There may be a lot of neutrinos around, but they are extremely hard to detect. The fact that you see a bunch of them at a time and a place where you expect base

There may be a lot of neutrinos around, but they are extremely hard to detect. The fact that you see a bunch of them at a time and a place where you expect based on how they were created makes it very unlikely that they are not associated. There are craploads of neutrinos left over from the Big Bang (see http://en.wikipedia.org/wiki/Cosmic_neutrino_background http://en.wikipedia.org/wiki/Cosmic_neutrino_background) but they are very low energy and are impossible to detect. They are likely the closest you can find neutrinos at rest. How fast they go depends on their rest mass, which we only know to be small but nonzero.