S. Bussino

A bullet that doesn't just pierce one target but leaves marks in several layers of armor. That's roughly how superheavy dark matter behaves, and it's what the DarkSide-50 detector was built to catch for the first time. The usual suspects for dark matter (weakly interacting massive particles, or WIMPs) pass through matter almost unnoticed, occasionally bumping into a nucleus.

Inside the accelerator, particles collide, and for a fleeting moment a B meson is born — a heavy particle that lives for less than a billionth of a second. Usually, it decays into a shower of debris, but sometimes it transforms into just two particles: a muon and a neutrino. This rare path is like a lottery where the winning ticket appears once in every two million draws.

At Japan's KEK laboratory, electrons and their antimatter counterparts, positrons, collide inside the Belle II detector. In such collisions, new particles are born for a fleeting moment. Among them is J/ψ, a bound state of a charm quark and its antiquark.