Particle Physics Flashcards
Disintegration Energy
Energy released when a radioactive disintegration takes place spontaneously. (Q)
Wolfgang Pauli proposed…
the neutrino (ν). Not detected until 1956.
First Splitting of an Nucleus by Artificially Accelerated Particles
Cockroft (English) and Walton (Irish). 1932. Bombarded lithium with artificially accelerated protons. Also the first transmutation and artificially accelerated reaction.
Unified Atomic Mass Unit (U)
Used in particle physics in unified atomic mass units (instead of kg)
Anderson, (USA) 1932 found…
antimatter through the use of cloud chambers
Cloud Chamber
A chamber where moving charged particles produce tracks that can be seen.
Positron
Antiparticle of the electron. Same mass and amount of charge as the electron, opposite sign.
Pair Production
The creating of two particles from energy: particle and anti-particle. Charge and momentum are conserved.
hf= 2mc² + E(k1) +E(k2)
Dirac (1920)…
Predicted the existence of antiparticles.
1955
Antineutrons and antiprotons confirmed experimentally.
1995
CERN produced 9 antihydrogen atoms.
Pair annihilation
When particle and antiparticle are near each other and almost at rest they join together. Matter disappears and energy is produced.
e+ + e- = 2hf
Ancient Greek beliefs
Nature= 4 elements: air, water, fire, earth. Atoms make up everything, but were believed to be indivisible (atomos= indivisible in Greek)
Nineteenth Century
Atoms exist w/ forces between them, expected to be divisible and have internal structure w/ smaller particles.
Twentieth Century
-1911, Rutherford gold experiment= structure of atom and size, charge and mass of elements. Attracted by electrostatic forces.
-1932, neutron discovered w/ mass, size and lack of charge.
… strong nuclear force was discovered to keep neutrons and protons together in atom.
4 Fundamental Forces of Nature
(weakest to strongest)
- gravitational
- weak nuclear force
- electromagnetic force
- strong nuclear force
Gravitational Force
Attractive between particles w/ mass, v. weak unless large masses.
Distance= infinite.
Size= inversely perpendicular to distance squared.
Weak Nuclear Force
Felt by all particles. Less powerful than strong force.
Distance = 10^(-18)
Electrostatic Force
Binds electrons and protons together in atoms, and atoms and molecules together in matter.
Basis of all modern technology.
Exists between charged particles and magnetic forces.
Attractive or repulsive.
Size= inv. perp. to dis sq. Distance= infinite.
Strong nuclear force
Strongest force, only acts on certain particles.
V small range, 10^(-5)m.
Binds nucleus together against electrostatic force,
2 categories of particles
- leptons
- hadrons
Leptons
-Feel weak force only.
-No internal structure … elementary particle.
6 (all in log tables, incl. electron)
Hadrons
Feel both nuclear forces. Over 100 types split into 2 groups: mesons and baryons.
Elementary Particle
A particle that has no other particles inside it or no sub-parts to it.
