MODULE 8 IQ 5

Question 1

what are fundamental particles

Answer 1

fermions are particles which cannot be divided into smaller constituent particles
e.g. electrons, muons, quarks

Question 2

generations that decay to fermions

Answer 2

tau particle –> muons –> electrons

Question 3

electron (fermion) –> first generation

Answer 3

• both fundamental particle and subatomic particle
• belongs to group of particles called leptons
• 1st fundamental particle discovered by JJ Thomson in 1897

Question 4

muons (fermions) –> 2nd generation

Answer 4

• classified as leptons, but not a subatomic particle
• formed in atmospheric, high energy cosmic ray collisions
• negatively charged
• heavier than electrons

Question 5

Anderson and Neddermeyer discovery of muons

Answer 5

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

Question 6

Paul Dirac’s discovery of antiparticles

Answer 6

• 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

Question 7

antimatter pairs

Answer 7

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

Question 8

what is a antineutrino

Answer 8

Pauli proposed that the energy difference of the KE of electrons in beta minus decay, was attributed to the emission of another small particle

Question 9

KE of electron when decaying

Answer 9

energy produced between beta decay was shared between electron and antineutrino, following LOCOE
- antineutrinos would typically carry most of the energy, following LOCOM

Question 10

what are quarks

Answer 10

type of fermions (cannot be broken down any further)

Question 11

Deep Inelastic scattering experiment

Answer 11

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

Question 12

there are 3 generations of quarks:

Answer 12

1. up/down –> these are the most prevalent, smallest in size and most stable
2. charm/strange
3. top/bottom –> these are the least prevalent, largest in size and least stable

Question 13

hadrons quark composition

Answer 13

particles containing quarks

Question 14

baryons quark composition

Answer 14

particles containing 3 quarks

Question 15

mesons quark composition

Answer 15

particles containing 1 quark and 1 antiquark
- glued together by gluons

Question 16

protons quark composition

Answer 16

2 up quarks and 1 down quark

Question 17

neutrons quark composition

Answer 17

1 up quark and 2 down quark

Question 18

what are bosons

Answer 18

mediate the 4 fundamental forces

Question 19

SNF: gluons

Answer 19

• 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

Question 20

weak and nuclear force: W and Z boson

Answer 20

responsible for decay (radioactive, decay of 2nd and 3rd generation, nuclear fission)

Question 21

W bosons

Answer 21

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

Question 22

Z bosons

Answer 22

• electron-positron annihilation produces photons
• first coined by einstein when extended in planck’s EMR theory
• discovered in particle accelerators

Question 23

electromagnetic force: photons

Answer 23

• transmit electromagnetic forces
• first coined by einstein when extended in planck’s EMR theory
• these bosons have infinite range

Question 24

gravitational force: ‘gravitons’ (no evidence yet)

Answer 24

• not part of the standard model of matter
• large-scale –> haven’t integrated gravity into strong, weak, nuclear force & EMF

Question 25

what is the higgs field

Answer 25

field that allows fundamental particles to acquire mass
- responsible for all of the fermions’ mass
- predicted by the standard model of matter

Question 26

standard model of matter advantages

Answer 26

• 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

Question 27

standard model of matter disadvantages

Answer 27

• 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

Question 28

different types of particle accelerators

Answer 28

linear accelerator (LINAC), cyclotrons, synchrotrons

Question 29

linear accelerator (LINAC)

Answer 29

• 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

Question 30

cyclotrons

Answer 30

• 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

Question 31

synchrotrons

Answer 31

evolved from cyclotrons, but more efficient and widely used

Question 32

synchrotrons components

Answer 32

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