Evadman, your definition for a tachyon is confusued. You cannot define a tachyon using properties of traditional matter. A tachyon is a particle, that in its rest state is constantly moving a faster than light speeds. Tachyons do not have mass in the traditional sense, the have a negative mass weight, such as -10 grams. A Neutrino is not a tachyon, those are two completely different particles. Neutrinos are sub-light speed particles, from the lepton family, just like electrons. Electrons and neutrinos are different types of leptons (muons and tau's are the other two leptons). We do not know how to detect them. If we could look for a certain type of radiation, then we would have found them already. My neighbor is a world renound scientist who was one of the first people to propose the existance of the tachyon. He wrote a few papers on them. He proved using Einstein's E=mc^2 equation to show that as energy is added to a tachyon is slows down, and as energy is removed from a tachyon it speeds up. To get a tachyon to sub-light speeds, you need to add an infinite amount of energy (the opposite is true of sub-light speed matter, to get sub-light speed matter faster than light, an infinite amount of energy is required to be added), and to get a tachyon to move at infinite velocity, you must keep removing an infinite amount of energy (the opposite is true of sub-light speed matter, to get sub-light speed matter down to a stop, you must remove an infinite amount of energy).