This afternoon our experiment at Fermilab, the DZero collaboration, will announce the observation of the Omega_b baryon. This is an important discovery for DZero, the second major baryon state in as many years to be first observed by the experiment.
The discovery of the Omega itself was an important milestone on the development of particle physics, and this discovery of the related Omega_b state serves as a fitting bookend to a period of American dominance in accelerator-based particle physics. In 1964, the idea of baryons (particles like protons and neutrons) being made up of quarks was still very new and untested. The quark model proposed that year by Gell-Mann and Zweig was based on properties of particles previously observed, including a set of observation in 1962 of the Xi (related the last years discovery, the Xi_b). These observations seemed to predict a new baryon, which in the quark model would be composed of three strange type quarks, an (sss) system. It was a group at Brookhaven, led by future director Nick Samios and including Virgil Barnes, Bill Willis, and Ed Thorndike, who published the observation of a "Hyperon With Strangness Minus Three" in February, 1964, giving it the named proposed by Gell-Mann at the Rochester (now ICHEP) conference in 1962.
The Omega was the lynch pin in the establishment of the valence quark model. What followed was an intense period of research in the nature of quarks and their interactions, in which the quarks themselves became the main focus of research rather than the hunt for new meson or baryon states. The theoretical work of Feynmann, Glashow, Veltmann, Bjorken, and so many others in the later Sixties and Seventies, and the experimental observation of parton scattering at SLAC in 1969 by Friedman, Kendall, Taylor et alia, led to the development of a field theory for the quarks called Quantum Chromodynamics.It is the study of QCD and its predictions that is the main interest of our Markus Wobisch, and which is forming a key portion of our high energy physics group's analysis work at DZero and ATLAS. It is also key to the work of our medium energy particle group - Wells, Simicevic, Grimm and Johnston - as they try to understand such fundamental questions as the relative proportion of non-valence quarks such as the s-quark in protons.
Now, as we enter the twilight of accelerator-based physics in the United Sates, as our nation is preparing to no longer be the home of the highest energy collider in the world, in a beautiful act symmetry we find the cousin of the Omega, the (ssb) state known as the Omega_b, at the Fermilab Tevatron. Once again, the study of this baryon allows us the test the predictions of the quark model and the refinements possible from QCD, in the presence of the much heavier b-quark. It complements and fills in the elegant particle physics equivalent of the periodic table which is the various mesons and baryon "multiplets". But almost as importantly it forms a remarkable bookend to an unprecedented era of discovery and scientific research in this country, that proceeded in parallel with the Space Race and the breakthroughs in medicine and other fields, a time when the United Sates was the undisputed center of scientific research. We enter a new era when science well be more international and less centralized, with new nations like India and China playing an equally important role, and probably that is for the best.
But at the beginning, there was the Omega, and at the end there was the Omega_b.