Particles – Learning Outcomes  Describe the production of new particles in particle accelerators.  Discuss the history of fundamental particles.  Discuss the nature of anti-matter.  Describe pair production and annihilation. 1

Particle Accelerators  Early accelerators were linear accelerators, using a high voltage to accelerate charges.  These are limited by length. 2  Modern accelerators are circular accelerators using magnetic fields to continuously accelerate particles. by Riffsyphon1024 – public domain

Particle Accelerators 3

Fundamental Particles  Greeks: air, earth, fire, water.  Late 19 th century: periodic table elements, radiation.  By 1936: protons, neutrons, electrons.  Today: Quarks, leptons, bosons (more on these later), anti-matter (coming up next).  Current theory is called the Standard Model.  Future?: String theory, supersymmetry, quantum loops, m-theory – I have very little idea. 4

Anti-matter 5

Pair Production 6 by Junaidpv – CC-BY-SA-3.0

Pair Production  We must note conservation:  net charge before and after = 0.  mass-energy is conserved.  if electron and positron move off away from each other at the same angle, momentum is conserved. 7 by Junaidpv – CC-BY-SA-3.0

Pair Annihilation  Matter and anti-matter will annihilate if they have low kinetic energy and come into contact.  We only consider electron-positron annihilation.  This results in two high- energy photons being produced, which travel in opposite directions. 8

Pair Annihilation 9