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What we have Learned and Challenges Ahead
An experimental overview of SQM 2006Richard Seto
UCRStrangeness in Quark Matter 2006
UCLA, March 25-31, 2006
and more
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What I will cover ExperimentalExperimental overview (as requested)
For students – I will remind you of some some of the arguments – ask if I don’t
I chose to be clear rather than comprehensive
Flavor/Particle ID plays a critical role
Primarily RHIC data from SQM 06 SPS data – at the end
any misconceptions are mine Selection of topics/data are mine
with apologies
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Topics I will not cover or will only briefly mention
Chiral Symmetry restoration (!) Chemical equilibration Strangeness enhancement –”the horn, the
break” nucleon structure Fluctuations Exotics Astrophysics
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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?)
General picture is stable since ~ 2004 More data since QM 2005 More theory A clearer view
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Busy days at RHIC
4 experiments – BRAHMS, PHENIX, PHOBOS, STAR
p+p d+Au Au+Au Cu+Cu
200 GeV
130 GeV
62.4 GeV
22.4 GeV
Run 1 - 3 Run 4 - 5 Run 6 (?)
?
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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
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Hadronization(so I can introduce recombination)
reco
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Recombination and the baryon anomaly pbar/ varies with sNN in Cu+Cu
PHENIX Preliminary
dave morrison
Originally thought: particle production at “moderate” pTfrom mini-jet Fragmentation
pbar/- ratioCuCu central
At ISR pbar/- ~ 0.2
Heavy ion Collisions pbar/- ~0.7Increasing with energy
BUT
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Baryon/meson (pbar/-) at √s = 200 GeV AuAu
• Scales with Npart independent of system at =0 and 3.2
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Explanation: Recombination
Naively: recombine quasi-partons (“quasiquarks” – Gavai)
PT baryons pT 3 pT
mesons pT 2 pT
Problem: protons exhibit “jettiness”
+ Thermal 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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ReCo Model Modification (Hwa)
Premise:
Observables:
STAR Preliminary
STAR P
relim
inar
yThe production of Φ and Ω particles is almost exclusively from thermal s quarks even
out to 8 GeV/c
The ratio of Ω/Φ yields should rise linearly with pT
Mathew Lamont
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energy density“jet” energy loss
hardprobles
energyloss
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Baryon Transport: How much energy available from the collision?
• AGS->RHIC : Stopping -> Transparency
• Rapidity Loss <y>: 2±0.4: not linearly increase with ybeam
• Energy loss <E> per nucleon: 73±6 GeV • Available energy for excitation: ~3/4 of total energy~28 TeV
JH Lee
RHIC dataAuAu 200
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What is the energy density? “Jet quenching”
direct photons scale as Ncollsuppressed
suppression shows quenching independent of identity of produced hadron
dave morrison
AuAu 200 GeV
yield in A+A/number of equivalent p+p collisions
yield in p+pRAA =
Calculations:dNg/dy ~ 1000Wicks et al, nucl-th/0512076
~10-15 GeV/fm3
critial ~0.6 GeV/fm3
Direct γ
π0
η
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Au+Au and Cu+Cu sNN = 200 GeV
dave morrison
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Au+Au and Cu+Cu sNN = 200 GeV
dave morrison RAA Function of Npart independent of system
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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
• We see strong suppression even for heavy quark (charm).
What about heavy quarks? PHENIX
Alan Dion PHENIX
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RdAu is above/consistent with unity
RAA suppression up to ~0.6 in 40-80%
Suppression up to ~0.5 in 10-40%
Strong suppression up to ~0.2 in 0-5% centrality at high pT (4-8 GeV/c)
Charm high pT suppression is as strong as light hadrons!!!
Problem is – theorists have to go back to the drawing board (Steffen?)
STAR: Phys. Rev. Lett. 91 (2003) 172302
Haibin Zhang
What about heavy quarks? STAR
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Elliptic Flow (v2)Viscosity
Recombination
v2
v2
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Previous Results
If system free streams spatial anisotropy is lost v2 is not developed
Hence Early thermalization low viscosity
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: cold matter 0.16 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 partonicAND hadronicquarkquark 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)dave morrison
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PHENIX Preliminary
3) A recombination testrescale by quark number Au+Au collisions at sNN= 200 GeV
(mT - m0)dave morrison
Recombinationworks!
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v2 of strange hadrons from STAR
Talk: M. Oldenburg, Poster:Yan Lu
Mathew Lamont
PHENIX(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
26PHENIX(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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The - a test the
mass ~ proton quarks - meson
Sarah. Blythe
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)
Marcus. Oldenburg
Hydrodynamics and centrality
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Recombination and centrality?
recombination and number of quark scaling works for centrality dependence
Marcus Oldenburg
mid-centralperipheral central
Recombination works well. WHY?What is recombining?? DOF???A quasi-quark Plasma?
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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
addition of bottom to model improves fit at higher pt
for charm to flow interactions must be very strong
Viscosity small
Shingo Sakai, SQM’06
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)
Shingo Sakai
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Comment on a quantitative measure of the viscosity
Upgrades -microvertex detectors - to both STAR and PHENIX will allow measurement of D and B mesons directly
Theory – will take a while – (Steffen?)
Meanwhile – viscosity better become part of our ethos
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Back to the beginningHow does the sQGP get started?
a candidate - the CGC
CGC
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prediction: suppression in dAu collisions forward central
HongyanYang BRAHMS
Central Midcentral
CGC
for all particles
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What about charm? prompt muons charm(bottom) are suppressed in
dAu CGC
Xiaorong Wang, SQM 2006
Aud
Au d
North Arm
South Arm
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Initial Temperature
Tinitial
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Thermal photons - The Spectrum
Compare to thermal + pQCD• data consistent with
thermal + pQCD
Compare to thermal model
• data above thermal at high pT
• D. d’Enterria, D. Perresounko• nucl-th/0503054
Compare to NLO pQCD
• excess above pQCD
• L.E.Gordon and W. Vogelsang• Phys. Rev. D48, 3136 (1993)
2+1 hydro
T0ave=360 MeV(T0
max=570 MeV)
0=0.15 fm/c
The Future – PHENIX- HBD
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What have we learned Jet quenching
Charm quark energy loss, pretty well established Viscosity
Charm flows – further evidence that viscosity is small (interactions are strong)
Recombination baryon to meson ratio seems to obey recombination scaling All particles seem seem to obey v2 recombination scaling. [, ;Ω]
Some evidence for fine structure
Evidence for quasi-partons from Recombination/Lattice CGC
indications of charm suppression in dAu collisions at forward rapidity
RHIC is now studying a state of matter clearly above the transitionQuestion: So where is it? Deconfinement? Is there a critical point?
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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
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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
Andrew Glenn
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
Andrew Glenn
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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
Andry R
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RAA vs. pT in Au+Au/Cu+Cu
•Suppression of J/ yield at low pT in both Au+Au and Cu+Cu.•High pT J/ escape the medium? Leakage effect? [Phys. Lett. B 607 (2005)]
•Might one expect “pile up” at low pT for recombination+energy loss?Andrew Glenn
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The critical point?
connecting to lower energies
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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. J/ would be tough
T/Tc
ε/T4T/Tc
1
ε
critical point?
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Questions Can we measure quantitatively the viscosity?
Charm, bottom measurements THEORY
Do we understand why the interaction is so strong?
Chiral Symmetry? Do we understand the DOF?
Fluctuations measurements
Interplay of theory and experiment – very important
both in the “CGC” and the “sQGP”
thanks – its been fun!
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END