The dark lines in this picture are produced by charged particles as they force their way through liquid deuterium.
The highlighted track is an antiproton ,
produced in the decay of
an antilambda into an antiproton and a .
In the top left corner of the picture, this antiproton annihilates with a proton constituent of a deuteron, producing a 6-pronged annihilation 'star’. (If it had struck a neutron , the number of prongs would, by charge conservation, have to be odd.)
This event was important in particle physics because it was the first observation of the anti-particle of the omega minus .For details of this event, click here.
For another example of antiproton click on the picture below.