In 2012, the Higgs boson was discovered by the Large Hadron Collider with a mass of eV. This observation of the Higgs completed the Standard Model, of which the Higgs mechanism was an important theoretical but experimentally unobserved part.
There remain unexplained facts about physics and theoretical difficulties with current models of physics that might be explained by the introduction of new fundamental particles. One popular extension to the standard model is supersymmetry, which predicts that each particle has a heavier supersymmetric partner.
There are proposals for larger particle accelerators that could probe collisions at higher energies, such as the Future Circular Collider which, if constructed, would have a center of mass collision energy of eV, though physicists are sceptical that any new physics would be discovered by them. One particularly exciting form of new physics that could be discovered would be a particle in their energy range.
What will be the mass in eV of the next fundamental particle to be discovered?
Resolution will be the average mass listed for the particle by Particle Data Group once scientific consensus emerges that the particle observed is a new fundamental particle. If multiple new particles are discovered in the same window of time, the first will be considered to be the first to have been observed, even if it was not known to be a new fundamental particle at the time.
The question resolves ambiguously if no new fundamental particle is discovered by 2070.