Unit 1.7 Particles and Nuclear structure - Matter Flashcards
What are smaller than the atom, the once thought to be smallest fundamental particle?
Quarks and leptons
How many generations of matter are there?
3
Which generation do the quarks and leptons we’re looking at fall under?
I
Name the two leptons, including their symbols
Electron (e-) and Electron neutrino (Ve)
Name two quarks, including their symbols
Up (u) and down (d)
What’s the charge of an electron lepton?
-1
What’s the charge of an electron neutrino lepton?
0
What’s the charge of an up quark?
+2/3
What’s the charge of a down quark?
-1/3
What does each particle have?
An equivalent antiparticle
What’s similar and what’s different between a particle and an antiparticle?
They share the exact same properties (eg - mass) but have opposite charges, lepton numbers and baryon numbers
Which antiparticle can have two different names? What are they?
The antielectron or positron
What are the antileptons, including their symbols?
–
Antielectron/positron (e+) and electron antineutrino (Ve)
What do all antiparticle symbols use? Which one is an exception?
The little bar above the normal particle symbol, apart from e-, which changes to e+ in the antiparticle form
What are the antiquarks, including their symbols?
antiup (u) and antidown (d)
Antielectron/positron charge
+1
Electron antineutrino charge
0
Antiup charge
-2/3
Antidown charge
+1/3
What happens when a particle and an antiparticle meet?
They annihilate eachother and mass is converted into energy
What happens in the example of a particle and an antiparticle meeting, when an electron encounters a positron?
It releases two photons of gamma energy in opposite directions
Which are the lightest of subatomic particles?
Leptons
How do leptons exist?
Always exist separately and do not combine to form composite subatomic particles
What’s the lepton number of our leptons?
Both electrons and electron neutrinos have a lepton number of 1
What is the lepton number of the leptons antiparticles?
1-
Electrons charge
-1e
Electron neutrinos charge
0
How do quarks and antiquarks exist?
They do not exist separately. They combine to form composite subatomic particles
What do quarks and antiquarks combine to form?
composite subatomic particles, known as hadrons
What are there three types of?
Hadrons
What are the three types of hadrons?
Baryons, antibaryons and mesons
What do baryons consist of?
3 quarks
What do antibaryons consist of?
3 antiquarks
What do mesons consist of?
1 quark and 1 antiquark
What are not to be confused in this unit please?
Baron/lepton numbers and charges
What are all quarks baryon numbers?
+1/3
Antiquarks baryon number
-1/3
All baryons baryon number
1
Antibaryon baryon number
-1
What are the most commonly known baryons?
Protons and neutrons
What are protons and neutrons?
Baryons, the most commonly known ones
What does a quark composition make up?
Charge, NOT baryon number
Proton charge
1+
Proton baryon number
1
Proton quark composition
uud
(to make the charge of +1)
Neutron charge
0
Neutron baryon number
1
Neutron quark composition
udd
(to make a charge of 0)
What combine to form the pions?
The first generation of quarks and antiquarks
What do the first generation of quarks and antiquarks combine to form?
The pions
ℼ+ quark composition and charge
-
ud
1e charge
ℼ- quark composition and charge
-
ud
-1e
ℼ0 quark composition and charge
-
uu
0 charge
OR
-
dd
0 charge
(notice that there’s two possible ways of making of the neutral pion)
What are responsible for giving particles baryon numbers?
Quarks
What’s an electrons baryon number?
0
(remember - electrons are leptons, therefore they exist separately and do not have a quark composition. They do have a lepton number though, which is 1)
What other two baryons apart from protons and neutrons are common and what are their quark makeups and charges?
Δ- (delta minus) - ddd = -1
Δ++ (delta plus plus) - uuu = 2+
What are the pions?
Mesons
Proton and neutron symbols
p and n
What’s the phrase for leptons existing separately and on their own?
Fundamental
What are the fractions of charge for the quarks fractions of?
Fractions of the e charge (on the front of the data booklet in exam)
Why do we only look into 3 types of hadrons?
Only mesons and baryons have been observed
Up quark up number
+1
Up quark down number
0
Down quark up number
0
Down quark down number
+1
What is anything that isn’t an up or down quarks quark number?
0
What is an antiup quarks up number?
-1
What is an antidown quarks down number?
-1
What is the gravitational force experienced by?
All matter
What is the gravitational forces range?
Infinite
Additional comments on the gravitational interaction
Very weak - negligible except between large objects like planets
What is the weak force experienced by?
All leptons and all quarks so also all hadrons too
Weak force range
Very short
Additional comments on the weak force
Only significant when the e-m and strong interactions do not operate
What’s the electromagnetic (e-m) force experienced by?
all charged particles
Electromagnetic force range
Infinite
Additional comments on the electromagnetic force
Also experienced by neutral hadrons, as these are composed of quarks
What’s the strong force experienced by?
All quarks, so all hadrons
Strong force range
short
What are the four fundamental forces?
Gravitational, weak, electromagnetic (e-m), strong
What’s the phrase for being observed on an everyday scale?
Macroscopically
Which forces are observed macroscopically?
Electromagnetic and gravitational
What do we know with regular forces that they do when they’re close? Which force tells us this?
Electromagnetic forces tell us that protons ought to strongly repel as they’re so close
What are forces modelled using in the quantum world? What are they called?
Exchange particles - Bosons
What are bosons and what do they do?
Particles that “carry” the force- they govern the interaction
What are the types of boson?
The photon, the gluon, the W boson, the Z boson and the Higgs boson
Electromagnetic boson
Photon
Gravitational boson
Graviton
Strong boson
Gluon
Weak bosons
W+, W-, Z
What does Higgs Boson explain?
Why the photon has no mass whilst the W and Z bosons do, and also where electrons and other particles get their mass
What can the strong force do?
Overcome the large repulsion between protons
Which force is the strong force much stronger than, and by how much?
100x stronger than the electromagnetic force
Which force has the shortest lifetime?
Strong
Why is the strong forces range so small?
Within the nucleus of an atom, typically in collisions between particles
It becomes negligible at longer distances, therefore we have no everyday experiences of it
Which forces is the weak force much weaker than, and by how much?
Several magnitudes weaker than the strong and electromagnetic forces
What’s a common example of the weak force?
Particle decaying by beta emission
Which force always has a particular fermion that is always involved in its interactions? What is it?
The weak force - electro neutrinos
Which force includes a quark changing “flavour”?
The weak force
Which force is responsible for practically all phenomena encountered in ordinary life?
Electromagnetic force
Which force keeps electrons in orbit around a nucleus?
Electromagnetic
Which force holds atoms and molecules together?
Electromagnetic
What is always involved in an electromagnetic force? What is its symbol?
A photon (squirly Y)
Which is the weakest force?
Gravitational
Which force is dominant on a macroscopic scale? Why? What’s wrong with this?
Gravitational force, due to its large range
This causes problems within the standard model
Which force is not compatible with the current understanding of quantum mechanics?
The gravitational force
What’s the first question to ask yourself when forgoing out which force is responsible? If yes, what type of force is it?
Is there a neutrino present?
Weak
What’s a different indicator that leads immediately to the weak interaction?
Change of quark flavour
What’s the second question to ask when working out which force is responsible? If yes, which type of interaction is it?
Are all the particles made up of quarks? (all mesons or baryons)
Strong interaction
What’s the third question to ask to work out which force is responsible? If yes, which force is it?
Are the particles charged (quarks or electron and positron)?
Electromagnetic interaction
What’s another immediate sign that a reaction is electromagnetic?
A photon (squirly Y) is involved
Is the electromagnetic interaction experienced by neutral hadrons?
Yes, as these are composed of quarks
Which particle was instrumental in the development of quark theory?
Delta plus plus
Two features of the pi mesons
-Short lifetimes, in the order 10-8s
-Decay by weak interaction - 1 quark changes flavour, producing a neutrino
Which interaction do the pi mesons decay by?
Weak interaction
What’s the energy conservation rule?
Energy cannot be destroyed or created, simply transformed from one form to another
When balancing a particle equation, what do we need to be equal on both sides?
-Charge
-Lepton number
-Baryon number
What’s a useful trick for if you’re explaining why you chose a specific force involved in an interaction?
Point out ones it clearly can’t be, yanno things like neutrino involved probably is weak, or a change of flavour is weak
Which interaction consists of only quarks?
Strong force
Which is the only force involving leptons?
Weak force
What’s the lifetime of the strong force?
10-24s (shortest)
What’s the lifetime of the weak force?
10-8s
What’s the lifetime of the electromagnetic force?
10-12-10-18 s
Which force has a common example and what is it?
The weak force - particle decaying by beta emission
Word for insignificant in terms of forces
Negligible
Negligible
Insignificant and not worth considering (like the gravitational force unless experienced between large objects)
When does the strong force become negligible?
At longer distances
What’s a mesons baryon number?
0
What’s the only matter that isn’t effected by the gravitational force?
The photon
Describe the life span of the pions.
Which is the shortest and why?
Very short lifespans, especially pi0 as the quark and antiquark pair annihilate eachother
Why are neutrinos and anti neutrinos so difficult to detect?
-100,000s of times smaller than an electron, so they’re too small to detect with the current equipment
-No charge, so they don’t react with other atomic particles
Elementary particles
Not combinations of other particles (leptons)
Composite particles
Combination of other particles (quarks)
What does the fact that leptons are fundamental make them?
Structureless
What type of intereactions can electrons take part in?
All interactions except strong
In which type of reaction is the quark flavour not conserved?
Weak
Why are electron neutrinos so difficult to detect?
-100,000s of time smaller than electrons
-no equipment
-no charge = don’t react with other atomic particles
-interact via weak force, which has a very small range
What is everything for a photon?
0
In a conservation on up and down quarks, what is it important to do?
Break the particle into its quark makeup
What do you do with any of the equation questions involving symbols for elements e.g- 2
H
1
Just think - what protons and neutrons are in it? And work from there
Rate the forces in order of strength, starting from the weakest
-Gravitational
-Weak
-Electromagnetic
-Strong
what does the strong force have?
A short range
What do we have to do if a question asks “in quarks”?
Make sure we write out the whole formula (fractions and stuff), not just uud for example
Composite
Made up of quarks
(e.g - baryons, anti-baryons and mesons)
Word for ‘made up of quarks’ (e.g - baryons, anti-baryons and mesons)
Composite
Fundamental
Existing separately + do not combine to form composite subatomic particles
(e.g - leptons)
Which interaction is rare?
Weak interaction
What is the baryon number of a meson?
0
Which type of force doesn’t affect leptons?
Strong force
Which groups of particles are affected by the weak nuclear force?
Mesons, leptons, quarks
Which groups of particles are affected by the strong nuclear force?
Mesons and quarks
