What we have Learned and Challenges Ahead

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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



(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)


• Mass ordering observed at lower pT





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The same scaling behaviour is observed in 62 GeV data


PHENIX(open symbols):Phys. Rev. Lett. 91,182301 (2003)

Au+Au ĆsNN=62 GeV

STAR Preliminary• Mass ordering

observed at lower pT





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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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What we have Learned and Challenges Ahead