[Maximum number: 5]

A helium nucleus contains two protons.
In a model of the helium nucleus, each proton is considered to be a charged point mass. The separation of these point masses is assumed to be $2.0 \times 10^{-15} \mathrm{~m}$ .

(a)

Using your answers in (a), suggest why

[ 5 ]

(i)

there must be some other force between the protons in the nucleus,

[ 3 ]

(ii)

this additional force must have a short range.

[ 2 ]

[Maximum number: 1]

Which fundamental particles form a hadron?

A

leptons

B

nucleons

C

photons

D

quarks

[Maximum number: 1]

Which flavours of quark have charge $+\frac{2}{3} e$ ?

charm

strange

top

bottom

key

✓

$\boldsymbol{\times}$

✓

$\boldsymbol{\times}$

✓

x

$\boldsymbol{\chi}$

x

✓ = has charge $+\frac{2}{3} e$

$\boldsymbol{\times}$

✓

x= does not have charge $+\frac{2}{3} e$

$\boldsymbol{\chi}$

✓

$\boldsymbol{\chi}$

✓

(a)

Fluorine-18 $\left({ }_{9}^{18} \mathrm{~F}\right)$ is an isotope that decays to an isotope of oxygen ( O ) by the emission of a $\beta^{+}$ particle.

[ 1 ]

(i)

A quark in the fluorine-18 nucleus changes flavour during the decay. State this change of flavour. quark to quark.

[ 1 ]

(b)

A hadron has a charge of -2 e, where e is the elementary charge.

[ 3 ]

(i)

State and explain whether the hadron is a meson or a baryon.

[ 2 ]

(ii)

State a possible quark composition for the hadron.

[ 1 ]

(a)

Table 7.1 lists the names of three particles and possible classifications for them.

Table 7.1

Complete Table 7.1 by placing ticks $(\checkmark)$ in the boxes to indicate the classifications that apply to each particle.

[ 2 ]

(b)

The discovery of a particle with an unusual charge was an important step in the development of the theory of quarks. The particle is a hadron with a mass of $2.19 \times 10^{-27} \mathrm{~kg}$ and a charge of +2 e, where e is the elementary charge.

[ 2 ]

(i)

Determine a possible quark composition of a hadron with a charge of +2 e. Explain your reasoning.

[ 2 ]

[Maximum number: 1]

Which particle is not a fundamental particle?

A

electron

B

neutrino

C

neutron

D

top quark

[Maximum number: 1]

The diagrams show the quark composition of four different hadrons. One of the hadrons is a $\Sigma^{+}$ particle. It has a charge of +e, where e is the elementary charge.

Which hadron could be the $\Sigma^{+}$ particle?

A

B

C

D

key
u = up quark
d= down quark
s= strange quark

[Maximum number: 1]

What are the structures of the proton and of the neutron in terms of quarks?

up quark

down quark

up quark

down quark

1

2

1

2

1

2

1

2

1

[Maximum number: 1]

A positively charged meson consists of a quark and an antiquark.
What could be the quark and antiquark?

A

charm and antiup

B

down and antitop

C

strange and antibottom

D

up and antistrange

[Maximum number: 1]

What is the charge of a top antiquark?

A

$-\frac{2}{3}$

B

$-\frac{1}{3}$

C

$+\frac{1}{3}$

D

$+\frac{2}{3}$