11. The following strong interaction has been observed.
K– + p n + X
The
K–
is a strange meson of quark composition
.
The u quark has a charge of +2/3.
The d quark has a charge of –1/3.
Deduce the charge of the strange quark.
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(1)
Use the appropriate conservation law to decide whether particle X is positive, negative or neutral.
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(2)
Is particle X a baryon or a meson? Show how you obtained your answer.
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(2)
State the quark composition of X. Justify your answer.
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(3)
(Total 8 marks)
12. The family of quarks is shown below, together with the charge and mass of each.
-
quark
charge
mass (GeV/c2)
up
0.005
down
0.01
strange
0.2
charm
1.3
bottom
4.3
top
180
What is meant by “charge = ”?
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(2)
Calculate the mass of the strange quark in kilograms.
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Mass = ................................................. kg
(2)
What would be the charge and mass of the anti-particle to the charm quark? (Use the same units as in the table above.)
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(2)
The top quark was predicted by theoretical physicists several years before it was actually found experimentally in 1994. What made them confident that the top quark existed?
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(1)
Give one reason why it took such a long time to find experimental evidence for the top quark.
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(1)