Positron annihilation in flight

This picture is part of an electromagnetic shower in a neon-hydrogen mixture in the Fermilab 15-foot bubble chamber.

The highlighted track is a positron from an electron-positron pair. At the point where it appears to stop abruptly it has annihilated with an atomic electron, producing two photons, one of which 'materialises’ into in pair in the electric field of a neon nucleus. This happens about 11 cm in the bubble chamber from where the annihilation takes place.

For more details of this picture, click here.

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