Particle Questions that include Feynman Diagrams
Q7.
(a) The negative kaon, K–, has a strangeness of –1. Write down its quark composition.
su ![](../../../graphics/symbols/nuclides/ticksmall.png)
![](../../../graphics/symbols/nuclides/ticksmall.png)
(2 marks)
(b) The kaon, K– may decay into a muon and an antineutrino in the following way: ![](12.png)
(i) Complete the following table using ticks and crosses as indicated in the first row.
|
K– |
μ– |
ν μ |
charged particle |
![](../../../graphics/symbols/nuclides/dblueticksmall.png)
|
![](../../../graphics/symbols/nuclides/dblueticksmall.png)
|
X |
hadron |
![](../../../graphics/symbols/nuclides/ticksmall.png)
|
X |
X |
meson |
![](../../../graphics/symbols/nuclides/ticksmall.png)
|
X |
X |
baryon |
X |
X |
X |
lepton |
X |
![](../../../graphics/symbols/nuclides/ticksmall.png)
|
![](../../../graphics/symbols/nuclides/ticksmall.png)
|
One mark for each correct line ![](../../../graphics/symbols/nuclides/ticksmall.png)
![](../../../graphics/symbols/nuclides/ticksmall.png)
![](../../../graphics/symbols/nuclides/ticksmall.png)
- all ticks and crosses must be correct for a particular particle class to get the mark.
(ii) In the decay shown above, charge is conserved. Give another quantity that is conserved and a quantity that is not conserved in the decay of K–.
quantity conserved lepton number OR baryon number OR energy OR momentum ![](../../../graphics/symbols/nuclides/ticksmall.png)
quantity not conserved strangeness ![](../../../graphics/symbols/nuclides/ticksmall.png)
(6 marks)
(c) The Feynman diagram below represents the β+ decay process.
![](13A.png)
(i) What quantity changes continuously in moving from the bottom to the top of the diagram? Time ![](../../../graphics/symbols/nuclides/ticksmall.png)
(ii) Name the particles represented by the letters A to D.
(iii) What type of interaction is responsible for β+ decay? Weak Interaction ![](../../../graphics/symbols/nuclides/ticksmall.png)
(6 marks)
(Total 14 marks)