Physics News

When it's colliding protons, the LHC is a particle discovery machine. The protons themselves contain only a few quarks, so they don't create much noise that could hinder the search for exotic particles that may emerge from the tremendous energy unleashed by the collision. A few weeks back, however, CERN switched the collider over to smashing ions of lead, which have 82 protons each, which turns it into a fundamentally different machine. Although exotic particles spring out of these collisions as well, the focus instead is on the interactions of the particles that comprise the protons and neutrons of the lead ions. At the energies of these collisions, the protons and neutrons of an atom's nucleus break down into their component quarks and gluons and, for a tiny fraction of a second, undergo bulk interactions. The result is what researchers call a quark-gluon plasma (QGP), which hasn't been present in significant quantities since shortly after the origin of the Universe. As a result, one of the scientists who