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Particle Physics Questions

Q5.

(a) Mesons that contain a strange (or antistrange) quark are known as K-mesons or kaons. Mesons are a sub-group of a larger group of particles.

(i) State the name of this larger group of particles.

Hadrons

(1 mark)

 

(ii) Determine the charge on a kaon with a quark structure of u̅ s

(Using your data sheet)

-2/3 e (antiparticle has opposite charge) + -1/3e = -1e

(1 mark)

(b) A proposed decay for this kaon is

̅u s → µ+ + vµ

(i) Apply the law of conservation of strangeness to the proposed decay.

1 → 0 + 0

Strangeness is not conserved

(1 mark)

(ii) Comment on whether or not this decay is possible.

Strangeness is not conserved but decay is possible because it is a decay that proceeds via the weak nuclear force.

Strangeness has to be conserved in interactions that proceed via the strong nuclear force... the formation of strange particles - but they decay via the weak interaction.

(1 mark)

(Total 4 marks)