeV
T
time
Tinit=?PuresQGP
τ09
Pure water
Mixed phase
10
I.Temperatureunits 1eV~10,000K
Use E=kT
Measuring the Temperature: Black Body radiation (Serway)
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photons
photons
Photon energy(wavelength) spectrum gives temperature
How do you Measure T?
Make a measure of low pT photons (black body radiation)
Do a fit to models T~300 MeV
depending on Model Greater than TC!
◦ Tc ~190 MeV
IT’S HOT ENOUGH !
Thermal photons - Temperature from the data
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pQCD
Energy
Inte
nsity Thermal
photons
13
II. Jet quenching and energy density
Remember Rutherford Scattering?(Serway 29.1)
14
Hard Probes In Heavy Ion Collisions, aka Jet quenching
The experiment we would like to do – Rutherford Scattering of the QGP
PCM & clust. hadronization
NFD
NFD & hadronic TM
PCM & hadronic TM
CYM & LGT
string & hadronic TMhadronizationpre-equilibrium
QGP andhydrodynamic expansion
hadronic phaseand freeze-outHard parton
Softened Jet
ColorlessHadrons
ColoredQGP
Beams of colored quarks
“hard” probes Formed in initial collision with high
Q2 penetrate hot and dense matter sensitive to state of hot and dense matter
Energy loss by strong interaction jet quenching
Look at single particle: π0
Calculations:e ~10-15 GeV/fm3
ecritial ~0.6 GeV/fm3
direct photons scale as Ncoll
p0 suppressed by 5! High density Colored matter
What is the energy density? “Jet quenching”
AuAu 200 GeV
RAA
Direct γ
π0
η0.2
Correction Au=197 nucleons
Energy density is high Enough!
0
0
in AuAu collisions in pp collisions
pp
What about the “other” side?Jet correlations in proton-proton reactions.
Strong back-to-back peaks.
Jet correlations in central Gold-Gold.
Away side jet disappears for particles pT > 2 GeV
Jet correlations in central Gold-Gold.
Away side jet reappears for particles pT>200 MeV
Azimuthal Angular Correlations
Leading hadrons
Medium
Almost complete extinction of jetIs this remarkable? (me-2002) “As you might know, the most interesting
observation made at RHIC is that of the suppression of high-Energy hadrons, which may be an indication of jet quenching.
This is a remarkable effect. It is as if a bullet fired from a 22 rifle were stopped by a piece of tissue paper (actually by weight, the tissue paper would stop a bullet with 1000x the kinetic energy of an ordinary 22 bullet. Is this interesting? Just as a physical phenomena, it certainly seems to me to be quite extraordinary. The stuff that is being created - presumably a QGP is about the most viscous stuff on earth”.
dead wrong
right
Now that we have the Temperature and Energy density… (Serway again)
19
Monotonic Gas (3 degrees of freedom) E=3/2 nRT
Diatomic Gas (3+2=5 degrees of freedom) E=5/2nRT
Degrees of Freedom! (something about what it is…)
24
30g Tpe
Can we melt the hadrons and liberate quark and gluon degrees of freedom?
Energy density for “g” massless d.o.f. (bosons)Stefan Boltzmann law (Serway 17.10)
243
30Tpe
Hadronic Matter: quarks and gluons confinedFor T ~ 200 MeV, 3 pions with spin=0
2437
30Tpe
Quark Gluon Plasma:8 gluons;
2 light quark flavors, antiquarks,
2 spins, 3 colorsd.o.f=37!
a first guess: Degrees of Freedom
72 8 2 2 2 (3) 38s g s a f c
NDOF? a Sanity check - data
2437
30Tpe
2 4
30 30 40NDOFT
ep
243
30Tpe
310 15GeVfm
e ~ 0.300initialT GeV
Regular stuff “QGP”
good… But we really have no idea what the DOF really are
III. Viscosity
Flow, Hydrodynamics, Viscosity, Perfect Fluids….
YUK!
and String Theory
WHAT?!
Los Angles Times – May 2005
The subject of the flow of fluids, and particularly of water, fascinates everybody….
Fluids: Ask Feynman ( from Feynman Lecture Vol II)
Surely you’rejoking
Mr. Feynman
The subject of the flow of fluids, and particularly of water, fascinates everybody….we watch streams, waterfalls, and whirlpools, and we are fascinated by this substance which seems almost alive relative to solids. ….
[ ]
Viscosity and the equation of fluid flow
=density of fluid=potential (e.g. gravitational-think mgh)v=velocity of fluid elementp=pressure Bernoulli Sheer Viscocity
Non-ZERO Viscosity
smoke ring dissipates
[ ]
smoke ring diffuses
[ ]
ZERO Viscosity
smoke ring keeps its shape
note: you actually need viscosity to get the smoke ring started
does not diffuse
Viscosity dissipates momentum
Measuring viscosityFlow: A collective effect
2 2
2 2 2 cos 2x y
x y
p pv
p p
x
yz
Coordinate space: initial asymmetry
pressure
py
px
Momentum space: final asymmetry
28
dn/d ~ 1 + 2 v2(pT) cos (2 ) + ...Initial spatial anisotropy converted into momentum anisotropy. Efficiency of conversion depends on the properties of the medium.
Anisotropic Flow Conversion of spatial anisotropy to
momentum anisotropy depends on viscosity Same phenomena observed in gases of
strongly interacting atoms (Li6)weakly coupledfinite
viscosity
strongly coupled
viscosity=0
The RHIC fluid behaves like this, that is, viscocity~0
M. Gehm, et alScience 298 2179 (2002)
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Viscocity: Serway again
30
Weakly coupledlarge viscosity
Strongly coupledzero viscosity
Calculating the viscosity (from Feynman)
energy momentum stress tensor
31
Bigger F/A larger viscosityLarger viscosity smaller v0 Larger viscosity can act over larger d
y
xCan we calculate the viscosity ()?BIG problem, QCD in our regime is a strongly coupled theoryPerturbative techniques do NOT work
Einstein field eqn
To the rescue!String theory: Extra Dimensions
“QCD” strong couplingComplicated
Possibility to solve a strongly coupled theory! (for the first time??)
4d Boundary(we live here)
5d bulk theory z
dual
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An Analogy What is this??
In 3D – Its easy to see
Its a Hologram
Chessmen – a knight, bishop, king
Hmm... lets think. Its in 2D You’re kidding!
dual
using gauge-string duality
σ(0)=area of black hole horizon
“The key observation… is that the right hand side of the Kubo formula is known to be proportional to the classical absorption cross section of gravitons by black holes.”
8 G p
dualGravity
=4 SYM“QCD”strong coupling
Policastro, Son, Starinets hep-th 0104066“QCD” strong coupling
34
Gravity
finishing it up: we want /s (s=entropy)
Entropy black hole “branes”” Entropy
=4 SYM“QCD”Entropy
black hole Bekenstetein, Hawking
= Area of black hole horizon
SYM " "(0)
4GQCDs 1
4 4 Bs k
p p
Kovtun, Son, Starinets hep-th 0405231
=σ(0)
k=8.6 E -5 eV/K
This is believed to be a universal lower bound for a wide class ofGauge theories with a gravity dual
35
In ourUnits
We had 8 G p
Extracting /s from Data
Lo and behold best fit /s ~0.08 = 1/4p
STAR “non-flow” subtracted
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Phys.Rev.C78:034915 (2008)
V 2 Pe
rcen
t
cos4 BRHIC
Vis ityEntropy Density kp
sQGP – the most perfect fluid?
lowest viscositypossible?
4sp
helium waternitrogen
viscosity bound?
37
cos4 BRHIC
Vis ityEntropy Density kp
viscocity~0, i.e. A Perfect Fluid?
See “A Viscosity Bound Conjecture”, P. Kovtun, D.T. Son, A.O. Starinets, hep-th/0405231
◦ THE SHEAR VISCOSITY OF STRONGLY COUPLED N=4 SUPERSYMMETRIC YANG-MILLS PLASMA., G. Policastro, D.T. Son , A.O. Starinets, Phys.Rev.Lett.87:081601,2001 hep-th/0104066
lowest viscositypossible?
4sp
helium
waternitrogen
viscosity bound?
Meyer Lattice: /s = 0.134 (33)
RHIC
arXiv:0704.1801
38
14p
Some conclusions/thoughts Observations
◦Ti ~ 300 MeV > Tcritical
◦enormous stopping power energy density ~ 15 GeV/fm3 > critical energy
density ◦Strong flow signal viscosity/entropy density ~ 1/4π Perfect fluid
the stuff we are making at RHIC – sQGP◦Strongly Interacting Quark-Gluon-Plasma◦Interesting new connection String Theory and extra dimensions
Where are we? Like trying to study liquid water on a planet whose
temperature was a couple hundred degrees below 0o C by shooting ice cubes at each other
Some dates Newton 1687, Coulomb 1780 Boyle’s law ~1660 Thermo Otto von GuerickeOtto von Guericke 1650 Fluid dynamics Blaise Pascal (hydrostatics), Daniel Bernoulli (1700).
We have barely got to Boyle’s law ~1660
big future ahead of us – but I have no idea where it will lead. Perhaps sometime – far in the future, we will understand the world of
the strong interaction, as well as we do the world of the electro-magnetic interaction
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