14-jan-01w.a. zajc1 recreating the birth of the universe t.k hemmick university at stony brook

University at Stony Brook

Thomas K Hemmick1

Recreating the Recreating the Birth of the UniverseBirth of the Universe

T.K HemmickUniversity at Stony Brook


Thomas K Hemmick2

The Beginning of The Beginning of TimeTime

Time began with the Big Bang: All energy (matter) of the universe concentrated at a

single point in space and time. The universe expanded and cooled up to the

present day: ~3 Kelvin is the temperature of most of the universe. Except for a few “hot spots” where the expanding

matter has collapsed back in upon itself. How far back into time can we explain the

universe based upon our observations in the Lab?

What Physics do we use to explain each stage?


Thomas K Hemmick3

Evolution of the Evolution of the UniverseUniverse

Universe Expands and CoolsGravity…Newtonian/General Relativity

Universe too hot for electrons to bindE-M…Atomic (Plasma) Physics

Nucleosynthesis builds nuclei up to LiNuclear Force…Nuclear Physics

Too hot for nuclei to bindHadronic Gas—Nuclear/Particle

Physics

Too hot for quarks to bind!!!Quark Plasma…Standard Model

Physics


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Decoding the Decoding the AnalogyAnalogy

Sport ForceExchang

eParticle

Strength

Range

Calculable?

FRISBEE Electro-Magnetic(QED)

Photon Moderate

Infinite

Most accurate theory ever devised

CHESS Weak Force (unified w/ EM)

W+, W-, Z0 Weak Short Perfect

LOVE Strong Force (QCD)

8 gluons Strong Infinite

Nearly incalculable except for REALLY VIOLENT COLLISIONS!


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Electric vs. Color Electric vs. Color ForcesForces

Color Force The gluon carries color

charge, and so the force lines collapse into a “flux tube”.

As you pull apart quarks, the energy in the flux tube becomes sufficient to create new quarks.

Electric Force The electric field lines can be

thought of as the paths of virtual photons.

Because the photon does not carry electric charge, these lines extend out to infinity producing a force which decreases with separation.,

Trying to isolate a quark is as fruitless as trying to cut a string until it only has one end!

CONFINEMENT


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What about this Quark What about this Quark Soup?Soup?

If we imagine the early state of the universe, we imagine a situation in which protons and neutrons have separations smaller than their sizes.

In this case, the quarks would be expected to lose track of their true partners.

They become free of their immediate bonds, but they do not leave the system entirely.

They are deconfined, but not isolated similar to water and ice, water molecules are not fixed

in their location, but they also do not leave the glass.


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Phase DiagramsPhase Diagrams

Water

Nuclear Matter


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Making Plasma in the Making Plasma in the LabLab

Extremes of temperature/density are necessary to recreate the Quark-Gluon Plasma, the state of our universe for the first ~10 microseconds. Density threshold is when protons/neutrons

overlap 4X nuclear matter density = touching. 8X nuclear matter density should be plasma.

Temperature threshold should be located at “runaway” particle production.

The lightest meson is the pion (140 MeV/c2). When the temperature exceeds the mc2 of the pion,

runaway particle production ensues creating plasma. The necessary temperature is ~1012 Kelvin.

Question: Where do you get the OVEN? Answer: Heavy Ion Collisions!


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RHIC = Relativistic Heavy Ion Collider Located at Brookhaven National

Laboratory

RHICRHIC

10

RHIC SpecificationsRHIC Specifications 3.83 km circumference Two independent rings

120 bunches/ring 106 ns bunch crossing time

Can collide ~any nuclear species on ~any other species

Top Center-of-Mass Energy: 500 GeV for p-p 200 GeV/nucleon for Au-Au

Luminosity Au-Au: 2 x 1026 cm-2 s-1

p-p : 2 x 1032 cm-2 s-1 (polarized)

11

3344

1’1’

22

66

55


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RHIC’s ExperimentsRHIC’s Experiments

STAR


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RHIC in Fancy LanguageRHIC in Fancy Language

Explore non-perturbative “vacuum” by melting it Temperature scale Particle production Our ‘perturbative’ region

is filled with gluons quark-antiquark pairs

A Quark-Gluon Plasma (QGP) Experimental method:

Energetic collisions of heavy nuclei Experimental measurements:

Use probes that are Auto-generated Sensitive to all time/length scales

Perturbative Vacuum

ccMeV 200 ~)f 1/(~ mT

Color Screening

cc


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RHIC in Simple LanguageRHIC in Simple Language

Suppose… You lived in a frozen world where water existed only as

ice and ice comes in only quantized sizes ~ ice cubes and theoretical friends tell you there should be a liquid

phase and your only way to heat the ice is by colliding two ice

cubes So you form a “bunch” containing a billion ice cubes which you collide with another such bunch 10 million times per second which produces about 1000 IceCube-IceCube collisions

per second which you observe from the vicinity of Mars

Change the length scale by a factor of ~1013 You’re doing physics at RHIC!


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Nature’s providenceNature’s providenceHow can we hope to study such a complex system?

MFFDiL a

aˆ~

4

1

PARTICLES!

, e+e-,

+Kpn

Dd, J/Y,…


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Deducing Temperature from Deducing Temperature from ParticlesParticles

Maxwell knew the answer! Temperature is proportional to mean Kinetic

Energy Particles have an average velocity (or

momentum) related to the temperature. Particles have a known distribution of

velocities (momenta) centered around this average.

All the RHIC experiments strive to measure the momentum distributions of particles leaving the collision. Magnetic spectrometers measure momentum

of charged particles. A variety of methods identify the particle

species once the momentum is known: Time-of-Flight dE/dx


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1 meter of 1 Tesla field deflects p = 1 GeV/c by ~17O

Magnetic Magnetic SpectrometersSpectrometers

Cool Experiment: Hold a magnet near the screen of a B&W TV. The image distorts because the magnet bends

the electrons before they hit the screen. Why? :

meterTesla

cGeV

c

eRB

c

ep

/3.0,||

s

STAR

Bvc

e

dt

pd


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Particle Identification by TOFParticle Identification by TOF

The most direct way Measure by distance/time Typically done via scintillators

read-out with photomultiplier tubes Time resolutions ~ 100 ps

224

22

s

s

t

t

p

p

m

m

Performance: t ~ 100 ps on 5 m flight path P/K separation to ~ 2 GeV/c K/p separation to at least 4 GeV/c

K

p

e

Exercise: Show


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STAR

K p

e

Particle Identification by Particle Identification by dE/dxdE/dx

Elementary calculation of energy loss:Charged particles traversing material give

impulse to atomic electrons:

Ze

b

)(tE

x=t

b

ZedxtEedttEep yy

ey

22)()(

2

21

~2

)(transferEnergy

e

ey

m

p

dE/dx: The 1/ 2 survives

integration over impact parameters

Measure average energy loss to find b

Used in all four experiments


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Measuring SizesMeasuring Sizes

Borrow a technique from Astronomy: Two-Particle Intensity Interferometry Hanbury-Brown Twiss or “HBT” Bosons (integer spin particles like photons,

pions, Kaons, …) like each other: Enhanced probability of “close-by” emission

y

X

1

2

Source


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Momentum difference can be measured in all three directions: This yields 3 sizes:

“Long” (along beam) “Out” (toward detector) “Side” (left over

dimension)

Conventional wisdom: The “Long” axis includes

the memory of the incoming nuclei.

The “Out” axis appears longer than the “Side” axis thanks to the emission time:

Measuring ShapesMeasuring Shapes

22SideOut RR


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Run-2000Run-2000 First collisions:15-Jun-00 Last collisions: 04-Sep-

00 RHIC achieved its First

Year Goal (10% of design Luminosity).

Most of the data were recorded in the last few weeks of the run.

The first public presentation of RHIC results took place at the Quark Matter 2001 conference. January 15-20 Held at Stony Brook

University

Recorded ~5M events


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How Do You Detect How Do You Detect Plasma?Plasma?

During a plenary RHI talk at APS about 10 years ago, I wound up seated among “real” plasma physicists who made numerous comments: “These guys are stupid…”

Always a possibility. “…why don’t they just shoot a laser

through it and then they’d know if its plasma for sure!” Visible light laser…bad idea. Calibrated probe through QGP…good idea… …but not new. (Wang, Gyulassy, others…)


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The “Calibrated” Plasma The “Calibrated” Plasma ProbeProbe

Many Many results (concentrate on one). Hard scattering processes (JETS!) :

Occur at short time scales. Are “calculable” (even by experimentalists) in

simple models (e.g. Pythia) with appropriate fudging:

Intrinsic kT

K scaling factor. Find themselves enveloped by the medium Are “visible” at high pT despite the medium Promise to be our laser shining (or not) through

the dense medium created at RHIC. We can measure the ratio of observed to

expected particle yield at large momentum and it should drop below 1.0. Scaled proton-proton collisions provide

reference.


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Particle Spectra Particle Spectra EvolutionEvolution

“Peripheral”

Particle

Physics

“Central”

Nuclear

Physics“Thermal”

Production

Hard

Scattering


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RaaRaa We define the nuclear

modification factor as:

By definition, processes that scale with Nbinary will produce RAA=1.

RAA is what we get divided by what we expect.

RAA should be ~1.0

ddpdNddp

NdN

pR

T

NN

NNinel

binary

T

AA

evtTAA

2

21

)(

RAA is below 1 for both charged hadrons and neutral pions.

The neutral pions fall below the charged hadrons since they do not suffer proton contamination


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Away-side Jets Away-side Jets Missing!Missing!

STAR Experiment reconstructs azimuthal correlations.

Peak Around 0 are particles from “same side jet”.

Peak at +/- is the away-side jet.

In central collisions the away-side jet disappears!!!

Medium is black to jets.


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Quantifying the away-Quantifying the away-side.side.

Near-side jet/pp data ~1.0. Away-side jet/pp falls to ~0.2 in central collisions. Simple jet-quenching confirmed?

Not so fast…


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““Jet” Particle Jet” Particle CompositionComposition

Composition of jets violates normal pQCD! How could jet fragmentation be affected? Puzzles Puzzles Puzzles…


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Other Bizarre Other Bizarre Results:Results:

Azimuthal asymmetries beyond the “black almond” scenario.

The HBT interferometric technique for determining the lifetime of the particle source.

The theoretical community simply can’t explain the data. PS—This is the good news

???:

: 22

sideout

sideoutemission

RRExperiment

RRTheory


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Another Surprise!Another Surprise!

Rout<Rside!!!!! Normal theory cannot account for this Imaginary times of emission!!


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Possible Possible Explanation??Explanation??

Stony Brook theory student Derek Teaney (advisor E. Shuryak) calculated an exploding ball of QGP matter. The exploding ball

drives an external shell of ordinary matter to high velocities

Rout is the shell thickness

Rside is the ball size Shells of ordinary matter

Plasma


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Is it Soup Yet?Is it Soup Yet? RHIC physics in some reminds me of the

explorations of Christopher Columbus: He had a strong feeling that the earth was

round without having detailed calculations to back him up.

He traveled in exactly the wrong direction, as compared to conventional wisdom.

He discovered the new world… But he thought it was India!

Our status: We see jet quenching for the first time. We see results which defy all predictions

Hard proton production exceeds pion production Imaginary emission time

We could be in India (QGP), the New World, or just a place in Europe where the customs are VERY strange.


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SummarySummary RHIC is more exciting than we dared

hope: We see jet quenching for the first time. We see results which defy all predictions

Hard proton production exceeds pion production Imaginary emission time

Even the hard physics “reference” fails in the face of our new matter.

2002 run: d-Au collisions to finalize nuclear effects that

could fake jet suppression. p-p results for nucleon spin measurements.

2002-2003 run: Au-Au … for high statistics. Electromagnetic Probes!!


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SummarySummary Extreme Energy Density is a new

frontier for explorations of the state of the universe in the earliest times.

The RHIC machine has just come on line: The machine works The experiments work

The data from signatures of QGP as well as outright surprises…It’s not your Father’s Nuclear Matter anymore!

The real look into the system will come in the next run (May 2001): Electrons, Photons, Muons

We dream of India as our glorious destination

But maybe….We’ll find the new world instead.


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Electron Electron IdentificationIdentification

Problem: They’re rare

All tracks

Electron enriched sample (using RICH)

E/p matching for

p>0.5 GeV/c tracks Solution: Multiple

methods Cerenkov E(Calorimeter)/

p(tracking) matching


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charm e-

beauty e-Drell-Yan e-

Dalitz and conversions e-

Study by Mickey Chiu, J. Nagle

Why electrons?Why electrons? One reason: sensitivity to heavy flavor production

D0 K- +

D0 K- e+ e

D0 K- +

B0 D- +

B0 D- e+ e

B0 D- +

D0D0 +- K+ K-

D0D0 e+e- K+ K- ee

D0D0 +e- K+ K- e

Other reasons: vector mesons, virtual photons e+e-


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PHENIX

0 reconstruction

pT > 2 GeV/c

Asymmetry < 0.8

A good example of a “combinatoric” background Reconstruction is not done particle-by-particle Recall: 0 and there are ~2000 ‘s per unit rapidity

So: 0 1

0 2

0 3

0 N

Unfortunately, nature doesn’t use subscripts on photons

N correct combinations: ( ), ( ), … ( ),

N(N-1)/2 – N incorrect combinations ( ), ( ), …

Incorrect combinations ~ N2 (!)

Solution: Restrict N by pT cuts use high granularity, high resolution detector

00 Reconstruction Reconstruction


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BRAHMSBRAHMSAn experiment with an

emphasis: Quality PID spectra over a broad

range of rapidity and pT

Special emphasis: Where do the baryons go? How is directed energy

transferred to the reaction products?

Two magnetic dipole spectrometers in “classic” fixed-target configuration


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PHOBOSPHOBOS

An experiment with a philosophy: Global phenomena

large spatial sizes small momenta

Minimize the number of technologies:

All Si-strip tracking Si multiplicity

detection PMT-based TOF

Unbiased global look at very large number of collisions (~109)


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PHOBOS DetailsPHOBOS Details

Si tracking elements 15 planes/arm Front: “Pixels”

(1mm x 1mm) Rear: “Strips”

(0.67mm x 19mm) 56K channels/arm

Si multiplicity detector 22K channels || < 5.3


Thomas K Hemmick41

PHOBOS ResultsPHOBOS ResultsFirst results on dNch/d

for central events At ECM energies of

56 Gev 130 GeV

(per nucleon pair)

To appear in PRL (hep-ex/0007036)

X.N.Wang et al.

Hits in VTX

Hits in SPECTracks in SPEC

130 AGeV


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STARSTAR An experiment with a challenge:

Track ~ 2000 charged particles in || < 1

ZCal

Silicon Vertex Tracker

Central Trigger Barrel or TOF

FTPCs

Time Projection Chamber

Barrel EM Calorimeter

Vertex Position Detectors

Endcap Calorimeter

Magnet

Coils

TPC Endcap & MWPC

ZCal

RICH


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STAR ChallengeSTAR Challenge


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STAR EventSTAR Event

Data Taken June 25, 2000.

Pictures from Level 3 online display.

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STAR RealitySTAR Reality


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South muon Arm

North muon Arm

West Arm

East ArmCentral ArmsCoverage (E&W) -0.35< y < 0.35 30o <||< 120o

M(J/)= 20MeVM() =160MeV

Muon ArmsCoverage (N&S) -1.2< |y| <2.3 - < <M(J/)=105MeVM() =180MeV

3 station CSC5 layer MuID (10X0)p()>3GeV/c

GlobalMVD/BB/ZDC

PHENIXPHENIX An

experiment with something for everybody

A complex apparatus to measure Hadrons Muons Electrons Photons

Executive summary: High

resolution High

granularity

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PHENIX DesignPHENIX Design

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PHENIX RealityPHENIX Reality

January, 1999


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(See nucl-ex/0012008) Multiplicity grows significantly faster than N-

participants Growth consistent with a term that goes as N-

collisions (as expected from hard scattering)

collpart NBNAddN 0

28.088.0 A

12.034.0 B

PHENIX ResultsPHENIX Results


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SummarySummary

The RHIC heavy ion community has Constructed a set of experiments designed for

the first dedicated heavy ion collider Met great challenges in

Segmentation Dynamic range Data volumes Data analysis

Has begun operations with those same detectors

Quark Matter 2001 will See the first results of many new analyses See the promise and vitality of the entire RHIC

program

14-jan-01w.a. zajc1 recreating the birth of the universe t.k hemmick university at stony brook

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