Please tell me where I went wrong
Beyond the misnaming of the particle, neither statement seems very scientific to me.
I Am Not a Particle Physicist (IANAPP) but one basic flaw is that the statements both seem to be not very good examples of even coherent verbal thinking, much less the far more precise "language" of mathematics.
(1) the Briggs boson exists as it explains observations, iow the existence of the particle is consistent with our model
IANAPP but for starters it seems to me (how's that for weasel English?) that the statement would be couched in terms of probabilities. Also, parsing the English (which is but an impoverished proxy for math), I don't find it a very convincing cause-and-effect statement. The particle exists
because it aligns so nicely with our observations? Didn't the particle exist before there were people around to make observations?
(2) the Briggs boson exists
That may seem less scientific, but to my mind, it's at pretty much the same level, and I would struggle to explain why, except to say that among real particle physicists, evidence for the existence of the particle might be
so overwhelming that a safely analogous statement might be, "Evolution exists" or maybe "evolution happens."
And no matter how much precision you think you can introduce by inserting verbal qualifiers, you will fall short, because the language used to get to the core of these subjects is not English, or Mandarin, or Latin, but mathematics.
I am not putting this as clearly as I'd like; I'm sure there are valid arguments against my position.
I'm a lurker, a piker, a neophyte in this conversation, but not (I think) to the basic argument - it seems like half of all ISF topics boil down to this and rightfully so, IMO.