quarks

• quarks make up hadrons. the three types of quarks are the up quark, the down quark and the strange quark.
• strangeness is a quantum number so it can only take a certain set of values. strange particles, such as kaons, are created via the strong interaction but decay via the weak interaction. strangeness is conserved in the strong interaction, but is not conserved in the weak interaction. strange particles are always produced in pairs so the overall strangeness of 0 is conserved as one will have a strangeness of +1 and the other will have a strangeness of -1.
• baryons are made from three quarks.

  quark compositions:

  • proton = uud
  • neutron = udd
• mesons are made of two quarks: a quark and an antiquark. mesons include pions and kaons.
• pions are just made from combinations of up, down, anti up, and anti down quarks
• kaons have strangeness so they contain strange quarks as well as up, down, anti up and anti down quarks.
• in beta minus decay, a neutron is changed into a proton, meaning the quark composition changes from udd to uud, meaning a d quark changes into a u quark through the weak interaction.