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Physics - Section 1 - Particles - Part 2 - Coggle Diagram
Physics - Section 1 - Particles - Part 2
conservation laws and quantum numbers
conserved quantities in interactions
baryon number is conserved
lepton numbers for each family are conserved separately
electron-family and muon-family lepton numbers counted independantly
electric charge always conserved in any particle interaction
strangeness and interaction-dependence
strangeness conserved in strong interactions and can change in weak interactions by -1, 0 , +1
only the weak interaction can change quark type (e.g. d to u), enabling strangeness change
quark confinement and pair production
individual quarks cannot be isolated; attempting to separate them produces quark-antiquark pairs instead
confinement leads to meson formation rather than free quarks in experiments
forces and exchange particles
fundamental forces and gauge bosons
four fundamental forces: strong, weak, electromagnetic, gravity
weak gauge bosons: W+, W- ; affect all particle types
strong interaction mediated by pions (or gluons at quark level); affects hadrons only
electromagnetic gauge boson: virtual photon y, affects charged particles only
[gravity negligible for particle interactions at a-level]
exchange particle concepts and ranges
forces arise from exchange of virtual gauge bosons that exist briefly
virtual photon massless gives electromagnetic force infinite range
w bosons heavy, making weak interaction short range due to energy cost of virtual w creation
in the strong force, pions are exchanged between nucleons; at quark level gluons are exchanged between quarks
particle interaction diagrams and rules
diagram conventions and drawing rules
incoming particles drawn at bottom moving upward
baryons and leptons cannot cross sides of diagram
ensure charge balance on both sides of interaction
w bosons can carry charge across the diagram [a w- going left = w+ going right]
example interactions
electron capture and electron-proton collisions mediated by w bosons
electron capture shown as p + e- -> n + ve with a w+ from proton to electron
electron colliding with proton can show a W- from electron to proton producing same final state
electromagnetic repulsion between two protons mediated by virtual photon exchange particle
beta decays represented with w-boson-mediated quark changes