Scientists aren’t yet certain that electrons and their relatives are violating the Standard Model of particle physics, but the evidence is mounting. For decades physicists have sought signs of misbehaving particles—evidence of subtle cracks in the “Standard Model” of particle physics, the dominant theory describing the most fundamental building blocks of our universe. Although the Standard Model has proved strikingly accurate, scientists have long known some adjustments will be needed. Now, as a recent review paper in Nature documents, experimenters have started seeing suggestions of particles flouting the theory—but they’re not quite the violations theorists were looking for. The evidence...