Physicists have detected a long-sought particle process that may suggest new forces and particles exist in the universe

Once in a very great while, an ephemeral particle called a kaon arises and then quickly decays away into three other obscure entities. Whether or not this happens in a particular way has very little bearing on most of us, who will go about our lives without knowing either way. But to physicists who have been searching for this arcane process for decades, it matters a lot; finding out how often it happens could reveal hidden aspects of our universe.

Now, for the first time, scientists have observed this rare decay, and they have found that it might have slightly higher odds of occurring than its predicted chance of about one in 10 billion. If that turns out to be true, some unseen actor must be interfering in the decay—potentially a new particle or force previously unidentified in nature.