MODULE 8 IQ 5 Flashcards
what are fundamental particles
fermions are particles which cannot be divided into smaller constituent particles
e.g. electrons, muons, quarks
generations that decay to fermions
tau particle –> muons –> electrons
electron (fermion) –> first generation
- both fundamental particle and subatomic particle
- belongs to group of particles called leptons
- 1st fundamental particle discovered by JJ Thomson in 1897
muons (fermions) –> 2nd generation
- classified as leptons, but not a subatomic particle
- formed in atmospheric, high energy cosmic ray collisions
- negatively charged
- heavier than electrons
Anderson and Neddermeyer discovery of muons
applied external magnetic field to the cosmic radiation
- muon’s deflection trial was similar to that of the electrons however it had a radius of greater curvature
Paul Dirac’s discovery of antiparticles
- confirmed and discovered in cosmic rays by Carl Anderson in 1932
- gave rise to the concept of antimatter –> positrons have the same rest mass as the electron, however, opposite charges, spin, baryon/lepton numbers and strangeness
antimatter pairs
anderson found that when non-ionising photons would interact with a nucleus, it would produce 2 particle tracks that were identical to each other
- due to energy being converted to mass and vice versa
what is a antineutrino
Pauli proposed that the energy difference of the KE of electrons in beta minus decay, was attributed to the emission of another small particle
KE of electron when decaying
energy produced between beta decay was shared between electron and antineutrino, following LOCOE
- antineutrinos would typically carry most of the energy, following LOCOM
what are quarks
type of fermions (cannot be broken down any further)
Deep Inelastic scattering experiment
electrons were fired at high speeds into protons with a particle accelerator
- the inelastic collisions result in the transformation of KE, some of electrons’ KE was used to remove a quark from a proton
- protons are not fundamental particles as they can be broken into smaller particles
there are 3 generations of quarks:
- up/down –> these are the most prevalent, smallest in size and most stable
- charm/strange
- top/bottom –> these are the least prevalent, largest in size and least stable
hadrons quark composition
particles containing quarks
baryons quark composition
particles containing 3 quarks
mesons quark composition
particles containing 1 quark and 1 antiquark
- glued together by gluons
protons quark composition
2 up quarks and 1 down quark
neutrons quark composition
1 up quark and 2 down quark
what are bosons
mediate the 4 fundamental forces
SNF: gluons
- mediates strong force that holds nucleons together
- only interacts with quarks
- hadrons are all affected by NSF
- leptons do not interact with gluons –> fundamental particle –> not affected by SNF
weak and nuclear force: W and Z boson
responsible for decay (radioactive, decay of 2nd and 3rd generation, nuclear fission)
W bosons
beta minus decay: mediated by W minus boson –> decreases n:p ratio
beta plus decay: mediated by W plus boson –> increases n:p ratio
- discovered by high energy annihilations in particle accelerators
Z bosons
- electron-positron annihilation produces photons
- first coined by einstein when extended in planck’s EMR theory
- discovered in particle accelerators
electromagnetic force: photons
- transmit electromagnetic forces
- first coined by einstein when extended in planck’s EMR theory
- these bosons have infinite range
gravitational force: ‘gravitons’ (no evidence yet)
- not part of the standard model of matter
- large-scale –> haven’t integrated gravity into strong, weak, nuclear force & EMF
what is the higgs field
field that allows fundamental particles to acquire mass
- responsible for all of the fermions’ mass
- predicted by the standard model of matter
standard model of matter advantages
- explains composition of subatomic particle
- explains how fundamental forces are mediated, through understanding of bosons
- predicted and explained the nature of subatomic particles such as vector and gauge bosons
- consistent with several fields in the realm of quantum physics such as electroweak theory and quantum electrodynamics
standard model of matter disadvantages
- cannot explain how gravity is mediated, as there is no experimental evidence supporting the hypothesis of the graviton –> incompatible with the general theory of relativity
- cannot explain why the mass of subatomic particles is greater than the sum of constituents
- cannot explain the disproportionality between matter and dark matter
different types of particle accelerators
linear accelerator (LINAC), cyclotrons, synchrotrons
linear accelerator (LINAC)
- series of tubes connected to AC power supply
- particle will be attracted to the tube going forward and repelled by the tube behind it, causing it to accelerate at high speeds
- as charge accelerates, the required length of the tube becomes longer to maintain linear acceleration for the charge
cyclotrons
- uses both electric and magnetic fields
- magnetic field used to change direction –> as particle accelerates, radius of motion increases
- electric potential between the two ‘dees’ to accelerate the charged particle –> constant AC frequency provides electric field
synchrotrons
evolved from cyclotrons, but more efficient and widely used
synchrotrons components
LINAC: accelerates particles to high speeds
booster ring: magnetic fields further accelerate fast-moving particles produced from LINACs
storage ring: magnetic fields are used to maintain high-speed particles in centripetal motion –> produces EMR
