Subatomic Particles

In 1932, with the discovery of the neutron, the three basic constituents of an atom had been found. But in the same year a positive electron was discovered using cosmic rays.

Cosmic rays are very high-energy, charged particles that are produced in the Sun and other stars that continually bombard the Earth. Before particle accelerators were developed, cosmic rays were sued to examine high-energy nuclear collisions.

In the 1930s and 1940s, several new subatomic particles were discovered using cosmic rays. With the development of high-energy particle accelerators in the 1950s and 1960s, over 200 new subatomic particles were created in particle collisions. These short-lived particles were comparatively large (like neutrons and protons) and were called hadrons. Physicists initially thought all the new particles were fundamental particles but later discovered they were composed of more fundamental particles called quarks.

Murray Gell-Mann

• Fired electrons into nucleus
• Analysed kinetic energy, which should have been conserved through the collision (law of conservation of energy)
• Found the energy had been scattered (in a similar pattern to Rutherford’s gold foil experiment
• Concluded that there must be 3 points within the neutron causing this scattering, realising the neutron could not be a single solid particle
• Phenomenon now known as Deep Inelastic Scattering