Worksheets
Particles and interactions
Short Answers
1
(a) In the table identify the exchange particle(s) associated with the two fundamental
interactions given.
Interaction
Exchange particle(s)
Electro-weak
Strong
(b)
State why the exchange particles are known as elementary particles. .[1]
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(c) An exchange particle associated with the weak interaction has a mass of about 90
GeVc–2.
Estimate
(i)
the life-time of the particle. [3]
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(d) The diagram is a Feynman diagram that represents the strong interaction between
quarks.
blue antiquark
green quark
X
green quark
(i)
Identify the exchange particle X. [1]
blue antiquark
[2]
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(ii) Explain why the quarks have a colour associated with them. [2]
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2. The diagram below shows two fundamental interaction vertices, one for the
electromagnetic and the other for the weak interactions.
a)
Explain why in both vertices the incoming and the outgoing charged fermions above must
have the same electric charge. [2]
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b) The process e
e
occurs mostly via the electromagnetic interaction
and
Draw a Feynman diagram for the process e
(i)
(ii)
the electromagnetic interaction. [1]
the weak interaction.[1]
e
according to
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iii)
Identify the virtual particles in each of the Feynman diagrams that you drew in (i)
and (ii).
Virtual particle in (i):
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Virtual particle in (ii):
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( c) State one reason why the process e
electromagnetic interaction rather
e
than the weak interaction. [1]
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(d)
Electrons are accelerated to a total energy E and then collide with stationary positrons.
Determine the minimum total energy E of the electron for the reaction e
to take place.
Electron rest mass = 0.511 MeVc–2. Muon
rest mass = 105 MeVc–2.
[3]
e
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3. Describe the difference between an elementary particle and a composite particle
4. Neutrons and protons are classified as Hadrons whereas electrons are classified as leptons. Describe the
concept underlying the classification.
5. a) describe the properties of a neutrino.
b) Explain the reason that led Enrico Fermi to predict the existence of the neutrino.
6.
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7.
8.. a)state the Pauli exclusion theory
b) does the principle only apply to leptons?
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21.
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