Title: Physics 4511 Introduction to Nuclear and Particle Physics
1Physics 4511Introduction to Nuclear and
Particle Physics
- Plan for today
- Go over course syllabus and goals
- Introductory roadmaps
- Start review of relativistic kinematics
MN High Energy Physics group site has links to
lots of info PDG, SPIRES, labs, etc.
www.hep.umn.edu
2Why study nuclear and particle physics?
- Most fundamental of sciences elementary building
blocks of the Universe and their interactions. - The buck stops here. Biologists? chemists?other
physicists?nuclear physicists ?particle
physicists. Weve got nobody. - Coolest questions, best toys. How did the
Universe begin? How will it end? Can we
recreate the conditions of the Big Bang? Can we
learn more about the Universe by looking at gamma
rays, neutrinos, etc.? - Interesting spin-offs education, technology
(imaging, oil exploration, WWW!). - Worth a few gigabucks per year?
Graphic CERN
3Some basic terminology
- What is a particle?
- The propagation of momentum, energy and other
information through space-time. - The constituents of matter and other
closely-related objects. - Subatomic, elementary, fundamental,.
- Some seem to be truly elementary, others
composite. Some are stable, some are unstable.
All are small, 10-15 m or less. - What is a force (interaction)?
- Something that changes a particle in some way,
including possibly changing it into a different
kind of particle. - Classical physics fields and action-at-a-distance
. - Nonrelativistic QM fields (potentials) change
the state of a quantum mechanical system. - Relativistic QM wave functions are fields.
Interactions occur through the exchange of
force-carrying particles.
4Historical overview
An excellent summary of the history of subatomic
physics is provided by Griffiths in his
Introduction to Elementary Particles.
- 1873 Maxwell's theory of EM.
- 1895 Röntgens discovery of X-rays.
- The Curies separate radioactive elements.
- Thomson measures electron e/m proposes "plum
pudding" atom. - 1900 Planck explains blackbody radiation with
quantization, but doesnt believe it. - Einstein explains photoelectric effect with light
quantum and believes it (dual particle-wave
nature of photon). - Einstein comes to grips with Maxwell, asserts
that light speed is c for all observers and
follows this to inevitable consequences
equivalence of mass and energy, special
relativity. - 1911 Rutherford interprets experiments of Geiger
and Marsden. Alpha particles scattered at large
angles from gold show atom has small, dense,
positively charged nucleus. - 1913 Bohr constructs a theory of atomic
structure based on quantum ideas. - Rutherford presents evidence of proton heavier
nuclei composed of hydrogen nuclei. - 1921 Chadwick and Bieler suggest strong force
holding the nucleus together. - Compton confirms particle nature of photon
(X-ray). - 1920s Quantum mechanics developed by Bohr,
Schrödinger, deBroglie, Pauli, Born, Heisenberg,
and (combining quantum mechanics and special
relativity) Dirac. - 1927 Discovery of beta-decay, with continuous
energy spectrum that led to. - 1930 Paulis suggestion of neutrino carrying off
the rest of the energy in beta-decay. - 1931 Chadwick discovers neutron, launching
intensive study of nuclear binding and decay. - 1933 Anderson discovers the positron, recognized
as positively-charged counterpart to the
electron. This is the first demonstration of
antimatter, predicted by Dirac.
5- Fermi presents theory of beta decay, introducing
the weak interaction. - Yukawa describes nuclear interactions by exchange
of particles (mesons) between protons and
neutrons. From nuclear size, Yukawa concludes
mass of mesons 200 electron masses. - 1937 Muon discovered in cosmic rays, mistakenly
identified as Yukawas meson. - Muon recognized as incompatible with being
Yukawas meson, classified as a lepton, a heavier
copy of the electron. Rabi complains Who
ordered that?" - 1947 Pion (? meson) discovered in cosmic rays,
based on strong interactions in matter declared
to be the true Yukawa meson. - 1947 Feynman, Schwinger, Tomonaga, and others
develop quantum electrodynamics procedures to
calculate electromagnetic interactions,
properties of electrons, positrons, and photons.
Tools include Feynman diagrams. - The Berkeley synchro-cyclotron produces the first
artificial pions, followed by neutral pion
discovery in 1950. - 1949 K meson discovered, begins parade of
strange particles V particles (L0 and K0) in
1951, delta particles (D, D, D0, and D-) in
1952. - 1952 Glaser invents bubble chamber, Brookhaven
Cosmotron (1.3 GeV protons), starts operation,
begins population explosion of particle zoo. - 1953 -57 Scattering of electrons on nuclei
measures charge density distribution inside
protons and neutrons, with hints of internal
structure. - 1954 Yang and Mills formulate general framework
of gauge theories, basic element of Standard
Model. - Berkeley Bevatron starts operation Chamberlain
and Segre discover antiproton. - 1956 Lee and Yang speculate that weak interaction
might violate parity conservation (mirror
symmetry) and C.S. Wu quickly demonstrates it in
Cobalt-60 beta decays. - Schwinger, Glashow, others lay foundations for
unification of electromagnetic and weak
interactions, including (although not naming) the
weak intermediate vector bosons W and W-. - 1961-64 Gell-Mann, Neeman, Zweig postulate
quarks (u, d, s) to explain the zoo of particles
and their regular patterns. (Think Mendeleev.)
6- 1962 Lederman, Schwartz, Steinberger verify two
distinct types of neutrinos (electron and muon
neutrinos). - Glashow, Bjorken speculate about existence of a
fourth quark, dubbing it charm (c). - Cronin and Fitch observe CP violation in K-meson
decays. - Greenberg, Han, Nambu introduce the quark
property of color charge. This becomes the basis
for development in early 70s of strong
interaction theory, QCD, showing asymptotic
freedom (Politzer, Gross, Wilczek). - 1967 Weinberg, Salam independently propose
unification of electromagnetic and weak
interactions (electroweak). Theory predicts
existence of a neutral vector boson Z0. - Bjorken and Feynman interpret deep inelastic
scattering data (electrons on nuclei at SLAC) as
demonstrating point-like constituents of the
proton. Cautious interpretation partons, not
yet demonstrated to be the hypothetical quarks. - Observation of neutral currents weak
interactions with no charge exchanged, indicating
mediation by Z0. - 1974 J/? particle composed of charm and
anti-charm quarks observed by Richter at SLAC and
Ting at Brookhaven, verified as a new quark
flavor in 1976 by the Mark I experiment at SLAC
(discovery of D0 meson). - 1976 The tau lepton is discovered by Perl and
collaborators at SLAC. - 1978 Lederman and collaborators at Fermilab
discover the b-quark, verified as a new quark
flavor in 1980 as a new quark flavor (discovery
of B mesons) by the CLEO experiment at CESR. - 1979 Evidence for gluon (strong interaction
mediator) emission at DESY. - Discovery of W? and Z0 at CERN by group led by
Rubbia. - Measurement of Z0 width at LEP (CERN)
demonstrates exactly three generations of quarks
and leptons. - 1995 Discovery of the top quark at Fermilab by
the CDF and D0 experiments. - 1998 Observation of neutrino oscillations (i.e.
nonzero neutrino mass) by Super-K collaboration. - 2000-1 Observation and precise measurement of CP
violation using B-mesons by BABAR, BELLE
experiments. - Present Much understanding, many mysteries Will
the Higgs be found and origin of mass understood?
Will neutrinos explain Universes
matter/antimatter asymmetry? What is the Dark
Matter revealed through gravitational effects but
not observed? What is the Dark Energy that
accounts for the accelerating expansion of the
Universe? - 2009 The CERN Large Hadron Collider (LHC) will
deliver data that will clarify everythingor not!
7http//www.particleadventure.org/
8Read Das and Ferbel Appendix A and Chap. 1.
Homework 1 - Friday.
Relativistic Kinematics
- Review! Wherever you studied this before, look
at it again, e.g. Griffiths Electrodynamics Ch.
12, Jackson Ch. 11, etc. - Maxwell EM theory, Michelson-Morley experiment ?
Lorentz/FitzGeraldPoincaréEinstein ? Special
Theory of Relativity. - Inertial-reference-frame independence of the laws
of physics in general and the speed of light in
particular give...
Lorentz Transformation
9Lorentz 4-Vector
- Coordinates of event in 4D space-time.
- Energy-momentum vector or 4-momentum.
- Components of a 4-vector depend on the choice of
RF. - Laws of physics and certain physical quantities
derived from 4-vectors do not (Lorentz invariant).
Implied summation (Einstein)
10Lorentz Transformations
11Lorentz Invariant
- Just as a vectors length is invariant under a
coordinate transformation in classical physics,
there are quantities invariant under Lorentz
transformation in 4D space-time. - Scalar (or inner or dot) product of two 4-vectors
- E.g., the length of the space-time coordinate
4-vector
Invariant Spacetime Interval
- E.g., the magnitude of the 4-momentum
Energy-MomentumInvariant
12Nuts and Bolts
- In the rest frame (CM frame) of a particle
Rest Energy Rest Mass
Total Energy
- When T ltlt Mc2 we can safely use nonrelativistic
kinematics - Almost always for nuclear phenomena rarely for
particle physics