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LC Physics > Particle Physics > Flashcards

Particle Physics Flashcards

1
Q

Conservation in a nuclear reaction

A

In a nuclear reaction,

  • Mass-energy is conserved;
  • Momentum is conserved;
  • Electric charge is conserved
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2
Q

Disintegration energy

A

When radioactive disintegration happens randomly, disintegration energy is released, Q

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3
Q

Neutrino

A
  • When studying the decay of β–particles, Austrian physicist Wolfgang Pauli noted that the energy and momentum were not conserved
  • He proposed that a third particle, the neutrino (v) was formed
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4
Q

Cockcroft and Walton

A
  • Cockcroft (English) and Walton (Irish) performed first splitting of a nucleus by artificially accelerated particles
  • Bombarded Lithium with artificially accelerated protons
  • first artificial splitting of a nucleus
  • first transmutation (changing the nucleus of one atom into the nucleus of another) using artificially accelerated particles
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5
Q

Cockcroft and Walton (how)

A

-Used transformers, rectifiers and capacitors to make high dc voltage
-Voltage accelerated protons
-Protons injected from Hydrogen discharge tube into the acceleration tube
-Protons strike the Lithium at 45 degree angle
Products (Helium nuclei, α-particles) emitted at right angles
-Strike Zinc sulphide screens (scintillations seen)

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6
Q

Cockcrot and Walton - energy

A
  • Incident proton had energy of about 1 MeV
  • Kinetic energies of Helium nuclei was 17 MeV
  • There is a gain of energy in the experiment
  • came from the loss of mass
  • first experimental verification of Einstein’s equation E=mc2, earning Cockcroft and Walton the Nobel Prize in Physics in 1951
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7
Q

Particle Accelerators

A
  • When high energy particles collided, some of this energy is converted into matter
  • In order to accelerate particles to required high energies, special particle accelerators needed
  • The cyclotron developed
  • The first circular particle accelerator
  • Magnetic fields are used control the particle beams
  • Electric fields are used to accelerate
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8
Q

Particle accelerators - magnetic fields and electric fields

A
  • Magnetic fields are used control the particle beams

- Electric fields are used to accelerate

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9
Q

CERN

A
  • an underground circular particle accelerator in Switzerland
  • Smaller accelerator has a circumference of 7km
  • Larger accelerator has a circumference of 27km
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10
Q

Particle accelerators - discovery

A
  • Circular particle accelerators improved as time went on
  • Discovered collision of high energy protons resulted in many new particles being formed
  • The higher the energy made available by better particle accelerators, the greater the mass and variety of the new particles

p + p + energy -> p + p + additional particles

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11
Q

Building blocks of nature - Greeks

A

Earth, fire, wind, water

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12
Q

Building blocks of nature - 1932

A

proton, neutron, electron

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13
Q

Building blocks of nature - 1932 onwards

A

particle accelerators, CERN

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14
Q

the positron

A

American Carl David -Anderson discovered there is a particle which is just like the electron, but of opposite charge, the positron
-Has same mass, and charge size
-Known as the antiparticle of the electron
e+ Positrons, e- electrons
-Won the Nobel prize in 1936

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15
Q

Pair Production - definition

A
  • The creating of two particles from energy

- An example of the conversion of energy into matter

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16
Q

Pair production formula

A

hf = 2mc² + Eₖ₁ + Eₖ₂

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17
Q

Pair Production - what are produced

A

-A particle and it’s antiparticle are produced

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18
Q

Pair Production - what are conserved

A

-Momentum and electric charge are conserved

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19
Q

Pair Production - when it occurs

A

-Occurs when high energy γ–ray photon loses its energy (hf) when it collides with a nucleus

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20
Q

antiparticle

A
  • Each particle has an antiparticle, denoted with the same letter with a bar over it
  • E.g. nuetrino is v, then antineutrino as v
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21
Q

antiparticle research

A
  • English physicist Paul Dirac predicted the existence of antiparticles in the 1920’s
  • Confirmed in 1955
  • Physicists in CERN made antihydrogen atoms in 1995
22
Q

pair annihilation

A

-A particle and its antiparticle that are almost at rest and close to each other will come together and be destroyed, or annihilated

23
Q

Pair annihilation (Effects)

A

-Matter disappears
Energy is produced
-Momentum before and after is zero
-Two photons of equal energy moving in opposite directions are produced

24
Q

Pair annihilation formula

A

e+ + e- -> 2hf (gamma rays)

25
Q

Fundamental forces of nature

A
  • strong nuclear
  • electromagnetic
  • weak nuclear
  • gravitational
26
Q

Strong nuclear

  • relative strength
  • acts on
  • occurrence
  • range
A
  • relative strength: 1
  • acts on: protons, neutrons
  • occurrence: binds nucleus
  • range: short (10⁻¹⁵ m)
27
Q

Electromagnetic

  • relative strength
  • acts on
  • occurrence
  • range
A
  • relative strength: 10⁻²
  • acts on: charged particles
  • occurrence: binds atoms and molecules
  • range: infinite (inverse square law)
28
Q

Weak nuclear

  • relative strength
  • acts on
  • occurrence
  • range
A
  • relative strength: 10⁻⁷
  • acts on: all particles
  • occurrence: β-decay
  • range: short range (10⁻¹⁸ m)
29
Q

Gravitational

  • relative strength
  • acts on
  • occurrence
  • range
A
  • relative strength: 10⁻³⁸
  • acts on: all particles
  • occurrence: keeps universe together
  • range: infinite (inverse square law)
30
Q

mass of particles

A
  • The higher the energy of the colliding particles, the greater the variety of new particles produced
  • Mass of particles comes from the energy of the reactions m = E/c²
  • Wide variety of particles became known as “Particle Zoo” as there seemed to be no relationship between them
31
Q

classification of particles

A
  • Particles are classified according to whether they felt strong or weak forces
  • Two families emerged:
  • Leptons
  • Hadrons
32
Q

Leptons - what they are affected by

A

Affected by weak forces, and unaffected by strong ones

33
Q

Hadrons - what they are affected by

A

Affected by both strong and weak forces

34
Q

Leptons

A
  • A particle that does not feel a strong force
  • Considered to be elementary particles

-At present, 6 leptons and their antiparticles are known

35
Q

Elementary particles

A

Elementary particles are particles that have no other particles inside them or subparts to them (indivisible)

36
Q

Lepton particles

A
  1. Electron
  2. (Electron) Neutrino
  3. Muon
  4. (Muon) Neutrino
  5. Tau
  6. (Tau) Neutrino
37
Q

Lepton particles table

A

in ppt

38
Q

Hadrons

A
  • A particle that feels the strong force
  • Over 100 types of hadrons known
  • Can be divided into two families:
  • Baryons
  • Mesons
39
Q

Baryons

A

(Greek for heavy) Masses greater than or equal to protons

40
Q

Mesons

A

have masses between electrons and protons

41
Q

Baryons particles

A
  • Proton
  • Neutron
  • Lambda
  • Sigma
42
Q

baryons and mesons table

A

on ppt

43
Q

Mesons particles

A
  • Pion

- Kaon

44
Q

Quarks

A

Quarks are elementary particles out of which baryons and mesons are made

45
Q

Known quarks

A
  • There are six known quarks and their antiquarks:
  • Up (u)
  • down (d)
  • strange (s)
  • charmed (c)
  • top (t)
  • bottom (b)
46
Q

Quarks charge

A

Have a charge of either plus or minus 1/3e or 2/3e

47
Q

quarks table

A

on ppt

48
Q

Quarks history

A
  • Name first used by Gell-Mann

- James Joyce came up with it in Finnegan’s Wake “Three quarks for Muster Mark!”

49
Q

What they are made up of: Mesons

A

Made up of any one quark and any one antiquark

50
Q

What they are made up of: Baryons

A

Made up of any three quarks

51
Q

What they are made up of: Antibaryon

A

Made up of any three antiquarks

52
Q

identifying a particle given the quarsk

A

p378 on book

LC Physics (25 decks)

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