Finding the Ω_b ⁻ baryon

The Ω⁻ baryon played an important role in the evolution of particle theory. Its much heralded discovery in 1964 at precisely the mass (1.67 GeV) predicted by symmetry arguments about charge and strangeness led promptly to the quark model of the strongly interacting particles. The quark model described the Ω⁻ as a bound state of three strange (s) quarks. The relatively straightforward “naïve” quark model has long since been incorporated into quantum chromodynamics, a much more complete theory from which, however, precise predictions are notoriously hard to extract. But QCD does predict that the Ω⁻ should have a heavy-quark analogue, called Ω_b ⁻, with a mass of about 6.0 GeV—more than six times that of the proton. In the Ω_b ⁻, one of the three s quarks is replaced by the much heavier bottom (b) quark. Now, having combed through 10¹⁴ proton–antiproton...