Hmm, I think the effect would be more localized, and involve a lot of strange forms of matter. My guess is it would be similar to what happened to Anatoli Bugorski when he stuck his head into a proton beam.

That doesn't mean getting hit by this particle would feel like a punch, since what you feel when you get punched is a transfer of momentum rather than a transfer of energy.

Yep but just an easy first approximation since the article didn’t have any numbers on the momentum of the particle. I’m sure if you wanted a really good answer you would need more than momentum and actually need to analyze the products of the collision like another poster suggested.

Also wanted to share this table since energy expressed in eV sounds like big numbers but it’s nice to understand that the definition of the eV is small in our usual definition of energy.

Interesting. I see from your link that this particle had 1/6 of the energy of a lethal dose of x-rays.

I'm guessing I would probably survive, but certainly wouldn't volunteer to get hit with such a particle, and I'm guess that if it went through my brain stem or maybe my heart, there's a good chance it would kill me.

So I'm confused. If some specific relatively small devices (relatively to the size of the Earth) managed to pick up several of these over the years, surely some of these are hitting people? Are people randomly feeling like they got impacted (if not punched, as per a sister comment) out of nowhere? Apologies if this is a ridiculous question; physics was always my weak suit.

If you got hit by one of these then you wouldn't feel anything. The energy is about 50 joules, or about 1/2 of the heat that a human body produces in a second.

I wonder if it would kill a flea, or barring that, a bacterium.

Earth's atmosphere and magnetic field prevents these kinds of rays from reaching the surface of the Earth.