### Lecture.1

```Physics 357/457
Spring 2011
(Chapter 1: getting started)
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the elementary particles
the forces
the model
how can we understand it?
Elementary particle:
an entity not able to be further decomposed
with a unique set of properties
mass, m
charge, Q
spin : s =½ integer (fermion),
s = 0, 1, 2…(boson)
 flavor
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spin, charge & mass(energy)
Intrinsic property  “constituents” do not exist
We don’t know how to account for the property by classical,
quantum mechanical or relativistic (field theoretic) models
what is charge?
Charge (Q) is a quantity we have defined in order to describe how
certain particles (with this charge) interact. If the particles don’t
interact in the prescribed way, they don’t have charge.
The force, F, between two charges (and the classical mathematical
model, Coulomb’s Law, kQ1Q2/r2), was derived experimentally.
Subsequent to this we developed the ideas of electric fields, E=Q1F
electrostatic potentials, Ф, magnetic fields, B, (produced by moving
charges) and ultimately, Maxwell’s equations, the most rigorous
model in physics. These equations do not tell us what charge is.
In fact, as is usually the case, the model led us to a startling new
model (Quantum Electrodynamics) which “explains” why two charges
interact: they exchange photons (a new kind of particle with no
charge and travelling with the speed of light).
Still, we do not know what charge is.
charge
We do know that charge is “quantized”: it comes only
in multiples of the electronic charge, e = 1.6 x 10-19
Coulombs.
Furthermore, the electron itself, although having both
mass and charge, e , has a “size” so small that we are
able only to say it is smaller than what we can detect!
This is indeed a phenomenon!
the elementary particles
(as far as we know at this time)
six quarks (u d c s t b)
 six leptons (e ne m nm t nt)
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all have spin = ½  they are fermions
that’s it!
size
Like the electron, these elementary particles have
“sizes” smaller than we can detect.
Another phenomenon!
Particle  Antiparticle
Q  -Q
mm
an antiparticle is like a particle
going backwards in time
Building composite particles –
with sizes we can detect:
Quarks (q) can be bound together to form composite
particles, like protons, neutrons and pions.
But, we only find in the laboratory composite particles
corresponding to quark-antiquark or qqq combinations.
These composite particles of quarks are held together by
the strong force mediated by the exchange of gluons.
Like the electric charge producing Coulomb forces, the
color “charge” is carried by the quarks.
the forces
electromagnetic (photon)
weak ( W+ W- Z0)
 strong (8 gluons)
 gravitational ( graviton not yet observed)
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all have spin = 1 (or 2 for graviton)
 they are bosons
some particle
physics puzzles
While we have learned a great deal in
the 20th century, there are still many
things which are not known.
Dark
Energy:
http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/
Dark Energy
http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/
What Is Dark Energy?
More is unknown than is known. We know how much dark
energy there is because we know how it affects the Universe's
expansion. Other than that, it is a complete mystery. But it
is an important mystery. It turns out that roughly 70% of the
Universe is dark energy. Dark matter makes up about 25%.
The rest - everything on Earth, everything ever observed with
all of our instruments, all normal matter - adds up to less than
5% of the Universe. Come to think of it, maybe it shouldn't be
called "normal" matter at all, since it is such a small fraction
of the Universe.
Dark Matter
According to observations of structures larger than galaxies, as
well as Big Bang cosmology dark matter accounts for 23% of
the mass-energy density of the observable universe.
In comparison, ordinary matter accounts for only 4.6% of the
mass-energy density of the observable universe, with the
remainder being attributable to dark energy. From these
figures, dark matter constitutes 80% of the matter in the
universe, while ordinary matter makes up only 20%.
http://chandra.harvard.edu/xray_astro/dark_matter/index.html
Higgs Mechanism
The Higgs mechanism is a “model ” in which vector bosons
( W+ , W- and Z) can take on mass. Originally, they are massless.
At a point in time, when kT ~ 100 GeV, they undergo a
(symmetry breaking) transformation in which energy from
the vacuum becomes particle mass. We will talk about it later.
It was proposed in 1964 independently and almost simultaneously
by three groups of physicists:
François Englert and Robert Brout;,[5] by Peter Higgs,[6]
(who was inspired by the ideas of Philip Anderson); and by
Gerald Guralnik, C. R. Hagen, and Tom Kibble,.[7]
How can we understand
all this?
Feynman: we have to “imagine” what is going
on – that is the difficult part.
We “imagine” particle physics in terms of models, and
one of these is the Standard Model (SM). Gluons and
color charge and ideas of mass and the Higgs particle
also require models – extensions of the SM.
Since we need to use E = mc2 (creation and annihilation
of particles), we need to learn a bit about special
relativity and how to express the important assumptions
mathematically.
Where to find things
Particle chart source:
http://www.cpepweb.org/cpep_sm_large.html
Particle chart p357/457:
http://web.mst.edu/~hale/courses/Physics_357_457/particle_chart.2002.jpg
Quarks info:
http://hyperphysics.phy-astr.gsu.edu/hbase/particles/quark.html
Feynman on light:
Feynman on quark confinement:
Particle Adventure: (DOE and NSF funded)
Major Accelerators:
Physics 357/457
Instructor: Barbara Hale, 205 Physics
[email protected]
Text: Gordon Kane, Modern Elementary Particle Physics,
Addison-Wesley, New York, Updated Edition, 1993.
It is not necessary to purchase a text.
Copies of the lecture notes will available.
Note below References which will be useful for
A good reference for background material:
David Griffiths, Introduction to Elementary Particle Physics,
Wiley, New York.
Course Outline:
1. The elementary particles: Quarks and leptons
2. Field Theories, Quantum Electrodynamics (QED) and
Feynman diagrams
3. Unification of the Weak and Electromagnetic Interactions
4. The Standard Model, gauge invariance and gauge bosons
5. The Gluons and the Strong Force
6. Grand unified theories and Beyond
7. Particle Physics and Cosmology
Course Structure
There will be two exams (100 points each)
plus a comprehensive final (150 points).
Homework sets will count as one exam (100 points).
Total points = 200 + 100 + 150 = 450 points.
85% = A,
70% = B.
References for Elementary Particle Physics Topics
1. Donald Perkins, Introduction to High Energy Physics,
Addison-Wesley, New York (1987) 3rd Ed.
[description of experiments & results; uses little field theory]
2. R. Hagedorn, Relativistic Kinematics, Benjamin, New York (1964)
3. I.J.R. Aitchison, An Informal Introduction to Gauge Field Theories,
Cambridge University Press, London (1982)
4. Chris Quigg, Gauge Theories of the Strong, Weak and
Electromagnetic Interactions, Frontiers in Physics Lecture
Notes Series 56, Benjamin/Cummings, Reading Massachusetts
5. P. Becher, M. Bohm and H. Joos, Gauge Theories of Strong
and Electroweak Interactions, Wiley, New York (1984) [advanced]
6. Elliot Leader and Enrico Predazzi, An Introduction to Gauge
Theories and the 'New Physics', Cambridge University Press,
7. Kurt Gottfried and Victor F. Weisskopf, Concepts of Particle
Physics, Oxford Press, New York (1984) [written for nonspecialists]
8. Particles and Fields, Readings from Scientific American, W. H.
Freeman and Co. (1980) [ a good introduction; written for
Scientific American]
9. F. Halzen and Alan D. Martin, Quarks and Leptons, John
Wiley & Sons (1984)
10. New Particles Edited by J. L. Rosner, American Association
of Physics Teachers (AAPT) Reprint Books, (1981) [good review
of the history of particle discoveries up to 1981; also has some
'famous' reprints]
11. Steven Weinberg, The Discovery of Subatomic Particles,
(a Scientific American Book) W. H. Freeman (1983)
[historical approach; for nonspecialist]
12. L. B. Okun, Leptons and Quarks, North Holland, New York
13. P. Collins, A. Martin and E. Squires, Particle Physics and
Cosmology, John Wiley and Sons, New York (1991)
14. Stephen W. Hawking, A Brief History of Time, Bantam,
New York (1988)
15. Sheldon Glashow, Interactions, Warner, New York (1988)
16. Steven Weinberg, The First Three Minutes, Bantam,
New York (1977)
American Assoc. Physics Teachers 5112 Berwyn Rd., College Park,
MD 20740 (1987) (You can also purchase a poster from
the publisher.)
18. Gordon Kane, Modern Elementary Particle Physics,
Addison-Wesley, New York (1987), updated 1993.
19. David Griffiths, Introduction to Elementary Particle Physics,
Wiley, New York (1987)
20. W. S. C. Williams, Nuclear and Particle Physics,
Clarendon Press, Oxford (1991)
21. P. E. Hodgson, Nuclear Reactions and Nuclear Structure,
Clarendon Press, Oxford (1971)
22. J. M. Blatt and V. F. Weisskopf, Theoretical Nuclear Physics,
John Wiley & Sons, New York (1952)
23. John C. McGervey, Introduction to Modern Physics,
Academic Press, New York Second Edition (1983)
Chapters 10, 13-15
24. Arthur Beiser, Perspectives of Modern Physics,
McGraw-Hill, New York (1969) Chapters 21-24 Old book,
simple explanations.
25. Robert Eisberg and Robert Resnick,
Quantum Physics of Atoms, Molecules, Solids, Nuclei and Particles,
John Wiley and Sons (1985) Chapters 15 and 16
26. Robert Mann, An Introduction to Particle Physics and the
Standard Model, CRC Press, 2010, good reference.
27. B. R. Martin and G. Shaw, Particle Physics, Wiley, NY 2008
MORE:
Dark Matter, Dark Energy (NOVA):