Beauty in the Universe

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Beauty in the Universe
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Innermost Space

• High Energy Particle Physics is a study of the
  smallest pieces of matter.
• It investigates the deepest and most fundamental
  aspects of nature.
• It investigates (among other things) the nature
  of the universe immediately after the Big Bang.
• It also explores physics at temperatures not
  common for the past 15 billion years (or so).

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Periodic Table
Helium
Neon
All atoms are made of protons, neutrons and
electrons
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t
u
d
b
While quarks have similar electric charge, they
have vastly different masses (but zero size!)
c
s
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Why three dimensions?
What gives particles their mass?
Mysteries of the Quantum Universe
Are there new forces and symmetries that we dont
yet know?
Are the forces and particles of which we do know
just different faces of a deeper, unifying
principle?
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ae2/hc
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Fermi National Accelerator Laboratory(a.k.a.
Fermilab)

• Begun in 1968
• First beam 1972 (200, then 400 GeV)
• Upgrade 1983 (900 GeV)
• Upgrade 2001 (980 GeV)

Jargon alert 1 Giga Electron Volt (GeV) is
100,000 times more energy than the particle beam
in your TV. If you made a beam the hard way, it
would take 1,000,000,000 batteries
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• ? The Main Injector upgrade was completed in
  1999.
• ? The new accelerator increases the number of
• possible collisions per
  second by 10-20.
• ? DØ and CDF have undertaken massive
• upgrades
  to utilize the increased
• 
  collision rate.
• ? Run II began March 2001

Expected Number of Events
Huge statistics for precision physics at low
mass scales
1000
Formerly rare processes become high
statistics processes
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Increased reach for discovery physics at highest
masses
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Run II
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Run I
Increasing Violence of Collision
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How Do You Detect Collisions?

• Use one of two large multi-purpose particle
  detectors at Fermilab (DØ and CDF).
• Theyre designed to record collisions of protons
  colliding with antiprotons at nearly the speed of
  light.
• Theyre basically cameras.
• They let us look back in
  time.

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Typical Detector (Now)

• Weighs 5,000 tons
• Can inspect 10,000,000 collisions/second
• Will record 50 collisions/second
• Records approximately 10,000,000 bytes/second
• Will record 1015 (1,000,000,000,000,000) bytes
  in the next run (1 PetaByte).

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30
50
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Remarkable Photos
In this collision, a top and anti-top quark were
created, helping establish their existence
This collision is the most violent ever recorded
(and fully understood). It required
that particles hit within 10-19 m or 1/10,000
the size of a proton
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Modern Cosmology

• Approximately 15 billion years ago, all of the
  matter in the universe was concentrated at a
  single point
• A cataclysmic explosion (of biblical proportions
  perhaps?) called the Big Bang caused the matter
  to fly apart.

• In the intervening years, the universe has been
  expanding, cooling as it goes.

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• Now
• (13.7 billion years)

Stars form (1 billion years)
Atoms form (380,000 years)
Nuclei form (180 seconds)
Nucleons form (10-10 seconds)
Quarks differentiate (10-34 seconds?)
??? (Before that)
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Why three dimensions?
What gives particles their mass?
Mysteries of the Quantum Universe
Are there new forces and symmetries that we dont
yet know?
Back to the Mysteries
Are the forces and particles of which we do know
just different faces of a deeper, unifying
principle?
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In 1964, Peter Higgs postulated a physics
mechanism which gives all particles their
mass. This mechanism is a field which permeates
the universe. If this postulate is correct,
then one of the signatures is a particle
(called the Higgs Particle). Fermilabs Leon
Lederman co-authored a book on the subject
called The God Particle.
Undiscovered!
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Higgs An Analogy
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Hunting for Higgs

• For technical reasons, we look for Higgs bosons
  in association with a W or Z boson.

In the region where the Higgs boson is expected,
we expect it to decay nearly-exclusively into
b-quarks
b jet
electron
neutrino (MET)
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Symmetries
Translational
Rotational
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More Complex Symmetries
In a uniform gravitational field, a balls motion
is independent of vertical translation. The
origin from where potential energy is chosen is
irrelevant.
The equations of motion are symmetric under
vertical or horizontal translations.
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Complex Familiar Symmetries
y
r
r2
r1
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Complex Familiar Symmetries
r
Translations x ? x Dx y ? y Dy
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Complex Familiar Symmetries
y
r
Reflections x ? -x y ? -y
r2
r1
y
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Complex Familiar Symmetries
r
Rotations f ? -f
r2
r1
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Complex Familiar Symmetries
r
Charge Flip q ? - q
r2
r1
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Complex Familiar Symmetries
r
Bottom Line Electromagnetic force exhibits a
symmetry under Translation Rotation
Reflection Charge Congugation (and many
others)
r2
r1
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Fermions and Bosons
Fermions matter particles ½ integer
spin Bosons force particles integer
spin
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Unfamiliar Symmetries
One possible symmetry that is not yet observed is
the interchange of fermions (spin ½ particles)
and bosons (integral spin particles)
Known equation
Equation Fermions Bosons
Interchanged equation (pink ? green)
Equation Fermions Bosons
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Unfamiliar Symmetries
One possible symmetry that is not yet observed is
the interchange of fermions (spin ½ particles)
and bosons (integral spin particles)
Fermions Bosons
Known equation
Equation Fermions Bosons
Fermions Bosons
This New Symmetry is called SuperSymmetry (SUSY)
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SUSY Consequence

• SUSY quark squark
• SUSY lepton slepton
• SUSY boson bosino

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The Golden Tri-lepton SuperSymmetry Signature

• This is the easiest to observe signature for
  SUSY.
• No excess yet observed.

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The Conundrum of Gravity

• Why is gravity so much weaker (10-35) the
  other forces?
• Completely unknown
• One possibility is that gravity can access more
  dimensions than the other forces

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The Dimensionality of Space Affects a Forces
Strength

• Gauss Law

2D
3D
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Are More Dimensions Tenable?

• Newtons Law of Gravity
• Clearly indicates a 3D space structure.
• Or does it?

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Nature of Higher Dimensions

• What if the additional dimensions had a different
  shape?
• What if the additional dimensions were small?

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Access to Additional Dimensions

• What if gravity alone had access to the
  additional dimensions?

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Access to Additional Dimensions

• What if gravity alone had access to the
  additional dimensions?

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A Model with n Dimensions.

• Gravity communicating with these extra dimensions
  could produce an unexpectedly large number of
  electron or photon pairs.
• Thus, analysis of the production rate of
  electrons and photon provides sensitivity to
  these extra dimensions.
• Large energies are required to produce such
  pairs.

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Once again there are interesting events! (way
out on the mass tail.)

• ee pair gg pair

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Data-Model Comparison
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Data-Model Comparison
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Summary

• Particle physics allows us to study some of the
  deepest mysteries of reality.
• We know a whole bunch of stuff.
• The things we dont know, were studying like
  mad.
• The mysteries mentioned here are unsolved. We
  need help.

Send students.
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