2.1 & 2.2 Particles and Radiation Flashcards
2.1 atomic structure & decay equations 2.2 classification of particles
What are the 3 constituents of an atom?
protons
neutrons
electrons
what is the structure of an atom?
- at the centre of an atom is a nucleus
- the nucleus is formed of protons and neutrons
- they’re known as nucleons
- electrons orbit the nucleus in shells
What are the properties shown in the constituents of the atom?5
- charge
- relative charge
- mass
- relative mass
- specific charge
What is the charge of a proton?
1.6 x 10^-19
What is the relative charge of a proton?
+1
What is the mass of a proton?
1.67 x 10^-27
What is the relative mass of a proton?
1
What is the specific charge of a proton?
9.58 x^7
What is the charge and relative charge and specific charge of a neutron?
0
What is the mass of a neutron?
1.67 x 10^-27
What is the relative mass of a neutron?
1
What is the charge of an electron
-1.6 x 10^-19
What is the relative charge of an electron?
-1
What is the specific charge of electrons?
1.76 x 10^11
what is the mass of electrons?
9.11 x 10-31
What is the relative mass of an electron?
0.0005
What is the specific charge of a particle?
The charge to mass ratio
- calculated by dividing a particles charge by its mass
What is an isotope?
atoms with the same number of protons but different numbers of neutrons
What is the proton number denoted by?
Z
What is the nucleon number and what is it denoted by?
- number of protons and neutrons
- A
How do strong nuclear forces keep nuclei stable?
- by contracting the electrostatic force of repulsion between protons in the nucleus
- only acts on nucleons and has a very short range, - - —– where it is attractive up to separations of 3fm, and below separations of 0.5fm
What are unstable nuclei? 4
- those which have too many either protons, neutrons or both
- causing the strong nuclear forces to not be enough to keep them stable
- thus the nuclei will decay in order to become stable
- the type of decay experienced depends on the amount of each nucleon in them
What are the different types of decay?
- alpha decay
- beta-minus decay
What is alpha decay?
- occurs in large nuclei with too many both protons and neutrons
- proton number decreases by 2
- nucleon number decreases by 4
What is Beta-minus decay?
- occurs when nuclei which are neutron rich have too many neutrons
- the proton number increases by one
- nucleon number stays the same
What are antiparticles?
particles that have the same rest energy and mass but all its other properties are opposite the particles
What are photons?
- electromagnetic radiation travel in packets called photons
- they transfer energy
- have no mass
What is the relationship between photon energy and frequency of the electromagnetic radiation?
energy of photons is directly proportional to the frequency of electromagnetic radiation
What is the Planck constant?
- h
- 6.63 x 10^(-34)
What is beta-plus decay?
- high energy positron emitted from the nucleus
- when a proton turns into a neutron emitting a positron and an electron neutrino
- proton number decreases by one
- nucleon number remains the same
What is an electron neutrino?
- type of subatomic particle - - with no charge
- negligible - mass
- which is also emitted from the nucleus
What is an anti-neutrino?
- anti particle of a neutrino
- produced during beta minus decay
What is annihilation?
- when a particle meets its equivalent anti-particle they both are destroyed
- their mass is converted into energy in the form of two gamma ray photons
What happens when an electron and positron collide?
their mass is converted into energy in the form of 2 photons emitted in opposite directions
What is the minimum energy of 1 photon after annihilation?
the total rest mass energy of one particle is:
E=hf
What is the rest mass energy of one of the particles in annihilation?
E = hf = hc/gamma
what is pair production?
- opposite of annihilation
- when a photon interacts with a nucleus or atom and the energy of the photon is used to create a particle - antiparticle pair
What occurs when a photon with enough energy reacts with a nucleus?
produces an electron - positron pair
Why must the photon react with enough energy in pair production?
the energy of the photon must be above a certain value to provide the total rest mass energy of the particle-antiparticle pair
What is the minimum energy for a phone to undergo pair production?
the total rest mass energy of the particles produced
What direction do the particle and anti - particle move in pair production?
opposite directions due to the conservation of momentum
What are the two categories matter and antimatter are split into?
Hadrons and leptons
What are hadrons?
- groups of subatomic particles that are made up of quarks
- hadrons can feel the strong nuclear force
What are the 2 classes of hadrons?
Baryons (3 quarks)
Mesons (quark and anti-quark pair)
What are the common baryons?
protons, neutrons and their anti-particles
What are the common mesons?
pions and kaons and their anti particles
What is the quark structure of baryons?
3 quarks
What is the quark structure of mesons?
quark and anti-quark
What is a baryon number?
- depends on whether the particle is a baryon, anti-baryon or neither
- baryons have +1
- anti-baryons have -1
- particles not baryons have 0
- quantum number and is conserved in all interactions
What is the baryon number of up down and strange quarks?
- 1/3
- anti quarks have -1/3
What properties does the proton have as a baryon?
- most stable baryon
- longest half life of any baryons
- most baryons eventually decay to be a proton
- most stable as it is the lightest baryon
- radioactive decay occurs when heavier particles decay into lighter particles
- decay of the proton would therefore violate the conservation of baryon number
What are the most common mesons?
- pions
- kaons
What are properties of pions?
- lightest mesons
- more stable than most mesons
- originally discovered in cosmic rays
- can be observed in a cloud chamber
What are strong nuclear forces?
forces that keep protons and neutrons bound together in a nucleus and is one of the four fundamental interactions
- each of these interactions is caused by a particle exchange
What are pions?
- the exchange particle of the strong nuclear force
- strong force is transmitted between a proton and neutron bay the exchange of a piano
- pions mediate the strong nuclear forces
What is a gluon?
- an exchange particle of the strong force
What’s the difference between a pion and a gluon?
- gluons are responsible for binding quarks together
- referred to as the strong interaction
- pions are responsible for binding nucleons together
- referred to as the strong nuclear force
How are kaons produced?
by the strong interaction between pions and protons
Why do Kaons decay?
- they’re heavy and unstable this decay into pions normally
What is the lifetime of kaons and why?
- usually have long lifetimes
- because kaons contain a strange quark and longer lifetimes are characteristic of particles containing strange quarks
What is neutral kaon decay?
neutral kaon -> positive pion + negative pion
What are leptons?
- fundamental particles
- interact with other particles via the weak, gravitational or electromagnetic interactions
- not via the strong nuclear force
What makes a particle a fundamental particle?
not made up of any other particles
- i.e. no quarks
What are the most common lepton?
- electrons
- electron neutrino
- muon
- muon neutrino
and their anti-particles
How do positive pions decay?
positive pions -> anti-muon + muon neutrino
What is a lepton number?
- number of leptons in an interactions
- depends on whether the particle is a lepton, anti-lepton or neither
- lepton have +1
- anti-leptons have -1
- particles not leptons have 0
- quantum number that is conserved in all interactions
What is muon decay?
- muons decay into an electron
- anti muons decay into positrons
- muon decay occurs through the weak interaction
What is the Feynman diagram of muon decay?
- muon goes to muon neutrino
- then through W- boson it goes to
- anti electron neutrino and electron
What are the 3 quark flavours?
up
down
strange
What do all quarks have?
- charge
- baryon number
- strangeness
How is the charge of quarks relevant
the sum of them determine the charge of a hadron
What is the quark combination of baryons?
they’re not fundamental thus made up of 3 quarks
What is the quark combination of protons?
uud
What is the quark combination of neutrons?
udd
What is the quark combination of mesons?
pions and kaons are made up of a quark and anti-quark pair
What is the quark structure of pions?
positive pions - up, anti-down
negative pions - anti up, down
neutral pions - up, anti up or down, anti down
What is the quark combination of kaons?
positive kaons - up, anti-strange
negative kaons - anti-up, strange
neutral kaon - down, anti-strange or anti-down, strange
What are the properties of strange particles?
- produced through the strong interaction
- decay through weak interaction
- produced in quark - antiquark pairs
What is strangeness?
- quantum number, like baryon and lepton number
- conserved in every interaction except the weak interaction
- strange particles are produced in pairs (e.g. K+ and K-)
- particles with strange quark have -1
- with anti strange have +1
- with no quark have 0
What is the process of particle physics?
- a new theory is developed; may be hypothesis the existence of a new particle and its properties
- experiments carried out to find this new particle
- different experiments are combined to suggest a new discovery
- if confirmed usually repeated to reduce experimental uncertainty, the theory is then validated
- if validated the scientific community will accept it as the theory is more likely to be correct
What are particle accelerators used for?
to collide particles at very high speeds in order to
- produce new particles
- reveal the inner structure of particles
what happens in a particle accelerator?
particles collide at very high energies meaning they travel close to the speed of light
What are the 2 types of particle accelerators?
- linear
- circular
What is required in a circular particle accelerator and why?
- require extremely powerful superconducting magnets
- to keep high speed particles in a circular orbit
When experiments using particle accelerators occur why is it important it is done collaboratively?
- they’re expensive
- complicated pieces of equipment required to make a particle accelerator
- provides funding
- expertise to design
- construct and operate experiments successfully
What does LHC stand for?
large hadron colider
What is a large hadron collider?
- works largest and highest energy particle collider
- based at CERN in Geneva on the France, Swiss botder
- 2500 scientists work there, comprising of 110 nationalitiees
What are the 4 main detectors that the LHC Is made of?
- CMS
- LH Cb
- ATLAS
- ALICE
What occurs in the CMS portion of the LHS?
- confirmed existence of the Higgs Boson
- same scientific goals as ATLAS but a different magnetic system
What occurs in the LH Cb portion of the LHS?
- study of matter - antimatter asymmetry in particles containing the bottom quark
- discovery of the tetra - quark
What occurs in the ATLAS portion of the LHS?
- discovery of the Higgs boson
- search for dark matter
- search for physics beyond the standard model
What occurs in the ALICE portion of the LHS?
- proton beams collide head on at each detector
- study of quark-gluon plasma
