Particle Physicists Are Getting a First Glimpse Into the ‘Zeptoverse’

While crashing protons together at nearly the speed of light, scientists at CERN found evidence of one of the most improbable decays of matter—so unlikely that it’s a phenomenon physicists have been hoping to observe for more than four decades. The collision produced numerous particles, including some known as neutral B mesons, and scientists found signals indicating that one of these had decayed into a muon and an antimuon.

Mesons decay all the time. These tiny particles, smaller than atoms, arise from collisions between other particles and exist only briefly before transforming into other particles. Muons, on the other hand, are similar to the electrons found in atoms, but about 200 times heavier.