63
Modern Nuclear Physics: Recreating the Creation of the Universe Rene Bellwied Rene Bellwied Wayne State University Wayne State University ( [email protected] [email protected] ) ) The Universe and its beginning The Universe and its beginning Remaining Puzzles in Cosmology Remaining Puzzles in Cosmology How to recreate creation How to recreate creation The latest evidence The latest evidence

Modern Nuclear Physics: Recreating the Creation of the Universe Rene Bellwied Wayne State University ([email protected]) [email protected]

  • View
    226

  • Download
    1

Embed Size (px)

Citation preview

Modern Nuclear Physics:Recreating the Creation of

the UniverseRene BellwiedRene Bellwied

Wayne State UniversityWayne State University(([email protected]@physics.wayne.edu))

The Universe and its beginningThe Universe and its beginning Remaining Puzzles in CosmologyRemaining Puzzles in Cosmology How to recreate creationHow to recreate creation The latest evidenceThe latest evidence

Newton’s Universe Paradox The universe is not empty. The universe is not empty.

It contains matter with mass.It contains matter with mass. Attraction of gravity is present. Attraction of gravity is present.

If the universe has existed forever and is If the universe has existed forever and is static, (i.e. has no net pattern of motion), static, (i.e. has no net pattern of motion), there must be enough time for gravity to there must be enough time for gravity to collapse the universe.collapse the universe.

Why did it not happen ? Why did it not happen ?

Why has it not Collapsed?

Newton knew of 3 ways to resolve this Newton knew of 3 ways to resolve this paradox. paradox. Universe is infinite in volume and Universe is infinite in volume and

massmass Universe is expanding fast enough to Universe is expanding fast enough to

overcome the gravitational attraction.overcome the gravitational attraction. Universe has a beginning and/or an Universe has a beginning and/or an

end. end.

Newton’s Choice…

Last two ways violate the assumptions of Last two ways violate the assumptions of an eternal and static universe, of course. an eternal and static universe, of course.

Newton chose the infinite universe option.Newton chose the infinite universe option. Notice that you are able to arrive at the Notice that you are able to arrive at the

conclusion of an infinite universe from just conclusion of an infinite universe from just one observation: the universe is not one observation: the universe is not empty. No telescopes are needed, just the empty. No telescopes are needed, just the ability to follow a train of logical thought ability to follow a train of logical thought to its conclusion. to its conclusion.

Olbers' Paradox and the Dark Night Sky Another simple observation is that the visible Another simple observation is that the visible

night sky is dark. night sky is dark.

IFIF the universe is infinite, eternal, and static, the universe is infinite, eternal, and static, then the sky should be as bright as the surface then the sky should be as bright as the surface of the Sun all of the time! of the Sun all of the time! Heinrich OlbersHeinrich Olbers (lived 1758--1840) (lived 1758--1840)

popularized this paradox in 1826popularized this paradox in 1826

This problem is called This problem is called Olbers' Paradox Olbers' Paradox (1826)(1826). .

Statement of the Paradox

If the universe is If the universe is uniformly filled with stars, uniformly filled with stars, then no matter which then no matter which direction you look, your direction you look, your line of sight will line of sight will eventually intersect a star eventually intersect a star (or other bright thing). (or other bright thing).

Known that stars are Known that stars are grouped into galaxies, but grouped into galaxies, but the paradox remains: your the paradox remains: your line of sight will line of sight will eventually intersect a eventually intersect a galaxy. galaxy.

How it works….

The brightnesses of stars does decrease with The brightnesses of stars does decrease with greater distancegreater distance remember the inverse square lawremember the inverse square law

BUT there are more stars further out. BUT there are more stars further out. number of stars within a spherical shell around number of stars within a spherical shell around

us increases by the same amount as their us increases by the same amount as their brightness decreases. brightness decreases.

Therefore, each shell of stars should have the Therefore, each shell of stars should have the same overall luminosity and because there are a same overall luminosity and because there are a lot of ever bigger shells in an infinite universe, lot of ever bigger shells in an infinite universe, there should be a lot of light! there should be a lot of light!

An Expanding Universe

Edwin Hubble and Milton Humason discovered (1920) that Edwin Hubble and Milton Humason discovered (1920) that the universe is not static it is expanding. the universe is not static it is expanding.

This is enough to resolve the paradox. This is enough to resolve the paradox. As the universe expands, the light waves are stretched As the universe expands, the light waves are stretched

out and the energy is reduced. out and the energy is reduced. Also, the time to receive the light is also lengthened Also, the time to receive the light is also lengthened

over the time it took to emit the photon. over the time it took to emit the photon.

Let there be light The Hertzsprung-The Hertzsprung-

Russell DiagramRussell Diagram Relation betweenRelation between mass mass

andand temperature, light temperature, light output, lifetime.output, lifetime.Stars shine because of Stars shine because of nuclear fusion reactions in nuclear fusion reactions in their core. The more their core. The more luminous they are, the luminous they are, the more reactions are taking more reactions are taking place in their cores.place in their cores.

Wien’s Law Temperature Cool stars will have the peak of their continuous Cool stars will have the peak of their continuous

spectrum at long (red) wavelengths. spectrum at long (red) wavelengths. As the temperature of a star increases, the peak of its As the temperature of a star increases, the peak of its

continuous spectrum shifts to shorter (blue) continuous spectrum shifts to shorter (blue)

wavelengths.wavelengths.

Doppler Effect

Case (a)Case (a) Object (source) moving towards Object (source) moving towards

observer A at velocity “v”observer A at velocity “v” Observer “A” sees compressed Observer “A” sees compressed

wave, I.e. wave, I.e. shorter wavelength, shorter wavelength, higher frequencyhigher frequency..

Observer “B” see stretched Observer “B” see stretched wave, I.e. longer wavelength, wave, I.e. longer wavelength, lower frequency.lower frequency.

Case (b)Case (b) Stationary sourceStationary source Observer “A” and “B” see Observer “A” and “B” see same same

wavelengthwavelength..

SourceObserver A Observer B

v

(a)

SourceObserver A Observer B

(b)

Doppler Effect with Stars A star's motion causes a wavelength shift in its light A star's motion causes a wavelength shift in its light

emission spectrum, which depends on speed and emission spectrum, which depends on speed and direction of motion. direction of motion.

If star is moving If star is moving towardtoward you, the waves are you, the waves are compressed, so their wavelength is compressed, so their wavelength is shorter = shorter = blueshiftblueshift. .

If the object is moving If the object is moving awayaway from you, the waves are from you, the waves are stretched out, so their wavelength is stretched out, so their wavelength is longer = longer = redshiftredshift. .

Relativity and Universe Expansion

This explanation also works if you are moving and the This explanation also works if you are moving and the object is stationary or if both you and the object are moving. object is stationary or if both you and the object are moving.

The doppler effect tells you about the The doppler effect tells you about the relativerelative motion of the motion of the object with respect to you. object with respect to you.

Important fact:Important fact: The spectral lines of nearly all of the galaxies in the The spectral lines of nearly all of the galaxies in the

universe are shifted to the red end of the spectrum. universe are shifted to the red end of the spectrum. This means that the galaxies are moving away from the This means that the galaxies are moving away from the

Milky Way galaxy.Milky Way galaxy. This is evidence for the expansion of the universe. This is evidence for the expansion of the universe.

Uniform Expansion

The The Hubble lawHubble law, speed = , speed = HHoo × distance, says the × distance, says the

expansion is uniform. expansion is uniform. The The Hubble constantHubble constant, , HHoo,, is the slope of the line is the slope of the line

relating the speed of the galaxies away from each relating the speed of the galaxies away from each other and their distance apart from each other. other and their distance apart from each other. It indicates the rate of the expansion. It indicates the rate of the expansion. If the slope is steep (large If the slope is steep (large HHoo),), then the expansion rate then the expansion rate

is large and the galaxies did not need much time to get is large and the galaxies did not need much time to get to where they are now. to where they are now.

Hubble Law

Hubble and Humason (1931): Hubble and Humason (1931): the Galactic recession speed = the Galactic recession speed = HH × distance, × distance,

where where HH is a number now called the is a number now called the Hubble Hubble constant.constant.

This relation is called the This relation is called the Hubble LawHubble Law and the and the Hubble constantHubble constant is the slope of the line. is the slope of the line.

Age of the Universe

Age of the universe can be estimated from the simple Age of the universe can be estimated from the simple relation of relation of time = distance/speed.time = distance/speed.

The Hubble Law can be rewritten The Hubble Law can be rewritten 1/1/HHoo = distance/speed. = distance/speed.

The Hubble constant tells you the age of the universe, The Hubble constant tells you the age of the universe, i.e., how long the galaxies have been expanding away i.e., how long the galaxies have been expanding away from each other: from each other: Age = 1/Age = 1/HHoo. .

Age upper limit since the expansion has been slowing Age upper limit since the expansion has been slowing down due to gravity. down due to gravity.

Some preliminary Conclusions

Expansion of the universe means that galaxies Expansion of the universe means that galaxies were much closer together long ago. were much closer together long ago.

This implies that there is a finite age to the This implies that there is a finite age to the universe, it is not eternal. universe, it is not eternal.

Even if the universe is infinite, the light from Even if the universe is infinite, the light from places places veryvery far away will not have had enough far away will not have had enough time to reach us. This will make the sky dark. time to reach us. This will make the sky dark.

Star Count in the Galaxy

RoughRough guess of the number of stars in our guess of the number of stars in our galaxy obtained by dividing the Galaxy's galaxy obtained by dividing the Galaxy's total mass by the mass of a typical star (e.g., total mass by the mass of a typical star (e.g., 1 solar mass). 1 solar mass). The result is about 200 billion stars! The result is about 200 billion stars!

The actual number of stars could be several The actual number of stars could be several tens of billions less or more than this tens of billions less or more than this approximate value. approximate value.

How stars like the sun evolve

How heavy stars evolve

Black Hole Formation After a supernovae explosion, if the core remnant has a mass After a supernovae explosion, if the core remnant has a mass

greater than greater than 3 solar masses3 solar masses, then not even the super-compressed , then not even the super-compressed degenerate neutrons can hold the core up against its own gravity.degenerate neutrons can hold the core up against its own gravity.

As the core implodes it briefly makes a neutron star for just long As the core implodes it briefly makes a neutron star for just long enough to produce the supernova explosion. Supernovae are rare enough to produce the supernova explosion. Supernovae are rare (one every 25 years in our galaxy of 200 billion stars!)(one every 25 years in our galaxy of 200 billion stars!)

Gravity finally wins and compresses everything to a mathematical Gravity finally wins and compresses everything to a mathematical point at the center. The point object is a point at the center. The point object is a black holeblack hole..

Ultra-strong gravity

The gravity of the point mass is strong enough The gravity of the point mass is strong enough close to the center that nothing can escape, not even close to the center that nothing can escape, not even light! Within a certain distance of the point mass, light! Within a certain distance of the point mass, the the escape velocityescape velocity is greater than the speed of is greater than the speed of light. light.

The distance at which the escape velocity equals The distance at which the escape velocity equals the speed of light is called the the speed of light is called the event horizon (or event horizon (or Schwarzschild radius)Schwarzschild radius) because no information because no information from within that distance of the point mass will be from within that distance of the point mass will be able to make it to the outside. able to make it to the outside.

Spiral Galaxies Andromeda Galaxy Andromeda Galaxy

M31 near the Milky M31 near the Milky Way. Way.

NGC 2997 large NGC 2997 large face-on spiral face-on spiral galaxy (Sc). galaxy (Sc).

Masses of Galaxies

Masses of galaxies are found from the orbital motion of their Masses of galaxies are found from the orbital motion of their stars. Stars in a more massive galaxy orbit faster than those in stars. Stars in a more massive galaxy orbit faster than those in a lower mass galaxy because the greater gravity force of the a lower mass galaxy because the greater gravity force of the massive galaxy causes larger accelerations of its stars. massive galaxy causes larger accelerations of its stars.

By measuring the star speeds, one finds out how much By measuring the star speeds, one finds out how much gravity there is in the galaxy. The rotation curve shows how gravity there is in the galaxy. The rotation curve shows how orbital speeds in a galaxy depend on their distance from the orbital speeds in a galaxy depend on their distance from the galaxy's center.galaxy's center. Orbital speed is found from the doppler shifts Orbital speed is found from the doppler shifts of the 21-cm line radiation from the atomic hydrogen gas. of the 21-cm line radiation from the atomic hydrogen gas.

Since gravity depends on mass and distance, knowing the size Since gravity depends on mass and distance, knowing the size of the star orbits enables you to derive the galaxy's mass. of the star orbits enables you to derive the galaxy's mass.

A Mass Problem The stars and gas in most galaxies The stars and gas in most galaxies

move much quicker than expected move much quicker than expected from the luminosity of the galaxies. from the luminosity of the galaxies.

In spiral galaxies, the rotation curve In spiral galaxies, the rotation curve remains at about the same value at remains at about the same value at great distances from the center (it is great distances from the center (it is said to be ``flat''). said to be ``flat'').

This means that the enclosed mass This means that the enclosed mass continues to increase even though continues to increase even though the amount of visible, luminous the amount of visible, luminous matter falls off at large distances matter falls off at large distances from the center. from the center.

Something else must be adding to the gravity of the Something else must be adding to the gravity of the galaxies without shining. We call it Dark Matter ! galaxies without shining. We call it Dark Matter ! According to measurements it accounts for 90% of the According to measurements it accounts for 90% of the mass in the universe.mass in the universe.

What is Dark Matter ? We don’t know (yet)

White dwarfs, brown dwarfs, black holes, massive neutrinos, White dwarfs, brown dwarfs, black holes, massive neutrinos, although intriguing are very unlikely to account for most of the although intriguing are very unlikely to account for most of the dark matter. The dwarfs are generally called Massive compact dark matter. The dwarfs are generally called Massive compact halo objects (MACHOS)halo objects (MACHOS)

New exotic particles or formations are more likely:New exotic particles or formations are more likely: Weakly interacting massive particles (WIMPS)Weakly interacting massive particles (WIMPS) Matter based on exotic quark configurations (e.g. strange Matter based on exotic quark configurations (e.g. strange

Quark matter)Quark matter)

If these states exist somewhere in the universe If these states exist somewhere in the universe wouldn’t they have been produced in the early wouldn’t they have been produced in the early universe ?universe ?

Evidence for the Big Bang Galaxies are distributed fairly uniformily across the sky Galaxies are distributed fairly uniformily across the sky

between a lot of void (Obler’s paradox)between a lot of void (Obler’s paradox) Background radiation was predicted, and has been found, Background radiation was predicted, and has been found,

to be exactly 2.73 K everywhere in the universe. to be exactly 2.73 K everywhere in the universe. Variations as measured by a NASA satellite named COBE Variations as measured by a NASA satellite named COBE (Cosmic Background Explorer) are less than 0.0001 K.(Cosmic Background Explorer) are less than 0.0001 K.

What happened at the beginning ?

A Cosmic Timeline AgeAge Energy Energy Matter in universe Matter in universe 00 10101919 GeV GeV grand unified theory of all forcesgrand unified theory of all forces

1010-35-35 s s 10101414 GeV GeV 11stst phase transition phase transition

(strong: q,g + electroweak: g, l,n)(strong: q,g + electroweak: g, l,n)

1010-10-10 ss 101022 GeV GeV 22ndnd phase transition phase transition(strong: q,g + electro: g + weak: l,n)(strong: q,g + electro: g + weak: l,n)

1010-5-5 s s 0.2 GeV0.2 GeV 33rdrd phase transition phase transition(strong:hadrons + electro:g + weak: l,n)(strong:hadrons + electro:g + weak: l,n)

3 min.3 min. 0.1 MeV0.1 MeV nucleinuclei

6*106*1055 years years 0.3 eV0.3 eV atomsatoms

NowNow 3*103*10-4-4 eV = 3 K eV = 3 K(15 billion years)(15 billion years)

The Grand Unification Theory (GUT)

An Inflationary Universe

The universe expanded to a point where the The universe expanded to a point where the unified forces of nature started to decouple. unified forces of nature started to decouple. When the strong force decoupled a major When the strong force decoupled a major amount of energy was released and the amount of energy was released and the universe expanded by a facto 10universe expanded by a facto 103030 in less in less than 10than 10-36-36 seconds. This rapid expansion is seconds. This rapid expansion is called called inflationinflation

Going back in time

time

temperature

~ 100 s after Big Bang

Nucleosynthesis begins

In the beginning quark – gluon

plasma

~ 10 s after Big Bang

Hadron Synthesisstrong force binds quarks and gluons in massive objects: protons, neutrons mass ~ 1 GeV

STARSTAR

The RHIC Complex

1. Tandem Van de Graaff

2. Heavy Ion Transfer Line

3. Booster

4. Alternating Gradient Synchrotron (AGS)

5. AGS-to-RHIC Transfer Line

6. RHIC ring

1. Tandem Van de Graaff

2. Heavy Ion Transfer Line

3. Booster

4. Alternating Gradient Synchrotron (AGS)

5. AGS-to-RHIC Transfer Line

6. RHIC ring

11

33 44

66

22

55

Let’s go for the ‘Mini-Bang’ We need a system that is small so that we can We need a system that is small so that we can

accelerate it to very high speeds. accelerate it to very high speeds. (99.9% of the speed of light)(99.9% of the speed of light)

But we need a system (i.e. a chunk of matter and But we need a system (i.e. a chunk of matter and not just a single particle) so that the system can not just a single particle) so that the system can follow simple rules of thermodynamics and form a follow simple rules of thermodynamics and form a new state of matter in a particular phase.new state of matter in a particular phase.

We use heavy ions (e.g. a Gold ion which is made We use heavy ions (e.g. a Gold ion which is made of 197 protons and neutrons). It is tiny (about a of 197 protons and neutrons). It is tiny (about a 10-10-1414 m diameter) but it is a finite volume that can m diameter) but it is a finite volume that can be exposed to pressure and temperaturebe exposed to pressure and temperature

What are we trying to do ? We try to force a phase transition of the matter we We try to force a phase transition of the matter we

know (e.g. our Gold nucleus) to a new state of know (e.g. our Gold nucleus) to a new state of matter predicted by the Big-Bang, called a Quark-matter predicted by the Big-Bang, called a Quark-Gluon Plasma (QGP)Gluon Plasma (QGP)

We try to do that by following thermodynamics:We try to do that by following thermodynamics: PV = nRTPV = nRT

A system of volume V can change if exposed to A system of volume V can change if exposed to pressure P or temperature T.pressure P or temperature T.

An example: water, ice, and steam

pressure

This is a simple phase diagram

The temperature inside

The temperature inside a heavy ion The temperature inside a heavy ion collision at RHIC can exceed 1000 billion collision at RHIC can exceed 1000 billion degrees !!degrees !!

That’s about 10,000 times the temperature That’s about 10,000 times the temperature of the sunof the sun

How to create a QGP ?energy = temperature & density =

pressure

Let’s collide two heavy nuclei (1)

Let’s collide two heavy nuclei (2)

What is a Quark-Gluon Plasma?

An atom contains a nucleus...

…which contains protons and neutrons...

…which contain up and down quarks.

Let’s study all phases of the process

Freeze-out

Hadron Gas

Phase Transition

Plasma-phase

Pre-EquilibriumHard

scattering

If the QGP was formed, it will only live for 10-21 s !!!!BUT does matter come out of this phase the same way it went in ???

The STAR Experiment 450 scientists from 50 international institutions

Conceptual Conceptual OverviewOverview

Conceptual Conceptual OverviewOverview

The STAR Experiment construction from 1992-2000

data taking from 2000-2010 (?)

Overview while Overview while under under

constructionconstruction

Overview while Overview while under under

constructionconstruction

The STAR Experiment (TPC)

Construction in progressConstruction in progress

The STAR Experiment (SVT)Construction in progressConstruction in progress

The STAR Experiment (SVT)

The happy crew The happy crew after 8 long yearsafter 8 long yearsThe happy crew The happy crew

after 8 long yearsafter 8 long years

Actual Collision in STAR (1)

Actual STAR data Actual STAR data

for a for a

peripheral collisionperipheral collision

Actual STAR data Actual STAR data

for a for a

peripheral collisionperipheral collision

Actual Collision in STAR (2)

Actual STAR data Actual STAR data for a central for a central

collisioncollision

Actual STAR data Actual STAR data for a central for a central

collisioncollision

What is going on ?

A Au nucleus consists of 79 protons and 118 neutrons = 197 A Au nucleus consists of 79 protons and 118 neutrons = 197 particles -> 394 particles totalparticles -> 394 particles total

p and n consist of u- and d-quarksp and n consist of u- and d-quarks

After the collision we measure about 10,000 particles in the After the collision we measure about 10,000 particles in the debris!debris!

measured particles: p, measured particles: p, , K, , K, , d, J/, d, J/YY many particles contain s-quarks, some even c-quarksmany particles contain s-quarks, some even c-quarks Energy converts to matter, but does the matter go through a Energy converts to matter, but does the matter go through a

phase transition ?phase transition ?

How Do We Measure Things ?

particles go from the inside-outparticles go from the inside-out they have to traverse certain detectorsthey have to traverse certain detectors they should stop in the outermost detectorthey should stop in the outermost detector the particle should not change its properties when the particle should not change its properties when

traversing the inner detectortraversing the inner detector DETECT but don’t DEFLECT !!!DETECT but don’t DEFLECT !!! inner detectors have to be very thin (low radiation inner detectors have to be very thin (low radiation

length): easy with gas, challenge with solid state length): easy with gas, challenge with solid state materials (Silicon).materials (Silicon).

What do we have to check ?

If there was a transition to a different phase, then this phase If there was a transition to a different phase, then this phase could only last very shortly. The only evidence we have to check could only last very shortly. The only evidence we have to check is the collision debris.is the collision debris.

Check the make-up of the debris:Check the make-up of the debris: which particles have been formed ?which particles have been formed ? how many of them ?how many of them ? are they emitted statistically (Boltzmann distribution) ?are they emitted statistically (Boltzmann distribution) ? what are their kinematics (speed, momentum, angular what are their kinematics (speed, momentum, angular

distributions) ?distributions) ? are they correlated in coordinate or momentum space ?are they correlated in coordinate or momentum space ? do they move collectively ?do they move collectively ?

Signatures of the QGP phase

Phase transitions are signaled thermodynamically by a ‘step function’ when plotting temperature vs. Phase transitions are signaled thermodynamically by a ‘step function’ when plotting temperature vs. entropy (i.e. # of degrees of freedom. entropy (i.e. # of degrees of freedom.

The temperature (or energy) is used to increase the number of degrees of freedom rather than heat the The temperature (or energy) is used to increase the number of degrees of freedom rather than heat the existing form of matter. existing form of matter.

In the simplest approximation the number of degrees of freedom should scale with the particle multiplicity. In the simplest approximation the number of degrees of freedom should scale with the particle multiplicity.

At the step some signatures dropAt the step some signatures drop

and some signatures riseand some signatures rise

Phase transitions are signaled thermodynamically by a ‘step function’ when plotting temperature vs. Phase transitions are signaled thermodynamically by a ‘step function’ when plotting temperature vs. entropy (i.e. # of degrees of freedom. entropy (i.e. # of degrees of freedom.

The temperature (or energy) is used to increase the number of degrees of freedom rather than heat the The temperature (or energy) is used to increase the number of degrees of freedom rather than heat the existing form of matter. existing form of matter.

In the simplest approximation the number of degrees of freedom should scale with the particle multiplicity. In the simplest approximation the number of degrees of freedom should scale with the particle multiplicity.

At the step some signatures dropAt the step some signatures drop

and some signatures riseand some signatures rise

How do we know what happened ?

We have to compare to a system that did definitely We have to compare to a system that did definitely not go through a phase transition (a reference not go through a phase transition (a reference collision)collision)

Two options:Two options: A proton-proton collision compared to a Gold-A proton-proton collision compared to a Gold-

Gold collision does not generate a big enough Gold collision does not generate a big enough volume to generate a plasma phasevolume to generate a plasma phase

A peripheral Gold-Gold collision compared to a A peripheral Gold-Gold collision compared to a central one does not generate enough energy central one does not generate enough energy and volume to generate a plasma phaseand volume to generate a plasma phase

Time scales of the collision (simulated)

hadronization

initial state

pre-equilibrium

QGP andhydrodynamic expansion

hadronic phaseand freeze-out

PCM & clust. hadronization

NFD

NFD & hadronic TM

PCM & hadronic TM

CYM & LGT

string & hadronic TM1 fm/c 5 fm/c 10 fm/c 50 fm/c time

dN/dt

Chemical freeze outKinetic freeze out

Measurements:HBTBalance functionResonances

Time scales according to STAR data

dN/dt

1 fm/c 5 fm/c 10 fm/c 20 fm/ctimeChemical freeze out

Kinetic freeze out

Balance function (require flow)Resonance survival

Rlong (and HBT wrt reaction plane)

Rout, RsidePCM & clust. hadronization

NFD

NFD & hadronic TM

PCM & hadronic TM

CYM & LGT

string & hadronic TM

PCM & clust. hadronization

NFD

NFD & hadronic TM

PCM & hadronic TM

CYM & LGT

string & hadronic TM

PCM & clust. hadronization

NFD

NFD & hadronic TM

PCM & hadronic TM

CYM & LGT

string & hadronic TM

Evidence: Some particles are suppressed If the phase is very dense (QGP) than certain particles get absorbedIf the phase is very dense (QGP) than certain particles get absorbed

?

If things are produced in pairs then one might make it out and the other one not.

Central Au + Au

Peripheral Au + Au

STAR Preliminary

If things require the fusion of very heavy rare quarks they might be suppressed in a dense medium

Evidence: Some particles are enhanced Remember dark matter ? Well, we didn’t find clumps of it yet, but we Remember dark matter ? Well, we didn’t find clumps of it yet, but we

found increased production of strange quark particlesfound increased production of strange quark particles

What is our present conclusion ? The interpretation of bulk properties in heavy ion systems is complex. We have

indications of unusual behavior in rare, fast decoupling, and high momentum probes. Our system behaves like matter, not a collection of elementary particles, and we have the tools to study it.

We could declare discovery of the QGP but we have more things to study and we don’t have the ‘smoking gun’ yet. Further exploration will take a few years, but the first steps were very exciting and very successful.