Subatomic oddity hints at pentaparticle family: “Physicists at a European particle accelerator say they’ve spotted a never-before-seen elementary particle composed of five of the fundamental constituents known as quarks and antiquarks. In contrast, protons and neutrons contain three quarks, and no particle is known to have four quarks. The new report marks only the second sighting ever of a five-quark particle, the first one having been found last summer by three independent groups working in the United States, Japan, and Russia…

The discovery of a new family of quark-containing particles may help physicists fill in blanks in their understanding of quark interactions, says theorist Frank Wilczek of MIT. For one thing, it could end what had been a puzzling absence of evidence for particles with groupings containing more than three quarks or antiquarks, which theorists for decades have been expecting to show up in accelerators.” —Science News