1 Interacting Quark Gluon Plasma - the Primordial Perfect Fluid An overview of findings at RHIC Richard Seto University of California, Riverside Helsinki, Finland April 27, 2006
Jan 06, 2016
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The Strongly Interacting Quark Gluon Plasma - the Primordial Perfect Fluid
An overview of findings at RHICRichard Seto
University of California, Riverside
Helsinki, Finland April 27, 2006
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In the Beginning…
what is “quark soup” like?
had
ron
s
quark-hadronQCDphase transition
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Phases
T
Tc
Quark Soup
Hadrons
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Lattice Calculations
T
Tc
• Transition – Sharp Crossover at RHIC• That’s OK – 1st order for all practical
purposes
Lattice Calculations:Tc = 170 15% MeV critical ~ 0.6 GeV/fm3
Sharp Crossover
Relativistic Heavy IonsRHIC
~degrees of freedomdifference between S-B and lattice
interactionsinteractions(in hindsight)
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RHICRHIC
Capable of colliding ~any nuclear species on ~any other species
Energy: 500 GeV for p-p 200 GeV for Au-Au
(per N-N collision) Design Luminosity
Au-Au: 2 x 1026 cm-2 s-
1
p-p : 2 x 1032 cm-2 s-
1 (polarized)
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RHIC’s ExperimentsRHIC’s Experiments
STASTARR
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What we know: RHIC What we know
System appears thermally and chemically equilibrated This happens early <2 fm/c
Energy density high >10 GeV/fm3
parton energy loss is large viscosity/entropy, η/s is low ( conjecture ~1/4π?) DOF ~ “quasi-quarks” ????
General picture is stable since ~ 2004 More data since QM 2005 More theory A clearer view
what is “quark soup” like?
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A cartoon – the life history of the sQGP
0.1 1
0.1
~Energ
y
Densi
ty
(GeV
/fm
3)
10~Time (fm)
10
100
L. McLerran
(modified by R.S.)
Elliptic flow
Cross over(wanna be1st order)4
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CGC “glasma” T. Lappi
Strongly Interacting
Recombination
~some reinteraction
Thermalization
hard probes
Partonic
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energy density“jet” energy loss
hardprobles
energyloss
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Using high pUsing high pTT particles aka particles aka “Jets” “Jets”
p+p
d+Au
2
2
/11 " "
/AuAu T
AAcollisions pp T
dN dydpR for normal collisions
n dN dydp
Au+Au
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peripheral Au+Au
What is the energy density? “Jet quenching”
direct photons scale as NcolldAu hadrons scale as Ncollperiph AuAu π0 scale as Ncoll
central π0 suppressed
hadron suppression shows quenching independent of identity of produced hadron
AuAu 200 GeV
Calculations:dNg/dy ~ 1000Wicks et al, nucl-th/0512076
ε ~10-15 GeV/fm3
ε critial ~0.6 GeV/fm3
Au+Au
d+Au
Direct γ
π0
η
RAA =1 for “normal collissions”
Central AuAu
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Jet on 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
Thermalizedpartons
pp AuAu
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light
(M.Djordjevic PRL 94 (2004))
How is the energy lost? The sQGP has enormous stopping power
rifle bullet stopped in a tissue Original idea – energy loss by gluon radiation In 2001, Dokshitzer and Kharzeev showed “dead
cone” effect charm quark small energy loss
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(3) q_hat = 14 GeV2/fm
(2) q_hat = 4 GeV2/fm
(1) q_hat = 0 GeV2/fm
(4) dNg /dy = 1000
Theory curves (1-3) from N. Armesto, et al., PRD 71, 054027
(4) from M. Djordjevic, M. Gyullasy, S.Wicks, PRL 94, 112301
What about heavy quarks? (electrons from c and b)
Charm high pT suppression ~ light hadrons!!!
Problem – difficult to reconcile with gluon radiative energy loss
theorists have to go back to the drawing board
Large Energy loss of partons energy density far in excess of critical energy density
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Hadronizationand Recombination
hints of the DOF
reco
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Recombination and the baryon anomaly pbar/π varies with √sNN in Cu+Cu
PHENIX PreliminaryOriginally thought:
particle production at “moderate” pTfrom mini-jet Fragmentation pbar/π- ratio
CuCu central
At ISR pbar/π- ~ 0.2
Heavy ion Collisions pbar/π- ~0.7Increasing with energy
BUT
200 GeV
22 GeV
higher energy
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Explanation: Recombination – a hint at the DOF
Naively: recombine quasi-partons (“quasiquarks” – Gavai)
PT
baryons pT 3 pT
mesons pT 2 pT
+ Thermal “quark” spectrum
Large pbar/π
This implies that we begin in a “quasi-partonic” thermal system
Mueller et al, Hwa et al, Ko et al
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Elliptic Flow (v2)Early Thermalizationand Recombination
v2
v2
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Flow: A collective effect
Elliptic flow = v2 = 2nd fourier coefficient of momentum anisotropy
really?
x
yz
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.
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early thermalization?
If system free streams spatial anisotropy is lost v2 is not developed
PHENIXHuovinen et al
(Teany et al, Huovinen et al)
detailed hydro calculations (QGP+mixed+RG, zero viscosity)
therm ~ 0.6 -1.0 fm/c ~15-25GeV/fm3 (ref: crit ~0.6 GeV/fm3)
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Recombination and v2
1) Three regions of v2
geometry-driven momentum anisotropy
geometry-driven absorption anisotropy
STAR preliminary
from partonicAND hadronicmassmass dependent dependent
from partonicquarkquark number dependent number dependent
Maya Shimomura, SQM’06
v2
v2
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PHENIX Preliminary
2) Data from minimum bias Au+Au collisions at √sNN= 200 GeV
(mT - m0)
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PHENIX Preliminary
3) A recombination testrescale by quark number Au+Au collisions at √sNN= 200 GeV
(mT - m0)Recombinationworks!
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The - a test the
mass ~ proton quarks - meson
V2 behaves as recombinationsays it should
ALL hadrons seem to obey quark number scaling!
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Hydro works in min-bias not as function of centrality
initial cond? (Rafelski)
Hydrodynamics (in the hadronic phase) and centrality
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Recombination and centrality?
recombination and number of quark scaling works for centrality dependence
mid-centralperipheral central
Recombination works well. WHY?What is recombining?? DOF???A quasi-quark Plasma? “constituent quarks”
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different degrees of freedom introduce different correlations between conserved charges
• assumption: conservation of charge @ hadronization local in rapidity
• introduce baryon-number strangeness correlation:
• system of particles:
• connection to Lattice susceptibilities:
DOF and Baryon-Strangeness Correlations
2 223 3BS
BS B S BSC
SS S
23 k k kk
BSk kk
n B SC
n S
3 BSBS
SS
C
QP-QGP: CBS=1
HG: CBS~ 2/3
BS-QGP: CBS~0.61
CBS: V. Koch, A. Majumder & J. Randrup, PRL95 182301 (2005)
BS-QGP: E. Shuryak, I. Zahed, PRC70 021901 (2004); PRD70 054507 (2004)
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CBS & CQS: Lattice & Lessons
Gavai & Gupta, PRD 73, 14006, 2006
T>TC: CBS=1
• mesonic as well as baryonic bound-states ruled out via χBS and μB-derivatives thereof
Lattice confirms quasi-quark nature of flavor carriers in the deconfined phase
Gavai, Majumder
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v2 heavy quarks and viscosity
The stone in the river
or the concrete canoe
University of Wisconsin Badgers engineer third-straight concrete canoe title
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Flow, viscosity, and strong coupling 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, viscocity~0
M. Gehm, et alScience 298 2179 (2002)
now throw a stone in there
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Heavy quarks: Single electron v2
data prefers charm flow
for charm to flow interactions must be very strong
Viscosity small
Greco, Ko, Rapp PLB 595 (2004) 202
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B meson contribution heavy quark electron v2
B electron v2 reduces heavy quark electron v2 @ high pT
We need to directly measure D’s and B’s
pT
based on quark coalescence model c, b reso ; c,b get v2 by elastic scat. in QGP
Hendrik, Greco, Rappnucl-th/0508055 w.o. B meson (c flow)
w. B meson (c,b flow)
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Flow, Hydrodynamics, Viscosity, Perfect Fluds….
YUK!
and String Theory
WHAT?!
Los Angles Times – May 2005
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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. ….
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[ ]
Viscosity and the equation of fluid flow
=density of fluid
=potential (e.g. gravitational-think mgh)
v=velocity of fluid element
p=pressure Bernoulli Sheer Viscocity
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Non-ZERO Viscosity
smoke ring dissipates
[ ]
smoke ring diffuses
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[ ]
ZERO Viscosity
smoke ring keeps its shape
note: you actually need viscosity to get the smoke ring started
does not diffuse
Viscosity dissipates momentum
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the low-brow sheer force(stress) is:
Can we anyone calculate the viscosity?A primer on viscosity (Feynman again)
energy momentum stress tensor
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Using Maldecena 10-D string theory Using Maldecena 10-D string theory magicmagic
i.e. AdS/CFT dualityi.e. AdS/CFT duality
σ(0)=area of 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 three-branes.”
8 G
dualGravity“QCD”strong strong couplingcoupling
Policastro, Son, Starinets hep-th 0104066
N=4 supersymmetry ~ almost QCD “SYM” (OK the coupling constant doesn’t run, but I am interested in the strong coupling case, there are a bunch of extra particles so we will divide by the entropy to get rid of the extra DOF…)
“QCD”Gravity
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finishing it up to get finishing it up to get ηη/s/s
Entropy black hole “branes” Entropy
“QCD”
Entropyblack hole Bekenstetein, Hawking
= Area of black hole horizon
" "
black hole area
4GQCDs
136 104 B
Kss k
Kovtun, Son, Starinets hep-th 0405231
σ(0)=area of horizon
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viscocity~0, i.e. A Perfect viscocity~0, i.e. A Perfect Fluid?Fluid?
cos
4 BRHIC
Vis ity
Entropy Density k
lowest viscositypossible?
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
helium water
nitrogenviscosity bound?
RHIC ~ 1?JPG, 30(2004) 1221
T=10T=101212 KK
4
s
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When will we make a quantitative measure of When will we make a quantitative measure of the viscositythe viscosity
Upgrades -microvertex detectors - to both STAR and PHENIX will allow measurement of D and B mesons directly
Theory – will take a while
Meanwhile – viscosity better become part of our ethos
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A strongly InteractingA strongly Interacting QGP?QGP?
RHIC data: nearing hydrodynamic prediction with zero viscosity early thermalization strong coupling
weakly coupled weakly coupled QGP? QGP?
q qscreening length
Old picture short screening length
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A strongly Interacting QGPA strongly Interacting QGP
RHIC data: nearing hydrodynamic prediction with zero viscosity early thermalization strong coupling
sQGPsQGP
screening length
New picture Long screening length Long range correlations
New Lattice DataJ//ψ stays together
at > TCF. Karsch et al, Journal of Physics G 30
(2004) 887
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Deconfinement and Screening (a puzzle)
Debyescreening
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A Theory update which bothers experimentalists
J/ “melts” at T>1.5 TC (Agnes Mocsy, Peter Petereczky)
“Screening likely not responsible for quarkonia suppression” (Agnes Mocsy, Peter Petereczky)
“You have to use the right potential” (CY Wong)
Does quarkonia suppression tell us anything about deconfinement!???
Who is right?!!
an experimentalist
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J/ suppression
screening
regeneration
sum
Suppression similar in amount to SPS
consistent with screening+ regeneration
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|y|<0.35 1.2<|y|<2.4
Aside: RAA of J/ in Au+Au/Cu+Cu
Constrained by d+Au
Most things depend on Npart independent of species Why is J/ at y=0 different for Cu and Au? Corona? Might help in understanding suppression mechanism
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<pT2> as a function of Ncol
Au+Au = RED
Cu+Cu = BLUE
Dashed: without recombination
Solid: includes recombination
Recombination modelmatches better to the data...
nucl-th/0505055
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Recombination predictions vs rapidity
Recombination ( Thews et al., nucl-th/0505055 ) predicts a narrower rapidity distribution with an increasing Npart.
Going from p+p to the most central Au+Au : no significant change seen in the shape of the rapidity distribution.
No recombinationAll recombination
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RAA vs. pT in Au+Au/Cu+Cu
•Suppression of J/Y yield at low pT in both Au+Au and Cu+Cu.•High pT J/Y escape the medium? Leakage effect? [Phys. Lett. B 607 (2005)]
•Might one expect “pile up” at low pT for recombination+energy loss?
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Questions What is the energy loss mechanism for hard quarks? Can we get a good measure of the initial temperature? Chiral Symmetry? Deconfinement? Any Clue? Is the CGC really the initial state for the sQGP Can we measure quantitatively the viscosity?
THEORY
More General Questions Do we understand why the interaction is so strong? Do we understand the DOF?
Interplay of theory and experiment – very important
both in the “CGC” and the “sQGP”
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The FutureRHIC IIRHIC II
increase in LuminosityHigh L at lower energies- the critical point
PHENIX- upgradesPHENIX- upgradesThe Nosecone Calorimeter
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What would we like to measure?
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What would we like to measure? What is the energy loss mechanism for hard quarks?
Jet tomography (high pT PID, jet-jet and -jet) Can we get a good measure of the initial temperature? Chiral Symmetry?
Electromagnetic radiation (e+epair continuum, LMVM) Deconfinement? Any Clue?
Quarkonium (J/, ’ , c and (1s),(2s),(3s)) Is the CGC really the initial state for the sQGP
gluon saturation in nuclei (particle production at forward rapidity)
Can we measure quantitatively the viscosity? Heavy flavor (c- and b-production)
What is the energy loss mechanism for hard quarks? Jet tomography (high pT PID, jet-jet and -jet)
Can we get a good measure of the initial temperature? Chiral Symmetry?
Electromagnetic radiation (e+epair continuum, LMVM) Deconfinement? Any Clue?
Quarkonium (J/, ’ , c and (1s),(2s),(3s)) Is the CGC really the initial state for the sQGP
gluon saturation in nuclei (particle production at forward rapidity)
Can we measure quantitatively the viscosity? Heavy flavor (c- and b-production)
requires highestAA luminosity
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Dalitz/conversion rejection (HBD) Precision vertex tracking (VTX)
PID (k,p,p) to 10 GeV (Aerogel/TOF)
High rate trigger (μ trigger) Precision vertex tracking (FVTX)
Electron and photon measurements Muon arm acceptance (NCC) Very forward (MPC)
PHENIX Detector Upgrades at a Glance Central arms:
Electron and Photon measurements Electromagnetic calorimeter Precision momentum determination
Hadron identification
Muon arms: Muon
Identification Momentum determination
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2006 2007 2008 2009 2010 2011 2012
x4 Lum
RHIC II
HBD
VTX-barrel
VTX-endcap
NCCNCC
MuTrigger
DAQ
R&D Phase Construction Phase Ready for Data
PHENIX/RHIC Upgrades Schedule
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The PHENIX central EMCAL
The central EMCAL has been one of the most important subdetectors in PHENIX
done with a calorimeter -0.35<η<0.35 and ½ of 2π
ε~ 10-15 GeV/fm3
/1
/TAA
AATbinary pp
dN dpR
N dN dp
AuAu
dAu
π 0
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What is proposed?the NoseCone Calorimeter
NCC NCC
-3 -2 -1 0 1 2 3 η
0
cove
rage
2π
EMC
EMC
ηη coverage from 1 to 3 coverage from 1 to 3RHIC II – luminosity x10 RHIC II – luminosity x10 PHENIX acceptance x10PHENIX acceptance x10
Precision measurements possiblePrecision measurements possible
Note: DOE-1st NCC, collabor- 2nd NCC
VTX & FVTX
near full coverage for tracking and calorimetrynear full coverage for tracking and calorimetry
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•What is the Physics I? QCD: Heavy Ion Physics and the sQGP
Heavy Ions Getting a picture of collision system
This is why the CAT scan so important. STM. Energy density (tomography) changes with rapidity large
rapidity coverage Calibrated probe: photon-jets – need large acceptance
Understanding deconfinement, Tc Recently lattice: J/ψ melts at >Tc
χcγJ/ψ – must go to forward rapidity probably the only detector capable of doing this at RHIC
jetE E γ
Leading hadronsπ0
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What is the Physics II? QCD: Proton Nucleus Physics and the Colored Glass Condensate
More saturation at Lower x y~log(1/x) Lower x forward rapidity
xG(x)
x
measure gluon saturationvia direct photonsin forward region
The Colored Glass Condensate:The Initial Condition for HeavyIon Collisions?
Low
er
x
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What is the Physics III?QCD: polarized pp collisions and the Spin of the Proton
Where is the spin of the proton? Idea: Measure the gluon spin contribution ΔG ΔG may be dominated by contributions from low-x
where gluons are most abundant y~log(1/x) So low x is forward rapidity
e.g. y~2 for x=10-2
Go to Forward RapidityxG(x)
x
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Where is it?
Edouard/Andrey
NCC 0.9 < h < 3.0
HBD
NCC
VTX
NCC
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What is it? The parts of the NCC
Silicon pads1.5x1.5 cm2
Tungsten 3 mm (EM) & 15mm (HAD)
500 um pitch Strips (“StriPixels”)
EM1electromagnetic
EM2electromagnetic
HADhadron identifier
SM“shower max”
PS“pre-shower”
18%4%
E
E E
Depth: 42X0 (1.6 λABS)
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Silicon pads1.5x1.5 cm2
Tungsten 3 mm (EM) & 15mm (HAD)
HADhadron identifier
SM“shower max”
PS“pre-shower”
18%4%
E
E E
Depth: 42X0 (1.6λABS)
30 GeV π0
The PS and SMDetectors:
identifying π0s
500 um pitch Strips (“StriPixels”)
SM
What is it? The parts of the NCC
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What has the NCC crew accomplished?Prototype in Test Beam at Protvino
Edouard
σ = 10%
10 GeV electron
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How Much and When?Schedule and cost Scope of proposal to DOE:
1 NCC ~ $4M Begin Funding in FY2008 All Critical physics can be done with 1 NCC
Complete Construction in 2010 Reviewed my external committee
recommend start of funding FY 2008 in less than 18 months!
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NCC - 2 Build second NCC from Collaboration funds
Actively seeking funds from International Collaborators
Japan, Korea, Russia, Czech Republic, …
Added Benefits: Factor ×2 in rate for rare processes Exploit muon spectrometer acceptance in pA collisions, can study both sides simultaneously
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Come join us!
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Connecting to lower energies unique things (so far)
ρ broadening break in Inverse
slopes @ √sNN~5
AGS/SPS/RHIC similarities strangeness
enhancement J/psi suppression
Ways to look wait for GSI wait for JPARK RHIC ~ 5GeV
Survival probability corrected for normal absorption
energy density
Karsch, Kharzeev, Satz
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Think Carefully Varying beam energy
varies energy density – not T Looking for a sharp
“step” probably will not work at least not in T
But we also vary ρBaryon
Could we find the Critical point?
Rare probes e.g. leptons???
T/Tc
ε/T4T/Tc
1
ε
critical point?
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RHIC II-electron cooling (Roser) x10 increase in L
over x4 from design No apparent show-stoppers
for RHIC collisions at Ecm = 5-50 GeV/n AuAu
Pre-cooling in AGS 10x luminosity ?
Electron beam cooling would make this a fantastic facility: ~100x luminosity,
Exp
ecte
d Z
DC
(w
hole
vert
ex M
B)
Rate
[H
z]
Possible increase in luminosityfor lower energiesx1000?
AGSequivalent
CERNequivalent
assume x100
PresentFullEnergy
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spares
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ReCo Model Modification (Hwa)
Premise:
Observables:
STAR Preliminary
STAR P
relim
inar
yThe production of Φ and
Ω particles is almost exclusively from thermal strange quarks even out
to 8 GeV/c
The ratio of Ω/Φ yields should rise linearly with pT
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v2 of strange hadrons from STARPHENIX(open symbols):Phys. Rev. Lett. 91,182301 (2003)
• Mass ordering observed at lower pT
fit by hydro in hadronic phase
• v2 saturates for pT > 3 GeV/c
• Clear baryon/meson difference at intermediate to high pT observed
• New, high statistics measurement shows deviation from ideal scaling . Mesons above 1. baryons below 1
77PHENIX(open symbols):Phys. Rev. Lett. 91,182301 (2003)
v2 of strange hadrons from STAR
• Mass ordering observed at lower pT
fit by hydro in hadronic phase
• v2 saturates for pT > 3 GeV/c
• Clear baryon/meson difference at intermediate to high pT observed
• New, high statistics measurement shows deviation from ideal scaling . Mesons above 1. baryons below 1
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The same scaling behaviour is observed in 62 GeV data
v2 of strange hadrons from STAR
PHENIX(open symbols):Phys. Rev. Lett. 91,182301 (2003)
Au+Au ĆsNN=62 GeV
STAR Preliminary• Mass ordering
observed at lower pT
fit by hydro in hadronic phase
• v2 saturates for pT > 3 GeV/c
• Clear baryon/meson difference at intermediate to high pT observed
• New, high statistics measurement shows deviation from ideal scaling . Mesons above 1. baryons below 1
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Baryon/meson (pbar/-) at √s = 200 GeV AuAu
• Scales with Npart independent of system at h=0 and 3.2