Fig4_3 Invisible gamma ray photon

Fig4_3  Invisible gamma ray photon

Fig. 4.3 . An invisible gamma ray photon (top) produces an electron and a positron, short for positive electron, seen by curved tracks in a bubble chamber. Both the electron and the positron are bent into circular tracks by the instrumentís magnetic field, moving in opposite direction because of their opposite electrical charge and spiraling into a smaller circular motion as they lose energy. In this upper pair, some of the photonís energy is taken up in displacing an atomic electron, which shoots off towards bottom left. In the lower example, all of a gamma rayís energy goes into the production of the electron-positron pair. As a result, these particles are more energetic than the upper pair, and their tracks do not curve so tightly in the chamberís magnetic field. (Schematic of a Lawrence Berkeley Laboratory bubble chamber image, reproduced by Frank Close, Michael Marten and Christine Sutton in The Particle Explosion, New York: Oxford University Press 1987.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University