Superluminal Paradox and Neutrino
  Einstein's theory of special relativity(SR) and the principle of causality imply that the speed of any moving object can not exceed that of light in a vacuum($c$).However,there were many attempts in literature discussing the particle moving with speed $u>c$(called as superluminal particle or tachyon)either in the scheme of SR or beyond it.These theories all encountered a series of insurmountable difficulties which will be named ``superluminal paradox''in this paper.We will analyze it in some detail and then prove that the paradox disappears unambiguously in quantum theory,which is compatible with SR.Most likely,the superluminal particle in real world is just a kind of known particle,the neutrino. 
Guang-jiong Ni