Introduction to Particle Physics Professor Lynn Cominsky

1
Introduction to Particle PhysicsProfessor Lynn
Cominsky
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Big Bang Timeline
Planck Era
We are here
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Epos Chronicles Planck Time
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Big Bang Revisited

• Extrapolating back in time, we conclude that the
  Universe must have begun as a singularity a
  place where the laws of physics and even space
  and time break down
• However, our theories of space and time break
  down before the singularity at a time known as
  the Planck time
• The Planck scale refers to the limits of mass,
  length, temperature and time that are what can be
  measured using the Uncertainty principle

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Planck scale activity

• The goal of this activity is to calculate the
  Planck mass, length, time and energy.
• Remember

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Unified Forces

• The 4 forces are all unified (and therefore
  symmetric) at the Planck scale energy

The phase transition which splits off the strong
nuclear force is what triggers inflation
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The Vacuum Era

• Planck era
• 10-43 s after the Big Bang
• Temperature (kT) 1019 GeV
• Beginning of time time and space are no longer
  separate entities
• Emergence of spacetime
• Inflationary era
• lt 10-10 s, kT 100 GeV
• Vacuum energy dominates, driving Universe to
  enormous size
• Fluctuations may be formed that eventually turn
  into large scale structure

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Epos Chronicles Inflation
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Radiation Era

• Creation of Light
• gt10-36 s after Big Bang - kT 100 GeV
• Vacuum energy turns into light, and equal amounts
  of matter vs. anti-matter
• Gravitational attraction begins
• Background radiation energy originates
• Dark matter may be formed

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Radiation Era

• Creation of Baryonic Matter (Baryogenesis)
• gt10-36 s after Big Bang
• Temperature (kT) 100 GeV
• A small excess of quarks and electrons is formed
  (compared to anti-quarks and anti-electrons)
• Electroweak (Unification) Era
• 10-10 s after the Big Bang, kT 100 GeV
• Forces and matter become distinguishable forms of
  energy with different behavior
• Masses of particles are defined
• May include baryogenesis

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Radiation Era

• Strong Era
• 10-4 s after the Big Bang - kT 0.2 Gev
• Quark soup turns into neutrons and protons
• Dark matter may be formed
• Electroweak Decoupling
• 1 s after the Big Bang - kT 1 MeV
• Neutrons and protons no longer interchange
  (leaving 7 p for each n)
• Cosmic neutrino background is formed
• Electrons and positrons annihilate, adding energy
  to the cosmic background radiation, and an excess
  of electrons

12
Radiation Era

• Creation of light element nuclei
• 100 s after the Big Bang kT 0.1 MeV
• Nucleosynthesis begins as neutrons and protons
  are cool enough to stick together to form Helium,
  some Deuterium, and a little bit of Lithium
• Precise elemental abundances are established
• Radiation Decoupling
• 1 month after the Big Bang kT 500 eV
• Interactions between matter and radiation are
  fewer and farther between
• Blackbody background spectrum is determined

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Big Bang Timeline
Radiation Era
We are here
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Atomic Particles

• Atoms are made of protons, neutrons and electrons
• 99.999999999999
• of the atom is empty space
• Electrons have locations described by
  probability functions
• Nuclei have protons and neutrons

mp 1836 me
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Leptons

• An electron is the most common example of a
  lepton particles which appear pointlike
• Neutrinos are also leptons
• There are 3 generations of leptons, each has a
  massive particle and an associated neutrino
• Each lepton also has an anti-lepton (for example
  the electron and positron)
• Heavier leptons decay into lighter leptons plus
  neutrinos (but lepton number must be conserved in
  these decays)
• Lepton number 1 for leptons, -1 for
  anti-leptons, and 0 for non-leptons

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Types of Leptons
Lepton Charge Mass (GeV/c2)
Electron neutrino 0 0
Electron -1 0.000511
Muon neutrino 0 0
Muon -1 0.106
Tau neutrino 0 0
Tau -1 175
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Quarks

• Experiments have shown that protons and neutrons
  are made of smaller particles
• We call them quarks, a phrase coined by Murray
  Gellman after James Joyces three quarks for
  Muster Mark
• Every quark has an anti-quark

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Atomic sizes

• Atoms are about 10-10 m
• Nuclei are about 10-14 m
• Protons are about 10-15 m
• The size of electrons and quarks has not been
  measured, but they are at least 1000 times
  smaller than a proton

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Types of Quarks
Flavor Charge Mass (GeV/c2)
Up 2/3 0.003
Down -1/3 0.006
Charm 2/3 1.3
Strange -1/3 0.1
Top 2/3 175
Bottom -1/3 4.3

• Quarks come in three generations
• All normal matter is made of the lightest 2
  quarks

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Quarks

• Physics Chanteuse
• Up, down, charm, strange, top and bottom
• The world is made up of quarks and leptons

Quark Sing-A-long
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Combining Quarks

• Particles made of quarks are called hadrons
• 3 quarks can combine to make a baryon (examples
  are protons and neutrons)
• A quark and an anti-quark can combine to make a
  meson (examples are muons, pions and kaons)

• Fractional quark electromagnetic charges add to
  integers in all hadrons

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Baryon numbers

• Baryon numbers are only approximately conserved
  in particle interactions
• The baryon number is defined on the basis of
  quarks and anti-quarks
• NB 1/3 (Q Q)
• What is the baryon number of a proton?
• What is the baryon number of a pi meson?

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Rules of the game activity

• Analyze the observed particle events to see what
  the combination rules are

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Color charges

• Each quark has a color charge and each
  anti-quark has an anti-color charge
• Particles made of quarks are color neutral,
  either RBG or color anti-color

Quarks are continually changing their colors
they are not one color
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Gluon exchange

• Quarks exchange gluons within a nucleon

movie
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Atomic Forces

• Electrons are bound to nucleus by Coulomb
  (electromagnetic) force
• Protons in nucleus are held together by residual
  strong nuclear force
• Neutrons can beta-decay into protons by weak
  nuclear force, emitting an electron and an
  anti-neutrino

n p e n
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Fundamental Forces

• Gravity and the electromagnetic forces both have
  infinite range but gravity is 1036 times weaker
  at a given distance
• The strong and weak forces are both short range
  forces (lt10-14 m)
• The weak force is 10-8 times weaker than the
  strong force within a nucleus

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Force Carriers

• Each force has a particle which carries the force
  
• Photons carry the electromagnetic force between
  charged particles. Photons are not affected by
  the EM force.
• Gluons carry the strong force between color
  charged quarks but they are affected by the
  strong force.

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Force Carriers

• Separating two quarks creates more quarks as
  energy from the color-force field increases until
  it is enough to form 2 new quarks
• Weak force is carried by W and Z particles
  heavier quarks and leptons decay into lighter
  ones by changing flavor

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Force Summary
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End of Part 1

• Next you will hear from Helen Quinn, Professor at
  SLAC
• Prof. Quinn got her PhD at Stanford, but is
  originally from Australia
• She also worked at DESY (German accelerator) and
  at Harvard
• The Peccei-Quinn theory has been proposed to
  explain why strong interactions maintain CP
  symmetry when weak ones do not (more about CP
  symmetry later.)

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Tuesday AM

• Discussion what were the hardest concepts for
  you to understand yesterday?

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Particle Decays

• Nuclear decay nucleus splits into smaller
  constituents
• Particle decay fundamental particles decay
  (transform) into other (totally different)
  fundamental particles
• How does this happen?
• What are the rules?

Any difference in masses is carried away as
kinetic energy by new particles
s
u
c
W
d
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Weak Particle Decays

• Fundamental particle decays into another, less
  massive, fundamental particle plus a
  force-carrier particle
• This is always a W-boson for fundamental
  particles
• In this example, the charm quark decays into a W
  plus strange quark.
• The force-carrier particle then decays into other
  fundamental particles (in this example, W decays
  into up and down quarks)
• However, the mass of the W boson is 80.4 GeV/c2
  this is much more than a quark!

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Virtual particles

• So how does a charm quark decay into something
  that is heavier than itself?
• The answer lies in the Uncertainty principle
• The W-boson only lives for a very short time (3
  x 10-25 s)
• Its heavy mass limits the range of the weak force
  (It is equal to EM at 10-18 m.)
• Since it lives for such a short time, it is known
  as a virtual particle
• Initial energy and final energy (including
  kinetic energy of final particles) are still
  equal.
• Flavors can change, charges can change.

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Electromagnetic Decays

• Example p0 meson is made of a quark-anti-quark
  pair, which can annihilate, creating two photons
• Photons are the force-carriers for the EM force.
• Photons are massless, hence the range of the EM
  force is infinite
• Neither colors or charge change.

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Strong decays

• The hc particle is a charm-anticharm meson. It
  can undergo a strong decay into two gluons (which
  emerge as hadrons).
• Gluons are strong-force carrier particles, and
  they mediate decays involving color changes.
• Charge does not change, but color changes.

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Annihilations

• Two anti-particles annihilate, create
  force-carrier particles, which then decay into an
  entirely new pair of particles (or maybe two
  photons)

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Unifying Forces

• Weak and electromagnetic forces have been unified
  into the electroweak force
• They have equal strength at 10-18 m
• Weak force is so much weaker at larger distances
  because the W and Z particles are massive and the
  photon is massless
• Attempts to unify the strong force with the
  electroweak force are called Grand Unified
  Theories
• There is no accepted GUT at present

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Gravity

• Gravity may be carried by the graviton it has
  not yet been detected
• Gravity is not relevant on the sub-atomic scale
  because it is so weak
• Scientists are trying to find a Theory of
  Eveything which can connect General Relativity
  (the current theory of gravity) to the other 3
  forces
• There is no accepted Theory of Everything (TOE)
  at present

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Spin

• Spin is a purely quantum mechanical property
  which can be measured and which must be conserved
  in particle interactions
• Particles with half-integer spin are fermions
• Particles with integer spin are bosons

Graviton has spin 2
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Quantum numbers

• Electric charge (fractional for quarks, integer
  for everything else)
• Spin (half-integer or integer)
• Color charge (overall neutral in particles)
• Flavor (type of quark)
• Lepton family number (electron, muon or tau)
• Fermions obey the Pauli exclusion principle no
  2 fermions in the same atom can have identical
  quantum numbers
• Bosons do not obey the Pauli principle

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Standard Model

• 6 quarks (and 6 anti-quarks)
• 6 leptons (and 6 anti-leptons)
• 4 forces
• Force carriers (g, W, W-, Zo, 8 gluons, graviton)

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Some questions

• Do free quarks exist? Did they ever?
• Why do we observe matter and almost no antimatter
  if we believe there is a symmetry between the two
  in the universe?
• Why can't the Standard Model predict a particle's
  mass?
• Are quarks and leptons actually fundamental, or
  made up of even more fundamental particles?
• Why are there exactly three generations of quarks
  and leptons?
• How does gravity fit into all of this?

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Particle Accelerators

• The Standard Model of particle physics has been
  tested by many experiments performed in particle
  accelerators
• Accelerators come in two types hadron and
  lepton
• Heavier particles can be made by colliding
  lighter particles that have added kinetic energy
  (because Emc2)
• Detectors are used to record the shower of new
  particles that results from the collision of the
  particle/anti-particle beams

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Cloud Chamber Demo

• We have a diffusion cloud chamber that will show
  us some particle tracks

High Voltage
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Types of particles

• Alpha particles Helium nuclei
• Beta particles either electrons or positrons
• Gamma particles photons
• Cosmic rays mostly protons, but also nuclei of
  other elements.
• Which will we see in our Cloud Chamber?

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How it works

• a and b particles ionize molecules of the alcohol
  in the cloud chamber
• Vapor condenses on the ionized nuclei in the
  chamber
• The drops of condensation appear to make tracks
  when lit up
• X- and gamma-rays make energetic electrons, or
  e/e- pairs
• Can you predict which types of tracks are made by
  the various types of particles?

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Bubble chamber

• Same principle as cloud chamber, but uses
  super-heated gas rather than super-cooled liquid
• Anti-proton enters at bottom turns into 8
  pions, one of which decays into a muon and a
  neutrino

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How to make particle beams

• Electrons Heating a metal causes electrons to be
  ejected. A television, like a cathode ray tube,
  uses this mechanism.
• Protons They can easily be obtained by ionizing
  hydrogen.
• Antiparticles To get antiparticles, first have
  energetic particles hit a target. Then pairs of
  particles and antiparticles will be created via
  virtual photons or gluons. Magnetic fields can be
  used to separate them.
• Particles are accelerated by changes in EM fields
  that push them along.

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Types of accelerators

• Different types of collisions
• Fixed target Shoot a particle at a fixed target.
  
• Colliding beams Two beams of particles are made
  to cross each other. (Creates more energy since
  two beams of particles are accelerated.)
• Accelerators are shaped in one of two ways
• Linacs Linear accelerators, in which the
  particle starts at one end and comes out the
  other. (Example SLAC, which uses leptons.)
• Synchrotrons Accelerators built in a circle, in
  which the particle goes around and around and
  around (steered by magnetic fields). (Example
  Fermilab and CERN, which use hadrons.)

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FermiLab

• Tevatron collides protons and anti-protons at 2
  TeV

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FermiLab

• The top quark was discovered at Fermilab and 20
  years later, Fermilab observed single top quarks
  (not in pairs)
• Main goal is search for Higgs boson, new physics
  (CDF)
• Other experiments are looking for
• matter/anti-matter asymmetry in decays of Kaons
  and other mesons
• Neutrino oscillations from neutrinos made at
  Fermilab, traveling to Soudan mine (Minnesota,
  450 miles away) and other long-baseline neutrino
  experiments
• Many scientists collaborating on CMS at LHC
  (CERN)
• Dark matter searches (CDMS)
• Ongoing work on future experiments, such as a
  muon collider, more neutrino detectors

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A tour of the CDF detector

• Virtual reality movie made at Fermilab by Joe
  Boudreau

movie
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FermiLab

• Only 1 out of 1010 collisions produces a top
  quark
• Computer analyzes detector pattern to find
  mesons, a positron and evidence for a neutrino
• Physicists deduce that this pattern also requires
  a W and b quark which come from a top quark decay

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Find Mass of Top Quark

• Analyze the events that are seen in the D0
  detector
• For each jet or particle, find the x- and y-
  components of the momentum (using a protractor).
  The amplitude of the momentum for each is given
  on the plot
• What is the missing momentum? (x- and y-
  components)
• What is the amplitude?

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Figures for activity
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Now find the top quark mass

• Since all the momenta were expressed in units of
  GeV/c, you can add them all up
• This collision made a top and anti-top pair so
  the total of all the momentum amplitudes is the
  momentum of 2 tops
• How did your answer compare to the measured value
  of 173 GeV/c ?

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After the break.
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Field Theories

• 1865 James Maxwell unifies electricity and
  magnetism in the first field theory
• Fields were proposed to explain how forces are
  carried between particles
• Einsteins theory of General Relativity is
  another example of a field theory

electromagnetic wave
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Particles and Fields

• Fields carry energy through spacetime
• Fields are present everywhere, including the
  vacuum (which is the lowest energy state of all
  the fields)
• Fields can act like both waves and particles
• Wave-like fields are called forces
• Particle-like fields are called matter or photons
• Matter interacts with other matter through forces

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Quantum Electrodynamics

• Quantum mechanics describes the laws of motion of
  sub-atomic particles
• Interactions between sub-atomic particles are
  described by quantum field theories
• QED is the quantum field theory which describes
  electromagnetic interactions at the sub-atomic
  level
• Predictions from QED calculations are accurate to
  one part in a trillion

63
Quantum Electrodynamics

• The 1965 Nobel prize for QED was awarded to
  Richard Feynman, Julian Schwinger and Sin-Itiro
  Tomonaga
• Feynman diagrams are used to show the relation
  between particles and force carriers for all four
  forces

64
Electro-weak Unification

• 1979 Nobel Prize awarded to Steven Weinberg,
  Abdus Salam, and Sheldon Glashow for the
  development of a unified field theory of
  electroweak interactions
• They predicted the W and Z bosons (which were
  discovered in 1983, Nobel in 1984 to Carlo Rubbia
  and Simon van der Meer)

65
Electro-weak Unification

• Q If the electromagnetic and weak interactions
  are really two sides of the same coin, then why
  are the W and Z particles so massive (80 GeV)
  while the photon is massless?
• A In the early Universe, when the characteristic
  energy kT gt 80 GeV, the electromagnetic and weak
  forces were united. As the Universe cooled out of
  the electroweak era, spontaneous symmetry
  breaking occurred which split out the W and Z

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Symmetry Breaking

• Here is an example it is unclear which glass
  goes with which place setting until the first one
  is chosen

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Spontaneous Symmetry Breaking

• Balance a pencil on its tip it has an equal
  chance to fall over in each direction. But when
  it falls over, it chooses a specific direction,
  and breaks the initial symmetry
• Hydrogen and oxygen are symmetric molecules, yet
  when they combine to make water, the molecule has
  a characteristic angle of 105 degrees between the
  Hydrogen atoms.

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Symmetries

• Physical laws display mathematical symmetry
• Rotate a square through space by 90o - it will
  look exactly the same
• Rotate a circle by any angle it will also
  appear the same
• Because a circle has more choices of rotation
  angle, it is said to have a larger symmetry
• Physical laws can be invariant with respect to
  changes in location, time or other types of
  transformations (rotation, velocity, etc.)

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Symmetries

• Patterns in the properties of particles can be
  described by mathematical symmetries which act on
  internal spaces properties of the particles
  themselves, rather than its spacetime environment
• Protons and neutrons are regarded as two
  different directions in an abstract internal
  space although their charges are different,
  they have identical strong interactions
  (nucleons)
• This is another example of a broken symmetry
  which is thought to be unified at higher energies

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Transformation Laws

• Laws of physics are the same at any location in
  space this means that the universe is invariant
  under a spatial transformation
• What if you reflect points in space through a
  mirror parity transformation? (P) No!
• What if you turn every particle into its
  anti-particle charge conjugation (C)? No!
• But invariance is regained (almost) if you
  combine C and P CP violation occurs at about
  0.2 level (First proved with Kaons.)

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CP Violation

• CP means charge-parity, aka time-reversal
  symmetry the symmetry that results from
  interchanging a particle with its anti-particle
  and sending it through a 3D mirror
• CP violations were first observed in decays of
  K-mesons vs. anti-K-mesons the decays happened
  at different rates (1980 Nobel, James Cronin and
  Val Fitch)
• Studies of flavor changing interactions with K
  and B mesons should tell us more about CP physics

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CP Violation

• Kaons oscillate between two types short-lived
  (green) which decay into 2 pions and long-lived
  (red), which decay into 3 pions
• Both indirect and direct CP violation have now
  been observed
• The weak force is responsible for these
  violations

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CP Violation song

• Written by Logan Whitehurst (formerly of the Jr.
  Science club, then in the Velvet Teen, now
  deceased) for my Cosmology class many years ago
• http//www.juniorscienceclub.com/loganarchive/eart
  hisbig/2120sid_sheinberg_sings__cp_vi.mp3
• Sid Sheinberg sings! CP Violation Song

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Particle Accelerators-SLAC

• 2 mile long accelerator which can make up to 50
  GeV electrons and positrons
• Discovered the charm quark (also discovered at
  Brookhaven) and tau lepton ran an accelerator
  producing huge numbers of B mesons.
• Now doing photon science Linac Coherent Light
  Source

LCLS is using x-ray laser beams to probe inside
of atoms, removing one electron at a time
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SLAC B-factory

• Goal is to understand the imbalance between
  matter and anti-matter in the Universe
• 1 out of every billion matter particles must have
  survived annihilation
• Decay rates of Bs and anti-Bs should be different
• Explanation goes beyond the standard model

76
BaBar Experiment

• SLAC accelerator was used (until 2008) as an
  asymmetric B-meson factory, making B-mesons and
  anti-B-mesons out of 9 GeV electrons and 3.1 GeV
  positrons. CP violation is observed in some of
  these decays.
• Half of the 2008 Nobel Prize in Physics was
  awarded to Makoto Kobayashi and Toshihide Maskawa
  for their theory which simultaneously explained
  the source of matter/antimatter asymmetries in
  particle interactions and predicted the existence
  of the third generation of fundamental particles.
  The BABAR experiment at the SLAC National
  Accelerator Laboratory in the U.S., together with
  the Belle experiment at KEK in Japan, recently
  provided experimental confirmation of the theory,
  some thirty years after it was published, through
  precision measurements of matter/antimatter
  asymmetries. The other half of the Nobel prize
  went to Yoichiro Nambu for his theory of
  spontaneous symmetry breaking.

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Quantum Chromodynamics

• QCD is the quantum field theory which describes
  the interactions between quarks and gluons
• It is difficult to use QCD to make predictions
  because the gluons carry a color charge and
  interact with each other
• QCD is a non-linear theory which can only be
  calculated approximately - 10 accuracy for mass
  of proton calculations take months of
  supercomputer time

78
Quantum Chromodynamics

• 1969 Nobel to Murray Gell-Mann for quark
  classification scheme
• Internal symmetry in the pattern of quarks
  predicted the W- particle and its mass

79
Gauge Theories

• Gauge theories are quantum field theories that
  have local symmetries ? physical laws remain the
  same when particle properties are exchanged at
  different locations in spacetime
• Local internal symmetries actually require force
  carrier particles whose interactions create the
  forces
• QED is an Abelian gauge theory
• Electro-weak Unification is a non-Abelian gauge
  theory (1999 Nobel to tHooft and Veltman)

80
Abelian Transformations
2D rotations are the same in either order
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Non-Abelian Transformation
3D rotations are not the same in either order
82
Beyond the Standard Model

• Standard model describes every particle and
  interaction that has ever been observed in a
  laboratory
• It has 18 arbitrary constants that are put in by
  hand where do these come from?
• The masses of the W and Z particles are not
  easily predictable from the Standard Model
• The Standard Model also does not predict the
  pattern of masses and the generational structure
  is a new symmetry needed?

83
18 Free Parameters

• Fundamental electroweak mass scale (1)
• Strengths of the 3 forces (3)
• Masses of e-, m and t (3)
• Masses of u, c and t quarks (3)
• Masses of d, s and b quarks (3)
• Strength of flavor changing weak force (1)
• Magnitude of CP symmetry breaking (3)
• Higgs boson mass (1)

84
Grand Unification of Forces

• Strengths of three forces depend on the energy at
  which the observations are made
• Supersymmetric theories can unify the forces at
  higher energies than we can observe

85
Supersymmetry

• Supersymmetry is a larger symmetry that treats
  the 3 forces as broken pieces of a larger whole,
  and can predict all the properties and
  interactions of the particles
• Predicts a combination of coupling constants that
  agrees with what is measured in the electroweak
  unification regime
• Predicts supersymmetric particle partners for
  each existing particle (the lightest sparticle
  is also known as a WIMP)

86
Supersymmetry

• Sparticles have not yet been seen, but require
  experiments which can get to energies near 1 TeV
  (LHC? Fermi?)
• GUTs allow the conversion of quarks to leptons
  through the exchange of a very massive particle
• Since protons are made of quarks, this
  interaction would cause protons to decay
• Non-supersymmetric GUTs predict short lifetimes
  for protons, and have been ruled out

87
Proton Decay

• Supersymmetric predicted proton decay rate is a
  few per year per 50,000 metric tons (SuperK
  volume)
• SuperKamiokande finds a proton lifetime gt 1033
  years (no events are seen in over three years
  study of a huge volume of protons) can
  eventually reach 1034 years

88
Neutrino Oscillations

• A pion decays in the upper atmosphere to a muon
  and a muon neutrino
• Neutrinos oscillate flavors between muon and tau

89
Neutrino Oscillations

• High energy neutrinos that travel a short
  distance do not change their flavor
• Low energy neutrinos that travel a long distance
  have a 50 chance of changing flavors

90
Neutrino Oscillations

• K2K (KEK to SuperK) was an experiment testing
  neutrino oscillation results
• Neutrinos produced at KEK were measured at near
  detector and then shot 250 km across Japan to
  SuperK detectors
• Final results from runs during 1999-2004 158/-
  9 expected, 112 detected ? oscillations!
• Seeing oscillations means that neutrinos are not
  massless, as assumed in the Standard Model

91
Epos Chronicles Higgs Boson
92
Origin of Mass

• Electroweak unification predicts the existence of
  yet another particle, the Higgs boson
• The Higgs boson is a neutral particle with zero
  spin which is the force carrier for the Higgs
  field
• The Higgs boson breaks the electro-weak symmetry
  which gives the W and Z much heavier masses than
  the photon
• Interactions with the Higgs field are theorized
  to give mass to all the other particles

93
Higgs Boson

• Standard model physics predicts the mass of the
  Higgs to be less than 150 GeV/c2.
• However if there is physics beyond the standard
  model, then the Higgs mass could be as high as
  1.4 TeV/c2
• The data gathered at CERN (before LHC) set lower
  limit of 114.4 GeV/c2
• As of January 2010, combined data from two
  experiments at Fermilab ruled out masses between
  162 - 166 GeV/c2
• LHC runs began again on March 30, 2010.

94
CERN

• European Center for Particle Physics
• Near Geneva, on France-Swiss border
• CERN now has the Large Hadron Collider (LHC)
• LHC is now the worlds highest energy accelerator
  now colliding two beams of protons at 3.4 TeV,
  with a design limit of 7 TeV. (Also uses lead
  nuclei at up to 574 GeV.)

95
CERN

• LHC detectors (designed to study 14 TeV energy
  scale, same as 10-12 s after Big Bang)
• ATLAS (looking for the Higgs boson et al.)
• CMS (Higgs, electro-weak symmetry breaking)
• ALICE (quark-gluon plasma studies)
• LHCb (matter/anti-matter asymmetry using B
  mesons)

96
How to find a Higgs

• Two quarks each emit a W or Z boson which combine
  to make a neutral Higgs.

97
LHC rap

• http//www.youtube.com/watch?vj50ZssEojtM
• Now approaching 6 million views

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Theory of Everything

• Mathematical unification of gravity with the
  other 3 forces (which are governed by quantum
  mechanics)
• Einstein was the first to try (and fail) to
  develop a ToE unifying general relativity with
  quantum mechanics
• Supersymmetry quantum gravity and string theory
  are two attempts to develop a ToE

99
Anthropic Principle

• Anthropic principle - physical forces and
  constants are precisely balanced to allow life
• Is this balance an accident or part of a grand
  design by a grand designer?
• If the laws of physics completely explain the
  creation of the Universe, then what role would
  there be for a Creator? (Hawking)
• If there really is a ToE, then the beauty and
  order of the physical laws indicate that a
  Creator must have originated the laws (Davies)

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Summary

• Particle physics does a good job explaining
  observed particles and forces
• Newest experiments are finding physics beyond
  the standard model
• The search for the Higgs is the most important
  experiment going on today
• Or maybe the search for supersymmetric particles
  which could be dark matter..

101
Web Resources

• The Particle Adventure http//particleadventure.
  org/
• Georgia State University Hyperphysics
  http//hyperphysics.phy-astr.gsu.edu/hbase/hframe.
  html
• National Research Council study of Elementary
  Particle Physics http//www.nap.edu/readingroom/bo
  oks/particle/contents
• Boston University HEP site http//hep.bu.edu
• Nobel Prizes http//www.nobel.se
• Brookhaven National Laboratory (RHIC)
  http//www.rhic.bnl.gov

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extras
103
Relativistic Heavy Ion Collider

• Brookhaven National Laboratory
• Collides gold ions to form quark-gluon plasma to
  simulate Big Bang conditions
• QGP has never been made on Earth but should exist
  inside neutron stars

104
Relativistic Heavy Ion Collider
105
RHIC Quark-Gluon Plasma
RHIC collision simulations
106
Relativistic Heavy Ion Collider

• Brookhaven National Laboratory
• Collides gold ions to form quark-gluon plasma to
  simulate Big Bang conditions
• QGP has never been made on Earth but should exist
  inside neutron stars

107
RHIC Quark-Gluon Plasma