14-Jan-01W.A. Zajc1 Recreating the Birth of the Universe

University at Stony Brook

Barbara Jacak1

Recreating the Recreating the Birth of the UniverseBirth of the Universe


Barbara Jacak2

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?


Barbara Jacak3

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


Barbara Jacak4

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!


Barbara Jacak5

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


Barbara Jacak6

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.


Barbara Jacak7

Phase DiagramsPhase Diagrams

Water

Nuclear Matter


Barbara Jacak8

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!


Barbara Jacak9

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


Barbara Jacak11

RHIC’s ExperimentsRHIC’s Experiments

STAR


Barbara Jacak12

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


Barbara Jacak13

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!


Barbara Jacak14

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

MFFDiL aa

ˆ~

4

1

PARTICLES!

, e+e-,

+Kpn

Dd, J/Y,…


Barbara Jacak15

We want to knowWe want to know

How many particles are produced? What are their momenta?

what temperature matter do they come from?

What kind of particles? hadrons or photons or electrons (or muons)? how many of each kind?

how do they interact with each other? are they normal hadrons or did they come

from a plasma? did anything happen to them on their way

out of the collision?


Barbara Jacak16

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


Barbara Jacak17

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


Barbara Jacak18

Particle Identification by TOFParticle Identification by TOF

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

read-out with photomultiplier tubes Time resolutions ~ 100 ps

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


Barbara Jacak19

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

During a plenary RHIC talk at APS about 10 years ago, “real” plasma physicists made some 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…)


Barbara Jacak20

The “Calibrated” Plasma The “Calibrated” Plasma ProbeProbe

Need something that feels the strong interaction not light!

best bet: quarks or gluons (seen as JETS of particles!) “created” by kicking out of the original nuclei number and distribution you start with is

calculable they are enveloped by the medium

“visible” at high momentum 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. proton-proton collisions provide reference.


Barbara Jacak21

Particle Spectra Particle Spectra EvolutionEvolution

“Peripheral”

Particle

Physics

“Central”

Nuclear

Physics“Thermal”

Production

Hard

Scattering


Barbara Jacak22

a common plasma a common plasma techniquetechnique

hadrons

q

q

hadronsleadingparticle

leading particle

schematic view of jet production

calculate proberate & distributionwith pQCD

look for modificationby medium

d+Au collisions provide the control

transmission of probes which interact with plasmafor QGP: fast g and light quarks


Barbara Jacak23

observed vs. observed vs. expectedexpected

high energy photons: EM interaction, escape plasma pions and other hadrons: strong interaction, absorbed


Barbara Jacak24

how about the partner?how about the partner?STAR PRL 90, 082302 (2003)

Central Au + Au

Peripheral Au + Au

Medium is opaque!→ high density strong interactions


Barbara Jacak25

SummarySummary

RHIC is more exciting than we dared hope: We see a hot plasma for the first time.

It is opaque to particles which feel the strong interaction.

The opaqueness is only when there is a large volume and the matter is hot. d-Au collisions serves as control experiment. p-p collisions calibrate the probe.

Next steps: measure temperature of the plasma is it like a gas or more like a liquid?


Barbara Jacak26

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


Barbara Jacak27

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-


Barbara Jacak28

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


Barbara Jacak29

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


Barbara Jacak30

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)


Barbara Jacak31

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


Barbara Jacak32

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


Barbara Jacak33

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


Barbara Jacak34

STAR ChallengeSTAR Challenge


Barbara Jacak35

STAR EventSTAR Event

Data Taken June 25, 2000.

Pictures from Level 3 online display.

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STAR RealitySTAR Reality


Barbara Jacak37

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

Barbara Jacak39

PHENIX RealityPHENIX Reality

January, 1999


Barbara Jacak40

(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 A12.034.0 B

PHENIX ResultsPHENIX Results


Barbara Jacak41

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

Documents

14-Jan-01W.A. Zajc1 Recreating the Birth of the Universe