A NEW FORM OF NUCLEAR MATTER has been detected at the CERN lab in Geneva. Results from seven different experiments, conducted at CERN over a span of several years, were announced at a series of seminars today. In the experiments a high energy beam of lead ions (160 GeV/nucleon, times 208 nucleons, for a total energy of about 33 TeV) smashes into fixed targets of lead or gold atoms. The center-of-mass energy of these collisions, the true energy available for producing new matter, is about 3.5 TeV. From the debris that flies out of the smashups, the CERN scientists estimate that the "temperature" of the ensuing nuclear fireball might have been as high as 240 MeV (under these extreme conditions energy units are substituted for degrees kelvin), well above the temperature where new nuclear effects are expected to occur.

In the CERN collisions the effective, momentary, nuclear matter density was calculated to be 20 times normal nuclear density. It is not quite certain whether the novel nuclear state is some kind of denser arrangement of known nuclear matter or a manifestation of the much-sought quark-gluon plasma (QGP), in which quarks, and the gluons which normally bind the quarks into clumps of two quarks (mesons) or three quarks (baryons), spill together in a seething soup analogous to the condition of ionized atoms in a plasma. Such a nuclear plasma might have existed in the very early universe only microseconds after the big bang.

Evidence for the transition from a hadron phase (baryons and mesons) into a QGP phase was expected to consist of (1) an enhanced production of strange mesons, (2) a decrease in the production of heavy psi mesons (each consisting of a charm and anticharm quarks), and (3) an increase in the creation of energetic photons and lepton-antilepton pairs. Just this sort of (indirect) evidence (at least of types 1 and 2) has now turned up in the CERN data. (CERN press release, www.cern.ch).

To demonstrate the existence of QGP more directly, one would like the plasma state to last longer, and one should observe the sorts of particle jets and gamma rays that come with still higher-energy fireballs. That energy (about 40 TeV, center-of-mass) will be available in the next few months at the Relativistic Heavy Ion Collider undergoing final preparations at Brookhaven.