3.2.1 Particles Flashcards
Relative mass of a proton?
1
Relative mass of an electron?
0.0005
Relative mass of a neutron?
1
Relative charge on a proton?
1
Relative charge on a neutron?
0
Relative charge on an electron?
-1
What is the nucleon number?
Number of protons + number of neutrons
What letter can be used to represent the nucleon number?
A
What are isotopes?
Atoms with a different number of neutrons, but the same number of protons
What is a radioisotope?
An isotope that is radioactive
What is carbon 14 used in?
Carbon dating
What is the specific charge of a nucleus or ion?
Its charge per unit mass
What is specific charge used in?
Mass spectrometry to identify nuclei
How to calculate specific charge?
specific charger= Charge / mass
Units for specific charge?
Ckg⁻¹
What is each type of nucleus called?
A nuclide
What is the range of the strong force?
3 fm (small)
What is 1 fm in m?
10⁻¹⁵ m
What does the strong force act between?
Nucleons (e.g. protons and neutrons)
Is the strong force attractive or repulsive?
Both
Why is the strong force both attractive and repulsive?
Otherwise the nucleus would collapse or explode
When is the strong force attractive?
> 0.5 fm
When is the strong force repulsive?
< 0.5 fm
For light nuclei, what is the ratio of neutrons to protons?
Proton number = neutron number → the two particles must exist together
For heavy nuclei, what is the ratio of neutrons to protons?
More neutrons than protons (and very large nuclei and radioactive)
What is equilibrium separation?
A point when the resultant force is zero and the attractive and repulsive forces balance
What is the decay of americium-241 used for?
Smoke alarms
What is the decay of polonium-210 used for?
Ionisers
What force is responsible for beta decay?
The weak force
How strong is the weak force?
1 millionth the value of the strong force
How does the range of the weak force compare to that of the strong force?
It has a smaller range
What does the weak force act on?
Leptons and hadrons
What are the types of beta decay?
β+ and β-
When does beta decay occur?
When the nucleus emits an electron or a positron
What does a free neutron decay into in beta decay?
A proton, an electron and an anti-neutrino
What does a free proton decay into in beta decay?
A neutron, a positron and a neutrino
What type of beta decay is it when a free neutron decays into a proton?
β-
What type of beta decay is it when a free proton decays into a neutron?
β+
Why it called β- decay when a neutron decays into a proton?
An electron is produced
Why is it called β+ decay when a proton decays into a neutron?
A positron is produced
What are the energies of the particles emitted in beta and alpha decay?
• beta decay - beta particles emitted have a range of energies
• alpha decay - monoenergetic
What happens to the unaccounted-for energy in beta decay?
It is carried away by the neutrinos
What happens if the nucleus is still unstable after emitting alpha or beta radiation?
It is in an excited state, and gives off gamma radiation
What type of wave is gamma?
Electromagnetic
What is the mass and charge of gamma?
Has no mass or charge
What does the strong force overcome?
The electrostatic forces of repulsion between protons in the nucleus
Why was the existence of the neutrino hypothesised?
To account for conservation of energy in beta decay
What type of particle are neutrinos?
Leptons
What does an electromagnetic wave consist of?
An electric wave and a magnetic wave which travel together in phase
When are electromagnetic waves emitted?
When a charged particle loses energy
When can a charged particle lose energy (and an electromagnetic wave emitted as a result)?
• when a fast moving electron is stopped, slows down or changes direction
• when electrons move to a lower energy shell
In what form is electromagnetic radiation emitted?
Photons - bursts or packets of energy
How do photons travel?
In one direction only in a straight line
What happens to an atom’s energy when it emits a photon?
Its energy changes by an amount equal to the photon energy
What is the amount of energy contained in each quantum proportional to?
The frequency of the radiation
the equation for energy of a photon is found on the data sheet what do the symbols stand for?
E=hf=hc/λ
E=hf=hc/λ
E= energy in joules
h= planc constant (found on data sheet)
f= frequency (hz)
c=speed of light (3x10^8)
λ= wavelength (m)
What is the Planck constant measured in?
joule-seconds, Js
What is photon energy usually given in?
Electron-volts (eV)
What is one electron volt defined as?
The energy transferred when an electron is moved through a p.d. of 1V
What is the value of 1 eV?
1.6 x 10⁻¹⁹ J
What was Dirac’s theory about particles and antiparticles?
For every type of particle, there is a corresponding antiparticle that:
• annihilates the particle and itself if they meet, converting total mass to photons
• has same rest mass and opposite charge
When does annihilation occur?
When a particle and its corresponding antiparticle meet and their mass is converted into radiation energy
What can the rest energy of an antiparticle be calculated from?
By using the rest mass of the colliding particles and E=mc²
E= energy (joules)
m= mass (kg)
c= speed of light (ms)
What is pair production?
When a photon (γ) with enough energy can change into a particle antiparticle pair
What is minimum energy required by the photon in pair production?
The rest energy of the particle pair
What are the four fundamental interactions?
• strong
• electromagnetic
• weak
• graviational
What is the exchange particle for strong interaction? what particles does the strong interaction affect?
gluon (for quarks)
pion (for nucleons)
hadrons feel the strong force only
what’s the mass of a w gauge boson?
the mass of a w boson is around 100 times that of a proton and hence it has a tiny range.
What is the exchange particle for electromagnetic interaction? what particles are affected?
A virtual Photon γ. has zero rest mass + infinite range
only charged particles are affected
What is the exchange particle for weak interaction? what does it affect?
The weak interaction exchange particle is the W boson.
The weak force affects all particle types.
What is the exchange particle for gravitational interaction?
Graviton
Generally, what happens when two particles interact?
They exert equal and opposite forces on each other
What happens if two protons approach each other?
They repel and move away
Why do protons repel when they approach each other?
Due to the electromagnetic interaction and the exchange of a virtual photon
What would happen if we tried to intercept virtual photons?
We would stop the exchange from happening
What is the interaction model of repulsive forces?
Two people on skateboards facing each other - throwing a ball between them causes them to move away from each other
What is the interaction model of attractive forces?
Two people on skateboards - throw a boomerang and momentum causes them to move towards each other
In interaction diagrams, what do the straight and wavy lines represent?
• the lines do NOT represent the paths of the particles
• the wavy line shows the exchange particle and w bosons carry charge from one side of the diagram to the other.
What must be conserved in interaction diagrams?
Charge, lepton and baryon number
Describe the interaction diagram between two protons.
• lines show protons approaching
• wavy line shows virtual photon as the exchange particle
• then shows that protons move away
Describe the interaction diagram between a neutron and a neutrino.
• lines show neutron and neutrino approaching
• wavy line shows W⁻ boson as the exchange particle
• then shows that a proton and an electron move away
Describe the interaction diagram between a proton and an anti-neutrino.
• lines show proton approaching an anti-neutrino
• wavy line shows W⁺ boson as the exchange particle
• then shows that a neutron and a positron move away
Describe the interaction diagram for electron capture.
• lines show a proton and electron approaching each other
• wavy line shows W⁺ boson as the exchange particle
• then shows that a neutron and a neutrino move away
Describe the interaction diagram for β- decay.
• line shows neutron
• wavy line shows W⁻ boson as the exchange particle
• then shows that a proton, electron and anti-neutrino move away
Describe the interaction diagram for β+ decay.
• line shows proton
• wavy line shows W⁺ boson as the exchange particle
• then shows that a neutron, positron and neutrino move away
What is the process of electron capture?
When a proton in a proton-rich nucleus turns into a neutron, as a result of interacting with an inner shell electron from outside the nucleus
Why can’t strong or electromagnetic interaction be responsible for beta decay?
• strong force holds neutrons and protons in a nucleus together, but doesn’t cause neutron to change into proton
• electromagnetic force only when a charged particle loses energy → neutron not charged
What do leptons exist as?
Particles on their own
What do quarks exist as?
Only exist bound together
Examples of leptons?
• electron
• electron neutrino
• muon
• tau
Which leptons are constituents of ordinary matter (1st family)?
• electons
• electron neutrinos
Which leptons are only found in cosmic rays and particle accelerators?
• muon
• muon neutrino
• tau
• tau neutrino
Charge on an electron neutrino?
0
Which quarks are part of the 1st family?
• up
• down
Which quarks are part of the 2nd family?
• charm
• strange
Which quarks are part of the 3rd family?
• top
• bottom
Which quarks are protons made up of?
Two up quarks and one down quark
Which quarks are neutrons made up of?
One up quark and two down quarks
Which quarks are antiprotons made up of?
Two antiup quarks and one antidown quark
What is the charge on an up quark?
0.6666666667
What is the charge on a down quark?
- 1/3
What is the charge on an antiup quark?
- 2/3
What is the charge on an antidown quark?
0.3333333333
What is a muon?
A heavier relative of the electron
What is the charge on a muon?
-1
What is a tau?
A heavier relative of the electron and muon
What is the charge on a tau?
-1
What is a strange particle?
A heavier relative of the down quark
What are hadrons?
Particles that feel the strong force
How do hadrons decay?
Weak interaction
What groups are hadrons split into?
• baryons - 3 quarks
• mesons - 2 quarks
Are protons and neutrons fundamental? Why is this?
No, they are made up of quarks
Are protons and neutrons mesons or baryons? Why is this?
Baryons - they are made up of three quarks
What is the only stable baryon?
Protons
What is the pion?
The exchange particle of the strong nuclear force
What do strange particles contain?
A strange quark
How are strange particles produced?
Strong interaction
How do strange particles decay?
Weak interaction
When is strangeness conserved?
Only in strong interactions
What do Kaons decay into?
Pions
Do leptons feel the strong force?
No
What force are leptons affected by?
Weak interaction
What do muons decay into?
Electrons
What can leptons and antileptons interact to produce?
Hadrons
How fast do neutrinos travel?
Almost as fast as light
How can leptons change into other leptons?
Weak interaction
Baryon number on up quarks?
1/3
Baryon number on down quarks?
1/3
Baryon number on strange quarks?
1/3
Baryon number on anti-up quarks?
-1/3
Baryon number on anti-down quarks?
-1/3
Baryon number on anti-strange quarks?
-1/3
Strangeness of an up quark?
0
Strangeness of a down quark?
0
Strangeness of a strange quark?
-1
Strangeness of an anti-strange quark?
1
What do mesons consist of?
A quark and an antiquark
What do pions consist of?
Up and down quarks
What do kaons consist of?
A strange quark and either an up or down quark
What charge can pions have?
Zero charge, or positively/negatively charged
What are the kaon combinations?
• strange-antiup (-1)
• strange-antidown (0)
• antistrange-down (0)
• antistrange-up (+1)
When does beta decay occur?
When the nucleus emits an electron or a positron
What is conserved in beta decay?
Charge, spin, baryon number and lepton number
What else needs to be conserved (along with charge, spin, baryon and lepton no.) in particle reactions?
Energy and momentum
what are the two types of hadrons?
hadrons are made of baryons and mesons
what are the mesons quark compositions?
an equal number of quarks and antiquarks
Describe the nuclear model of an atom.
• Central nucleus containing protons and neutrons • Electrons orbit the nucleus
What are nucleons?
Protons and neutrons
What is the collective name for protons and neutrons?
Nucleons
How the charge and mass of protons, neutrons and electrons usually given?
• It can be given and coulombs and kilograms, but the numbers are very small (e.g. +1.60 x 10^-19 coulombs) • Therefore, the RELATIVE charges and masses are used instead sometimes (e.g. +1)
Do you need to learn the charges and masses of protons, electrons and neutrons?
No, they are given to you in the exam. However, you need to know the RELATIVE charges and masses.
What is the unit for charge of particles?
Coulombs (C)
What is the unit for the mass of a particle?
Kilograms (kg)
What is the charge of protons, neutrons and electrons?
• Protons = + 1.60 x 10^-19 C • Neutrons = 0 C • Electrons = - 1.60 x 10^-19 C
What is the mass of protons, neutrons and electrons?
• Protons = 1.67 x 10^-27 kg • Neutrons = 1.67 x 10^-27 kg • Electrons = 9.11 x 10^-31 kg
What is the relative charge of protons, neutrons and electrons?
• Protons = +1 • Neutrons = 0 • Electrons = -1
What is the relative mass of protons, neutrons and electrons?
• Protons = 1 • Neutrons = 1 • Electrons = 0.0005
What is the symbol for proton number?
Z
What is the symbol Z?
The proton number
What does the proton number determine?
Which element the atom is of.
What does the electron number determine?
The chemical behaviour and reactions.
What is another name for the mass number?
The nucleon number.
What is the nucleon number?
The number of protons and neutrons.
What is the symbol for nucleon number?
A
What is the symbol A?
The nucleon number.
What is an atom’s relative atomic mass equal to?
The nucleon number (the number of protons and neutrons).
What are isotopes?
Atoms with the same number of protons but different number of neutrons.
What are the 3 isotopes of hydrogen and what is their composition?
• Hydrogen - 1 proton, 0 neutrons • Deuterium - 1 proton, 1 neutron • Tritium - 1 proton, 2 neutrons
How does changing the number of neutrons in atom affect it?
• Doesn’t affect the chemical properties • Affects the stability of the nucleus -> May cause decay
How can isotopes be used to find out how old a sample is?
The amount of radioactive carbon-14 left in a sample can be used to calculate the approximate age (if the object is made of organic matter).
Why can carbon-14 be used to find out how old stuff is?
• All living things contain the same percentage of carbon-14 taken in from the atmosphere • After they die, the amount of carbon-14 decreases with time as it decays • Looking at a sample, the amount of carbon-14 tells you how old it is
What is specific charge?
The ratio of the charge of a particle to its mass.
What is the unit for specific charge?
Coulombs per kilogram (C/kg)
What is the equation for specific charge?
Specific charge = Charge / Mass
What would happen in the nucleus if the strong attraction didn’t exist?
Electrostatic repulsion would overcome gravity and the particles would fly apart.
What does the strong nuclear force do?
Binds nucleons together in the nucleus.
What are the properties of the strong nuclear force?
• Stronger than the electrostatic force • Very short range - only a few femtometres (the size of a nucleus) • Works equally between all nucleons (i.e. The force is the same between proton-proton, neutron-neutron, neutron-proton) • At very short separations, it is repulsive. At larger separations, it is attractive.
Describe how the strong nuclear force changes with separation.
• At very small separations (below 0.5fm), it is repulsive • At the “equilibrium distance” (about 0.5fm), no force is exerted • At larger separations (over 0.5fm), it is attractive. It reaches a maximum attractive value and then falls rapidly. It is almost zero past 3fm.
Why must the strong nuclear force be repulsive at very small separations?
Otherwise it would crush the nucleus to a point.
In what nuclei does alpha emission happen and why?
• Very big nuclei, like uranium and radium. • The nuclei are too massive for the strong nuclear force to keep them stable.
What happens to proton number and nucleon number when alpha decay happens?
• Proton number decreases by 2 • Nucleon number decreases by 4
Compare when alpha and beta emission happen.
• Alpha emission -> In very large nuclei • Beta emission -> In neutron-rich nuclei
What is the range of alpha particles and how can this be observed?
• Very short • By looking at tracks left by alpha particles in a cloud chamber or by using a Geiger counter to observe how count rate drops with distance
What is beta-minus decay?
The changing of a neutron into a proton, while emitting an electron and antineutrino from the nucleus.
In what nuclei does beta-minus decay happen and why?
• Neutron-rich nuclei • Having many more neutrons than protons in the nucleus makes it unstable
What happens to proton number and nucleon number when beta-minus decay happens?
• Proton number increases by 1 • Nucleon number stays the same
What is the range of beta particles?
Much greater than alpha particles.
What does the antineutrino in beta decay do?
Carries away some energy and momentum.
Describe how the first hypothesis about neutrinos was created.
• Scientists at first thought only electrons were emitted during beta decay. • However, it was observed that the energy after beta decay was less than before beta decay. • This led to the idea that another particle was emitted too, which carried the missing energy. • It would have to have no charge and almost zero mass. • This was later found to be the neutrino.
Remember to revise the graph of the strong nuclear force.
What is the order of the EM spectrum by increasing frequency?
• Radio waves • Microwaves • Infrared • Visible light • UV • X-rays • Gamma rays
What equation links frequency and wavelength of EM waves?
Frequency = Speed of Light in Vacuum / Wavelength f = c / lambda (NOTE: This is a variation of the “v = f x lambda” equation)
What is the speed of light in a vacuum?
3.00 x 10^8 m/s
What are photons?
Packets of electromagnetic radiation.
When are EM waves emitted?
When a charged particle loses energy. This can be when: • A fast-moving electron is stopped • An electron in a shell moves to a shell of lower energy
Describe the structure of an EM wave.
A magnetic wave and an electric wave at 90* to each other and to the direction of travel. They are in phase. (See diagram pg 8 of textbook)
What is the equation for the energy of a photon?
Energy (J) = Planck’s constant (Js) x Frequency (Hz) E = h x f
What is the wavelength of visible light?
400-700nm
What is Planck’s constant?
6.63 x 10^-34 Js
What is the equation for the power of a laser?
Power = No. of photons passing a point per second x Photon energy P = n x E = n x h x f
What units may be used to give the energy of a photon?
Joules (J) or Mega electronvolts (MeV)
How many joules is one MeV?
1.60 x 10^-13 J
What equation can be used to calculate the rest energy of a particle?
E = m x c^2
What is an electronvolt?
The energy that one electron would gain when accelerated through a potential difference of 1 volt.
How do you convert from joules to MeV?
Divide by 1.6 x 10^-13.
What is an antiparticle?
A corresponding particle to a particle with the same mass and rest energy, but opposite charge.
What is the general unit for rest energy?
MeV
Describe simply the idea of energy and mass equivalence.
Energy can turn into mass and mass can turn into energy.
What is the rest energy of a particle?
The “energy equivalent” of the particle’s mass.
What happens in terms of mass production when energy is converted into mass?
Equal amounts of matter and antimatter are produced.
What is the antiparticle of the proton?
Antiproton
What is the antiparticle of the neutron?
Antineutron
What is the antiparticle of the electron?
Positron
What is the antiparticle of the neutrino?
Antineutrino
What is beta-plus decay?
• When a proton turns into a neutron, and a positron and neutrino are emitted. • It is not a natural form of decay and it only happens in experiments.
What is pair production?
When a photon turns into a particle and antiparticle.
When can pair production happen?
When the photon has enough energy to produce the mass of the particle and antiparticle.
Which photons have enough energy to produce mass through pair production?
Gamma ray photons.
Where does pair production usually happen and why?
Near the nucleus, which helps conserve momentum.
What are the most common particles produced by pair production and why?
Electron-positron pairs because they have low mass.
The minimum energy of a photon in pair production is equal to…
…the total rest energy of the particles produced.
What is the symbol for rest energy?
E0
What is the equation for the minimum energy of a photon during pair production?
Minimum energy of photon = 2 x Rest energy of each particle produced Emin = 2E0 or h x fmin = 2E0
What happens when a particle and antiparticle meet?
• Annihilation • All of the mass of the particles is converted back to energy.
The total minimum energy of both photons produced in annihilation is equal to…
… the total of the minimum energies of the particle and antiparticle.
What is the energy for the minimum energy of a photon produced in annihilation?
Total minimum energy of both photons = Total minimum energy of particle and antiparticle 2Emin = 2E0 …and so… Emin = E0
Is the interaction between two distant objects instantaneous?
No - this is explained by the need for exchange particles, which cause forces.
What is the collective name for exchange particles?
Gauge bosons
What are the four fundamental forces?
• Weak nuclear force • Strong nuclear force • Electromagnetic force • Gravity
What is the exchange particle of electromagnetic force?
Virtual photon (gamma symbol)
What particles are affected by the electromagnetic force?
Charged particles
What is the exchange particle of the weak nuclear force?
W+, W- and Z0 bosons
What particles are affected by the weak nuclear force?
All types
What is the exchange particle of the strong nuclear force?
• Gluons exchanged between quarks • Pions exchanged between nucleons
What particles are affected by the strong nuclear force?
Hadrons only
What is the exchange particle of gravity?
Graviton
What particles are affected by gravity?
All types
Is particle physics concerned with gravity?
Not really - it is usually ignored because it is very feeble unless large masses are involved.
What is the mass of a W boson?
About 100 times that of a proton.
Compare and explain the ranges of a W boson and a photon.
• W boson - Very short range because it has a large mass. This means it requires a lot of energy to create and can’t travel very far. • Photon - Infinite range because it has zero mass.
What are the different types of line on a Feynman diagram used to represent?
• Gauge bosons (exchange particles) - wiggly lines • Other particles - straight lines
What are the rules for drawing Feynman diagrams?
• Incoming particles start at the bottom and move upwards • Baryons and leptons can’t cross from one side to the other • Make sure charges on both sides balance • A W- particle going to the left has the same effect as a W+ parcial going to the right
What exchange particle is involved in two electrons repelling each other?
Virtual (gamma) photon
What are electron capture and electron-proton collisions?
• Electron capture is when a proton and electron are attracted by the electromagnetic interaction and a W+ boson goes from the proton to the electron, causing a neutron and neutrino to be formed. • Electron collision is when the proton and electron collide. The same products are formed but a W- boson travels from the electron to the proton instead.
What is the difference between electron capture and electron-proton collision?
• In electron capture, a W+ boson travels from the proton to the electron. • In electron-proton collisions, a W- travels from the electron to the proton.
What is the particle equation for beta-minus decay?
Neutron -> Proton + Electron + Antineutrino
What is the particle equation for beta-plus decay?
Proton -> Neutron + Positron + Neutrino
Why is an antineutrino produced in beta-minus decay, while a neutrino is produced in beta-plus decay?
To conserve lepton number.
What is a virtual particle?
Particles which exist for only a very short time and cannot be detected.
Remember to learn specific Feynman diagrams.
Practice drawing our a spider diagram of the different types of particles.
Do it!
What are hadrons?
Particles that feel the strong nuclear force. They are not fundamental.
What are hadrons made of?
Quarks
Are hadrons fundamental particles?
No, they are made of quarks.
What are the two types of hadrons?
• Baryons • Mesons
What is the difference between baryons and mesons?
• Baryons - Made of 3 quarks and decay into a proton directly or indirectly • Mesons - Made of a quark and antiquark and do not decay into a proton
Name some baryons.
• Protons • Neutrons • Other particles (e.g. Sigmas)
What is the only stable baryon?
Proton - this means all baryons will decay in sequence and eventually form a proton.
Are antibaryons found in ordinary matter?
No, because they annihilate with baryons.
What values are particles given in baryon number conservation?
• Baryons = +1 • Antibaryons = -1 • Other particles = 0
What are some examples of antibaryons?
• Antiprotons • Antineutrons
Why does beta decay happen?
Neutrons are not stable baryons, but protons are, so a neutron will decay into a proton.
Are mesons stable?
No
What are the different types of meson?
Pions and kaons
What is another name for a pion?
Pi-meson
What is another name for a kaon?
K-meson
What is the difference between pions and kaons?
• Pions - Lighter, less unstable, not strange • Kaons - Heavier, more unstable, strange
What happens to kaons?
They decay into pions.
How were pions and kaons discovered?
In cosmic rays.
How do mesons interact with baryons?
Through the strong force.
What are the general rules for determining the type of interaction in a reaction?
• If any leptons involved at all -> Weak interaction • If strangeness isn’t conserved -> Weak interaction • All others -> Strong interaction
What are leptons?
Particles that do not feel the strong interaction. They are fundamental.
What are the different leptons?
• Electrons • Muons • Neutrinos • Tau
What happens to muons?
The eventually decay into electrons. This is because muons are unstable.
What can muons be described as?
Heavy electrons.
What is the mass and charge of neutrinos?
• Mass - Almost zero • Charge - Zero
How does lepton conservation work?
• There are 3 generations of lepton number - electron, muon and tau • Each lepton number must be conserved separately • Each normal lepton and its respective neutrino is given a lepton number of +1 • Each anti-lepton and its respective antineutrino is given a lepton number of -1
What are the symbols for each lepton number?
• Electron lepton number = Le • Muon lepton number = Lmuon • Tau lepton number = Lt
What are antiparticles of hadrons made from?
Antiquarks
How do strange particles (e.g. kaons) interact?
• Created by the strong interaction • Decay via the weak interaction
Strange particles are always produced in pairs (e.g. K+ and K-). Why?
The strangeness cancels out to become 0, so that strangeness is conserved. Therefore, the reaction is a strong interaction.
What are the types of quark?
•Up • Down • Strange
What is the charge of an up quark?
0.6666666667
What is the charge of a down quark?
-1/3
What is the charge of a strange quark?
-1/3
What is the charge of an anti-up antiquark?
-2/3
What is the charge of an anti-down antiquark?
0.3333333333
What is the charge of an anti-strange antiquark?
0.3333333333
What is the strangeness of a strange quark?
-1
What is the strangeness of an anti-strange antiquark?
1
What is unusual about strangeness?
• It is not ALWAYS conserved • Strange quarks are given a strangeness of -1 and anti-strange antiquarks are given a strangeness of +1
What quarks make up a proton?
uud
What quarks make up an antiproton?
anti-u, anti-u, anti-d
What quarks make up a neutron?
udd
What quarks make up an antineutron?
anti-u, anti-d, anti-d
What are baryons made of?
3 quarks
What are mesons made of?
A quark and an antiquark
What is the antiparticle of a pi-plus meson?
A pi-minus meson.
Remember to revise the diagram on mesons.
What is a weak interaction in terms of quarks?
A weak interaction is something that changes the quark type (e.g. A neutron (udd) turning into a proton (uud))
What properties are conserved in an interaction?
• Charge • Baryon number • Strangeness (only in strong interactions) • Lepton number (all 3 generations separately)
Can a quark exist on its own?
No.
What is quark confinement?
The idea that quarks cannot exist not their own.
Through which interaction do hadrons tend to decay?
Weak
Describe the mass, range and charge of a W boson.
• Non-zero rest mass • 0.001fm range • Can be positively or negatively charged
What are the quarks in a K0 meson?
• Anti-s • d
What are the quarks in an anti-K0 meson?
• s • Anti-d
