A Charming New Particle

摘要

PHYSICISTS HAVE FOUND hundreds of particles made of quarks over the years. Protons and neutrons, for example, are made from "up" and "down" quarks, the two most common and lightest of the six so-called flavors of quarks. But the latest particle discovery, announced at CERN in July, stands out because it's composed of one up quark and two of an uncommon quark flavor called charm.