Quarks, Leptons, Bosons, the LHC and all that.

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Quarks, Leptons, Bosons, the LHC and all that.

• Tony Liss
• OLLI Lecture
• September 23, 2008

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Some HE Physicist Principles

• We are reductionists (and proud of it!)
• Our worldview is that there are a small number of
  fundamental constituents, interacting via a small
  number of forces, that make up the Universe as we
  know it.
• This picture has worked extremely well for about
  2000 years.
• The modern version has been untangled using
  particle beams of ever increasing energy.

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The Standard Model
The matter around us is made up of quarks and
leptons
Electromagnetic Strong Weak Gravity
And held together by four forces, each with a
force carrier
????
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The Standard Model
The matter around us is made up of quarks and
leptons
Helium Atom
The marriage of quantum mechanics and special
relativity required that antiparticles exist.
particleadventure.org
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Why High Energy?

• From quantum theory we know
• l 1/p Wavelength is inversely proportional
  to momentum
• If you want to see small things you need short
  wavelengths (thats why electron microscopes were
  invented) and short wavelengths means high
  momentum (and energy).
• From relativity we know
• EMc2
• If you want to create a heavy particle (large M)
  you need a lot of energy.

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Unification of the Forces
Higgs Bosons born here?
Electric Magnetic Weak Strong
Electromagnetic
Electroweak
?
Very (very)High Energy
Low Energy
High Energy
Part way to Einsteins dream!
Theory works up to here Thats the region we
want to probe with the LHC.
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CERN- LHC
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Fermilab
Protons anti-protons collide at 2 TeV (2 x 1012
electron volts)
The worlds highest energy particle accelerator!!
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Fermilab Makes Top Quarks
The heaviest known elementary particle. Discovered
in 1994!
Why is it so heavy??
We dont know
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The Large Hadron Collider
2.7mi
The worlds largest, highest energy, accelerator
300 feet underground outside of Geneva,
Switzerland. The LHC collides intense beams of
protons 40 million times per second at 14 TeV
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France
Grapes
Cows
Switzerland
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Inside the Tunnel
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ATLAS Detector at CERN
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ATLAS is VERY BIG
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ATLAS
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Who Is ATLAS?

• ATLAS is one of four large experiments at LHC
• The ATLAS collaboration consists of
• 2500 physicists including
• 700 graduate students from
• 169 different institutions in
• 37 different countries

ATLAS is a United Nations of particle physics.
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ATLAS, The Movie

• http//atlas.ch

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Some of What LHC Can Study

• Higgs Boson
• Understanding M
• Supersymmetry
• Dark Matter?
• Extra Dimensions
• Quantum Gravity/String Theory
• Dark Energy
• We dont even know how to look for this
• Heavy gauge bosons
• New forces?
• Precision top quark studies
• New physics?
• Diboson production
• From the Higgs?
• Quark and lepton substructure
• Are fundamental particles fundamental?
• etc. etc.

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Lets Pick Two

• Higgs Boson
• Supersymmetry

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What is The Higgs?

• Named after Peter Higgs
• It gives mass to the fundamental particles (if,
  in fact, it exists)

Without the Higgs (or something) the theory
requires that all these fundamental particles
have M0. But we know thats not the case.
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FMa
The idea is that the Higgs field exists
throughout all space. As particles try to move
through this field they interact with it and are
slowed down. Heavier particles are those that
interact more strongly
MF/a
In quantum mechanics there is a particle
associated with a field (quantum of the field).
The photon is the quantum of the electromagnetic
field. The Higgs boson is the quantum of the
Higgs Field.
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Finding the Higgs

• The Higgs couples to mass
• It decays to the heaviest particles available

Easy, but rare
Hard, but copious
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This is a simulation of the production and decay
of a Higgs to two Z bosons. The Z bosons
themselves decay, one to a pair of electrons and
the other to a pair of muons.
mm-
ee-
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Supersymmetry (SUSY)
Make SUSY particles at an accelerator

• Every quark, lepton and force carrier has a SUSY
  partner (sparticles).
• Sparticles would be made copiously in the early
  (HOT) universe.
• They all decay away quickly, except for the
  lightest one (neutralino), which has nowhere to
  go.

www.science.doe.gov/hep/EME2004/03-what-is.html
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Why is this an attractive idea?
SUSY Unified Forces

• Einsteins dream of a Unified Field Theory, now
  needs SUSY

• SUSY helps with unifying the forces.
• SUSY is a necessary ingredient of quantum gravity
  theories.
• We know that the universe is filled with dark
  matter.
• Dark matter is not made of quarks and leptons
  the Standard Model has no dark matter candidates.
• Dark matter interacts very weakly with normal
  matter (or else we would have found it already).
• The lightest SUSY particle is a perfect
  candidate.

No SUSY
SUSY
EM
Strength of force
Strength of force
weak
strong
Energy
Energy
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Dark Matter
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Dark Matters Everywhere
In Galaxies
And clusters of galaxies
Speed of stuff out here
Motion of a galaxy out here
Doesnt match luminous matter in here!
Doesnt agree with luminous matter in here
The Hydra Galactic Cluster
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Physics 211

• Momentum is conserved
• Before the protons collide they have equal and
  opposite momentum The total momentum is zero.
• Therefore The total momentum of all the stuff
  created in the collision must also be zero.

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A Simulated SUSY Event
Missing momentum carried away by invisible
particle
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About Those Black Holes

• Creating microscopic black holes at the LHC would
  be
• A MAJOR BREAKTHROUGH IN SCIENCE!
• INCREDIBLY EXCITING
• NOBEL PRIZE STUFF
• NOT AT ALL DANGEROUS
• REALLY

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About Black Holes

• The microscopic black holes that might be created
  at LHC are so small they evaporate instantly
  according to Steven Hawking.
• But what if Hawkings wrong?
• Cosmic rays reach much higher energies than the
  LHC and have been having collisions for billions
  of years any black holes created have not done
  much damage.

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About Black Holes

• Black holes dont suck everything in.
• Only stuff inside the Schwarzschild radius.
• If the sun suddenly became a black hole, the
  Earths orbit would not change (but wed get very
  cold). The Schwarzschild radius of the sun is 3
  kilometers.
• The Schwarzschild radius of a 1 TeV black hole is
  about 10-18 m thats about 1/1000th of the size
  of a proton.
• Theres nothing around such a black hole for it
  to suck in!

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Final Words

• After 25 years of planning and 15 years of design
  and construction, the LHC is finally about to
  turn on.
• This is the chance of a lifetime.
• Our understanding of the way the Universe works
  is about to be revolutionized.
• We just dont know exactly how