Unit 1.7) Particles and nuclear Physics

Question 1

What are the main constituents(parts)
of an atom?

Answer 1

Proton
Neutron
Electron

Question 2

What is the letter associated with a proton number?

Answer 2

z

Question 3

What is a nucleon?

Answer 3

A part of the nucleus: a proton or a neutron

Question 4

What letter represents nucleon number?

Answer 4

A

Question 5

What is the strong nuclear force?

Answer 5

The fundamental force that keeps the nucleus stable by counteracting the electrostatic force of repulsion between protons.

Question 6

Describe the range of the strong force

Answer 6

Repulsive up to 0.5fm
Attractive from 0.5-3fm
Negligible past 3fm.

Question 7

What makes a nucleus unstable

Answer 7

Nuclei which have too many protons, neutrons, or both.
Too many protons means the electrostatic force is too strong and pushes them apart.
Too many neutrons or both will make the nucleus larger than the range of the strong force, so it will no longer be held together

Question 8

What is an anti-particle

Answer 8

For each particle there is an antiparticle which has the same rest energy and mass, the opposite charge, and will annihilate with the particle if they ever come in contact

Question 9

True or false?
‘Every fundamental particle has a antiparticle
Can leptons and anti leptons combine together to form particles or can quarks and anti quarks combine together to form particles.

Answer 9

True
anti up quarks, anti down quarks.
anti electrons, anti neutrinos,
all anti particles have the same mass but opposite charge, ie electron goes from +1 to -1.
Leptons and anti leptons do not combine together and exist separately whereas quarks and antiquarks combine to to form composite subatomic particles known as baryons.

Question 10

Antiparticle of an electron

Answer 10

Positron

Question 11

What is the antiparticle of pion with neutral charge.

Answer 11

Its antiparticle is itself

Question 12

Explain the process of annihilation

Answer 12

When a particle and its corresponding antiparticle come into contact with each other, they will annihilate.
The mass of the particle and antiparticle is converted back to energy in the form of 2 gamma ray photons which are released in opposite directions to conserve momentum.

Question 13

What is pair production

Answer 13

When a gamma photon has sufficient energy, it can be converted into a corresponding particle-antiparticle pair

Question 14

Name the four fundamental forces

Answer 14

Gravity
Electromagnetic/electrostatic
Weak nuclear
Strong nuclear

Question 15

The virtual photon is the exchange particle of which force?

Answer 15

The electromagnetic force

Question 16

What type of particles are affected by the strong nuclear force

Answer 16

Hadrons

Question 17

What is the exchange particle of the weak nuclear force

Answer 17

The W boson

Question 18

What does the electromagnetic force act on?

Answer 18

It acts on all charged objects. For example: when a positively charged ball repels another positively charged ball

Question 19

When does the weak nuclear interaction occur?

Answer 19

When Quark character changes (a quark changes into another quark). It affects all type of particles

Question 20

What properties must be conserved in particle interactions?

Answer 20

Energy
Charge
Baryon Number
Lepton Number
Momentum
Strangeness(only in strong interactions-it can change by + or -1 in weak interactions.

Question 21

What is a lepton

Answer 21

A fundamental particle not made of quarks and does not experience the strong nuclear force

Question 22

What is a hadron

Answer 22

A particle made of quarks that are held together by the strong force. Mesons and baryons are hadrons.

Question 23

What are the classes of hadrons

Answer 23

Baryons(three quarks)
anti-baryons(three anti quarks)
Mesons(1Quark, 1 antiquark)
all baryons number is 1 all anti baryons number is -1.
All mesons have a baryon number of 0

Question 24

The pion and kaon are both examples of which class of particle?

Answer 24

Mesons

Question 25

The pion can be an exchange particle for which force?

Answer 25

The strong nuclear force.

Question 26

What does a kaon decay into?

Answer 26

Pions

Question 27

Give some examples of baryons

Answer 27

Proton-uud quark composition
Neutron-udd quark composition

Question 28

What is significant about a proton

Answer 28

It is the only stable baryon.
All baryons will eventually decay into protons.

Question 29

Examples of leptons

Answer 29

Electron, Muon, Neutrino,(all the above’s antiparticles)

Question 30

What does a muon decay into

Answer 30

An electron, muon neutrino and electron antineutrino.

Question 31

lepton numbers for electrons and muons before and after muon decay.

Answer 31

electron lepton number is zero before and after.
Lepton number for muons before and after is 1.

Question 32

What is the strangeness value of a strange quark

Answer 32

-1

Question 33

Is strangeness always conserved in the weak interaction.

Answer 33

No. Strangeness is only conserved in the strong interaction. In weak interactions it can change by 0,-1 or +1.

Question 34

Strange particles are produced through the___ interaction and decay through the____ interaction.

Answer 34

Produced through the strong, decayed through the weak.

Question 35

State the relative charge for an electron, electron neutrino, an up quark and a down quark.

Answer 35

Electron - 1
Electron neutrino: 0
Up quark: +2/3
Down quark: -1/3

Question 36

What is the symbol for a positron

Answer 36

e^+ (or sometimes B^+ in beta decay)

Question 37

Symbol for anti-up quark

Answer 37

__
U

Question 38

What is the quark composition of a proton and neutron

Answer 38

Proton: uud
Neutron: udd(or ddu)

Question 39

what is the first generation of quarks?

Answer 39

up quarks(u) and down quarks(u)
up quark charge is 2/3
down quark charge is -1/3

Question 40

what is the first generation of leptons?

Answer 40

Electron(e^-) and electron neutrino(Ve)
Electron charge is -1
Electron neutrino charge is 0.
They both have a lepton number of 1 there anti particles have a lepton number of -1.

Question 41

What are the two possible makeups of the neutral pion(pion=0)?

Answer 41

1)uu^-
Charge = +⅔ e + -⅔ e = 0
2)dd^- Charge = -⅓ e + +⅓ e = 0

Question 42

How do you identify the force involved in a reaction?

Answer 42

Strong interactions (lifetime 10-24s)

Only hadrons are involved.
There is no change in quark flavour.
These are typically involved in collisions between particles.

Electromagnetic interactions (lifetime 10-12-10-18 s)

The particles must be charged or have charged components. Although a neutron is uncharged, it consists of charged quarks.
There is no change in quark flavour.
One or more photons may be emitted.

Weak interactions (lifetime 10-8 s)

Neutral leptons (neutrinos) are involved.
There may be a change in quark flavour.

Question 43

What are the conservation laws for particles?

Answer 43

The baryon and lepton numbers must be conserved, the same before and after the decay of a particle.
It is important to consider the quarks involved in the reaction:
udd→uud+e
−
+
v
ˉ

e
​

In this reaction, one of the d quarks has changed to a u quark. This is known as a quark flavour change and, along with neutrino involvement, is exclusive to a weak interaction.