Of Particular Significance

A long-expected [and not-so-exciting] particle finally observed

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 07/21/2011

No less than Fox News reports that Fermilab has found a new particle!  And it’s true, but this is one of those places where the word “particle” is not descriptive.  This is a new [but totally expected!] HADRON, a particle made from other known particles — quarks, antiquarks and gluons.

Just as a Proton is (and isn’t!!!) a combination of two up quarks and a down quark, a Neutron is a combination of an up quark and two down quarks.  Then (among many others) there is a particle called the Chi (oops ! what was I thinking? probably distracted by talks about Higgs particles) the Xi [pronounced like ski with the k and s reverse], a neutron cousin, which has an up quark, a down quark and a strange quark.  There’s a Xi_c, another cousin, where the strange quark is replaced by a charm quark.  And guess what?

There’s a Xi_b, with an up quark,  a down quark, and a bottom quark.

We’ve known for more than 30 years that the Xi_b would be there in nature.  It just took a heck of a lot of data before anyone could identify it cleanly.  Apparently that has finally happened, at the CDF experiment.

Fox News reminds the reader that “Earlier this year, Fermilab scientists thought they’d discovered another never-before-seen particle. That discovery turned out to be a fluke, however.”    But this statement is balderdash.  [I’ll provide an article on this soon.]  First, the only people who said “discovery” were in the press.  A hint is not a discovery; nor is the hint of an excess seen at CDF necessarily due to a new particle.  Second, it was not a statistical fluke, though it may have been an error; but in any case the jury is still out, and arguments continue between CDF and DZero.  And third, there is a big difference between a never-before-seen-but-completely-expected-hadron (as in today’s news) and a never-before-seen-and-completely-unexpected-new-type-of-particle (as in the news earlier in the year!!!)

The usual lesson: don’t get your science news from the press!

[But don’t trust me when it comes to naming exotic hadrons either.  Thanks, readers.]

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4 Responses

  1. Yes, please do clarify! Wired and LIvescience, among others, are calling this particle Xi sub b instead of Chi. Which is the proper letter?

    Thanks for the blog post, though – these things are always made out to be huge discoveries in the mainstream news while real physicists like yourself know that the explanation isn’t quite so simplistic.

  2. Thanks for this! Question. In your post you call the new quark a “Chi” quark (Greek letter χ) but on the Fox News report they call it “Xi” (Greek letter ξ, pronounced like “foxy” without the “fo-“). I’m guessing that you know what you’re talking about, and somehow things got lost in translation in the Fox News Report. Clarify?

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