Xu Feng

An electron beam strikes a proton like a billiard ball hitting another ball. But between them is no empty space: the particles exchange virtual photons and Z bosons, like players passing a ball behind their backs. This exchange slightly alters the scattering trajectory, and hidden within it is a hint of new physics.

In 1946, proposed a method that revolutionized archaeology: determining age by the decay of radiocarbon. The clock ticks: every 5730 years, half of the atoms vanish. But why so slowly? For a light nucleus, this is an anomaly — typical lifetimes are millions of times shorter. The mystery held for seven decades.

A scale capable of weighing the invisible: that's exactly how the ratio of decays of light mesons (pion and kaon) into electrons and muons works. If nature follows the same rules for all generations of particles, the pans of this scale show a strictly defined number. But if an unknown force lurks somewhere, the needle will waver.