eta meson

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.

Holding a phone number in your head while people shout and slam doors around you is nearly impossible. That's roughly the life of a quantum bit, a qubit, in an ordinary material: the nuclei of neighboring atoms, like tiny magnets, constantly jostle it and erase information. To keep a qubit from forgetting, you need to find it a quiet spot.

Quarks are the tiny building blocks that make up protons and neutrons. Usually, they stick together in pairs: a particle and its mirror-image antiparticle. But sometimes quarks form more exotic combinations, which physicists call exotic states.

A spinning top, set in motion on a perfect surface, topples from the slightest tremor. Likewise, a quantum bit, created at a defect in a diamond, has its state destroyed by magnetic disorder from impurities and external interference.

In proton collisions at the Large Hadron Collider, physicists have for the first time caught a particle with two charm quarks. It is called Ξcc+ (pronounced "ksi-ksi-plus") and resembles a bead with not one but two heavy nuclei.

In the BEPCII accelerator, electrons and positrons collide, producing billions of particles. Among them is the J/ψ meson, which lives for less than a billionth of a second. Its decay sometimes yields an eta meson (ηc), an even shorter-lived clump of quarks.

At a particle accelerator in Beijing, electrons collide with positrons, and for a fleeting moment, a particle called eta-c is born. It lives for a tiny fraction of a second and then decays into other particles. One of the rarest paths is to split into two photons, particles of light. Until now, no one could say exactly how often this happens.

A magnetic compass in a test tube sounds like a magic trick, but it's pure physics. In a solution of fumarate (a salt of malic acid), carbon-13 nuclei behave like tiny spinning tops.

In 1976, Gerard 't Hooft noticed that the vacuum of a gauge theory is not as simple as it seems: it possesses a topological structure that manifests itself in a nonzero topological susceptibility.

A tuning fork cut from a perfect metal rings at a single frequency. Its sound is as pure as a mathematical formula. But clamp it in a vise or dip it in a viscous liquid, and the tone smears, picks up noise, and loses its sharpness. The nucleus of scandium-45 behaves much the same way when placed in a crystal lattice.