Tachyons are proof to me that travel beyond the speed of light is possible.
Nope.
We've observed two decay products that we *think* come from a single larger particle, that when the decay trajectories and momentum are resolved, seem to imply an FTL component before that. The pre-decay particle has never been seen, and we have no idea if we have all the post collision/breakdown etc products accounted for.
We can't really *see* the anti-neutrino produced by Neutron decay, but we know the mass/charge ratio of enough particles to know where the resultant mass, momentum and energy are and how enough hadron interactions work.
There's literally no proof any particle exists or travels faster than light.