Fermilab experiment fails to confirm new particle claim

Jun 13, 2011 by Lisa Zyga report
DZero data: If DZero were to detect the new particle that CDF detected, there should have been a signal around 145 GeV/c2 (dashed line). The red peak below 100 GeV/c2 is a feature of W and Z boson decays that is predicted by the Standard Model. Image credit: Fermilab

(PhysOrg.com) -- In April, scientists at one of Fermilab’s two particle detectors, CDF, observed what they thought might be a new particle not predicted by the Standard Model. But now, scientists at the lab’s second detector, DZero, have cross-checked the observation with their own independent data and analysis tools, and have found no evidence of a new particle. Instead, the DZero data are in agreement with predictions from the Standard Model.

Originally, CDF scientists observed the possible new particle when analyzing proton-antiproton collisions that produce a W boson - a particle associated with the weak nuclear force - and two jets of particles. At a collision energy of about 145 GeV, the scientists observed about 253 more electrons and muons than expected. The excess implies the existence of a particle with a mass of 145 GeV, but no known have this mass. The finding led the scientists to predict the existence of a new particle with a mass of 145 GeV that decays into an extra W boson that in turn decays into electrons and muons, in addition to other decay products. Some theorists suggested that the new particle might provide evidence for a fifth fundamental force of nature known as "technicolor.”

At first, the effect at CDF had a magnitude of three standard deviations, or “three sigma,” which means that there is about a 1 in 1,000 chance that the result is attributable to some statistical fluctuation in the data. In particle physics, the three-sigma level of certainty is intriguing, but a five-sigma level (about a 1 in 1 million chance that the result is a fluke) is needed to claim a discovery. Then, at a conference on May 30th at Blois, France, CDF co-spokesperson Giovanni Punzi announced that the scientists had analyzed more data and the effect was now at just below the five-sigma level.

So DZero’s failure to confirm the same excess at 145 GeV is a bit of a letdown. On the other hand, it raises the question of what exactly is causing the discrepancy between the two results. Fermilab has two detectors for this very reason, to check each other’s results. However, disagreements like this one don’t occur very often. For the more than 500 measurements that CDF and DZero have independently detected and analyzed over the past 10 years, the results have agreed more than 99% of the time.

“This is exactly how science works,” said DZero co-spokesperson Stefan Sӧldner-Rembold in a Fermilab press release. “Independent verification of any new observation is the key principle of scientific research. At the Tevatron, we have two experiments that, by design, can check each other.”

Going forward, Fermilab plans to create a task force that will consist of scientists from both CDF and DZero to coordinate an analysis of the two detectors’ results in order to understand the disagreement.

The investigation for the possible 145-GeV particle could be one of the last opportunities to discover new physics at ’s Tevatron, at least while it’s still running. The collidor is scheduled to be shut down this September due to budget cuts at the US Department of Energy. After the final shutdown, scientists will still have billions of collision events to sift through, and they expect that data analysis will continue for at least five more years.

Explore further: Simultaneous imaging of ferromagnetic and ferroelectric domains

More information: DZero paper (submitted to Physical Review Letters) and CDF paper (published in Physical Review Letters)

via: Fermilab press release, BBC News, Wired

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User comments : 16

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orgon
2.3 / 5 (8) Jun 13, 2011
It's somehow strange situation for me. The first detector has found the "bumb" with five sigma, i.e. with 10E-6 uncertainty, whereas the second excluded it with 10-5 uncertainty. Why they didn't checked it during writing the article about it before few weeks? Apparently even quite large teams of physicists aren't prone against sensationalism... It's all about the cooperation of physicists within single laboratory.
Pyle
4.4 / 5 (13) Jun 13, 2011
orgon: I know you know better. Sifting through the volume of data collected for these experiments takes a large amount of time. As stated in the article, there is predicted to be five years worth of data to review after Tevatron shuts down. CDF identified a blip. The D0 data for that same event period was immediately focused on and now they find the two detectors don't agree.

As the spokesperson at DZero stated: "This is exactly how science works".

Leave your hypercritical nonsense elsewhere.

These findings don't deny that CDF saw something. Now what needs to be determined is what it saw. Detector error? Contamination from external source? (i.e. cosmic ray, neutrino, ???)
TabulaMentis
1 / 5 (3) Jun 13, 2011
I wonder what relationship technicolor and the Z2 boson may share, if any, with a new fifth force? Does anyone out there know?
FrankHerbert
2.1 / 5 (10) Jun 13, 2011
For those in similar articles always claiming scientists' penchant for hyperbole/dishonesty in securing funds: what funds were gained from this claim? If your paranoia were correct, wouldn't Fermilab have gotten more funds before disproving their own claim?

orgon
3 / 5 (5) Jun 13, 2011
Leave your hypercritical nonsense elsewhere
It's not the only case. This recent CDF preprint
http://arxiv.org/abs/1103.2782
has been refused with D0 collaboration, too:
http://arxiv.org/abs/1106.2063

The rumors of Higgs boson finding leaked from both Tevatron, both LHC recently are the cases of the similar nature. They were both denied with officials a few days later.
http://www.bbc.co...10625172
http://www.time.c...,00.html
ubavontuba
1 / 5 (2) Jun 13, 2011
Hmm... This is a puzzler. Could it have been a quantum resonance effect?
eachus
5 / 5 (3) Jun 14, 2011
The data for or against the new particle is much less than 1% of the events examined at either detector. The events examined were downselected from a huge amount of data. If you look at the actual D0 presentation, you will see that it identifies several cases where the software versions used to estimate the background events are different.

And finally, it is not a case of there is no peak at 145 GeV in the D0 data. What they are saying is that 1) their data is consistent with the Standard Model, or 2) with a particle of much smaller cross-section than CDF collaboration saw.

Expect both collaborations to now work together to try to identify whether the simulation software they are using to predict the background is producing the difference in what is "seen" at the two detectors. What should come out of this is a better characterization of the background, or it could identify differences in the sensitivity of the two detectors to this type of event. Lots more work to do...
Vendicar_Decarian
4 / 5 (4) Jun 14, 2011
"Why they didn't checked it during writing the article about it before few weeks?" - orgon

It is all part of Lucifer's global conspiracy to establish a one world government.

In reality, what you have seen is the result of an open process, where research results are released before the final result is nailed down.

Team A gets a result - puts it up on line. Team B then begins the process of confirmation which takes months, and publishes their results on line.

Team A and Team B have already begun a process of reviewing their methods and analytic techniques in order to understand the discrepancy.

Peteri
5 / 5 (3) Jun 14, 2011
In reality, what you have seen is the result of an open process, where research results are released before the final result is nailed down.

Team A gets a result - puts it up on line. Team B then begins the process of confirmation which takes months, and publishes their results on line.

Team A and Team B have already begun a process of reviewing their methods and analytic techniques in order to understand the discrepancy.


Indeed, an example of science in action, rather than inaction! ;-)
FrankHerbert
1.7 / 5 (6) Jun 14, 2011
No, I don't think you guys understand. These scientists are really inter-dimensional lizards summoned by George Soros to destroy the free market! WAKE UP PEOPLE!
Ricochet
5 / 5 (1) Jun 14, 2011
Maybe they need to pit George Soros vs. Tom Cruise in the LHC and see what kind of particles they produce...
ubavontuba
1 / 5 (1) Jun 14, 2011
Who's using "aaaaaaaaa" and "johnnyb71" to downrank people? If you got something to say, say it.
TabulaMentis
3.3 / 5 (4) Jun 15, 2011
Who's using "aaaaaaaaa" and "johnnyb71" to downrank people? If you got something to say, say it.
The star rating system Physorg.com likes to use needs to be done away with. People who have something to say need to say it and not just go around rating comments without a reason for their action. The star rating system is misleading causing people to have the wrong opinion about a statement just become of how many stars a comment gets. It is the words, not the stars that count.
Pyle
3.3 / 5 (4) Jun 16, 2011
I love the star rating system. It's FUN! It let's me know I am getting under someone's skin, or if somebody finds my comment at least a little relevant.

I will agree that the ratings are sometimes misleading. I would encourage anybody that got this far in this thread that if you disagree with a comment's rating click on the username who got rated, click the little arrow thingy in the center bar and see who rated them. It says a lot about the criticism to know where it is coming from. I pride myself in dogbert 1's.
TabulaMentis
1 / 5 (1) Jun 19, 2011
Click on the username who got rated, click the little arrow thingy in the center bar and see who rated them.
That is being sneaky!!!
TSpcLb
not rated yet Aug 03, 2011
Seems like my father's prediction of them finding a new lepton at this energy is reaching its climax... Certainly hope it's right, because the last 30 years of his theoretical research would be proven to be a good use of time! (For more info visit tri-space-lab.com) Good hunting Fermilab (& CERN)!