Mystery bump at Tevatron

With great fanfare the CDF experiment released a paper on Wed. April 6, 2011 saying that they had found a significant discrepany from the Standard Model of particle physics just months before the Tevatron is scheduled to shut down. Is it a new particle, a statistical fluke, or a “budgetron”?

The media was given access to the discovery before the physics community, so there was already a New York TImes article on April 5. Another example of the disturbing trend of science by press release.

FermiLab Physicists May Have Found New Particle
The results, if they hold up, could be a spectacular last hurrah for Fermilab’s Tevatron, once the world’s most powerful particle accelerator and now slated to go dark forever in September or earlier, whenever Fermilab runs out of money to operate it.
[1104.0699] Invariant Mass Distribution of Jet Pairs Produced in Association with a W boson in ppbar Collisions at sqrt(s) = 1.96 TeV
Apr 4, 2011 … arXiv . org > hep-ex > arXiv : 1104.0699 . Search or Article-id. (Help | Advanced search) … Link back to: arXiv , form interface, contact.
The bump appears in the combined mass of two QCD jets produced alongside a W boson.
The Tevatron goes bump | Jon Butterworth, Life & physics | Science |
This week the CDF experiment at the Tevatron proton-antiproton collider caused a stir with this paper and a special seminar. This is a common situation in scientific research. The result is (a) really important if confirmed and (b) in need of confirmation before everyone is certain of it.
Anomalies at Fermilab | Cosmic Variance | Discover Magazine
The Tevatron accelerator at Fermilab is shutting down soon, for some unavoidable reasons (the LHC is taking over) and some frustrating ones (we’re out of money). But there may be life in the old beast yet; a couple of intriguing anomalies have particle theorists raising their eyebrows in charmingly understated excitement.
Mystery Atom Discovery Has Physicists Abuzz
In a development physicists are calling "huge," "tantalizing" and "unexpected," researchers have measured a signal that could herald a new kind of particle or force of nature. Yet the finding is not yet conclusive, and leaves many researchers skeptical. The discovery comes from an atom smasher called the Tevatron at the Fermilab physics laboratory in Batavia, Ill.

It was quickly pointed out that knowing the energy of the jets is extremely important, and an error in this step could be the explanation of the effect.  An animated gif by Tommaso Tabarelli de Fatis dramatically shows the how big this effect could be.

The Jet Energy Scale As An Explanation Of The CDF Signal
In my post about the new CDF signal of a mysterious new resonance decaying to jet pairs, there is an active comments thread. I posted there a graph crafted by Tommaso Tabarelli de Fatis, a CMS collaborator, who picked the CDF data and simulation and

May 20, The CDF collaboration blesses an updated analysis with more data but the results are withheld from other physicists until it can reviewed by lab director Pierre Odone.

May 30, In a talk by Giovanni Punzi at the Blois conference, CDF announces that with added data the significance of the bump has increased to 4.8 sigma, which is almost enough to proclaim a discovery.
RÉSONAANCES: CDF: Wjj bump almost 5 sigma!!!
Today at the conference Rencontres de Blois the CDF collaboration presented an update on the invariant mass of 2 jets produced in association with a W boson. Recall that 2 months ago CDF posted a paper based of 4.3 fb-1 of data claiming that this observable displays an unexpected bump near 150 GeV with a significance of 3.2 sigma.
June 10, The D0 (pronounced D-Zero) experiment at the Tevatron reveals their independent analysis of their own data.  They find that the hypothetical CDF particle is ruled out at 99.999% confidence level.
Fermilab’s D0 detector shows no sign of the CDF "bump" that could have signalled physics beyond the Standard Model:
June 10, 2011
Tevatron teams clash over new physics : Nature News
Nature – the world’s best science and medicine on your desktop

A task force is set up to get to the bottom of the discrepancy. The task force will include Fermilab theorists Estia Eichten and Keith Ellis.

#Fermilab finds no new particle in 2nd experiment, forming task force to figure out what’s up:
June 10, 2011
Fermilab Today
Two months ago, CDF scientists reported an unexpected excess of proton-antiproton collisions that produce a W boson accompanied by two jets of particles. One possible explanation for the excess could be the existence of a new, unanticipated particle. Now the DZero collaboration has finished an independent analysis that tests the CDF result.
Panel probes new particle results
The head of the US’ biggest particle physics lab has appointed an expert committee to establish whether or not a new, unanticipated sub-atomic particle has been detected by scientists. Such a discovery, hinted at by experts in April, would mark one of the most radical changes to physics in years.
Sept. 30, The Tevatron is shutdown for good. So far the panel has not made any progress, each of the experiments blames the other. maybe only the LHC can resolve the story…

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One Response to “Mystery bump at Tevatron”

  1. kinetic energy says:

    interesting document, ill guess well have to wait and see how this thing pans out