2.3 Conservation Laws & Particle Interactions

In positron emission an up quark is changed to a down quark.

The following decay equation for this is incorrect.

 

Which row correctly describes the checking a student would do to find the error?

	charge	baryon number	lepton number
A	conserved	not conserved	conserved
B	conserved	conserved	not conserved
C	not conserved	not conserved	conserved
D	not conserved	conserved	not conserved

The following Feynman diagram shows the baryons and leptons in a nuclear decay

Which of the four Feynman diagrams, A to D, is physically equivalent to the diagram given for this decay?

The graph shows an isotope of uranium (U) with its corresponding nucleon and proton numbers.

This isotope of uranium decays by alpha emission to become thorium (Th), which then undergoes β-decay to become protactinium (Pa), which undergoes a further β-decay to become a different isotope of uranium.

How does the quark composition of the nucleus change in the conversion of thorium to uranium?

Equation 1 shows the decay of a proton p, and equation 2 shows the decay of a Xi baryon, Ξ⁰.

Neither of the two decay equations are permitted. For each one, identify which properties are not conserved.

Equation 1: 

Equation 2: 

	Equation 1	Equation 2
A	charge and lepton number	baryon number
B	charge and lepton number	charge and lepton number
C	baryon number	lepton number and baryon number
D	charge	charge

Which of the following processes and Feynman diagrams, A to D, correspond to the following decay equation?

A particle is found to be affected by both the electromagnetic force and the strong force.

Which one of the following could it be?

	symbol	charge / e	quark structure
A	Σ+	+1	uus
B	Σ0	0	uds
C	e–	–1	not applicable
D	n	0	udd

A proton decays into a neutron, a positron, and a neutrino, as shown.

 

It cannot decay into a neutron and a neutrino without the emission of the positron.

Which of the following conservation laws would not be conserved if it did?

1. charge
2. lepton number
3. strangeness
4. baryon number

Equation 1 shows the decay of a neutron, and Equation 2 shows the decay of a Sigma baryon.

Neither of the two decay equations are permitted. For each one, identify which property is not conserved.

Equation 1: 

Equation 2: 

	Equation 1	Equation 2
A	charge	baryon number
B	lepton number	baryon number
C	baryon number	lepton number
D	lepton number	charge

The decay of a  kaon is given by the equation

What are particles X and Y?

	Particle X	Particle Y
A
B
C
D

Which row in the table, A to D, does not give the correct exchange particle for the process described?

	Process	Exchange particle
A	electron capture	virtual photon
B	mechanism for binding quarks together	gluon
C	electrostatic repulsion of electrons	virtual photon
D	decay	W boson

Which row, A to D in the table, does not show the correct interactions experienced by the type of particle?

	Particle	Strong interaction	Weak interaction
A	lepton	no	yes
B	meson	yes	yes
C	hadron	yes	no
D	baryon	yes	yes

The decay of a  baryon is given by the equation

  

Which row, A to D in the table, correctly identifies the charge, baryon number and lepton number of particle X?

	Charge	Baryon number	Lepton number
A	–1	0	0
B	0	0	0
C	1	1	0
D	0	–1	1

This Feynman diagram shows particles interacting via a W^– boson. Which of the following particle choices are correct?

	1	2	3	4
A	Proton	Neutron	Neutrino	β+ particle
B	Neutron	Proton	Muon neutrino	β- particle
C	Up quark	Down quark	Electron neutrino	Muon neutrino
D	Down quark	Up quark	Anti-neutrino	β- particle

Complete the following β⁺ decay.

	1	2	3	4
A	Proton	Neutrino	boson	Neutron
B	Up quark	Antineutrino	boson	Strange quark
C	Proton	Neutrino	boson	Neutron
D	Up quark	Antineutrino	boson	Down quark

Four possible combinations of quarks are shown. Which ones have the same charge?

The decay of a muon is given by the equation

Which row correctly identifies the charge, baryon number and lepton number of particle X?

	Charge	Baryon number	Lepton number
A	–1	-1	0
B	0	0	1
C	1	0	0
D	0	1	1

Which row, A to D in the table, does not give the correct exchange particle for the process described?

	Process	Exchange particle
A	strong nuclear force	pion
B	strong nuclear force	gluon
C	attractive force between galaxies	graviton
D	magnetic repulsion	gluon