• Strange particles are particles that include a?strange?or?anti-strange?quark
• An example of these are?kaons
• Strange particles always:
  • Are produced through the?strong?interaction
  • Decay through the?weak?interaction
  • Are produced in quark-antiquark?pairs

   

• An example of a kaon production could be:

Kaons are produced through the strong interaction. This is shown by the gluon exchange particle.

• An example of kaon decay could be:

Kaons decay via the weak interaction. This is shown by the W+?boson.

• Strangeness,?S, like baryon and lepton number, is a?quantum number
• Strangeness is conserved in every interaction except the?weak interaction
• This means that strange particles are always produced in?pairs?(e.g. K+ and K–)
• S?depends on whether the particle contains a strange quark, anti-strange quark, or no strange quarks
  • Particles with an anti-strange quark have?S?= +1
  • Particle with a strange quark have?S?= –1
  • Particles with no strange quark have?S?= 0

   

Only particles with a strange quark have a strangeness of +1 or –1

• Strangeness can change by 0, +1 or –1 in weak interactions

Step 1: Determine the strangeness,?S?of each particle

• • • Since sigma baryon has one?s?quark, it has?S?= –1
    • The proton and pion has no strange particles, so they have?S?= 0

     

Step 2:?Determine strangeness,?S?on both sides of the equation

• • • The sigma baryon has a?S?= –1 but the meson and proton have a?S?= 0

     

–1 = 0 + 0

Step 3:?Comment on the conservation of strangeness

• • • Since S is not conserved on both sides of the decay equation (only changed by –1), this decay is via the weak interaction
    • This is because S is conserved in all other types of interaction (strong and EM), but isn't always conserved in weak interactions