What is conserved in a Feynman diagram?
The simple answer is – everything! If there’s a symmetry in your theory then the associated Noether charge must be conserved at a Feynman vertex. A simple and elegant rule, and one of the great strengths of Feynman’s method.
What is a tree level Feynman diagram?
These diagrams are called “Feynman diagrams” or “Feynman graphs”. In higher order of perturbation theory the diagrams would contain loops of particles. These leading order graphs are called “tree-level”graphs (we confine ourselves to such tree-level graphs in these lectures).
What does a strange quark decay into?
Up quark
Strange quark
| Composition | Elementary particle |
|---|---|
| Theorized | Murray Gell-Mann (1964) George Zweig (1964) |
| Discovered | 1968, SLAC |
| Mass | 95+9 −3 MeV/c2 |
| Decays into | Up quark |
How is the decay of a neutral pion visualized?
This contrasts with the three-particle decay of the neutral pion in which the emitted particles have a range of energies and momenta. The decay proceeds by the weak interaction and can be visualized in terms of Feynman diagrams. To conserve momentum, the muon must have the same value of pc in the opposite direction.
What are the rules in the Feynman diagram?
The Feynman rules tell how to associate a number with each Feynman diagram. There are several basic rules from which the number is constructed: Rule 0: a factor of i. Rule 1: an operator for each vertex, the precise form of which depends on the theory and the particular particles involved.
How are the Feynman rules used to calculate complex numbers?
It turns out that are simple rules for calculating the complex number represented by each diagram. These are called the Feynman rules. In quantum \\feld theory we can derive these rules from the Lagrangian density, but in this course we will simply quote the rules relevant for the Standard Model. 1American physicist (1918-1988).
How are SPIN1 2 fermions treated in Feynman diagrams?
EMtimes a matrix, in fact a Dirac gamma matrix, allowing the spin direction of the electron as represented by a 4-component spinor. For now we will ignore this complication and for the purpose of Feynman diagrams treat all spin1 2 fermions, such as electrons, muons, or quarks, as spinless.
