Fermilab's CDF observes Omega-sub-b baryon

Jun 29, 2009
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).

(PhysOrg.com) -- At a recent physics seminar at the Department of Energy’s Fermi National Accelerator Laboratory, Fermilab physicist Pat Lukens of the CDF experiment announced the observation of a new particle, the Omega-sub-b (Ωb). 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 has about six times the proton’s mass.

The observation of this “doubly strange” particle, predicted by the Standard 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 formed of three quarks, the most common examples being the proton and neutron. The Tevatron particle accelerator at Fermilab is unique in its ability to produce baryons containing the b quark, and the large data samples now available after many years of successful running enable experimenters to find and study these rare particles. The observation opens a new window for scientists to investigate its properties and better understand this rare object.

Combing through almost half a quadrillion (1000 billion) proton-antiproton collisions produced by Fermilab's Tevatron particle collider, the CDF collaboration isolated 16 examples in which the particles emerging from a collision revealed the distinctive signature of the Omega-sub-b. Once produced, the Omega-sub-b travels a fraction of a millimeter before it decays into lighter particles. This decay, mediated by the weak force, occurs in about a trillionth of a second. In fact, CDF has performed the first ever measurement of the Omega-sub-b lifetime and obtained 1.13 +0.53-0.40 (stat.) ±0.02(syst.) trillionths of a second.

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.

In August 2008, the DZero experiment announced its own observation of the Omega-sub-b based on a smaller sample of Tevatron data. Interestingly, the new CDF observation announced here is in direct conflict with the earlier DZero result. The CDF physicists measured the Omega-sub-b mass to be 6054.4 ±6.8(stat.) ±0.9(syst.) MeV/c2, compared to DZero’s 6165±10(stat.)±13(syst.) MeV/c2. These two experimental results are statistically inconsistent with each other leaving scientists from both experiments wondering whether they are measuring the same particle. Furthermore, the experiments observed different rates of production of this particle. Perhaps most interesting is that neither experiment sees a hint of evidence for the particle at the other’s measured value.

Although the latest result announced by CDF agrees with theoretical expectation for the Omega-sub-b both in the measured production rate and in the mass value, further investigation is needed to solve the puzzle of these conflicting results.

The Omega-sub-b discovery follows the observation of the Cascade-b-minus baryon (Ξb), first observed at the Tevatron in 2007, and two types of Sigma-sub-b baryons (Σb), discovered at the Tevatron in 2006.

The CDF collaboration submitted a paper that summarizes the details of its discovery to the journal Physical Review D. It is available online at: arxiv.org/abs/0905.3123

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User comments : 8

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Shootist
5 / 5 (2) Jun 29, 2009
A thousand billion is a trillion. A million billion is a quadrillion.
Icester
5 / 5 (2) Jun 29, 2009
They should've said "zillionz" (as in "how much money does Richie Rich have?")

Really though, this is a awesome accomplishment.
Question
1.6 / 5 (7) Jun 29, 2009
This whole quark model is just modern day alchemistry. In half a quadrillion collisions one could find a score of anything one was looking for. Really, 1/3 charges: Absolutely no proof of that. And to think we are spending billions on this stuff. How about spending it on more efficient solar panels?
jonnyboy
3.7 / 5 (7) Jun 29, 2009
This whole quark model is just modern day alchemistry. In half a quadrillion collisions one could find a score of anything one was looking for. Really, 1/3 charges: Absolutely no proof of that. And to think we are spending billions on this stuff. How about spending it on more efficient solar panels?


one might wonder if in half a quadrillion comments you would ever say anything intelligent, yet alone 15 or 20 times.
Quantum_Conundrum
1 / 5 (5) Jun 29, 2009
jonnyboy:

Have you ever seen anything electronic that runs with "zero static"? Probably not.

How can anyone take these results seriously?

We are talking about something allegedly the size of a proton moving near the speed of light, produced "spontaneously" and "randomly" in a collision, and they are claiming to have actually measured its characteristics to absurd degrees of accuracy and precision.
pseudophonist
3.8 / 5 (4) Jun 30, 2009
jonnyboy:



Have you ever seen anything electronic that runs with "zero static"? Probably not.



How can anyone take these results seriously?



We are talking about something allegedly the size of a proton moving near the speed of light, produced "spontaneously" and "randomly" in a collision, and they are claiming to have actually measured its characteristics to absurd degrees of accuracy and precision.


You're basically accusing these people of scientific fraud and I have my doubts as to whether you're qualified in enough fields to do that. At least be sceptical in a constructive way.
E_L_Earnhardt
5 / 5 (1) Jun 30, 2009
The "electron" hardly needs a "non-descriptive" title as we detect it in various roles, speeds, and orbits. This energy bearing particle is more predictable in function and describes the mechanics
of creation and life!
Mr_Morden
5 / 5 (1) Jul 07, 2009
Believe it or not, "Question" sounds like one of the religious types that doubts anything scientific due to it being more complex than they can understand. Evolution, the Big Bang, Plate Tectonics, Carbon Dating, and now sub atomic particles. When will the ignorance end? The Earth is roughly round not flat, and certainly not the center of the universe. Either learn the subject and gain the insight you lack, or trust those who do. Biblical texts don't address the substructure of atoms!