Particle Physics (PP) Flashcards
Fundamental particles:
No internal structure
Composite Particles:
have some internal structure
Proton quark composition:
UUD
Neutron quark composition:
UDD
Relative proton charge:
+1
Relative neutron charge:
0
Relative electron charge:
-1
Charge (C) of proton:
1.6x10 -19
Charge (C) of neutron:
0
Charge (C) of electron:
-1.6x10 -19
Mass (KG) of proton:
1.67x10 -27
Mass (KG) of neutron:
1.67x10 -27
Mass (KG) of electron:
9.11x10 -31
What is an AMU?
Atomic mass unit is one twelfth of the mass of a carbon-12 nucleus
How much is one Amu?
1.66x10 -27
Isotope:
Atom with different number of neutrons but same number of atoms and electrons
What is the specific charge:
Charge per unit mass of a particle
What is the equation for specific charge?
Charge (C) / Mass (Kg) = CKg-1
Why does an electron have a higher specific charge than a proton?
Although they both have the same magnitude of charge, the electron has a lower mass, so in the equation specific charge equation the specific charge of an electron will be higher.
What are the three features of antimatter?
Same exact mass, opposite charge, annihilates if it meets its matter pair, converting the total mass into photons.
State the antiparticle: electron
Positron
State the antiparticle: neutron
antineutron
State the antiparticle: neutrino
antineutrino
State the antiparticle: proton
antiproton
How is light described in the quantum model of light?
To be made up of small packets of energy called photons
State the photon energy equation:
plank’s constant x frequency
How is frequency related to wavelength?
wave speed = wavelength x frequency
State the equation for photon energy that includes wave speed and wavelength:
E = hc/wavelength
What does the number of photons determine?
the intensity of light
state the equation for power:
power = number of photons per second x hf
state the equation for power:
power = number of photons per second x hf
What is an electron volt?
the energy gained by an electron moving through a potential difference of 1V.
What does the Einstein equation state?
E=mc2 states the relationship between the mass of particle/antiparticle and its minimum energy
What is the rest mass?
the minimum mass of a particle when it is stationary
What is the rest energy?
The minimum amount of energy stored as mass when a particle is stationary
Can mass be conserved?
No, it can be converted into energy and vice versa.
Is energy conserved in particle reactions?
Yes
In particle physics calculations what must you consider regarding energy?
The rest energy and kinetic energy.
Total energy of particle =
rest energy + kinetic energy
What is annihilation?
When a particle and antiparticle collide, producing at least two photons to conserve momentum.
In annihilation, when does the minimum photon energy occur?
When the particle and antiparticle have no kinetic energy.
particle + antiparticle ->
photon + photon
In annihilation and pair production total energy is conserved:
energy of photons –> rest energy of particles + kinetic energy of particles
What is pair production?
The creation of a particle and antiparticle from a photon.
photon ->
particle + antiparticle
When does alpha radiation occur?
When a nucleus contains too many nucleons it decays by emitting an alpha particle.
Two features of alpha radiation:
short range and ionising
composition of alpha decay:
4
2
How is beta decay evidence for the neutrino?
Wolfgang Pauli hypothesised that a small neutral particle was created and had some effect on the energy of the reaction. Must be neutral hence hard to detect.
What are the three types of neutrino?
(anti)electron neutrinos, (anti)muon neutrinos, (anti)tan neutrinos
Three features of a neutrino:
Travel close to the speed of light, extremely small mass, no charge
When does beta - radiation occur?
when a nucleus contains too many neutrons
What is the simple equation for beta minus decay?
Neutron: proton + electron + antineutrino
What is the composition of beta - decay?
0
-1
Two features of beta - :
ionising and long ranged
Why can the kinetic energy of a beta particle vary?
When it leaves the nucleus, as the energy is released it is shared between the electron (beta particle) and neutrino
When does beta + decay occur?
When a nucleus has too may protons
Equation for beta + decay:
proton –> neutron + positron + neutrino
Composition of beta + decay:
0
1
How would you write a neutrino?
0
V
0
Features of beta + decay:
long ranged and ionising
When does gamma radiation/decay occur:
when a nucleus has too much energy and releases a photon
What is gamma radiation a part of?
EM radiaiton
What must there be for electron capture to occur?
the electron must have enough energy to create a neutron
Why does electron capture only happen from electrons with large nuclei?
large potential energy
What happens during electron capture?
Electrons from a higher energy shell fall into lower energy shell and emit and x-ray
Can a free neutron decay?
A free neutron can decay into a proton (the rest energy decreases, the energy goes to the kinetic energy of the particles)
Equation for electron capture:
proton + electron –> neutron + neutrino
Can a free proton decay?
A free proton can decay into a neutron (the rest energy increases so energy is required for this to happen)
free neutron decay equation:
neutron -> proton + B- + antineutrino
free proton decay equation:
proton -> neutron + B+ + neutrino
Draw the graph for electromagnetic force:
top to bottom y axis = repulsive to attractive (kN) -20-20
left to right x axis = separation (fm) 0-5
reciprocal graph type shape
Draw the graph for the strong force:
top to bottom y axis = repulsive to attractive (kN) -20-20
left to right x axis = separation (fm) 0-5
cross x axis at 0.5
Straight line down from 20 -> -20
curve upwards at around 1.5 on x axis
plateau at 3 and almost reach x axis at 5
What are exchange particles?
Virtual particles that cannot be detected directly but are exchanged during interactions
what are the four fundaments forces and what they are felt by:
Strong force - quarks
Weak force - all particles
EM force - charged particles
gravitation - particles with mass
What is the exchange particle of strong force?
pions between baryons
What is the exchange particle of the EM force?
virtual photons
What is the exchange particle of the weak force?
W+ and W-
What are the three main branches of particle classification?
hadrons, exchange particles and leptons
what is a hadron?
Particle made up of quarks and antiquarks, can interact via strong force
What are the two subcategories of hadrons?
baryons and mesons
What is a baryon?
Containing 3 quarks
What is a meson?
Containing 2 quarks
What is a lepton?
Cannot interact via strong force (i.e. electrons and neutrinos)
What are the two sub categories of leptons?
Charged and uncharged
What is an example of a charged lepton?
electron
What is an example of an uncharged lepton?
Neutrino
Through what forces can leptons interact?
Weak and EM
What are muons?
Particles that share the characteristics of electrons but have higher mass
Through what force do muons interact?
Weak force
μ- –>
(via W-) electron + anti electron neutrino + muon neutrino
μ+ –>
(via W+) positron + electron neutrino + anti muon neutrino
Through what forces can hadrons interact?
Weak force, strong force and EM
What are the 12 types of quarks?
(anti) up, (anti) down, (anti) strange, (anti) top, (anti) bottom, (anti) charm
What are the only stable baryons?
Protons
what will an isolated proton not do?
will not spontaneously decay as there is not a lighter particle for it to decay into
What are the two different types of mesons?
Pions and kaons
How can you describe the masses of mesons?
Their masses are in-between electrons and protons
How are mesons usually formed?
via the strong interaction
list all the mesons:
π+ π- π0 K+ K- K0
overall what quarks do mesons contain?
a quark and antiquark pair
What do K mesons decay into?
pi mesons, muons, antineutrinos or antimuons, neutrons
What do charge pions decay into?
antineutrinos or antineutrinos, muons, neutrinos
What do uncharged pions decay into?
high energy photons
What do muons and anti muons decay into?
electrons, antineutrinos or positrons, neutrinos
What (2) must be conserved in ALL interactions
energy and momentum
Particles only decay into….
other particles that have a smaller rest energy
What (5) other things must be conserved in particle interactions?
charge, lepton number, baryon number, quark fractions, strangeness
What is lepton number?
No. leptons - No. anti leptons
what is baryon number?
No. baryons - No. antibaryons
What is strangeness?
No. antistrange quarks - No. strange quarks
Which leptons have a lepton number 1?
electron, electron neutrino, muon-, muon neutrino
Which leptons have a lepton number -1?
positron, anti electron neutrino, muon+, anti muon neutrino
What has a baryon number of 1?
Baryons (neutrons and protons)
What has a baryon number of -1?
Non baryons
State the muon lepton number of all corresponding particles:
μ+ e+ V̄μ Ve
-1 0 -1 0
State the electron lepton number of all corresponding particles:
μ+ e+ V̄μ Ve
0 -1 0 +1
Why is lepton number conserved?
- leptons are created as particle anti particle pair
- leptons can be destroyed by annihilation
- leptons can turn into different types of leptons
Why is baryon number conserved?
- Quarks can be created in particle antiparticles pair
- Quarks can be destroyed in annihilation
- in weak interactions, quarks can turn form one type into another
How did strangeness come about?
scientists discovered that certain reactions that should be allowed, never occurred whilst others occurred very slowly, they realised these interactions which weren’t observed in reality but worked in theory only involved certain hadrons. Scientists deduced that there must be some other property which hadrons posses = strangeness
What can happen to quarks in EM interactions?
In EM interactions quarks CANNOT turn from one type to another
What happens to quarks in weak interactions?
IN weak interactions quarks CAN turn from one quark to another
In which interactions must strangeness be conserved?
strong interactions
In which interactions must strangeness not necessarily be conserved?
Weak
Up quark charge:
+2/3
Down quark charge:
-1/3
Strange quark charge:
-1/3
Anti up quark charge:
-2/3
Anti down quark charge:
+1/3
Anti strange quark charge:
+1/3
Strange quark strangeness:
-1
Anti strange quark strangeness:
+1
Strangeness of non strange quarks:
0
Baryon number of all non anti quarks:
+1/3
Baryon number of all anti quarks:
-1/3
Quark composition: π+
up + anti down
Quark composition π0
up + anti up OR down + anti down OR strange + anti strange
Quark composition of π-
anti up + down
Quark composition of K+
up + anti strange
Quark composition of K0
down + anti strange
Quark composition of anti K0
anti down + strange
Quark composition of K-
anti up + strange
Strangeness of K+
+1
Strangeness of K0
+1
Strangeness of anti K0
-1
Strangeness of K-
-1
