Do you want to bookmark your favorite articles and stories to read or refer to later? Start your freelance membership today. Join today Already a member? Scientists say they might have found the reason we’re here. A neglected ancient particle could hold the clue to why the universe exists. For years, scientists have been concerned with a central question: how matter could overcome antimatter, after the Big Bang. Current theories suggest that each of them should have annihilated each other after a big explosion, leaving a universe composed of pure energy. That clearly didn’t happen, given that we’re here. But physicists have never been able to explain exactly why. Now, researchers say a clue could have been hidden in a neutrino, one of the lightest particles in the universe. A neglected relative of those particles, called an ‘uncoupled’ heavy neutrino, could have helped matter survive as the universe was born. “This uncoupled heavy neutrino has long been dismissed as an irrelevant detail in particle physics,” said Rishav Roshan of the University of Southampton, one of the authors of the new paper. “However, it decays incredibly slowly. As the cosmos cooled after the Big Bang, the particle lived long enough to temporarily take over the energy density of the universe and triggered a period dominated by matter.” Previously, researchers had ignored that particle because they thought it was too weak to have an effect on others, the researchers said. But in fact, it was more powerful than they thought, the new paper suggests, and may help us understand why the matter that makes us and everything else was able to survive. “The fact that we are here proves that an asymmetry occurred between matter and antimatter,” Dr. Roshan said. “The uncoupled neutrino changed the temperature in the early universe in which fundamental particles, such as electrons and other leptons, interacted with their antiparticles with the help of the standard model Higgs boson. “This temperature acts as a switch that shapes how the matter-antimatter imbalance formed.” The findings would not only help explain how we could have existed, but also what has happened in the universe since then. It could help us better understand the mystery of dark matter, the material which makes up most of the mass of the universe but is so far completely invisible, for example. The researchers suggest that the new work could lead to even more theoretical investigation into how the theory would fit with our current understanding of the birth of the universe. Physical Review Letters.
