physics - the standard model

elementary particle

the smallest particles in the universe and cannot be broken down further.

antiparticle

the opposite of an elementary particle in charge but the same in mass.

quarks

up, down, top, bottom, strange, charm

baryons

hadrons made up of three anti-quarks, held together by strong nuclear force.

mesons

composed of one quark and one anti-quark held together by the strong nuclear force.

leptons

electron, tau, muon, electron neutrino, tau neutrino, and muon neutrino

strong nuclear force

strongest force, mediatino particle is the gluon

weak nuclear force

third strongest force, mediated by the W and Z bosons

electromagnetic forces

second strongest force, mediated by photons

lepton numbers

difference between leptons and antileptons, L = n1 - n1/

baryon number

B= 1/3(nq-nq/)

what must happen for particle reactions to be observed

baryon and lepton numbers have to be conserved

electron- electron interactions

electrons move together, like charges cause repulsion causing them to slow down, electrons come close enough to exchange a (virtual) photon, and move away from each other with changed velocities.

electron-positiron interactions

electron and positron move closer together, when close enough exchange virtual photon and scatter off with changed velocities.

neutron decaying into a proton

down quark turns into an up quark producing a W- boson, boson decays into an electron and electron neutrino, beta-negative decay occurs and can be referred to as quark flavour change.

types of symmetry particle interactions

charge reversal, time reversal, and crossing symmetry

What are the two rules of symmetry

energy and momentum conservation must be obeyed.

Charge reversal

interactions are not affected if all changes are swapped.

time-reversal

interactions look the same if the flow of time is reversed - products become reactants, and reactants become products.

crossing symmetry

for any interaction that can occur, any particle can be replaced by its antiparticle on the other side of the interaction and still occur.