14-jan-01w.a. zajc1 recreating the birth of the universe t.k hemmick university at stony brook
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University at Stony Brook
Thomas K Hemmick1
Recreating the Recreating the Birth of the UniverseBirth of the Universe
T.K HemmickUniversity at Stony Brook
University 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?
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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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Thomas K Hemmick4
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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Thomas K Hemmick5
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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Thomas K Hemmick6
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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Thomas K Hemmick7
Phase DiagramsPhase Diagrams
Water
Nuclear Matter
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Thomas K Hemmick8
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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Thomas K Hemmick9
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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Thomas K Hemmick11
RHIC’s ExperimentsRHIC’s Experiments
STAR
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Thomas K Hemmick12
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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Thomas K Hemmick13
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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Thomas K Hemmick14
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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Thomas K Hemmick15
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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Thomas K Hemmick16
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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Thomas K Hemmick17
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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Thomas K Hemmick18
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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Thomas K Hemmick20
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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Thomas K Hemmick22
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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Thomas K Hemmick23
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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Thomas K Hemmick24
Particle Spectra Particle Spectra EvolutionEvolution
“Peripheral”
Particle
Physics
“Central”
Nuclear
Physics“Thermal”
Production
Hard
Scattering
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Thomas K Hemmick25
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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Thomas K Hemmick26
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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Thomas K Hemmick27
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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Thomas K Hemmick28
““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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Thomas K Hemmick32
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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Thomas K Hemmick33
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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Thomas K Hemmick34
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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Thomas K Hemmick35
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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Thomas K Hemmick36
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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Thomas K Hemmick37
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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Thomas K Hemmick38
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
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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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Thomas K Hemmick42
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.
45
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
47
PHENIX DesignPHENIX Design
Thomas K Hemmick48
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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Thomas K Hemmick50
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
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