Fermilab's CDF observes Omega-sub-b baryon

Fermilab's CDF observes Omega-sub-b baryonAt a recent physics seminar at the Department of Energy's Fermi NationalAccelerator Laboratory, Fermilab physicist Pat Lukens of the CDFexperiment announced the observation of a new particle, the Omega-sub-b.The particle contains three quarks: two strange quarks and a bottom quark(s-s-b). It is an exotic relative of the much more common proton and hasabout six times the proton's mass.The observation of this "doubly strange" particle, predicted by theStandard Model, is significant because it strengthens physicists'confidence in their understanding of how quarks form matter. In addition,it conflicts with a 2008 result announced by CDF's sister experiment,DZero.The Omega-sub-b is the latest entry in the "periodic table of baryons."Baryons are particles formed of three quarks, the most common examplesbeing the proton and neutron. The Tevatron particle accelerator atFermilab is unique in its ability to produce baryons containing the bquark, and the large data samples now available after many years ofsuccessful running enable experimenters to find and study these rareparticles. The observation opens a new window for scientists toinvestigate its properties and better understand this rare object.Combing through almost half a quadrillion (1000 billion) proton-antiprotoncollisions produced by Fermilab's Tevatron particle collider, the CDFcollaboration isolated 16 examples in which the particles emerging from acollision revealed the distinctive signature of the Omega-sub-b. Onceproduced, the Omega-sub-b travels a fraction of a millimeter before itdecays into lighter particles. This decay, mediated by the weak force,occurs in about a trillionth of a second. In fact, CDF has performed thefirst ever measurement of the Omega-sub-b lifetime and obtained 1.13+0.53-0.40(stat.) ± 0.02(syst.) trillionths of a second.In August 2008, the DZero experiment announced its own observation of theOmega-sub-b based on a smaller sample of Tevatron data. Interestingly,the new CDF observation announced here is in direct conflict with theearlier DZero result. The CDF physicists measured the Omega-sub-b mass tobe 6054.4 ± 6.8(stat.) ± 0.9(syst.) MeV/c^2, compared to DZero's 6165 ±10(stat.) ± 13(syst.) MeV/c^2. These two experimental results arestatistically inconsistent with each other, leaving scientists from bothexperiments wondering whether they are measuring the same particle.Furthermore, the experiments observed different rates of production ofthis particle. Perhaps most interesting is that neither experiment sees ahint of evidence for the particle at the other's measured value.Although the latest result announced by CDF agrees with theoreticalexpectation for the Omega-sub-b both in the measured production rate andin the mass value, further investigation is needed to solve the puzzle ofthese conflicting results.The Omega-sub-b discovery follows the observation of the Cascade-b-minusbaryon, first observed at the Tevatron in 2007, and two types ofSigma-sub-b baryons, discovered at the Tevatron in 2006.The CDF collaboration submitted a paper that summarizes the details of itsdiscovery to the journal Physical Review D. It is available online at:http://arxiv.org/abs/0905.3123CDF is an international experiment of about 600 physicists from 62institutions in 15 countries. It is supported by the U.S. Department ofenergy, the National Science Foundation and a number of internationalfunding agencies. Fermilab is a national laboratory funded by the Officeof Science of the U.S. Department of Energy, operated under contract byFermi Research Alliance, LLC.