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Physics 4511 Introduction to Nuclear and Particle Physics

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Title: Physics 4511 Introduction to Nuclear and Particle Physics


1
Physics 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
2
Why 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
3
Some 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.

4
Historical 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!

7
http//www.particleadventure.org/
8
Read 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
9
Lorentz 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)
10
Lorentz Transformations
11
Lorentz 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
12
Nuts 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
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