Charmed-Strange Mesons

From ScienceDaily.com

High-energy physicists devoted to recreating the conditions at the beginning of the universe have for the first time observed a new way to produce those basic particles of atoms, protons and neutrons.

Confirming a decades-old prediction, the physicists with the CLEO collaboration say they observed a rare and extremely short-lived subatomic particle with the unusual name of “charmed-strange meson” decay into a proton and anti-neutron...

The Cornell Electron Storage Ring accelerator, or CESR, collides electrons with positrons at energies ranging from 3 to 5 billion electron volts — producing many short-lived, elementary and rare particles of interest to physicists. CLEO, the large experimental detector designed to detect the accelerator collisions, is a joint project of nearly two dozen institutions in the U.S., Canada and England.

Among the products of the CESR collisions are the charmed-strange mesons, which exist for less than one-trillionth of a second before decaying into other more stable particles. Although charmed mesons have been studied for 30 years, no one had ever observed one decaying into a proton or neutron, as theory had predicted. This is notable because about 10 percent of all the collisions in the accelerator produce protons and neutrons.

Yelton did not detect the anti-neutron directly but rather inferred its presence from data on energy and momentum of other particles.

All told, he found 13 instances of charmed-strange mesons decaying into protons and anti-neutrons, retrieving and identifying those events from data on millions and millions of different collisions and their aftermaths...

“Observation of these rare decays has the promise of increasing our understanding of the underlying mechanisms of how the world is put together,” he said...