Particle Physics- Unit 1

Question 1

What is specific charge?

Answer 1

Total charge÷Total mass

Question 2

Isotope definition

Answer 2

An atom with the same number of protons but a different number of neutrons

Question 3

Specific charge units

Answer 3

Ckg^-1

Question 4

Why must teams of scientists collaborate for advances to be made?

Answer 4

Results of experiments must be peer reviewed before they’re confirmed

Particle accelerators are expensive so collaboration helps spread the cost

Many skills and disciplines required

Question 5

4 fundamental forces

Answer 5

Gravity
Electromagnetic
Strong nuclear
Weak nuclear

Question 6

What does the strong nuclear force do?

Answer 6

Hold the nucleus of atoms together because gravity is too weak at this scale.
Is also responsible for decay/creation of particles

Question 7

What does the weak nuclear force do?

Answer 7

Responsible for the decay/creation of atoms

Question 8

What does the electromagnetic force do?

Answer 8

All objects with charge are repelled or attracted to eachother

Question 9

What does gravity do?

Answer 9

All objects with mass are attracted to eachother

Question 10

What is 1 femtometer in meters

Answer 10

1x10^-15

Question 11

What happens to the SNF is nucleons are 0-0.5 fm apart

Answer 11

It is repulsive

Question 12

What happens to the SNF if nucleons are 0.5-3 fm apart

Answer 12

It is attractive

Question 13

What happens to the SNF beyond 3 fm?

Answer 13

No effect

Question 14

When does beta minus decay occur?

Answer 14

When a nucleus is neutron rich(has too many neutrons)

Question 15

When does alpha decay occur?

Answer 15

Unstable nucleus
-Too much mass
-Too much energy
-Imbalance of protons/neutrons

Question 16

What is produced in beta minus decay?

Answer 16

Anti neutrino

Question 17

What is the energy of a photon directly proportional to?

Answer 17

It’s frequency

Question 18

What property is the same in a particle and it’s corresponding antiparticle?

Answer 18

Mass

Question 19

What happens when matter and antimatter meet?

Answer 19

They annihilate

Question 20

What energy is released in annihilation?

Answer 20

The rest energy(energy stored in the mass of the matter/antimatter)

Question 21

How many joules in one electronvolt

Answer 21

1mev=1.6x10^-19 J

Question 22

Mega prefix

Answer 22

10^6

Question 23

What is pair production

Answer 23

A high energy photon converts it’s energy into a particle and corresponding antiparticle pair

Question 24

What is needed for a photon to produce a particle and an antiparticle?

Answer 24

It’s energy at a minimum must equal the rest energies of the 2 particles produced

Question 25

The more energetic the photon:

Answer 25

-Heavier particles produced -Particles with extra kinetic energy -Lots of smaller particles

Question 26

How are the photons emitted after annihilation?

Answer 26

They are emitted in opposite directions to conserve momentum

Question 27

What's the difference between baryons and mesons?

Answer 27

Baryons are made of 3 quarks Mesons are made of a quark and an antiquark

Question 28

Hadrons vs leptons

Answer 28

-Hadrons feel the SNF, leptons can't -Hadrons can be broken up into quarks whereas leptons are fundamental

Question 29

What's the only stable hadron?

Answer 29

Protons

Question 30

What's the only stable lepton?

Answer 30

Electrons

Question 31

What's a muon?

Answer 31

A big unstable electron

Question 32

4 meson rules to find quark composition of a meson

Answer 32

-Must contain a quark + antiquark -Charge must add up to +1,-1,0 -If strangeness=0 - - > pion -If strangeness≠0 - - > Kaon

Question 33

What is always conserved?

Answer 33

Charge Baryon number Lepton electron number Lepton muon number Strangeness(Strong interaction)

Question 34

Exchange particle of electromagnetic force

Answer 34

Virtual photon

Question 35

Exchange particle of weak nuclear force

Answer 35

W+ and W- bosons

Question 36

Exchange particle of strong nuclear force

Answer 36

Pions if force between nucleus Gluons if force between quarks

Question 37

Feynman diagram rules

Answer 37

Before interaction at bottom After interaction at top Baryons on the left Leptons on the right

Question 38

Range of weak nuclear force

Answer 38

Very short

Question 39

Range of strong nuclear force

Answer 39

3fm

Question 40

Range of gravity

Answer 40

Infinite

Question 41

Range of electromagnetic force

Answer 41

Infinite

Question 42

How is the nucleon number calculated.

Answer 42

Is it calculated from the different isotopes that exist for each element

Question 43

What quark transformation happens in beta minus decay

Answer 43

Down quark becomes up quark

Question 44

How does the weak nuclear force operate

Answer 44

It used w+ or W- bosons or conserve energy/momentum

Question 45

Proton quark composition

Answer 45

Uud

Question 46

Neutron quark composition

Answer 46

Udd

Question 47

Why do SNF and wnf have short ranges?

Answer 47

The mass of these large exchange particles require large amounts of energy to be borrowed (to create it). Meaning, it only exists for a short time and hence had a short range.

Question 48

Why must the strong nuclear force be repulsive at small separations?

Answer 48

If it wasn't it would crush nucleus to a point

Question 49

Range of alpha particles

Answer 49

Short range in air

Question 50

How were neutrinos hypothesised?

Answer 50

-Experiments showed the energy of particles after Bega decay was less than before -Wolfgang Paulo suggested another particle was emitted too which carried the missing energy -Had to be neutral to conserve charge -Observed 25 years later

Question 51

What is the minimum energy for pair production

Answer 51

Total rest energy of the particles produced

Question 52

Quark confinement

Answer 52

It's not possible to get a quark by itself

Question 53

When is strangeness always conserved? When is it sometimes conserved?

Answer 53

Always: Strong interaction Sometimes: Weak interaction

Question 54

How do mesons interact with baryons?

Answer 54

Via the strong force

Question 55

How are strange particles created and decayed?

Answer 55

Created via strong interaction Decayed by weak interaction

Question 56

Kaons

Answer 56

Kaons are heavier and more unstable than pions Short lifetime Decay into pions

Question 57

Name the particle believed to be responsible for mass

Answer 57

Higgs boson

Question 58

Name the particle that is difficult to detect

Answer 58

Anti neutrino

Question 59

Beta minus decay exchange particle

Answer 59

W- boson

Question 60

Exchange particle definition

Answer 60

Force carrier for the 4 fundamental forces

Question 61

Explain why there is a minimum energy for a photon to do pair production

Answer 61

Because the photon needs to provide enough energy to provide for the rest mass

Question 62

Explain why there is a minimum energy for pair production

Answer 62

Energy of photon just provide at least the rest masses of the particle and antiparticle

Question 63

How to calculate frequency of annihilation

Answer 63

Find the energy first Then you need to divide this by 2 Because there are 2 photons

Question 64

Role or exchange particles

Answer 64

-Transfer energy -Transfer momentum -Transfer force

Question 65

Why are 2 photons produced in annihilation?

Answer 65

momentum must be conserved so need two photons travelling in different direction

Question 66

How do we know if an interaction is WNF?

Answer 66

-Strangeness not conserved -Decay

Question 67

electron capture and electron-proton collision equation

Answer 67

p+e- -> n + ve

Question 68

Electron capture exchange particle

Answer 68

W+ boson

Question 69

Electron proton collision exchange particle

Answer 69

W- boson