[Moonman62]

Here is the photograph that constitutes the discovery of the positron in 1932, 4 years after it was hypothesized by Dirac. There it is. That's a discovery.

That's not a positron, per se.

[dr_lew]

That's not a positron, per se.

Just as a contrail is not an airplane, I guess. But it's a sure trace of one. It's not a perfect analogy, because particle tracks are the only classical manifestation of the particle, which would otherwise remain in the realm of the noumenal.

With the J/Psi in the 1970's, and others I think, the discoveries were no longer tracks of particles, but "bumps" in interaction cross-sections vs. energy that indicated an interaction mediated by a particle of a particular mass, which could hardly be said to have existed. I think the Higgs discovery was an extreme version of this sort of thing.