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
Decoding the Analogy
5
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
6
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.

7
Phase Diagrams
Nuclear Matter
Water
8
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!

9
RHIC

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

10
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
11
RHICs Experiments
12
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

13
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!

14
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!
15
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

16
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
17
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

18
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

19
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

20
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

21
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

22
How Do You Detect 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 dont they just shoot a laser through it
  and then theyd know if its plasma for sure!
• Visible light laserbad idea.
• Calibrated probe through QGPgood idea
• but not new. (Wang, Gyulassy, others)

23
The Calibrated Plasma Probe

• 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.

24
Particle Spectra Evolution
25
Raa

• We define the nuclear modification factor as
• By definition, processes that scale with Nbinary
  will produce RAA1.
• RAA is what we get divided by what we expect.
• RAA should be 1.0

26
Away-side Jets Missing!

• STAR Experiment reconstructs azimuthal
  correlations.
• Peak Around 0 are particles from same side jet.
• Peak at /- p is the away-side jet.
• In central collisions the away-side jet
  disappears!!!
• Medium is black to jets.

27
Quantifying the away-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

28
Jet Particle Composition

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

29
Other Bizarre Results

• Azimuthal asymmetries beyond the black almond
  scenario.
• The HBT interferometric technique for determining
  the lifetime of the particle source.
• The theoretical community simply cant explain
  the data.
• PSThis is the good news ?

30
Another Surprise!

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

31
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
32
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.

33
Summary

• 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!!

34
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.

35
Electron Identification

• Problem Theyre rare

• Solution Multiple methods
• Cerenkov
• E(Calorimeter)/p(tracking) matching

36
Why electrons?

• One reason sensitivity to heavy flavor production

• Other reasons vector mesons, virtual photons ?
  ee-

37
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

38
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

39
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)

40
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

41
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.
42
STAR

• An experiment with a challenge
• Track 2000 charged particles in h lt 1

43
STAR Challenge
44
STAR Event
Data Taken June 25, 2000. Pictures from Level 3
online display.
45
STAR Reality
46
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
47
PHENIX Design
48
PHENIX Reality
January, 1999
49
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)

50
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