So, let me explain why one could NEVER receive an ETI signal with particle detectors. As I mentioned yesterday, in addition to electromagnetic radiation, our galaxy is filled with charged particles known as comic rays (for historical reasons). These particles are highly energetic, traveling at relativistic speeds, so one could think to use them to communicate across galactic distances, instead of light.
But it turns out that our galaxy (like other galaxies) consists of turbulent magnetic fields distributed non-uniformly. Even our Sun has a strong magnetic field and so does the Earth. From physics 101 we know that charged particles are deflected