Particle Physics Questions

Q14. The diagram represents the decay of a particle X into a particle Y and two other particles.

The quark structure of particles X and Y are shown in the diagram.

(a) Deduce the name of particle X.

udd has zero charge - is a neutron

udu has a charge of +1 - is a proton

n p + β^- +

X is a neutron

[1 mark]

(b) State the type of interaction that occurs in this decay.

Weak interaction

[1 mark]

Bosons

[1 mark]

(d) Show clearly how charge and baryon number are conserved in this interaction.

You should include reference to all the particles, including the quarks, in your answer.

udd (baryon) udu (baryon) + β^- (lepton) + (antilepton)

n p + β^- +

Charge:

(+2/3, -1/3, -1/3)(2/3, -1/3, 2/3) + (-1) + (+1)

(0)(+1) + (-1) + (+1)

Baryon number:

(+1/3, +1/3, +1/3) (+1/3, +1/3, +1/3) + (0) + (0)

1 1 + 0 + 0

[2 marks]

(e) Name the only stable baryon.

proton

[1 mark]

(f) A muon is an unstable particle.

State the names of the particles that are produced when a muon decays.

Electron, an electron anti-neutrino and a muon neutrino

Positron, an electron neutrino and a muon anti-neutrino

No credit was given for symbols - they asked you for the name of the particles!

[1 mark]

(Total 7 marks)