How did they register rare events previously?

Looking through thousands of photos using own eyes, no computers

By the end of 1972, in the bubble chamber experiment Gargamelle, for the first time it was recorded an event of interaction of a muon neutrino with an electron, in which they exchanged a neutral Z-boson, referred to as neutral current. Results of particle interaction in the chamber were being fixed on photographs, among which a robot was selecting those similar to an expected picture of the interaction — a fast electron that appeared ‘from nowhere’. The robot had looked through the first 100 thousand pictures, but did not find the exactly corresponding picture. Meanwhile, a careful post-graduate still noticed a picture very similar to what was expected. That inspired the rest of the staff to further research in the hope of finding many of these interactions, but in the next year study of about half a million shots gave only two more such interactions. Nevertheless, their detection was a decisive argument in favor of the modern theory of electroweak interactions.

On the photographs from a bubble chamber  paths of elementary particles are visible

The discovery of the neutral current has required viewing huge number of images.


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