What are elementary particles,
and why should we care?
Dhiman Chakraborty
(dhiman@nicadd.niu.edu)
QuarkNet Masterclass, NIU, 14 March, 2012
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
2
The fundamental questions
• What is the world made of?
• What holds it together?
• How did it all start?
• What does the future hold?
• What/who else is out there?
“What is it that breathes fire into the equations and makes a
universe for them to describe? Why does the universe go
to all the bother of existing?”
– Stephen Hawking
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
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Unsolved mysteries
Driven by new puzzles in the understanding of our physical
world, particle physicists are finding paths to new wonders
and startling discoveries. Experiments may even find
hidden extra dimensions, mini black holes, and/or
evidence of string theory.
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
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Unsolved mysteries
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
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Unsolved mysteries
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
6
Unsolved mysteries
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
7
Unsolved mysteries
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NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
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The small
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The large
Graphics courtesy: NASA
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Elementary particles & cosmology
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Exploring the Universe with Hubble
Ultra-Deep Field reveals galaxies
forming and evolving
Photo courtesy: NASA
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The extremes are connected
• We want to explain the structure and phenomena at the largest scales
(cosmology), in terms of the smallest (particle physics).
• Particle physicists, in turn, are getting their cues from cosmological
observations.
• The two are inextricably coupled. Fortunately, they are also easier to
model precisely than anything in between. Systems in biology,
economics, geology etc. are far more complex.
• Particle astrophysics is a rapidly growing field.
• 95% of what constitutes the Universe is yet unknown/ unobserved.
Some of it must be explained by particle physics.
• A revolution of unparalleled proportions is around the corner.
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
12
Composition of the Universe
Graphics courtesy: NASA
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Ways to study structures
•
Cosmology: Look at the object object at all possible wavelengths
•
Particle physics: Shoot all possible probes at the object
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
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To probe small distances, we need high
energies: E = 2/ , where is the
wavelength of probe
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
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Matter and interactions
“Matter”: made of Fermions.
– Spin-(2n+1)/2 particles that do not share a quantum state.
– Consequently, their production, annihilation, or decay must
be associated with either another fermion or an “antifermion”. This results in the conservation of number of
matter particles.
“Interactions”: mediated by Bosons.
– Spin-n particles that gladly share a quantum state.
– Can be radiated, absorbed, or decayed singly. Thus, the
number of bosons is not conserved.
– Bosons can interact among themselves.
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
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The four forces (carried by bosons)
•Affects everything,
•Infinite range,
•No neutralization
•Dominant at
planetary-to-cosmic
scales
•No quantum
description yet.
•Affects all fermions,
•Very short (subnuclear) range,
•Not a binding force,
•Only interaction to
cause transmutation of
matter.
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
•Affects only
electrically charged
bodies,
•Infinite range,
•Bound states are
often neutral
•Prominent at
atomic-to-stellar
scales
•Affects only “color”ed objects (quarks &
gluons),
•Very short (nuclear)
range,
•Strong neutralization
•Dominant at nuclear
scales 18
The matter particles (fermions)
a
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Elementary particles & cosmology
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Beyond SM: Grand Unification
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Unification of forces
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Diagram courtesy: H. Murayama
Elementary particles & cosmology
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- Dhiman Chakraborty
Unification theories
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Open questions
• What makes fundamental particles massive?
• Why do fermions come in multiple “flavor”s? Could it be
related to their mass?
• What can we learn from the neutrinos?
• Are there undiscovered principles of nature? New
symmetries? New physical laws? “Extra” dimensions? Do
all forces unify at high energies?
• What happened to all the antimatter?
• How can we explain the “Dark Energy”?
• What constitutes the “Dark Matter”?
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
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The many connections
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
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A timeline of HEP Colliders
The LHC is almost certain
to make revolutionary
discoveries within first 2-3
years of full-scale
operation.
The ILC/NLC will help us
make high- precision
measure-ments pin down
the details of any new
TeV-scale physics.
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
25
Fermilab
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Collider Detectors
DØ
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CDF
Elementary particles & cosmology
- Dhiman Chakraborty
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A top-antitop event
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Elementary particles & cosmology
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A top-antitop event
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NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
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The Large Hadron Collider (LHC) at CERN
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LHC parameters
Circumference
26.7 km (16.56 mi)
Collision Energy
7+7 TeV
Injection energy
0.45 TeV
Crossing angle
300 μrad
Particles per bunch
1011
Number of bunches
2808
Dipole field
8.33 Tesla
Number of dipole magnets
1232
Number of quadrupole magnets
about 600
Number of corrector magnets
about 7000
Luminosity
1034 cm-2s-1
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Elementary particles & cosmology
- Dhiman Chakraborty
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The ATLAS detector at LHC
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Elementary particles & cosmology
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Outlook
• A large number of particle physics, astrophysics, and
cosmology projects – both theoretical and experimental –
are underway. They complement each other toward a
common goal – to solve the most fundamental mysteries
of nature.
• It is a truly INTERNATIONAL effort.
• We are living through a revolution in our understanding of
the Universe on both the smallest and the largest scales.
• The next decade or two will usher us into a new era of
observation and comprehension.
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
33
THANK YOU!
Feel free to contact the speaker
for more information
dhiman@nicadd.niu.edu
QuarkNet Masterclass
NIU, 14 March 2012
Elementary particles & cosmology
- Dhiman Chakraborty
34