RHIC'S FIRST COLLISIONS ARE GOLDEN. In a long-awaited development, Brookhaven's Relativistic Heavy Ion Collider (RHIC) produced its first collisions on June 12, when researchers witnessed gold ions (with an energy of 30 GeV per nucleon) smashing into each other to generate a fireworks display of roughly 1,000 symmetrical particle tracks. (See figure at Physics News Graphics).

Containing four advanced detectors (named BRAHMS, PHENIX, PHOBOS, and STAR), the RHIC facility aims to produce and study quark-gluon plasma (QGP), a hypothetical hot, dense soup of single quarks and gluons last believed to exist naturally in the first millionth of a second after the Big Bang. Subsequently, as the universe expanded and cooled, quarks assembled into extremely-hard-to-tear-apart two- or three-member groups (mesons and baryons, respectively) held together by gluons.

With the eventual goal being 100 GeV per nucleon in each of two heavy-ion beams, the RHIC collisions will produce temperatures and particle densities tens of thousands of times greater than those even at the centers of stars. Besides creating the QGP, other goals include colliding protons at high energies to make what should be the first definitive measurement of the contribution of gluons to the proton's spin.

Also, researchers plan to search for violations of such fundamental physics symmetries as P (parity) and CP (charge-parity) that would come about because of the strong nuclear force; previously the nonconservation of P and CP has only come about because of the weak nuclear force. One of the first major venues for the discussion of prospective RHIC results is expected to be the Quark Matter 2001 Conference in Long Island, NY in January 2001. (Brookhaven release at http://www.pubaf.bnl.gov/pr/bnlpr060800.html; also see Physics Today, October 1999.)