particles

• What must be conserved in particle interactions?

  Charge

  Energy

  Momentum

  Baryon number

  Lepton number
• Rest energy of kaons

  494 MeV (K+/-)

  498 MeV (K0)
• Rest energy of pions

  140 MeV (π+/-)

  135 MeV (π0)
• Rest energy of a muon

  106 MeV
• Rest energy of electron

  0.511 MeV
• Rest energy of neutron

  939 MeV
• Rest energy of proton

  938 MeV
• Using conservation of energy: When particles collide with other particles, the rest energy of the products =

  Rest energy of the products = total energy before - kinetic energy of the products
• What is the Feynman diagram for electron capture?

  proton + electron > neutron + neutrino

  
• What is the Feynman diagram for beta plus decay?

  proton > neutron + positron + electron neutrino

  
• Describe the process of electron capture (a proton capturing an electron)


  A nuclear proton captures an electron from the surrounding cloud and becomes a neutron. This can also happen when a proton and electron collide at high speeds
• What is beta plus decay?

  A proton changes into a neutron by emitting a W+ boson which decays into a positron and a neutrino

  
• What is the Feynman diagram for beta minus decay?

  neutron > proton + electron + electron antineutrino

  
• What is beta minus decay?

  A neutron changes into a proton by emitting a W- boson which decays into an electron and an anti-neutrino

  
• What are the rules for drawing Feynman diagrams?

  1. Exchange particles represented as wiggly lines

  2. Other particles represented by straight lines

  3. Incoming particles start at the bottom and travel up

  4. Baryons on the left side and leptons on the right
• What is the only stable baryon?

  The proton (into which other baryons eventually decay)
• What is the exchange particle for the weak nuclear force?

  W Boson
• What is the exchange particle for the electromagnetic force?

  Photon
• What is the exchange particle of the strong nuclear force?


  Pion
• What is an exchange particle?

  A virtual particle that mediates the interaction between two particles
• What are the four fundamental interactions?

  Gravity, electromagnetic, weak nuclear, strong nuclear

  
• Baryon number rule


  In any reaction, the total baryon number is conserved
• What is the strangeness of a quark?

  -1
• Strangeness rule for weak interactions

  In a weak interaction, strangeness can change by 0, +1 or -1
• Strangeness rule for strong interactions

  In any strong interaction, strangeness is always conserved
• Quark composition of K⁻

  -us (anti-up, strange)

  
• Quark composition of K⁰

  d-s or -ds (down, anti-strange or anti-strange, down)

  
• Quark composition of K⁺

  u-s (up, anti-strange)

  
• Quark composition of π⁰

  -uu or -dd (anti-up, up or anti-down, down)

  
• Quark composition of π⁻

  -ud (anti-up, down)

  
• Quark composition of π⁺

  u-d (up, anti-down)

  
• Quark composition of proton

  uud

  
• Quark composition of neutron

  udd

  
• Baryon number of a strange quark

  +1/3
• Strangeness of a strange quark


  -1
• Charge of a strange quark

  -1/3
• Baryon number of a down quark

  +1/3
• Strangeness of a down quark

  0
• Charge of a down quark

  -1/3
• Baryon number of an up quark

  +1/3