Particle Physics
- Created by: claire
- Created on: 01-12-13 13:32
Particles and Antiparticles
Pair Production
Photon with sufficient energy can change into a particle-anitparticle pair
hf=2E
Annihilation
Particle and corresponding antiparticle meet and mass is converted into radiation energy. 2 photons produced as a single photon would take away momentum which isn't allowed as no outside forces act.
hf=E
Particle Interaction
Electromagnetic Force
Electromagnetic force between 2 charged objects is due to exchange of virtual photons
Weak Nuclear Force
Causes neutron to change into proton or vice verca (beta plus and minus decay)
Causes neutrino to interact with neutron and make it change into a proton and emit an electron
Causes antineutrino to interact with proton and make it change into a proton and emit a positron
Causes proton in proton rich nucleus to interact with inner-shell electron and change into a neutron. Electron changes into a neutrino
Interactions due to exchange particles - W bosons
Strong Nuclear Force
Overcomes electrostatic force of repulsion between protons and keeps protons and neutrons together
Particles
Muon - negative charge, greater rest mass than electron - decay into electrons and antineutrinos, positrons and neutrinos
Pion - negative, positive, neutral charge, greater rest mass than muon, less than proton - produced and decay through strong interaction - charged decay into muons and antineutrinos, antimuons and neutrinos. Neutral decays into high energy photons
Kaon - negative, positive, neutral charge, greater rest mass than pion, less than proton - produced through strong interaction, decay through weak interaction - decay into pions, muons and antineutrons, antimuons and neutrinos
Particles
Hadrons - interact through strong interaction and electromagnetic if charged - decay through weak interaction - protons, neutrons, pions, kaons
Baryons - protons and neutrons - decay into protons
Mesons - pions and kaons
Leptons - interact through weak interaction and through electromagnetic if charged - electrons, muons, neutrinos
rest energy of products=total energy before-kinetic energy of products
Leptons
Leptons and antileptons can interact to produce hadrons
Neutrinos and antineutrinos produced in beta decays are different from those produced in muon decays. Muon decay creates neutrino, antineutrino and muon when they interact with protons and neutrons. If only one type of neutrino and antineutrino, equal numbers of electrons and muons would be produced. Muon neutrino and electron neutrino (antineutrinos)
In an interaction between a lepton and hadron, a neutrino or antineutrino can change into a corresponding charged lepton
In muon decay, the muon changes into a muon antineutrino, an electron and electron antineutrino
Quarks and Antiquarks
Strangeness
Kaons decay into pions or pions and protons. They decay through weak interaction.
- Kaons that decay into pions are K mesons
- Other kaons have different rest masses greater than protons and decay either in sequence or directly into protons and pions
Strangeness is always sconserved in strong interaction but not weak interaction
Quarks
Mesons consist of a quark and antiquark.
- Neutral pion can be any quark-corresponding antiquark
- Each pair of charged mesons is a particle-antiparticle pair
- The antiparticle of any meosn is a quark-antiquark pair, another meson
Baryons consist of 3 quarks or 3 antiquarks for an antibaryon
- Proton - uud
- Neutron - udd
- Antiproton - udd (antiquarks)
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