particle physics

Question 1

conservation in a nuclear reaction

Answer 1

1. mass-energy
2. momentum
3. electric charge

Question 2

Disintegration energy (Q)

Answer 2

energy released when a radioactive disintegration takes place

Question 3

wolfgang pauli

Answer 3

proposed existence of 3rd particle emitted during beta decay, the neutrino in 1931 to account for loss of energy/momentum during beta decay i.e. conservation of energy/momentum did not work for b-decay

Question 4

enrico fermi

Answer 4

named neutrino

Question 5

cowan and reines

Answer 5

first to detect neutrino. only interacts very weakly with matter which is why it went undetected for so long

Question 6

john cockroft and ernest walton

Answer 6

produced a nuclear disintegration by bombarding lithium with artificially accelerated protons
-1st artificial splitting of a nucleus
-1st transmutation using artificially accelerated particles
-first experimental verification of E = mc^
-won nobel prize

Question 7

rutherford

Answer 7

first artificial transmutation
-bombarded nitrogen with a-particles

Question 8

paul dirac

Answer 8

predicted the existence of antiparticles (antimatter) and positrons mathematically

Question 9

segre and chamberlin

Answer 9

discovered antiproton

Question 10

carl david anderson

Answer 10

discovered positron (first known antiparticle) by observing it in a cloud chamber

Question 11

positron

Answer 11

antiparticle of the electron (same mass, opposite charge)
-produced tracks in a cloud chamber similar to an electron but was deflected in the opposite direction in a magnetic field

Question 12

pair production

Answer 12

the creating of 2 particles from energy.

-in pair production a particle and its antiparticle are created and momentum and charge are conserved
-occurs when high energy gamma ray photon loses its energy (hf) when it collides with a nucleus

Question 13

pair production equation

Answer 13

hf = 2mc^2 + Ek1 + Ek2

Question 14

pair annihilation

Answer 14

when 2 antiparticles are almost at rest and near each other they join together and disappear producing energy
-momentum before is almost 0 so momentum after must be 0. as a result 2 photons are produced in opposite directions

Question 15

pair annihilation formula

Answer 15

e+ + e- = 2hf

Question 16

ernest o’lawrence

Answer 16

developed first circular particle accelerator (cyclotron)
-elec. fields used for constant acceleration of particles
-magnetic fields used to control position of particles

Question 17

fundamental forces of nature

Answer 17

1. strong nuclear
2. electromagnetic
3. weak nuclear
4. gravitational

*check sheet for more info

Question 18

particle zoo

Answer 18

until the 1960s the different varieties of particles being produced by high energy collisions were called the particle zoo as there was no apparent way of categorising them

Question 19

families of particles

Answer 19

1. hadrons –> baryons (3 quarks) or mesons (1 quark 1 antiquark)
2. leptons (elementary particles)

Question 20

elementary particles

Answer 20

have no other particles inside i.e. cannot be broken into smaller particles

Question 21

leptons

Answer 21

elementary particles
-dont feel strong force
-feel weak force
-affected by gravitational and electromagnetic force (if charged)

Question 22

lepton family (check sheet for more info)

Answer 22

1. electron, electron neutrino (and antiparticles for both)
2. muon and muon neutrino
3. tau and tau neutrino

Question 23

hadrons

Answer 23

particles made up of quarks. split into two groups, baryons (3quarks) and mesons (1quark 1antiquark).
-feel strong and weak nuclear force
-affected by grav. and elec. force (if charged)
-

Question 24

baryons

Answer 24

made of any 3 quarks and mass > or = mass of proton. antibaryons made of 3 antiquarks

Question 25

mesons

Answer 25

made of any 1 quark and 1 antiquark and have mass between that of protons and electrons

Question 26

hadron family (baryons) *more info on sheet

Answer 26

1. proton (uud) - and antiparticle 2. neutron (udd) 3. lambda (uds) 4. sigma (uus)

Question 27

hadron family (mesons)

Answer 27

1. pion (ud_) d bar = anti down --> &antiparticle 2. kaon (us_)

Question 28

quarks *see sheet for types + charges

Answer 28

elementary particles that have a charge of +-1/3 or +-2/3

Question 29

proton quarks

Answer 29

uud

Question 30

neutron quarks

Answer 30

udd

Question 31

lambda quarks

Answer 31

uds

Question 32

sigma quarks

Answer 32

uus

Question 33

pion quarks

Answer 33

ud_

Question 34

kaon quarks

Answer 34

us_

Question 35

linear particle accelerator benefits

Answer 35

They are easier to build. * They do not require large magnets. * less expensive. circular need huge radii to bring particles to high energy states. higher cost of constructing circular accelerator. * Charged particles radiate away energy when accelerated. At high energy state, radiation loss is less for linear accelerator compared to circular accelerator.

Question 36

gell-mann and zweig

Answer 36

independently proposed the existence of quarks. gell-man took the name quark from james joyce's 'finnegan's wake' -discovered by bombarding protons with high speed electrons. they were deflected through different angles meaning protons consisted of some sort of particles

Question 37

circular particle accelerator benefits

Answer 37

-can accelerate particles to very high energies without needing a very long tunnel - cost -easier to force particle collisions

Question 38

why are neutrinos hard to detect

Answer 38

1. very small mass 2. no charge 3. interact weakly with matter