Unit 1.5 Flashcards Preview

Physics 1 - Particles, quantum phenomena and electricity > Unit 1.5 > Flashcards

Flashcards in Unit 1.5 Deck (90)
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1
Q

What happens when a cosmic particle enters the Earth’s atmosphere

A

it creates new short-lived particles and antiparticles, as well as photons by colliding with gas atoms in the atmosphere including: the muon, the pion and the kaon

2
Q

Why is the K meson called a strange particle

A

It is produced via the strong interaction but interacts via the weak interaction, but decay products include the pi meson

3
Q

How else can the K meson be produced

A

by an accelerator

4
Q

What are hadrons

A

Particles and antiparticles that can interact through the (weak and) strong interaction e.g. protons, neutrons, pi mesons and K mesons.

5
Q

What are leptons

A

Particles and antiparticles that only act through the weak interaction and not interact through the strong interaction e.g. electrons, muons and neutrinos.

6
Q

Leptons interact through the ____ interaction and through the _______ interaction if _____

A

weak
electromagnetic
charged

7
Q

Hadrons interact through the ____ interaction and through the _______ interaction if _____

A

strong

electromagnetic

8
Q

Hadrons decay through the ____ interaction apart from the ____ because…

A

Weak
Proton
It is stable

9
Q

What two particles both interact through the electromagnetic interaction and both are negatively charged

A

A muon and a pi meson

10
Q

1 similarity and 1 difference between the pion and the kaon

A

both interact through the strong nuclear interaction but the pi meson involves protons in its decay

11
Q

1 similarity and 1 difference between the K^0 meson and neutron

A

no charge

neutron is a baryon and kaon is a meson

12
Q

Hadrons are divided into two groups called…

A

mesons and baryons

13
Q

Kaons decay into

A

pions, muons and antineutrinos, antimuons and neutrinos

Via the weak interaction

14
Q

Charged pions decay into

A

muons and muon antineutrinos
or
antimuons and muon neutrinos

15
Q

The pi^0 meson decays into

A

high energy photons

16
Q

Muons and antimuons decay into

A

electrons and antineutrinos and muon neutrino
or
positrons and neutrinos and electron antimuon

17
Q

The decays always obey the conservation rules for…

A

energy
momentum
charge

18
Q

What are baryons

A

protons and all other hadrons (including neutrons) that decay into protons

19
Q

What are mesons

A

all hadrons that do not include protons in their decay products

20
Q

What is the LHC and what does it do

A

large hadron collider is a accelerator that boosts the kinetic energy of the charged particles and causes collision s

21
Q

total energy of the particles and antiparticles before the collision =

A

rest energy+kinetic energy

22
Q

The rest energy of the products +

A

total energy before – the kinetic energy of the products

23
Q

Proton interaction

A

Strong, weak decay

Electromagnetic

24
Q

Neutron interaction

A

Strong, weak decay

25
Q

Electron interaction

A

Weak, electromagnetic

26
Q

Neutrino interaction

A

Weak

27
Q

Muon m- interaction

A

Weak, electromagnetic

28
Q

Pi meson interaction

A

Strong, electromagnetic (if charged)

29
Q

K meson interaction

A

Strong, electromagnetic (if charged)

30
Q

Where do muons, pions and kaons come from

A

Cosmic ray collisions

31
Q

What are pions and kaons

A

Bosons and mesons

32
Q

Muon half life

A

1.5 microseconds

33
Q

Pion half life

A

18 nanoseconds

34
Q

What two types do leptons come in

A
Charged (ionising particles with easily detectable tracks)
And uncharged (neutrinos)
35
Q

Why are leptons elementary

A

No internal structure so are not made of anything therefore is elementary

36
Q

What is the half life of a kaon

A

12 nanoseconds

37
Q

Where were neutrinos discovered

A

Nuclear reactors

38
Q

Leptons change into other leptons via the _____ nuclear force

A

Weak

39
Q

In any interaction, lepton number is ____

A

Conserved meaning the reaction/decay is permitted

40
Q

Particle lepton number

Antiparticle lepton number

A

1

-1

41
Q

Ve + p —> n + e-

Permitted or not?

A

L 1 0 |||| 0 1

Le 1 0 |||| 0 1

Lm 0 0 |||| 0 0

Lepton number is conserved so reaction is permitted

42
Q

Ve + n —> p- + e+

Permitted or not?

A

L: 1 0 |||| 0 -1 X
Le: 1 0 |||| 0 -1 X
Lm: 0 0 |||| 0 0 _/
Lepton number is not conserved so reaction/decay is not permitted

43
Q

Muon decay and the interaction

A

Weak interaction

Muon –> electron + muon neutrino + electron antineutrino

44
Q

Muon antineutrino + proton —>

A

Antimuon and neutron

45
Q

One similarity and one difference between electron and muon

A
  • equal charge

- different mass

46
Q

One similarity and one difference between electron neutrino and muon neutrino

A
  • equal rest mass
  • a muon cannot decay into an electron neutrino whereas an electron can, and an electron cannot decay into a muon neutrino whereas a muon can
47
Q
Electron
Positron
L
Le
Lμ
A
Electron:
L 1
Le 1
Lμ 0
Positron 
L -1
Le -1
Lμ 0
48
Q
Electron neutrino
Electron antineutrino
L
Le
Lμ
A
Electron neutrino:
L 1
Le 1
Lμ 0
Electron antineutrino:
L -1
Le -1
Lμ 0
49
Q
Muon
Antimuon
L
Le
Lμ
A
Muon
L 1
Le 0
Lμ 1
Antimuon 
L -1
Le 0
Lμ -1
50
Q
Muon neutrino
Muon antineutrino
L
Le
Lμ
A
Muon neutrino
L 1
Le 0
Lμ 1
Muon antineutrino
L -1
Le 0
Lμ -1
51
Q

What type of particle are quarks and what do they make up

A

Elementary

Hadrons (baryons and mesons)

52
Q

What type of quarks make up protons and neutrons

A

Up quarks

And down quarks

53
Q

How were quarks discovered

A

High energy electrons collide with stationary protons and neutrons which caused deep inelastic scattering (energy was being lost from the scattered protons) and because energy is conserved there must have been other particles carrying the ‘lost’ energy (quarks)

54
Q

Baryon’s generalised quark structure

A

3 quarks

55
Q

Meson’s generalised quark structure

A

Quark/antiquark pairs

56
Q

π+
π-
π0
Quark structure

A

u(anti)d
d(anti)u
Any quark/antiquark pair
u(anti)u d(anti)d s(anti)s

57
Q

Beta decay with quark changes

A

d=neutron –> u=proton
W-
Electron antineutrino –> electron

58
Q

Positron decay with quark structure

A

u=proton—>neutron=d
W+
Electron neutrino -> positron

59
Q

How is the Σ+ particle created (heavier than proton)

A

π0+ρ+ –> Σ+ + Κ0

60
Q

Strangeness means

A

Decays into a π meson

61
Q

How does the Σ+ particle decay

A

Σ+ –> π0 + ρ+

62
Q

The Σ particle is a
The K particle is a
Two similarities between them

A

Baryon
Meson

Both hadrons
Both interact via the strong nuclear interaction so strangeness is conserved

63
Q

The Σ particle and K meson decay via the

A

weak interaction

64
Q

Is strangeness conserved in all cases

A

No, only in the strong interaction not the weak interactions

65
Q

Beta decay is what type of interaction

A

weak

66
Q

Explain how we know beta decay is weak interaction

A

Because quark flavour is not conserved in the weak interaction and during beta decay the quark flavour changes from a down quark (neutron) to an up quark (proton) therefore it isn’t conserved

67
Q

Building quarks - charge and strangeness of quarks/antiquarks

A

Antiquarks have exact opposite charge and strangeness to quarks on data sheet

68
Q

Neutron strangeness

A

0

69
Q

Sigma particles strangeness

A

-1

70
Q

Pion strangeness

A

0

71
Q

antiK0 and K- strangeness

A

-1

72
Q

K0 K+ strangeness

A

+1

73
Q

K mesons are

A

Strange particles that decay into pions

74
Q

The quark structure of an antiparticle of any meson is a

A

quark/antiquark pair

75
Q
K+
K-
K0
AntiK0
Quark structure
A

up anti strange
Strange anti up
Down anti strange
Strange anti down

76
Q

Σ+
Σ0
Σ-
Quark structure

A

uus
uds
dds

77
Q
Proton
Neutron
Antiproton
Antineutron
Quark structure
A

uud
udd
Anti(uud)
Anti(udd)

78
Q

One difference between kaon and pion

A

Kaon is strange whereas pion isn’t

79
Q

If strangeness is not conserved then it is what type of interaction

A

Weak

80
Q

What is always conserved

A

Baryon, lepton and quark number
Charge
Strangeness

81
Q

Baryon number for baryons, anti-baryons, mesons, leptons, protons, neutrons sigma particles

A

+1 for baryon (proton,neutron,sigma)
-1 for anti-baryon
0 for meson or lepton

82
Q

Mesons are not conserved because they are

A

Exchange particles for the strong interaction

83
Q

What are the exchange particles for the WNF and EMF

A

W+/W-

γ

84
Q

Baryon number for a quark and anti-quark is

A

1/3

-1/3

85
Q

1GeV =

A

1000MeV

1x10^9eV

86
Q

Is
p+p–>n+K++Σ+
Allowed

A
Baryon = 2/2
Lepton = 0/0
Strangeness = 0/0
Charge = 2/2
All conserved therefore allowed
87
Q

What are baryons and anti-baryons

A

Hadrons consisting of 3 quarks or anti-quarks

88
Q

Neutrinos are

A

leptons

89
Q

When does strangeness occur

A

When there are multiple possibilities for decay

90
Q

Electron proton collision and electron capture

A

Electron capture is w+ to the right

Electron proton collision is w- to left towards proton (very high speeds)