01/22/2009 francis marion university 1 the little big bang: relativistic nuclear collisions and the...

01/22/2009Francis Marion University

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The Little Big Bang: Relativistic Nuclear Collisions and the Physics at 1012 KNathan Grau

Columbia University, Nevis Laboratories


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Outline Top-down introduction to high energy physics

and the Quark-Gluon Plasma The Quark-Gluon Plasma now

What we know now from the Relativistic Heavy Ion Collider (RHIC)

The Quark-Gluon Plasma in the future What we are learning and will learn from the

Large Hadron Collider, string theory, and trapping supercold atoms


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Introduction and Background of High Energy Physics

WARNING!The units you are about to see and hear are “natural”c = hbar = kB = 1Energy in GeV, momentum GeV/c (p~mc), mass in GeV/c2 (E=mc2)

Some important numbers to set a scale:Proton mass = 1 GeV/c2

170 MeV = 1012 K (E=kBT)


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The Standard Model Lagrangian This is the culmination of 400+ years of physics research All current physics data is

explained Disclaimer: Gravity Not

Included Still not small enough to fit

on a T-shirt Good party trick: Ask where

the sign error is (there really is one!)


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The Standard Model Condensed

The particles (fields) 12 particles 4 force carriers

Their interactions are the fundamental forces of nature…


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Fundamental Forces: Electroweak 1/2 Electroweak Force =

Electricity and Magnetism Everything from transistors in

computers to wind is governed by this force

Actually a single force: Electromagnetic force

Interaction of two charged entities

Theory: Quantum Electrodynamics (QED)

Computer Chip

Hurricane Katrina


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Fundamental Forces: Electroweak 1/2 Electroweak Force =

Weak Force interaction of two “weakly”

charged particles It is why the sun shines. In the first part of the chain the

proton turns into a neutron.

p p p p

He

light


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Fundamental Forces: Strong Force

g g

gproton

g

g g

neutron Quarks combine to form

other particles Baryons (qqq): protons,

neutrons, etc. Mesons( ): pions, kaons,

etc. Held together by gluons

Quark charge is “color” of 3 types: red, green, blue Contrast that with 2 electric

charges: +,- Hadrons are color neutral =

white

€

qq


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g g

gproton

g

g g


other particles Baryons (qqq): protons,





white Theory: Quantum

Chromodynamics (QCD)

€

qq


10


g g

gproton

g

g g

neutron

Ca. 1970 view of the proton and the neutron.Only real improvement is that the proton bubbles with lots of gluons and pairs

€

qq

Quarks combine to form other particles Baryons (qqq): protons,





white Theory: Quantum

Chromodynamics (QCD)

€

qq


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Proton Structure

u

u

d

€

qq g

g

u

u

d

€

qq g

g

Proton at two instances in time The interior bubbles with pairs and gluons

€

qq


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Proton Structure Probability of

finding a gluon or quark of a given flavor with momentum fraction x = pq/pp

u, d = valence near x~10-1

s,c,b,g = sea


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Fundamental Forces: Strong Force Strong force also binds nuclei Clearly needed another nuclear force since an

electrically neutral neutron could not bind with a positive proton via electromagnetic force

In fact, individual proton and

neutron definitions are

blurred by quantum

mechanics Nucleus is a bag of quarks and

gluons


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Confinement

Quarks and gluons are confined - no evidence of their existence outside of (colorless) hadrons


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The Quark-Gluon Plasma: Unbinding the Bound


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The History of the Universe


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The Quark-Gluon Plasma The state of the universe before it cooled to allow

hadrons (protons, neutrons, etc.) to form t < 1 s after the Big Bang

Hence part of my title T > 1012 K

Hence the other part of my title R < 1 fm = size of the proton

It is a different state of matter than what exists today Can we reproduce it in a laboratory?

Allow a direct study of the strong interaction which is 1/2 of the Standard Model.


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QCD Phase Diagram A beginning

definition: A hot, dense state of weakly-interacting quarks and gluons over a distance greater than the size of the proton.

Quark-Antiquark imbalance


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Expected to occur at 1012K~170 MeV



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Expected to occur at 1012K~170 MeV Heavy Ion Collision Trajectory



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The Relativistic Heavy Ion Collider (RHIC) From Space

NYCNYC

I live hereI live here

RHIC

At Brookhaven National

Laboratory

RHIC

At Brookhaven National

Laboratory


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The Collider From The Air


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RHIC Vitals and Statistics

• Two independent rings 3.83 km in circumference

– 120 bunches/ring

– 106 ns crossing time

• Maximum Energy

– s½ = 500 GeV p+p

– s½ = 200 GeV/N-N A+A

• Design Luminosity

– Au+Au 2x1026 cm-2s-1

– p+p 2x1032 cm-2s-1 ( polarized)

• Capable of colliding any nuclear species on any other nuclear species

• Collision energy = two mosquitoes colliding

• Collision temperature: over 1 trillion degrees

• Over 35,500 kg (78,100 pounds) of helium

• Ring cooled to 4.6 Kelvin (-450 degrees F)

• Refrigerator uses 15 MW electricity

• 20 years, less than one gram of gold is used

• Quark-gluon plasma lasts less than 0.00000000000000000000001 seconds


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A Relativistic Heavy Ion Collision Two nuclei approach

one another Moving at v=0.9995c so

relativistically contracted Mostly pass through

one another Overlap region

converts energy into heat and particles to form the QGP

Peripheral collision Not fully overlapping See “participants” and

“spectators”

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Simulations by the Frankfurt UrQMD Group


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A Relativistic Heavy Ion Collision

Central (head-on) Au+Au Collision





Animation by Jeffery Mitchell (Brookhaven National Laboratory). Simulation by the UrQMD Collaboration


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Real Heavy Ion CollisionsSTAR


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Measuring

If is the quark-antiquark imbalance then measure anti-particle/particle ratios

Compare to a statistical model of hadronization

Note the species measured: K, K*, p,

M. Kaneta, N. Xu, nucl-th/0405068 (2004)


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Measuring M. Kaneta, N. Xu, nucl-th/0405068 (2004)





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Measuring M. Kaneta, N. Xu, nucl-th/0405068 (2004)

B~30 MeV





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Measuring T Look at the

photons Just like

COBE measures the CMB


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Measuring T: Photon Spectrum Yield of photons at

each momentum bin Dashed line is fit to

p+p data Extra photons in

Au+Au collisions exp(-pT/T) with

T = 221+/-23(stat.)+/-18(sys.) MeV

Other theoretical models are yield T from 300-600 MeV

Recall transition at T~170 MeV


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T = 221+/-23(stat.)+/-18(sys.) MeV



Central Au+Au

Non-central Au+Au


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T = 221+/-23(stat.)+/-18(sys.) MeV



Central Au+Au

Non-central Au+Au


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Intermediate Conclusion It seems like RHIC has indeed produced the

right conditions to produce a Quark-Gluon plasma.

But… Do we know it is thermalized? Is that temperature

from the photons really a temperature. What about other thermodynamic quantities:

pressure, entropy, etc.? Is there an equation of state?


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Getting at the Pressure: Elliptic Flow Non-overlapping

collisions of spherically symmetric nuclei results in a non-symetric overlap region Differential pressure

gradients if you think in terms of a fluid.

Use flow to measure Equation of State and speed of sound cs




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Azimuthal Distributions: v2

Particles have a harmonic distribution wrt the reaction plane.

v2 related to the strength of the modulation Dependent on

the particle’s momentum and mass

€

dN

dφ=

N

2π1+ 2v2 cos 2φ( ) + ...( )


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Compilation of Light Hadron v2 Data

Everything flows

Hydrodynamics fit data at low momentum Should not

work at high momentum

Can add K*, to this list as wellHydrodynamics = Fluid equations assuming

An equation of state and thermalization.


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v2 Scaling (I) With more

precise data scaling of baryons (p,n) and mesons (,K) observed.

€

KE T= mT − m = pT2 + m2 − m

baryons(qqq)

Mesons ( )

€

qq


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v2 Scaling (II) Divide by the

constituent quarks and a universal v2 curve exists! nq=3 for

baryons nq=2 for

mesons Can be used

to derive a speed of sound: cs = 0.35+/-0.05

€

KE T= mT − m = pT2 + m2 − m


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Heavy Quarks Flow Also! Heavy

Flavor(HF): c,b e

c,b flow as well!

Like boulders flowing in a small stream

Several models ofheavy flavor diffusionthrough the medium


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Strongly Interacting Plasma

Hydrodynamic models work Only works with QGP equation of state (not a hadron gas) Implies local thermodynamic equilibrium Have viscosity = 0!

The medium produced is a perfect fluid Fluid! Not a gas! Heavy flavors are also strongly coupled to the fluid Data used to obtain (shear)viscosity/entropy density /s Light hadron v2 indicates /s ~ 1/4 Heavy hadron v2 indicate /s ~ (1-2)/4


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The Future: The Effects of RHIC and New Experiments


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Should We Have Seen This Coming?

Lattic calculations (numerically solving QCD) indicate a phase transition

But new phase doesn’t reach the Stefan-Boltzmann limit The limit for non-

interacting paticles.

€

εQGP ≈ 34 εSB


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How Can We Make Headway? If particles are strongly coupled cannot use

perturbative methods to calculate Need a new tool that can calculate strongly

coupled field theories Why not use string theory????


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QuickTime™ and aTIFF (LZW) decompressor


5-D Anti-de Sitter

Black Hole

5th dim

AdS/CFT Correspondence

Maldecena’s Conjecture 1) Calculate some

quantities in a 5-D gravity

Anti-de Sitter (AdS) defines the General Relativity metric

4-D


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AdS/CFT Correspondence Maldecena’s

Conjecture 2) Apply a

dictionary to get analogous quantity in the dual conformal field theory (CFT)

CFT: scale invariant field theory

QCD is not quite scale invariant Shh don’t tell…


are needed to see this picture.AdS/CFT

J. Maldacena

E. Witten

et al.

Black Hole

5th dim

5-D Anti-de Sitter

4-D


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AdS/CFT Correspondence




are needed to see this picture.AdS/CFT

J. Maldacena

E. Witten

et al.

r0~1/TQGP

4-DQCD-like,strongly-coupledfluid at TQGP

Black Hole

Conformalboundary

5th dim

5-D Anti-de Sitter

4-D


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What Do Strings Tell Us? Limit of /s (looks like an uncertainty

relationship)

Checked by many different geometries - seems universal!




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/s For Physical Substances

Nothing comes close to the physical bound except the QGP at TC

Recall Light hadron v2 indicates

/s~1/4 Heavy hadron v2 indicate

/s~(1-2)/4 Most perfect fluid ever

measured in a laboratory




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New Overlap With Other Fields


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New Experiments: Large Hadron Collider (LHC) New, large,

higher-energy collider just turning on in CERN, Geneva Switzerland.

200 GeV Au+Au at RHIC to 5.5 TeV Pb+Pb at LHC

~100 m below

ground

27 km

5.5 TeV A+A14 TeV p+p


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The ATLAS Detector


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The ATLAS Detector

It floats!


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ATLAS vs. RHIC Acceptance

Unprecedented coverage to measure HI Collisions and their properties.

RHIC


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The Last 10 Years


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The Last 10 Years


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The Last 10 Years


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The Last 10 Years

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The Last 10 Years

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are needed to see this picture.QuickTime™ and a

TIFF (LZW) decompressorare needed to see this picture.




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The Last 10 Years




are needed to see this picture.QuickTime™ and a

TIFF (Uncompressed) decompressorare needed to see this picture.


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The Last 10 Years

Physics Publications in Refereed Journals BRAHMS - 19 PHENIX - 76 PHOBOS - ??? website down :( STAR - 86

10s of technical papers 1 “White Paper” after 2003 run summarizing

physics Before the strongly-interacting QGP


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The Last 10 Years

A phase transition in our understanding of the Quark Gluon Plasma has occurred: it is a strongly-interacting, perfect fluid!

Insights to calculating non-perturbative QCD has come from String Theory!

New experiments and overlaps with other fields will help us learn more about the matter that dominates the visible universe.


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Backup Slides


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The Standard Model Condensed


66


g g

gproton

g

g g


other particles Baryons: protons,

neutrons, etc. Mesons: pions, kaons, etc. Held together by gluons

Quarks have “color” charge is of 3 types: red, green, blue Contrast that with 2 electric

charges: +,- Quarks are confined -

no evidence of their existence outside of hadrons

Ca. 1970 view of the proton and the neutron.Only real improvement is that the proton bubbles with lots of gluons and pairs

€

qq


67

The Collider From Inside a DetectorBeam View

dN/d ~ 600Head-on (central) Au+Au

STAR


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AdS/CFT : QCD Correspondence Maldecena’s conjecture String theory is equivalent to a conformal (scale-

invariant) field theory in a lower dimension without gravity

Further it has been argued that strongly coupled field theories can be described by weak string theories.

Implication: strongly coupled QCD can be calculated by a gravity dual Gravity = General Relativity in many dimensions Lots of work in 5-dimensional Anti-de Sitter (AdS) space -

this just defines the metric connected with QCD in 4-dimensions.

01/22/2009 francis marion university 1 the little big bang: relativistic nuclear collisions and the...

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francis marion university

electroweak force

white slide

force carriers

single force

light slide

proton mass

weak force interaction