14-Jan-01W.A. Zajc1 Recreating the Birth of the Universe.
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Transcript of 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
University at Stony Brook
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?
University at Stony Brook
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
University at Stony Brook
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!
University at Stony Brook
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
University at Stony Brook
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.
University at Stony Brook
Barbara Jacak7
Phase DiagramsPhase Diagrams
Water
Nuclear Matter
University at Stony Brook
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!
University at Stony Brook
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
University at Stony Brook
Barbara Jacak11
RHIC’s ExperimentsRHIC’s Experiments
STAR
University at Stony Brook
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
University at Stony Brook
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!
University at Stony Brook
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,…
University at Stony Brook
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?
University at Stony Brook
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
University at Stony Brook
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
University at Stony Brook
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
University at Stony Brook
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…)
University at Stony Brook
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.
University at Stony Brook
Barbara Jacak21
Particle Spectra Particle Spectra EvolutionEvolution
“Peripheral”
Particle
Physics
“Central”
Nuclear
Physics“Thermal”
Production
Hard
Scattering
University at Stony Brook
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
University at Stony Brook
Barbara Jacak23
observed vs. observed vs. expectedexpected
high energy photons: EM interaction, escape plasma pions and other hadrons: strong interaction, absorbed
University at Stony Brook
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
University at Stony Brook
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?
University at Stony Brook
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
University at Stony Brook
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-
University at Stony Brook
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
University at Stony Brook
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
University at Stony Brook
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)
University at Stony Brook
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
University at Stony Brook
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
University at Stony Brook
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
University at Stony Brook
Barbara Jacak34
STAR ChallengeSTAR Challenge
University at Stony Brook
Barbara Jacak35
STAR EventSTAR Event
Data Taken June 25, 2000.
Pictures from Level 3 online display.
36
STAR RealitySTAR Reality
University at Stony Brook
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
38
PHENIX DesignPHENIX Design
Barbara Jacak39
PHENIX RealityPHENIX Reality
January, 1999
University at Stony Brook
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
University at Stony Brook
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