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Fermilabís CDF observes Omega-sub-b baryon:
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Six quarks--up, down, strange, charm, bottom and top--are the building blocks of matter. Protons and neutrons are made of up and down quarks, held together by the strong nuclear force. The CDF experiment now has observed the Omega-sub-b particle, which contains two strange quarks (s) and one bottom quark (b).



Once produced, the Omega-sub-b (Ωb) particle travels about a third of a millimeter before it disintegrates into two intermediate particles called J/Psi (J/ψ) and Omega-minus (Ω-). The J/Psi then promptly decays into a pair of muons. The Omega-minus baryon, on the other hand, can travel several centimeters and occasionally be measured in the CDF silicon vertex detector. The particle decays into an unstable particle called a Lambda (Λ) baryon along with a long-lived kaon particle (K). The Lambda baryon, which has no electric charge, also can travel several centimeters prior to decaying into a proton (p) and a pion (π). Credit: CDF collaboration.



Baryons are particles made of three quarks. The quark model predicts the combinations that exist with either spin J=1/2 (this graphic) or spin J=3/2. The graphic shows the various three-quark combinations with J=1/2 that are possible using the three lightest quarks--up, down and strange--and the bottom quark. The CDF collaboration observed the Omega-sub-b, highlighted in the graphic. There exist additional baryons involving the charm quark, which are not shown. The top quark, discovered at Fermilab in 1995, is too short-lived to become part of a baryon.



The CDF collaboration has observed 16 Omega-sub-b candidates in the data collected through October 2008. The mass of the Omega-sub-b is measured to be 6054.4 ± 6.8 MeV/c2. The lifetime of the Omega-sub-b is measured to be 1.13 ± 0.53 picoseconds. Credit: CDF collaboration.



The Fermilab accelerator complex accelerates protons and antiprotons close to the speed of light. Converting energy into mass, the Tevatron collider can produce particles that are heavier than the protons and antiprotons that are colliding. The Tevatron produces millions of proton-antiproton collisions per second, maximizing the chance for discovery. Two experiments, CDF and DZero, search for new types of particles emerging from the collisions.



The CDF detector, about the size of a 3-story house, weighs about 6,000 tons. Its subsystems record the "debris" emerging from high-energy proton-antiproton collisions. The detector surrounds the collision point and records the path, energy and charge of the particles emerging from the collisions. This information can be used to find and determine the properties of the Omega-sub-b particle.



Some of the 600 scientists of the CDF collaboration in front of Wilson Hall at Fermilab.



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Last modified: 06/29/2009 |