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Particle Questions that include Feynman Diagrams

Q1.

(a)

(i) What class of particle is represented by the combination of three antiquarks ?

Antibaryon

(Saying 'baryon' got you only one mark, as did saying 'hadron')

(ii) Name a hadron that has an antiparticle identical to itself.

πo The neutral pion is a combination of an up quark with an anti-up quark or a down quark with an anti-down quark. If you change the quarks to the anti version you get an anti-up with and up or an anti-down with a down - same thing!

(3 marks)

(b) The kaon K+ has a strangeness of +1.

(i) Give its quark composition.

Saying ' quark + antiquark' got you one mark for knowing that the kaon was a meson - to get the two marks you needed to name them.

us

(ii) The K+ may decay via the process . State the interaction responsible for this decay. weak interaction

When weak interaction occurs the quarks 'change flavour'. The main ones you deal with a re up to down and vice versa in beta decay. Here the strange quark has disappeared altogether! There has therefore been a 'change in flavour'.

(iii) The K+ may also decay via the process . Change each particle in this equation to its corresponding antiparticle in order to complete an allowed decay process for the negative kaon K–

(iv) Into what class of particle can both the μ+ and the νμ be placed? lepton

(v) State one difference between a positive muon, μ+, and a positron, e+.

mass or rest energy or stability

(6 marks)

(c) The diagram below shows a partially completed Feynman diagram of β- decay. Complete the diagram and label all the particles involved.

To learn how to work out how to draw these diagrams go to my page on Feynman diagrams - then use my powerpoint it takes you through the reasoning step by step!

(3 marks)

(Total 12 marks)