Number 290 (Story #2), October 9, 1996 by Phillip F. Schewe and Ben Stein THE THEORY OF BIG BANG NUCLEOSYNTHESIS (BBN) tells the saga of how nuclei, especially deuterium, helium, and lithium, were made in the early minutes of the universe (see Update 247). Along with the microwave background and the mutual recession of galaxies, the observed abundance of primordial He, D, and Li is one of the chief supports of big bang cosmology. Recent measurements, however, suggest that BBN estimates for D and He-3 abundance are too high, and that the theory (or the observations) must be amended. Physicists at Berkeley (Erich Holtmann, holtmann@theorm.lbl.gov) and the University of Tokyo tackle this problem by invoking a hypothetical exotic particle. The presence of such a particle (with the right mass and lifetime) in the early universe might, in the act of decaying, have provided a torrent of gamma rays which dismembered deuterium (into two hydrogens) and He-3 (into H and D), bringing their numbers into line with modern measurements. He-4, more tightly bound that He-3, would be relatively immune to the marauding gammas. If this scenario is correct, the particle in question might well have been a "gravitino," the fermion cousin of the graviton. Gravitinos are ordained as part of "supersymmetry," a theory which holds that all known fermions (such as electrons or quarks) have hypothetical boson counterparts and vice versa. (Holtmann et al., upcoming article in Physical Review Letters.)