Eh, there are always new studies suggesting that. They never pan out. And it’s not like dark matter is some crazy unicorn-- There’s nothing wrong with particles that don’t interact electromagnetically (heck, we already know of neutrinos). Saying “dark matter could exist” is like saying “the sound we’re hearing could be hoofed animals”.
Somebody had to do it.
The very first reply went right through you without interacting?
Essentially, they are the undetected bits coming out of certain nuclear reactions. They know what the total mass/energy of the particles were before the reaction and they add up the mass/energy of what the detectors see after. It turns out that there’s a consistent discrepancy between these two figures and they assumed it was carried away by some unknown and undetected particle. They labeled that particle “neutrino”. OK, that’s how they predicted their existence.
For their plentitude, they know that certain reactions that produce neutrinos are happening in the Sun. They can compute how many such reactions will be happening during a given period, so it’s relatively straightforward to compute how many are found 1 AU away from the Sun.
BTW, there are also neutrinos coming from all the stars in the sky and going through you as well. Not very many compared to those from the Sun, but then you don’t get much light from them either. Unless there’s a relatively nearby supernova. (“Nearby” here meaning somewhere in our galaxy or even in a satellite galaxy.) Then there’ll be lots of neutrinos going through you.
In fact, I saw a calculation once that, given the number of neutrinos produced by Supernova 1987a, and given the total mass of all human eyeballs, there were probably a few people on Earth who saw a tiny flash of light from a neutrino from the supernova.
Which is why, when we set up our first neutrino detector to detect the neutrinos coming from the Sun, we were disturbed to find that we were only finding about a third of what we expected.