Omega-minus particle

Omega minus particle—short lived baryon believed to be made up of three quarks called "strange" quarks. 

No other combinations seemed to be necessary to describe the full variation of the observed hadrons. This scheme even led to the prediction of other particles that were not known to exist in 1961. For example, in 1961 Gell-Mann not only predicted the Or (omega-minus) particle, but more importantly told experimentalists exactly how to produce it. The 2" particle was finally discovered in 1964. 

A bubble-chamber photograph of the discovery of the omega-minus particle... 

The eightfold-way theory had its first success when Gell-Mann used it to predict the existence of an as-yet-undiscovered particle, just as Mendeleev had predicted the existence of undiscovered evidence. Gell-Mann called the hypothetical particle the omega-minus (it had a negative charge). In 1964 experimentalists found the particle and confirmed that it had exactly the mass Gell-Mann said it would have. 

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