Particles Flashcards
Size of nucleus
1x10^-14m
Size of atom
1x10^-10m
How many times bigger is the atom than the nucleus
1000
Why is most of the atom empty space
Electrons orbit at relatively large distances compared to nucleus
Proton number
Z
Number of protons in a nucleus
Atomic number
Defines what element it is
Why is the electron number important
Tells you a lot about an atoms chemical behaviour and properties
Nucleon number
A
Number of nucleons
Mass number
Gives a good approximation of an atoms mass since electrons have negligible mass
Why are neutrons needed
Hold protons together
Why are protons useful
Identify element
Specific charge meaning
Ratio of a particles charge to mass in Coulombs per kilogram (Ckg^-1)
Formula for specific charge of a fundamental particle
Specific charge=Charge/Mass
Q=C/M
Why does the electron have the largest specific charge
Smallest mass by about 1840x
Why does the neutron have no specific charge
No charge
So not affected by fields and don’t deflect
Specific charge of nucleus
Q.nucleus/M.nucleus
(protons x 1.6x10^-19) / (nucleons x 1.67x10^-19)
Electrons ignored
Specific charge of an ion
Q.ion/M.ion
(nucleons x 1.67x10^-27) + (electrons x 9.11x10^-31)
What are isotopes
Same element, same proton and electron numbers
Different number of neutrons
What is isotopic data
The relative amounts of different isotopes of an element present in a substance
Name a use of one of hydrogens isotopes
Tritium
Used to illuminate fire exit signs without the need of electricity
Give an example of how isotopic data can be used
All living things contain carbon
% of radioactive carbon 14 pretty much the same for all living things’
Amount decreases after death as it decays to stable elements
Can calculate approximate ages of archaeological finds made of dead organic matter
By using the isotopic data to find the % of carbon left
Where does alpha decay occur
Large unstable nuclei
What is ejected in alpha decay
2 protons 2 neutrons
AKA a helium nucleus
What happens to the element as alpha decay occurs
Mass number decreases by 4
Atomic number decreases by 2
When does gamma decay happen
Nucleus has too much vibrational energy
Emitting gamma radiation
When does beta minus decay occur
Nucleus has too many neutrons for protons
Undergo Beta minus decay to improve its p:n
What is produced in beta minus decay
New element with one greater proton number
An electron emit
Electron antineutrino
What happens in beta minus decay
Neutron into proton
What happens to the nucleon number in beta decay
Nothing, stays the same
Electron is not a nucleon
Nucleon into nucleon
When does beta plus decay occur
When a nucleus has few too many neutrons to protons
Undergo to improve p:n
What happens in beta plus decay
Proton turns into a neutron
What is produced in beta plus decay
New element with one less proton
A positron emit
Electron neutrino
Alpha deflection
Small in magnetic and electric fields
Beta deflection
Larger in magnetic and electric fields
Gamma deflection
None
Pass straight through
No specific charge
Electron capture
Proton rich nuclei can capture an electron from inside the atom
Turning proton into a neutron
W+ boson from Proton
And an electron neutrino emit
Neutron emission
Unstable isotope with too many neutrons could eject a fast moving neutron
Proton emission
Unstable isotope with too few neutrons ejects a fast moving proton
Energy mass equivalency
E=mc^2
Mass and energy are interchangeable
Mass converted into energy in the right circumstance
Explain E=mc^2 variables
Energy in Joules
Mass in kg
Speed of light
Pro vs con for energy mass equivalency
Incredibly difficult to initiate
Potential to release insane amounts of energy
eV
Electron volt
Kinetic energy acquired by an electron when accelerated by a potential of 1 volt
J to eV
Divide by 1.6 x 10^-19
eV to J
x by 1.6 x 10^-19
Why is it hard to convert mass to energy
Can only be done using antimatter
Antiparticle
Every particle has an associated antiparticle with the same mass but an equal and opposite charge
Is the neutron the same as the anti-neutron
No
Other quantum properties like quantum spin differ
Annihilation
When a particles mass is converted into energy if it meets its corresponding antiparticle
Particle and antiparticle cease to exist
Producing two photons
To conserve momentum
Energy of the radiation in annihilation
Total energy of particle and antiparticle
Rest energies plus kinetic energies
E=mc^2 and E=0.5mv^2
Why are two photons produced in annihilation
To conserve momentum
Cannot conserve momentum with 1
Explain momentum change in annihilation
Particle + antiparticle = 0 momentum
2 photons produced, travelling in opposite directions means momentum after is also zero
Issue with annihilation
Produces lots of energy
Antimatter doesn’t occur naturally and can only be Created in particle accelerators
Currently the energy needed to store antimatter is far higher than the energy that can be produced
Why must particles and antiparticles be stored in magnetic fields
As soon as they meet they annihilate
Pair production
Very high energy photon of EM radiation ceases to exist, creating a particle and an associated antiparticle pain in its place
What is the excess energy used for in pair production
Kinetic energy of the particles
How does momentum change in pair production
Final momenta have equal and opposite vertical components
These cancel and the momentum remains unchanged
When can pair production occur
Photon energy >= mass energy of particle, antiparticle pair
What region are photons that spontaneously produce a particle antiparticle pair in
Gamma region of EM spectrum
When were antiprotons first created and discovered
1955
High energy protons collided with stationary protons
Creating protons and antiprotons
Why was the Higgs boson created so long after it was predicted to exist
Predicted in 1964
Proved in 2012 at CERN
It is the heaviest particle of the standard model
Particle collisions didn’t have enough energy to be greater than the Higgs bosons mass energy until 2012
What was the problem with initial beta decay interaction theories
Didn’t account for electron neutrino or electron antineutrino
When a neutron turned into a proton, the difference in mass energy created the beta particle
But when its kinetic energy was measured it was always less than that available
Must be another particle, no charge, low mass that shares the kinetic energy with beta particle
Explain the graph to alter beta decay theories
X=Kinetic energy of beta particles in MeV
Y=Number of beta particles
Curve going through origin and hitting X again before 0.6MeV
Steep initially, some beta had a small kinetic energy
Peaks soon, with many having a smallish kinetic energy
Slow decrease, a few having large kinetic energy
Not a single beta particle had 0.6MeV
Rest must be going to the electron antineutrino
Why was it hard to detect the antineutrino in beta decay
Very low mass
No charge
Observed in 1956
Neutrino abundance fact
Probably the most abundant particle in universe
Billion times more neutrinos than either protons or neutrons
Each second about 600 trillion pass through every square meter of earths surface
4 types of fundamental forces that act between particles
Strong
Weak
Electromagnetic
Gravity
What does the strong forces act on
All hadrons and quarks
Range of strong nuclear force
0-0.5fm is repulsive
0.5-3fm is attractive
Where fm = 10-¹⁵m
What is the strong force
Fundamental force
That acts on all hadrons and quarks
And holds nucleons in the nucleus together
What is the weak force
Fundamental force
That acts on quarks and leptons
Causing particles to decay
(Radioactive decay usually beta +/-)
What does the weak force act on
Quarks and leptons
Range of weak force
10-¹⁸m
What is the electromagnetic force
A fundamental force
Acting on all charges particles
Holding molecules and atoms together
Creating everyday forces
Examples of electromagnetic force
Tension
Drag
Push
Pull
Means friction and reaction forces can occur
Range of electromagnetic force
Infinite
Range of gravitational force
Infinite
What is the gravitational force
Fundamental force
Acting on all particles
Incredibly weak on a small scale so negligible in particle topic
What does the electromagnetic force act on
All charged particles
What does the gravitational force act on
All particles
2 forced acting on protons on nucleus
Electromagnetic between protons and protons trying to push them apart (replusion)
Strong force between protons and neutrons trying to pull them together (attractive)
Forces inside a hydrogen nucleus
No strong nuclear force
No electromagnetic force
No forces act between nucleons since only 1 proton
What if a nucleus was just protons
Electromagnetic force»_space;> Strong nuclear force
Would explode
Why do we have neutrons
Electromagnetic force»_space;> Strong nuclear force
Must be a neutral hadron so as to not add to EM
But contribute to SF
Increase the SF so SF=EM
How does beta minus decay alter forces in nucleus
No change to SF since still same number of hadrons
Increases EM since 1 more proton
Reduces difference between the two
So more stable nucleus
How does beta plus decay alter the forces in the nucleus
No change to SF since still same number of hadrons
Decreases EM since 1 less proton
Reduces difference between the two
So more stable nucleus
How many particles do I need to know about
12 (19 Inc antiparticles)
3 (6) Quarks
4 (8) Leptons
5 Bosons / exchange particles
List the quarks to know
Up
Down
Strange
Anti up
Anti down
Anti strange
What leptons do I need to know
Electron
Electron neutrino
Muon
Muon neutrino
Anti electron
Electron antineutrino
Anti Muon
Muon antineutrino
What exchange particles do I have no know
W boson Z boson Photon Gluon Higgs boson
What is a protons quark composition
uud
2/3 + 2/3 - 1/3 = +1
What is a neutrons quark composition
udd
2/3 - 1/3 -1/3 = 0
What is an antiprotons quark composition
uud
-2/3 -2/3 + 1/3 = -1
What is an antineutrons quark composition
udd
-2/3 + 1/3 + 1/3 = 0
How are muons produced
Particle accelerators
High energy cosmic ray showers
What are leptons
Fundamental particles involved in weak interactions (decays)
Why is the muon/antimuon different to electron/positron
Heavy electron/positron
Around 200 times more massive
What are hadrons
Particles composed of quarks and involved in strong interactions
Baryons and mesons
Important to remember about quarks existance
Quarks cannot exist individually
Must exist in pairs (mesons) or triplets (baryons)
Like charges can … a … to … eachother
Exchange
Photon
Repel
Opposite charges can … a … to … eachother
Exchange
Photon
Attract
Neutrino vs neutron
Neutrino is a fundamental particle whereas neutron is made of quarks
Gluon vs pion
Both exchange particles for strong force
Gluons act as exchange particles between quarks
Pions act as exchange particles between hadrons
Gluons hold quarks together inside hadrons
Pions hold hadrons together
What are the exchange particles associated with each type of force
Gravity = Graviton (don't need to know) Strong = Gluon/pion Electromagnetic = Photon Weak = Z/W boson
Difference between the exchange particles of strong force or electromagnetic force and weak
Z and W bosons both have mass but gluons and photons do not
Which bosons have mass
W+
W-
Z⁰
Which bosons have charge
W-
W+
Exchange particles in strong force interactions between quarks
Gluons
Exchange particles in strong force interactions between hadrons
Exchange pions
What is the higgs boson
Not an exchange particle
Creates a higgs field that gives mass to particles
What is conserved in all interactions/collisions
Total momentum Total energy Kinetic energy (if elastic) Charge Baryon number Lepton number Strangeness (in strong interactions)
Baryon number of pions and kaons
Mesons are not baryons so it’s 0
E.g 1/3 + - 1/3 = 0
What are mesons made of
1 quark and 1 antiquark
What are baryons made of
3 quarks or 3 antiquarks
Strangeness of a particle with 2 strange quarks
-2
Strangeness of a particle with 3 anti strange particles
+3
Pions
Mesons with strangeness of 0
Kaons
Mesons with strangeness
Quark composition of pi+
_
ud
Overall +1
Quark composition of pi⁰
uu dd ss
Charge is 0
Quark composition of pi-
_
ud
Charge is -1
Kaon production and decay
Produced in cosmic ray showers
And particle accelerators
By strong interaction
Decay by weak interaction into pions
Quark composition of K+
śu
Overall charge of +1
Quark composition of K⁰
_
sd
Overall charge of 0
Quark composition of anti K⁰
_
sd
Overall charge of 0
Quark composition of K-
_
su
Overall charge of -1
Quark composition of K-
_
su
Overall charge of
Quark composition of K-
_
su
Overall charge of
Quark composition of K-
_
su
Overall charge of -1
What do you do if you have a mixture of leptons
Separate into Le and Lu
Lepton electron and lepton muon
Electron Le and Lu
Le=+1
Lu=0
Electron neutrino Le and Lu
Le=+1
Lu=0
Anti electron/positron Le and Lu
Le=-1
Lu=0
Anti electron neutrino Le and Lu
Le=-1
Lu=0
Muon Le and Lu
Le=0
Lu=+1
Muon neutrino Le and Lu
Le=0
Lu=+1
Anti muon Le and Lu
Le=0
Lu=-1
Anti muon neutrino Le and Lu
Le=0
Lu=-1
When do you separate lepton number
When there’s electrons and muons
Le
Lu
Most stable lepton
Electron
Muons are short lived and quickly decay into electrons
Most stable baryon
Protons
Isolated neutrons will eventually decay into protons
Muon decay
u- —> e- + vu + ve
Muon (negative) into an electron, muon neutrino and an anti electron neutrino
Order for normal interactions without electrons and muons together
Q
B
L
S
Neutrino
Fundamental particle
No charge
Very small or zero mass
Interacts with other matter very weakly
Equation for feynman diagram at each junction for electron electron interaction
e2- —> e1- + gamma
e1- + gamma —> e2-
What goes on the y axis in feynman diagrams
Time
Exchange particles in beta minus decay
W- from neutron
Goes into beta- and anti ve in feynman diagram
Equations on the left junction for beta minus decay
n —> p + W-
d —> u + W-
How are particles and exchange particles represented on feynman diagrams
Straight lines for particles
Wiggly lines for exchange particles
Equation at right junction of beta minus decay
W- —> B- + anti ve
Same for quark composition feynman diagram
What exchange particles is involved in beta plus decay
W+
Comes from proton and into positron and electron neutrino
Equation on left junction for beta plus decay
p —> n + W+
u —> d + W+
Equation on right for beta plus decay
W+ —> B+ + ve
Same for quark composition diagram
Electron capture equation
p + e- —> n + ve
W+ boson as exchange particles from proton into electron
Exchange particles in electron proton collision
W- boson from electron to proton
Why is a colorimeter better than benedicts
Benedicts is only semi quantititive so only gives an idea of how much sugar is present by giving you a range of colours
Doesn’t tell you the concentration of sugar in the solution
Colorimeter is quantititive test so gives you a light intensity reading for light passing through the solution
Test for starch
Iodine
2 drops of potassium iodide solution to sample
A blue black colour indicates the presence of starch
What is the standard model
Table
With types of quarks
Types of leptons
And bosons (exchange particles)
Why do you get electron neutrino in beta plus decay
Left sides lepton number is zero
Without, right would be negative (antiparticle means -1 L)
So need an electron neutrino to add same amount of charge to get right hand side to zero
Why is an anti electron neutrino produced in beta minus decay
Left sides lepton number is zero
Without, right would be positive (+1 L)
So need an anti electron neutrino to decrease same amount of charge to get right hand side to zero
Strong nuclear force vs electromagnetic for range
Electromagnetic plateaus and never reaches 0 so range is infinite
SNF soon reaches zero after a few fm
Strange particle vs non strange particle
Strange has strangeness and a strange quark
Strange has a longer half life than expected
Strange decay by weak interaction
What will everything eventually decay into
Proton
What an an antiparticle
All properties are opposite
Except mass which is the same
Explain what is meant by electron capture
An atomic/shell/orbital electron Interacts with a proton In the nucleus By weak interaction Forming a neutron u>>>>d Neutrino released
State what roles exchange particles can play in an interaction
Transfer energy
Transfer momentum
Transfer force
Can sometimes transfer charge
What are exchange particles
Particles that are transferred between particls when a force acts between them
Most stable baryon
Proton
Uud
Most stable meson
Pion
Kaon decay into pions
Why isn’t it possible for a free proton to decay into a neutron without input of energy
Rest energy of neutron greater than rest energy of proton
So energy must be supplied
Scientists believe there is more matter than antimatter in the universe
Why is this surprising and what does it suggest about the interactions of particles in the early universe
Suprising since matter and antimatter must be created in equal amounts to conserve Barton, lepton and change number
Suggesting that the formation of the universe did not follow conservation laws
What determines the range of the force
Size of exchange particles
Heavier means shorter range
E.g W boson is very heavy, so short lived and hard to detect
But a virtual photon has no mass, so em has infinite range and can be detected
Z vs W boson
W has mass Z has mass
W charged Z no charge
Rest mass and charge of a photon
0
Describe what happens to the quarks in a neutron when beta minus decay occurs
Down into up
Via weak interaction
W- boson
How can the momentum and energy of a gamma Ray be determined from the properties of the electron positron pair
Both conserved in particle interaction
Total momentum before and total energy before is equal to the momentum of gamma Ray before
Energy after pair production
Rest energy + kinetic energy
Why can’t a kaon be sś
Strangeness would be zero
So would actually be a pion
Since kaons have a strangeness
