The Little Big Bang

1
The Little Big Bang

• Profs. Vicki Greene, Charles F. Maguire, and
  Julia Velkovska
• Physics 300 October 10, 2006

2
Relativistic Heavy Ion Physics

• Relativistic kinetic energy is close to (or
  greater than) the rest mass energy Emc2.
• Heavy any nucleus in practice from silicon to
  gold.
• Ion must remove electrons from atom in order to
  accelerate electromagnetically.

3
The Structure of the Atom
4
The Strong Force One of four fundamental forces

• Gravity
• Electricity
• The strong nuclear force between the quarks
  increases as the separation increases this is
  very different from gravitational or electric
  forces which get weaker very fast as you get away
  from the mass or charge

5
Quark-Gluon Plasma

• If quark-gluon plasma is formed in a RHIC
  collision, it will last less than
  0.00000000000000000000001 seconds. (10-23 s)

6
A Familiar Phase Transition
7
Evolution of the Universe
8
A Relativistic Heavy Ion Collision
9
RHIC - The Relativistic Heavy Ion Collider
10
Relativistic Heavy Ion Collider

• RHIC's two concentric rings are made up of 1,740
  superconducting magnets.
• RHIC is powered by over 1,600 miles of
  superconducting niobium titanium wire, wrapped
  around the RHIC magnets.

11
Interesting RHIC Facts

• In 20 years of running, RHIC will use less than
  one gram of gold (which costs about 30 today)
• RHIC uses enough helium to fill all the balloons
  in the Macy's Thanksgiving Day Parades for the
  next 100 years.
• To get the helium chilled down, RHIC's
  refrigerators draw 15 megawatts of electrical
  power. (One megawatt is enough to power 1,000
  homes.)
• RHIC's two large experiments, STAR and PHENIX,
  are bigger than houses. PHENIX weighs 3,000 tons
  and STAR weights 1,200 tons.
• RHIC costs about 99 million per year to operate

12
The PHENIX Detector
13
The PHENIX Detector
14
PHENIX Central Arms
East Carriage
Ring Imaging Cerenkov Drift Chamber
Beam-Beam Counter
Central Magnet
West Carriage
15
Pad Chambers from Vanderbilt
16
AuAu Collision at Center-of-Mass Energy of 200A
GeV
17
A collision between two gold nuclei in the PHENIX
experiment(200 GeV per nucleon)
18
Temperature

• The temperature inside a RHIC collision can
  exceed 1,000,000,000,000 degrees above absolute
  zero (thats one trillion degrees Kelvin)
• This is ten thousand times the temperature at the
  center of our sun.

19
How to pick the most head-on collisions
20
How to tell if we have a plasma

• Hard scatterings in nucleon collisions produce
  jets of particles.
• In the presence of a quark-gluon plasma, the jets
  lose much of their energy.
• Jet Quenching

Once quenched, the jets could not re-appear since
this would violate the 2nd Law of Thermodynamics
21
Particle Identification using Time Of Flight

• Time of Flight array
• lt120ps resolution
• Tracking system used for momentum reconstruction
• Resulting spectrum shows
• Both charge signs e/p/K/p
• Good signal/background!!

22
Have we done it?
23
RAA vs. RdA for Identified p0
Initial State Effects Only
dAu
Initial Final State Effects
AuAu
d-Au results rule out initial state effects as
the explanation for Jet Suppression at high pt
24
F?KK- RAA for Au-Au 200 GeV/c
D. Pal (VU)
F RAA looks like the p rather than the proton,
consistent with recombination models
25
Flow A collective effect

• Elliptic flow v2 2nd Fourier coefficient of
  momentum anisotropy

dn/d? 1 2 v2(pT) cos (2 ?)
... Initial spatial anisotropy is converted into
momentum anisotropy. Efficiency of the
conversion depends on the properties of the medium
26
Why does large flow imply early thermalization?

• Look at the converse for a free-streaming
  system, spatial anisotropy and thus v2 do not
  develop

From detailed hydrodynamics ?therm 0.6 -1.0
fm/c ?15-25 GeV/fm3 cold matter 0.16 GeV/fm3
Teany et al, Huovinen et al
27
Put the results together
The matter is strongly coupled
The matter is dense
We look forward to working with the theory
community to extract the properties of the matter

• gt 15 GeV/fm3
• dNg/dy gt 1100

Can we determine the properties of the matter?
Tave 300 - 400 MeV (?)
Vs ? e(dielec) ?
PHENIX preliminary
The matter modifies jets
The matter may melt but regenerate J/ys
The matter is hot
28
Summary Probing partonic state of dense matter

• RHIC has produced a strongly interacting,
  partonic state of dense matter
• We now have started probing the properties of the
  matter
• The energy loss mechanism and initial parton
  density from jet suppression and flow data of
  light and heavy quarks
• e gt15 GeV/fm3 and dNg/dy gt 1100
• the initial state temperature from thermal
  radiation
• T0ave 300-400 MeV?
• These high densities and temperatures are
  unprecedented
• We look forward to working with new graduate
  students to relate the wealth of experimental
  observables to the properties of matter.

29
(No Transcript)
30
Probing Partonic State of Matter
The matter is strongly coupled
The matter is dense
We look forward to working with the theory
community to extract the properties of the matter
PHENIX preliminary
The matter modifies jets
The matter may melt but regenerate J/ys
The matter is hot
31
Does This Mean We Have found the Quark-Gluon
Plasma?

• Almost certainly, and at least we have definitely
  found something extremely interesting.
• Theorists may find another explanation for these
  results, there may be another state of matter but
  this seems highly unlikely at this juncture
• We need to make more measurements in order to
  know what we have. Good scientists are careful
  people.
• Watch for another announcement in a few weeks
• These are exciting times for nuclear physics!