Physics is still grappling with two basic questions about the nature of matter: why is there more matter than antimatter, and where and what is all the dark matter? Meet the hypothetical X particle, the potential answer to both questions. ... Physicist Hooman Davoudiasl and a team of colleagues from both the US and Canada have proposed a new particle that solves both mysteries in one fell swoop, as well as possessing a couple very intriguing properties. This hypothetical particle, dubbed the X particle, would have a mass about 1000 times that of a proton, and it would commonly decay into a smaller particle.