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Recreating the Birth of the Universe

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Title: Recreating the Birth of the Universe


1
Recreating the Birth of the Universe
  • T.K HemmickUniversity at Stony Brook

2
The Beginning of Time
  • 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?

3
Evolution of the Universe
Too hot for quarks to bind!!! Quark
PlasmaStandard Model Physics
Too hot for nuclei to bind Hadronic
GasNuclear/Particle Physics
Nucleosynthesis builds nuclei up to Li Nuclear
ForceNuclear Physics
Universe too hot for electrons to bind E-MAtomic
(Plasma) Physics
  • Universe Expands and Cools
  • GravityNewtonian/General Relativity

4
Standard Model (simplified)
  • Imagine a college campus on a warm summer day
  • Students are uniformly distributed in an open
    field.

5
Standard Model II
  • Students who interact with the FRISBEE form a
    group.
  • These students are charged
  • Other students dont interact with the FRISBEE.
  • neutral or nerds
  • Now introduce CHESS into the campus!

6
Standard Model III
  • Some charged and some neutral students decide to
    play chess
  • Very short range interaction
  • More than one type of exchange particle
  • Finally, introduce LOVE into the college campus

7
Standard Model IV
  • All the remaining students form into tightly
    bound pairs
  • (and triples)
  • If you break up with one partner, you immediately
    find another (confinement)
  • Force grows stronger with separation

8
Decoding the Analogy
Sport Force ExchangeParticle 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!
9
Electric vs. Color Forces
  • 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.,
  • 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.
  • Trying to isolate a quark is as fruitless as
    trying to cut a string until it only has one end!

CONFINEMENT
10
What about this Quark 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.

11
Phase Diagrams
Nuclear Matter
Water
12
Making Plasma in the Lab
  • 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!

13
RHIC
  • RHIC Relativistic Heavy Ion Collider
  • Located at Brookhaven National Laboratory

14
RHIC 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)

6
5
1
3
4
1
2
15
RHICs Experiments
16
RHIC Video
17
How is RHIC Different?
  • Its dedicated to High Energy Heavy Ion Physics
  • Heavy ions will run 20-30 weeks/year
  • Its a collider
  • Detector systematics independent of ECM
  • (No thick targets!)
  • Its high energy
  • Access to non-perturbative phenomena
  • Jets (very violent calculable processes in the
    mix)
  • Non-linear dE/dx
  • Its detectors are comprehensive
  • All final state species measured with a suite of
    detectors that nonetheless have significant
    overlap for comparisons

18
RHIC 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 measurementsUse probes that are
  • Auto-generated
  • Sensitive to all time/length scales

19
RHIC 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
  • Youre doing physics at RHIC!

20
Natures providence
  • How can we hope to study such a complex system?

g, ee-, mm-
p, K, h, r, w, p, n, f, L, D, X, W, D, d, J/Y,
PARTICLES!
21
Deducing Temperature from Particles
  • 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

22
Magnetic Spectrometers
  • Cool Experiment
  • Hold a magnet near the screen of a BW TV.
  • The image distorts because the magnet bends the
    electrons before they hit the screen.
  • Why?

1 meter of 1 Tesla field deflects p 1 GeV/c by
17O
23
Particle Identification by TOF
  • The most direct way
  • Measure b by distance/time
  • Typically done via scintillators read-out with
    photomultiplier tubes
  • Time resolutions 100 ps

p
e
K
p
  • Exercise Show
  • Performance
  • dt 100 ps on 5 m flight path
  • P/K separation to 2 GeV/c
  • K/p separation to at least 4 GeV/c

24
Particle Identification by dE/dx
  • Elementary calculation of energy loss
  • Charged particles traversing material give
    impulse to atomic electrons
  • dE/dx
  • The 1/ b2 survives integration over impact
    parameters
  • Measure average energy loss to find b
  • Used in all four experiments

25
Measuring 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

26
Measuring Shapes
  • 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

27
Run-2000
  • First collisions15-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

28
Jet Quenching
  • At RHIC energies, some of the processes are
    calculable from first principles
  • Hard scattering
  • Jets
  • Violent collisions between quarks and gluons.
  • Excess yield at high momentum.
  • One effect of Plasma is the quenching of these
    jets.
  • They lose their energy while crossing the plasma.
  • They cool down to the soup temperature.

29
Jet Quenching Observed
  • Stony Brook Postdoc Federica Messer, presented
    PHENIX spectra of charged particles.
  • (should be dominated by pions).
  • BNL scientist (formed SB student) Gabor David
    presented measurements of neutral, IDENTIFIED
    pions.

30
Identified Particle Spectra
  • Stony Brook Postdoc Julia Velkovska presented
    identified charged particle spectra at high
    momentum
  • The proton production EXCEEDS the pion production
    at high momentum
  • NOONE PREDICTED THAT!
  • This causes the divergence between all-charged
    and neutral pions.

31
Where are the Jets?
Expectation
  • Charged particle production falls below the
    expectations by about a factor of two despite the
    proton contamination.
  • Neutral pion production is a factor of 10 below
    predictions.

32
Another Surprise!
  • RoutltRside!!!!!
  • Normal theory cannot account for this
  • Imaginary times of emission!!

33
Possible 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

Plasma
34
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.

35
Next Steps
  • Simple Language
  • After the icecubes collide and melt, fragments
    leave which are frozen by the time they reach us,
    masking the true nature of the early state.
  • Lesson Dont look at the fragments of frozen
    water which leave the collision, take a picture
    using light while the system is melted!
  • Sophisticated Language
  • Since hadrons are made of quarks, they reform and
    thereby lose information from the early stage.
  • Photons and leptons leave the plasma directly and
    give detailed information from the center of the
    collision!
  • Photons and leptons are rare and require more
    RHIC running.

36
Summary
  • 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
  • Its not your Fathers 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.
  • Well find the new world instead.

37
Electron Identification
  • Problem Theyre rare
  • Solution Multiple methods
  • Cerenkov
  • E(Calorimeter)/p(tracking) matching

38
Why electrons?
  • One reason sensitivity to heavy flavor production
  • Other reasons vector mesons, virtual photons ?
    ee-

39
p0 Reconstruction
  • A good example of a combinatoric background
  • Reconstruction is not done particle-by-particle
  • Recall p0 ? gg and there are 200 p0 s per unit
    rapidity
  • So p0 1 ? g1A g 1B p0 2 ? g2A g
    2B p0 3 ? g3A g 3B p0 N ? gNA g
    NB
  • .Unfortunately, nature doesnt use subscripts on
    photons
  • N correct combinations (g1A g 1B), (g2A g 2B),
    (gNA g NB),
  • N(N-1)/2 N incorrect combinations (g1A g 2A),
    (g1A g 2B),
  • Incorrect combinations N2 (!)
  • Solution Restrict N by pT cuts
    use high granularity, high resolution detector

40
BRAHMS
  • An 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

41
PHOBOS
  • 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)

42
PHOBOS 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
  • h lt 5.3

43
PHOBOS Results
  • First results on dNch/dh
  • 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.
44
STAR
  • An experiment with a challenge
  • Track 2000 charged particles in h lt 1

45
STAR Challenge
46
STAR Event
Data Taken June 25, 2000. Pictures from Level 3
online display.
47
STAR Reality
48
PHENIX
GlobalMVD/BB/ZDC
  • An experiment with something for everybody
  • A complex apparatus to measure
  • Hadrons
  • Muons
  • Electrons
  • Photons
  • Executive summary
  • High resolution
  • High granularity

Muon Arms Coverage (NS) -1.2lt y lt2.3 -p lt
f lt p DM(J/y )105MeV DM(g) 180MeV 3
station CSC 5 layer MuID (10X0) p(m)gt3GeV/c
West Arm
East Arm
South muon Arm
North muon Arm
Central Arms Coverage (EW) -0.35lt y lt 0.35
30o ltf lt 120o DM(J/y ) 20MeV DM(g) 160MeV
49
PHENIX Design
50
PHENIX Reality
January, 1999
51
PHENIX Results
  • (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)

52
Summary
  • 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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