Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

AQA A-Level Physics > Chapter 2 - Quarks and Leptons > Flashcards

Chapter 2 - Quarks and Leptons Flashcards

1
Q

What are cosmic rays?

A

High-Energy particles that travel through space from stars

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What happens when cosmic rays enter the Earth’s atmosphere?

A
  • Collide with gas atoms
  • Create new short-lived particles and anti-particles, as well as photons
  • Showers of these particles can be detected at ground level
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are most cosmic rays made up of?

A

Fast-moving protons or small nuclei

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a muon (μ)?

A
  • Heavy electron
  • Rest mass over 200 times the rest mass of the electron
  • Negatively charged
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a pion/π meson?

A
  • Can be positively charged (π+), negatively charged (π-), or neutral (π0)
  • Rest mass greater than a muon but less than a proton
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a Kaon/K meson?

A
  • Can be positively charged (K+), negatively charged (K-), or neutral (K0)
  • Rest mass greater than a pion but less than a proton
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How are pions and kaons created?

A
  • Produced in twos through the strong interaction
  • Protons moving at high speed crash into nuclei
  • Travel far beyond the nucleus in which they originate before they decay
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why are kaons known as strange particles?

A
  • Decay of kaons took much longer than expected
  • Decay included pions as the product
  • Therefore must decay via the weak interaction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How are strange particles created?

A
  • Created in particle accelerators
  • Protons collide head on with other protons at high speed
  • Kinetic energy of protons converted into mass
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What can a Kaon decay into?

A
  • Pions, or
  • A muon and an antineutrino, or
  • An antimuon and a neutrino
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What can a charged pion decay into?

A
  • A muon and an antineutrino, or
  • An antimuon and a neutrino
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What can a neutral pion decay into?

A

High energy photons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What can a muon decay into?

A

A muon neutrino, an electron and an electron antineutrino

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What can an antimuon decay into?

A

A muon antineutrino, a positron and an electron neutrino

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What can a proton interact by?

A
  • Strong nuclear force
  • Weak nuclear force
  • Electromagnetic force
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What can a neutron interact by?

A
  • Strong nuclear force
  • Weak nuclear force
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What can an electron interact by?

A
  • Weak nuclear force
  • Electromagnetic force
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What can a neutrino interact by?

A
  • Weak nuclear force
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What can a muon interact by?

A
  • Weak nuclear force
  • Electromagnetic force
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What can pions interact by?

A
  • Strong nuclear force
  • Weak nuclear force
  • Electromagnetic force (π+, π-)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What can kaons interact by?

A
  • Strong nuclear force
  • Weak nuclear force
  • Electromagnetic force (K+, K-)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are Hadrons?

A
  • Particles and antiparticles that can interact through the strong nuclear force
  • Interact through all four fundamental forces
  • Protons, Neutrons, π mesons, K mesons
  • Strong and heavy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are Leptons

A
  • Particles and antiparticles that cannot interact through the strong nuclear force
  • Interact through weak, gravitational and electromagnetic (if charged) interactions
  • Light and weak
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How do hadrons tend to decay?

A

Through the weak interaction
- Apart from protons, which are stable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Total energy before a collision equation
Total energy of particles and antiparticles before a collision = total rest energy + total kinetic energy
26
Total energy after a collision equation
Total energy of particles and antiparticles after a collision = total rest energy + total kinetic energy
27
Rest energy of products equation
Rest energy of products = total energy before - kinetic energy of the products
28
What are baryons?
- Hadrons that decay into protons, either directly or indirectly - Protons, neutrons
29
What are mesons?
- Hadrons that do not include protons in their decay products - Short-lived particles with greater rest masses than protons - Kaons, pions
30
What can leptons and anti-leptons interact to produce?
- Hadrons - Produce a quark and antiquark, which move away in opposite directions and produce a shower of hadrons
31
How can neutrinos differ from each other?
- Neutrinos and antineutrinos produced in beta decays are different from those produced in muon decays - Those from muon and antimuon decay create only muons and no electrons when they interact with protons and neutrons - If there were only one type of neutrino and antineutrino, equal numbers of electrons and muons would be produced - Muon neutrino - ν (μ) - Electron neutrino - v (e)
32
Lepton rules
Leptons: - Can change into other leptons through the weak interaction - Can be produced or annihilated in particle-antiparticle interaction - Cannot break down into non-leptons - are fundamental
33
What is a lepton number?
+1 for any lepton -1 for any antilepton 0 for any non-lepton
34
Lepton-Hadron interaction
In an interaction between a lepton and a hadron, a neutrino or antineutrino can change into a corresponding charged lepton v(e) + n → p + e- - LHS lepton number +1, RHS lepton number +1 ν(e) + n ⇏ ˉp + e+ - LHS lepton number +1, RHS lepton number -1 (positron)
35
What happens in muon decay?
The muon changes into a muon neutrino. An electron is created to conserve charge and a corresponding antineutrino to conserve lepton number μ- → e- + ˉv(e) + v(μ) - LHS charge -1, RHS charge -1 - LHS lepton number +1, RHS lepton number +1
36
Why is μ- → e- + v(e) + ˉv(μ) not possible?
- A muon can only change into a muon neutrino, not a muon antineutrino - An electron can only be created with an electron antineutrino
37
Decay and creation of strange particles
- All decay through the weak interaction - Those that decay into pions only are kaons - Others, such as the sigma particle, were found to: - Have different rest masses greater than that of a proton - Decay in sequence or directly into protons and pions - Strange particles are created in twos
38
When does conservation of strangeness apply?
- Strangeness is always conserved in a strong interaction - Strangeness can change by 0, +1, or -1 in weak interactions
39
What are quarks and antiquarks?
Smaller particles that make up other particles
40
Properties of an up quark (u)
- Charge +2/3 - Strangeness 0 - Baryon number +1/3
41
Properties of a down quark (d)
- Charge -1/3 - Strangess 0 - Baryon number +1/3
42
Properties of a strange quark (s)
- Charge -1/3 - Strangeness -1 - Baryon number +1/3
43
Properties of an up antiquark (ˉu)
- Charge -2/3 - Strangeness 0 - Baryon number -1/3
44
Properties of a down antiquark (ˉd)
- Charge +1/3 - Strangeness 0 - Baryon number -1/3
45
Properties of a strange antiquark (ˉs)
- Charge +1/3 - Strangeness +1 - Baryon number -1/3
46
Quark composition of a meson
- Mesons are hadrons, each consisting of a quark and an antiquark - The antiparticle of a meson is still a quark-antiquark pair and therefore another meson
47
Quark composition of a π- meson
dˉu: Charge -1 Strangeness 0 Baryon number 0
48
Quark composition of a π+ meson
uˉd: Charge +1 Strangeness 0 Baryon number 0
49
Quark composition of a π0 meson
uˉu or dˉd: Charge 0 Strangeness 0 Baryon number 0 *sˉs not called pions as they decay much faster than pions
50
Quark composition of a K+ meson
uˉs: Charge +1 Strangeness +1 Baryon number 0
51
Quark composition of a K- meson
sˉu: Charge -1 Strangeness -1 Baryon number 0
52
Quark composition of a K0 meson
dˉs: Charge 0 Strangeness +1 Baryon number 0
53
Quark composition of a ˉK0 meson
sˉd Charge 0 Strangeness -1 Baryon number 0
54
Quark composition of baryons
Three quarks
55
Quark composition of antibaryons
Three antiquarks
56
Quark composition of a proton
uud Charge +1 Strageness 0 Baryon number +1
57
Quark composition of a neutron
udd Charge 0 Strangeness 0 Baryon number +1
58
Quark composition of an antiproton
ˉuˉuˉd Charge +1 Strangeness 0 Baryon numver -1
59
Quark composition of an antineutron
ˉuˉdˉd Charge 0 Strangeness 0 Baryon number -1
60
What does a neutron decay into?
A proton, releasing an electron and an electron antineutrino (β- decay)
61
β- decay in quark terms
A down quark changes into an up quark: - neutron changes into a proton, releasing an electron and an electron antineutrino
62
β+ decay in quark terms
An up quark changes into a down quark: - proton changes into a neutron, releasing a positron and an electron neutrino
63
What is the conservation of lepton numbers?
In any change, the total lepton number for each lepton branch is equal to the total lepton number for that branch after the change *muon lepton number and electron lepton number must both be conserved - they are not the same thing
64
What is the conservation of strangess?
In any strong interaction, strangeness is always conserved
65
What is the conservation of baryon numbers?
In any reaction, the total baryon number of the individual quarks is conserved

AQA A-Level Physics (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions