[dooglius]

It looks like they detected a muon and are inferring a neutrino from the fact it went through a lot of solid. Couldn't it be any other weakly-interacting particle though?

[Sniffnoy]

How? Quarks can't change into leptons. Charged leptons can't change directly into other charged leptons. And neither charged leptons nor hadrons are going to pass through such a quantity of matter, as you say. I mean I assume other cases are technically possible but they don't seem very likely...

[AnimalMuppet]

Nit: As I read the article, they aren't sure that it went through any solid. Went through a lot of seawater, though. And your argument still applies.

[cozzyd]

It could be beyond the standard model physics but no other standard model particle could work other than a neutrino.

[nxpnsv]

Nothing else that we know of would create a muon of that energy deep inside bedrock.