01.Particle Physics Flashcards
What are nucleons?
Nucleons are what protons and neutrons are collectively known as.
What happens if you change the number of protons?
Creates a new element
What happens if you change the number of neutrons?
Creates an isotope
What happens if you change the number of electrons?
Creates a new ion
What is an isotope?
Atoms of the same element that contains the same number of protons and electrons but a different number of neutrons.
What does isotopic data mean?
The relative amounts of the different isotopes of an element present in a substance.
What do you use isotopic data for?
Estimating an isotopes age by looking at the amount of isotopes in a material.
What is specific charge?
The quantity of charge an object has per kilogram.
What is the equation for specific charge?
Specific Charge = Total Charge / Total Mass
What are the four fundamental forces?
Gravity
Electromagnetic
Strong Nuclear
Weak Nuclear
What is the strong nuclear force responsible for?
Holding the nucleus (nucleons) together, as well as the decay and creation of particles.
What does the strong nuclear force effect?
Nucleons
What are the properties of the strong nuclear force?
EITHER attractive or repulsive depending on distance.
Has a very short range.
What distances effect the strong nuclear force?
0.0-0.5 fm means the SNF will be repulsive
0.5-3.0 fm means the SNF will be attractive
>3 fm the SNF has NO effect
When nuclei are unstable what are they referred to as being?
Radioactive
What are the three main reasons why a nucleus might be unstable?
Too much mass
Imbalance of protons or neutrons
Too much energy
If a nucleus has too much mass what happens?
Alpha decay - ejects some particles
If a nucleus has an imbalance of protons and neutrons what happens?
Beta (+/-) decay - the weak nuclear force can change the particle type.
If a nucleus has too much energy what happens?
Gamma decay - releases some energy.
What happens when a particle undergoes alpha decay?
An alpha particle is released (2 protons and 2 neutrons)
Only done by very big nuclei.
When does beta MINUS decay occur?
When a nucleus has too many neutrons to be stable (neutron rich).
How does a neutron turn into a proton?
Via the weak nuclear force (this will change the element type).
What is a neutrino?
It has/is:
- virtually undetectable
- no charge
- almost zero mass
- and carries the extra away as kinetic energy
What are three pieces of equipment could be used to detect alpha and beta radiation?
1) Cloud chamber
2) Geiger counter
3) Spark counter
What are photons?
Electromagnetic radiation that travels in ‘packets’, that transfer energy and has no mass.
What can vary with photons?
Frequency
Wavelength
Energies
What is the order of the Electromagnetic spectrum? (Largest to smallest wavelength)
Radio
Microwave
Infared
Visible Light
Ultra violet
X-rays
Gamma rays
What has a longer wavelength, red light or blue light?
Red light, as they travel at the same speed but less red wavelengths pass a point per second.
E = h x f
Energy of photon = Planck’s constant x frequency
C = f x λ
Wave speed = frequency x wave length
E = (h x c) / λ
Energy of photon = (Planck’s constant x speed of light) / wavelength
What is the properties of an antiparticle?
Identical mass
But every other property is opposite
What happens when matter and anti-matter meet?
They annihilate
What is rest energy?
Energy stored within the mass of matter and antimatter, which is released during annihilation.
Why use electron volts?
1 Joule is a huge amount of energy for this scale, so we use a smaller unit.
What is an electron volt?
The kinetic energy gained by an electron if it passes through a potential difference (voltage) of 1V.
What is 1eV in Joules?
1.60 x 10^-19 J (the magnitude of charge of a proton)
What do you do to convert eV to J?
Multiply by 1.60 x 10^-19
What do you do to convert from J to eV?
Divide by 1.60 x 10^-19
What is annihilation?
When matter and anti-matter meet.
What happens during annihilation?
Energy is released as two identical photons.
They are then released in opposite directions to conserve momentum.
What does Eo stand for?
Rest energy
What does Emin stand for?
Energy of a photon
2Eo = 2Emin is used to calculate?
The energy required to turn matter and anti-matter into two photons.
What is pair production?
Energy being turned into matter.
If a photon has enough energy then under certain circumstances it will turn into a particle and its anti-particle.
What effects happens when the photon is more energetic? (pair production)
1) heavier particles produced
2) particles with extra kinetic energy
3) lots of smaller particles
In order for a photon to produce a particle and an anti-particle its energy must…
…at a minimum equal the rest energies of the two particles produced.
Emin = 2Eo is used to calculate?
The minimum amount of energy required for pair production.
How do you differentiate between a Hadron and Lepton?
1) A Hadron is made of quarks, but Leptons are fundemental
2) Hadrons can feel the Strong Nuclear Force (SNF) but Leptons can’t.
Name 4 examples of leptons.
1) electron
2) muon
3) electron neutrino
4) muon neutrino
(or their anti-particle)
What is the quark composition of a Baryon?
Made of 3 quarks
What is the quark composition of a Meson?
Made of 2 quarks
What meson has strangeness?
kaons
What do all baryons eventually decay into? Why?
Protons - they are the only stable baryon
What do all leptons eventually decay into? Why?
Electrons - they are the only stable lepton
What forces effect leptons?
The weak nuclear force, gravity and electromagnetism (if charged).
What forces effect hadrons?
Strong and weak nuclear force
What are quantum numbers?
Fundamental properties that must always be conserved (typically +1, 0, or -1)
What is the baryon number for:
a. A baryon
b. An anti-baryon
c. Things that are not a baryon
a. +1
b. -1
c. 0
Where were mesons discovered?
In cosmic rays from outer space.
Is a meson stable or unstable?
VERY unstable
How can mesons interact with baryons?
Via the strong nuclear force
What are the 6 types of quarks?
1) Up / Anti-up
2) Down / Anti-down
3) Strange / Anti-strange
What is the properties of a up quark?
Charge: +2/3
Baryon number: +1/3
Strangeness: 0
(opposite sign for an anti-up)
What is the properties of a down quark?
Charge: -1/3
Baryon number: +1/3
Strangeness: 0
(opposite sign for an anti-down)
What is the properties of a strange quark?
Charge: -1/3
Baryon number: +1/3
Strangeness: -1
(opposite sign for an anti-strange)
What is the quark composition for a proton?
up, up, down (uud)
(this will be the same for an anti-proton but with the anti-quarks)
What is the quark composition for a neutron?
up, down, down (udd)
(this will be the same for an anti-neutron but with the anti-quarks)
What are the four rules to work out the composition of a common meson?
(1) Must contain a quark and an anti-quark
(2) The charge must add up to either +1, 0, or -1
(3) If strangeness equals 0 it is a pion
(4) If strangeness does not equal 0 it is a kaon
Can all Hadrons have a mix of quarks and anti-quarks?
No, only mesons can have a mix
What is quark confinement?
The phenomenon that quarks are bound together by the strong nuclear force in groups of two or three.
The can move freely within this group, but they cannot escape or exist as isolated particles.
When a nucleus undergoes beta MINUS decay three things happen, what are they?
- An electron is emmitted
- An anti electron neutrino is emitted
- A neutron turns into a proton
What is the change in quark composition during beta MINUS decay?
Down quark turns into an Up quark
What is the change in quark composition during beta PLUS decay?
Up quark turns into a Down quark
When a nucleus undergoes beta PLUS decay three things happen, what are they?
- An positron is emmitted
- An electron neutrino is emitted
- A proton turns into a neutron
What are the 6 things always conserved?
Energy
Momentumn
Charge
Baryon number
Lepton number
Lepton muon number
What is sometimes conserved?
Strangeness
What is never conserved?
Mass
Why was strangeness introduced?
To explain the fact certain particles (such as Kaons) were created easily in particle collisions yet decayed much more slowly then expected for their large masses.
When is strangeness conserved?
During their creation, but not in their decay.
ALWAYS in strong interactions.
NOT ALWAYS in weak interactions.
How do we know if an interaction is strong?
1) Can’t involve leptons
2) Only invloves hadrons
3) Strangeness is conserved
How do we know if an interaction is weak?
1) Will probably invlove leptons
2) Usually 1 particle decaying into 2
3) Strangeness probably not conserved
What are the four fundamental forces?
1) Gravity
2) Electromagnetic
3) Strong nuclear
4) Weak nuclear
What does gravity do?
All objects with a mass are attracted to each other
What does the elctromagnetic force do?
All objects with charge are either attracted to or repelled from each other.
What does the strong nuclear force do?
Responsible for holding the nucleus of atoms together and for the decay and creation of particles.
What does the weak nuclear force do?
Responsible for the decay and creation of particle.
How does a proton know to repel another particle?
Exchange particles transmit forces between particles by exchanging momentumn and energy.
What are exchange particals also known as?
Guage bosons
What is the exchange paricle for gravity?
Graviton (not yet observed)
What is the properties of a graviton?
0 mass, 0 charge
Range = infinite
What is the exchange particle for the strong nuclear force?
Pions - force between nucleons
What is the properties of a Pion?
Has mass, has charge
Range = Very short
What is the exchange particle for the weak nuclear force?
W+ and W- Bosons
What are the properties of W+ and W- Bosons?
Has mass, has charge
Range = Very short
What is the exchange particle for the electromagnetic force?
Virtual Photons - ‘seeing’ it would stop the force transmitting
What are the properties of Virtual Photons?
0 mass, 0 charge
Range = Infinite
From the properties of exchange particles what can be observed?
The larger the particle the shorter the range.
What rules do Feynman diagrams follow?
1) Before interaction at bottom
2) After interaction at top
3) Baryons on left
4) Leptons on the right
