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Particle Questions that include Feynman Diagrams

Q2.

(a) An electron and a positron travelling with equal speeds meet head-on and annihilate, releasing 2.0 × 106 eV of energy. This energy is shared equally by two photons. Calculate the energy, in J, of each photon.

(1 mark)

(b) Complete the table by writing true or false in the right hand column. The first two lines have been completed as an example.

a neutron is a fundamental particle

false

an antineutron is not a fundamental particle

true

a neutron is a stable particle

 

an antineutron is an unstable particle

 

a neutron has a rest mass of 1.67 × 10–27 kg

 

a antineutron has a rest mass of –1.67 × 10–27 kg

 

a neutron has no charge

 

an antineutron has a charge of 1.60 × 10–19 C

 

 

(c)

(i) The exchange particle responsible for the weak interaction is either a W boson or a Z boson. Give the name of another exchange particle and the interaction for which it is responsible.

(ii) An antineutrino may be detected via its weak interaction with a proton as shown in the Feynman diagram below. Complete the labelling on the diagram.

(5 marks)

(Total 9 marks)