Particles Behaving Badly - NPR

"That situation is playing out now, as outlined in a recent review paper in Nature. The conundrum in question is the decay of a particle called a B-meson, and how many electrons, muons, and tau particles pop out after a collision. Physicists in a handful of experiments around the world have all observed a preponderance of tau particles—not what current theories would predict."

https://www.sciencefriday.com/segments/particles-behaving-badly/