Antimatter revealed

18 March 1998
 

Display the high resolution version

Five years after P.A.M.Dirac's historic papers that included the prediction of antimatter, in March 1933 Carl Anderson at Caltech published* the first example of an antiparticle - the positron, or antielectron, which he had discovered the previous year. This week's image shows the creation of many pairs of electrons and positrons in a bubble chamber, where charged particles leave trails of tiny bubbles. A magnetic field makes negative particles curl left and positive particles curl right. There are several examples where a positive and a negative particle appear together, as if from nowhere (more easily found on the larger image here). These are electrons (negative) and positrons (positive) created from photons, which have no electric charge and therefore leave no trail in the chamber. A closer look at the top left of the image (here) shows a particularly good example.This picture, from the neutrino experiment E632 performed at the Fermilab 15-ft bubble chamber, was found by a team at the University of Birmingham. It is particularly interesting as it can be used to estimate the mass of the positron.

(*See The Physical Review, 43 10 (1933))

Credit: G.T.Jones, Birmingham University / Fermi National Accelerator Laboratory

Please contact person or institution named for information about permission for public or commercial use.