Flash Player 9 (or above) is needed to view presentations.
We have detected that you do not have it on your computer. To install it, go here.

Like this presentation? Why not share!

Nuclear Physics






Total Views
Views on SlideShare
Embed Views



0 Embeds 0

No embeds



Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
Post Comment
Edit your comment

Nuclear Physics Nuclear Physics Presentation Transcript

  • What’s New in Nu-clear Physics Ed V Hungerford University of Houston According to Pogo: “ Nuclear Physics is not so new, and not so clear either.”
  • The Answers to our questions are only as good as the questions themselves Why did the tree grow in the notch in the fence ?
  • 75 years ago Nuclear Physics was New
    • The neutron had just been discovered
    • The Proton and Neutron were considered elementary particles
    • The nuclear force was not understood
    • Nuclear models were primitive and based on classical
    • liquids
    Today Nuclear Physics in some sense is Mature
    • Nucleons are not “elementary” but are composed of other
    • particles called quarks
    • The nuclear force is understood as an exchange of field quanta
    • called gluons
    • The nucleus is a VERY complicated interaction of many hadrons
    • whose interaction is described by a theory called Quantum
    • Chromodynamics
    Nuclear Physics is the Study of the effects of Many-body Hadronic Systems interacting via QCD
  • The Particles and Symmetries of the Standard Model 3 Families
  • There are 4 known interactions in nature
    • One of the fundamental driving philosophies of physics is the
    • assumption that these interactions can be “unified”
    • Two of these are manifestations of the same force (electroweak)
    • QCD is patterned after the electroweak interaction (gauge theory)
    • Gravity still lies outside a quantum theory
    • The new discovery of Dark Energy, if it is real, may imply a 5 th force
    Field QCD
  • The interaction of B with A occurs through the absorption of field quanta at B produced by A The Interaction through Fields A Field Quanta Particle B Particle A
  • QCD Features
    • An interaction that becomes stronger the greater
    • the distance and the lower the energy between interacting
    • particles
    • A weak interaction at short distances and high energies
    • A permanently bound quarks and gluons
    • A self interaction between the field quanta (gluons)
    • A highly non-linear theory greatly complicating
    • calculations and making intuitive predictions difficult
    • A symmetry of SU(3) expressed by 3 states of quarks
    • and Gluons (color)
  • The Quark and Gluon Constituents of the Baryon Gluon Field Valence Quarks Sea Quarks
  • Quantum ChromoDynamics (QCD) is the Theory of the Strong Interaction (Nuclear Force) Quarks and Gluons Flux Tube Linear Potential vs distance
  • How do we probe a Nucleon or a Nucleus To determine its Quark Content ? Incident Electron Incident Hadron
  • Emission of a Quark Stretches the “interaction String” When the string breaks, Quark- anti-quark pairs are produced This is called Hadronization of a Quark Jet Quark Scattering Long Range Nuclear force Collapses to quark-antiquark Exchange (Yukawa Interaction) the “interaction String”
  • Chiral Symmetry, and Mass Chiral symmetry is the fundamental symmetry of QCD But the particle must not have mass Right Handed Velocity Left Handed Velocity
  • The QCD Condensate Particles acquire mass through their interaction with the vacuum, i.e. the condensate of quarks and gluons in the vacuum A nucleon in a simple visualization, is a bubble in the vacuum condensate Interaction of these quarks with the condensate at the bubble surface gives an “effective” mass to the system. Chiral Symmetry is then said to be spontaneously broken
  • The Vacuum is NOT Empty This Computer simulation shows the instantaneous gluon field that might be Present in a vacuum. Red Indicates bending (winding) in the field lines perhaps a precursor to quark condensates
  • Phase Diagram of Matter Each of the 4 interactions is has its own impact on the existence of our Universe The Strong (nuclear) force is responsible for the creation and stability nuclear matter We Live Here
  • Studying the Vacuum and QCD Relativistic Colliding Nuclei Quark Gluon plasma Hadronization
  • Connecting the very large to the very small One of the more recent advances in physics has been to connect microscopic theory to macroscopic (cosmology) For example, stellar burning and supernovae produce the nuclei of which the Universe is composed We can use this information to look back in time, as well as discuss the present features in our universe
  • Mesons and baryons are composed of quarks Flavor SU(3) Symmetry Allows Placement of lowest Mesons And Baryons in Symmetry Octets
  • The Nuclear Equation of State Neutron Star Nuclear Matter
  • A modern cut-away view of a Neutron Star
  • Measuring Matter Creation in the Galaxy
  • Proton number vs Neutron Number Stability
  • The Present Model of a Supernovae
  • Inside a Supernova      Dense core 100 km M . 3x10 7 km 3000 km      n* 10 km M . >8 M  evolves ~10 7 yr
      • Extreme temp: photodissociates nuclei back to protons, neutrons and alphas.
    Neutronisation: p+e -  n+  e
      • e + +e -   +  ;  +    x +  x (all flavours equally)
     ~ few x  nuclear Huge thermal emission of neutrinos ~5-10 seconds Core bounces
  • Supernovae: Facts and Figures
    • Energy release ~3x10 46 J (the gravitational binding energy of the core), in about 10 seconds
      • Equivalent to 1000 times the energy emitted by the Sun in its entire lifetime.
      • Energy density of the core is equivalent to 1MT TNT per cubic micron.
      • 99% of energy released is in the form of neutrinos
      • ~1% is in the KE of the exploding matter
      • ~0.01% is in light – and that’s enough to make it as bright as an entire galaxy.
      • Probably site of the r-process .
    ¼ MT test (Dominic Truckee, 1962)
  • A Computer model of a Supernovae
  • A Brief Summary
    • Nuclear Science has tremendous breadth and complexity
    • After 75 years we have found some to the “right” questions to ask but
    • others remain
    • I have purposely avoided discussion of the more traditional nuclear studies
    • There are impressive new results and insights into nuclear matter. But these
    • require detailed exposition and are difficult to develop to grasp without some
    • prior knowledge.
    • As a mature, advanced science, there are significant applications in
    • Including the fields of Medicine, Computing, Industrial Products, Energy,
    • Finance, etc.
    • More than 50% of the Phd graduates in Nuclear Physics are employed
    • in industry, medicine, and national defense.
    Nuclear Physics is a vibrant, exciting Field