Fermi Lab's New Particle Discovery in Question

"Back in April physicists at Fermilab speculated that they may have discovered a new force or particle. But now another team has analyzed data from the collider and come to the exact opposite conclusion. From the article: 'But now, a rival team performing an independent analysis of Tevatron data has turned up no sign of the bump. It is using the same amount of data as CDF reported in April, but this data was collected at a different detector at the collider called DZero. "Nope, nothing here – sorry," says Dmitri Denisov, a spokesman for DZero.'"

Comments

Data sharing

[symes]

I think more than anything, this demonstrates why sharing data openly is such a good thing. Sure, not great news for those at Fermi Lab, but if scientists generally (especially those in the behavioural sciences...) were encouraged (or forced?) to allow others free access to their data then I'm sure a few surprising claims might be rewritten and a few interesting blips otherwise missed might be found.

Re:Data sharing

[The_Wilschon]

These experiments do not share their data openly (while the experiment is still taking data) because if they did, there would not be any data. The only way to get enough physicists to work on the experiment to make it run well enough to get any data is to restrict data access to those who do service work on the experiment. After the end of data taking, the data may be released, but I don't know the time table on which that typically occurs.

Re:Data sharing

[The_Wilschon]

It is probably more important to note that D0 handles their systematics a little bit differently. This is natural, because their detector is different, so their systematic errors are different. But there appears to be one particular systematic that they handled better than CDF, and CDF's less-good handling produced a bump-shaped mismodeling of the data. I don't want to say too much, but hint: quarks and gluons don't necessarily quite act alike in some important particulars.

Re:Data sharing

[delt0r]

Lots of Astronomy data is held by the "collection group" for a year or so to allow dibs on publication. ie all Hubble data is like this and all the big telescopes are like this (VLT etc). Particle physics is not that different. There is a embargo period IIRC and then its opened up.

It is hard to get funding if you don't get papers out. You won't get the papers out if you spend all the hard work of making the data available rather than analyzing it.

Re:Data sharing

[Anonymous Coward]

Ex particles guy writing here --- the reason that data isn't immediately shared is that data acquisition and first pass analysis have to be done before you even *think* about looking for new physics. Moreover, the detector systems are complex enough, that it is really hard to be sure the analysis works correctly when you were the one who built the bleedin' thing. Then there's the other half -- almost no detector has complete coverage -- certainly none of the detectors at FNAL or CERN do so you are at the mercy of Monte Carlo simulations to work out the corrections. So you have to do the experiment twice; once is the physical world and once in a virtual world. Mismatches between the worlds can easily lead to spurious signals. Not saying that astronomy is any easier -- at least as its practiced now a days. And WMAP, for example, doesn't seem to be giving away the raw data. There is some turf protection -- "we invested blood sweat and tears as well as years of our lives to build the detector -- we get first crack at the data" -- I don't think that's a bad thing.

The particle physics community does have the equivalent of a star map it's the Review of Particle Properties (RPP).

Re:Data sharing

[delt0r]

There is no requirement in Astronomy either as far as i know. We didn't publish a lot of our data, but it was available on request . But like in particle physics, colleagues expect it. A lot of data does not make it to the "public domain", but that is often more a issue of the time and money it costs to do so. This is true for every field and it was a lot more expensive 50 years ago which is why it something that has really only started to happen (lets face it, you didn't make a entire copy of plates from your telescope at every request).. Especially in particle physics where the data volumes are huge even compared to Astronomy standards.

Don't get me wrong i think the data should be made public as a requirement for publication in one form or another. However also working with big datasets myself i realize this is far from free or easy or fast even with today's technology. And modern collider data is a little on the crazy side in both volumes and what is needed to process it. Basically everyone who can use the data can pretty much get it.

Re:Data sharing

[chissg]

[Re-post non-AC] Star catalogs aren't data: they're the results of decades of observations, corroborations, corrections and debates over just exactly what that particular black spot on the white plate was. You want the raw telemetry from every telescope that isn't read out with a Mark I eyeball, and every plate ever taken and scientist's observation note from those that were? You want all the calibration data from WMAP, and all the histograms that were plotted to analyze them and turn them into corrections for the main data so they actually *mean* something? Particle physics, "data" is the 1s and 0s from every piece of sensory equipment in the detector hall, beam area and points between: often millions of readout channels, each of which means something and has its own quirks and problems that need to be measured and understood with more and different types of data (calibration, cosmic rays, etc). And, these readings are taken at frequencies between thousands and millions of times per second. We often have to analyze the data to a preliminary level just to decide whether they're worth keeping to analyze properly later because there's neither the bandwidth nor the storage space nor the computing power -- even now -- to keep them all. The LHC experiments store petabytes of data per month, and storage, access and transfer costs are significant: you pay for access to those data by contributing to the experiment. OK, now let's assume you get the raw data. Now what? Good luck with that. There's a reason scientist groups and expert contractors spend years and sometimes decades writing the reconstruction and analysis software for particle physics experiments: teasing useful results from the data are hard. If we were to spend our timing pointing out the rookie mistakes of every schmo who fiddled with the data for a while and thought he'd found something new, the work would never be done. "Heisenberg's Uncertainty Principle Untenable [icaap.org]," anyone?

old news?

[Anonymous Coward]

Wasn't there a story on slashdot just last week about the people who released the data saying the same thing?

http://science.slashdot.org/story/11/06/10/1455240/Data-Review-Brings-Major-Setback-In-Higgs-Boson-Hunt

oh, I guess there was.

Re:old news?

[bws111]

It is the same story. The older article just had a bad title.

Already known?

[MurukeshM]

What about this comment on the original /. post: D0 has done this same sort of analysis, and they do not see this bump. But, their background modeling procedure involves reweighting the expected distributions (from Monte Carlo) in delta R between the jets (sort of an angular separation between the jets), which is a variable that is strongly correlated with the dijet mass. That is, their background model would be expected to have a strong tendency to fill in a bump like this. Now, which model is more correct is open to question, but it is certainly true that whether or not this bump turns out to be from real new physics (unlikely, in my professional opinion), their procedure is almost guaranteed not to find it.

Re:Already known?

[The_Wilschon]

That was me. In the analysis released on Friday, D0 does not perform the delta R reweighting (this was a specific criticism that they sought to address). In spite of no delta R reweighting, they still do not see the bump. There are some systematic errors that they handle differently from CDF which are quite likely to explain the result. Some of my colleagues at CDF are investigating (and were investigating before this D0 release, because of a suggestion by a D0 physicist at the release of the original bump paper) these systematics and their effect on our ability to model the data well. I can't really comment further until results are released, however.

Re:Yeah Except

[Artifakt]

When the 'climategate' memos first came up, most of us noticed that they were about tree ring data, which was secondary to actual measured temperatures and such things in the 'man-made global warming' debate. Then some of us noticed that it was about a small percentage of trees growing at high altitudes, which made it all of tertiary significance at best.
People started arguing over whether the researchers were bending the rules of science or not, was it a political conspiracy or not, and endless arguments about who was deliberately eeeeville, when they should have been looking more at how much difference it made.
It all seemed analogous to people finding out that some government type had paid 20,000 dollars to put a neon light covered statue of Elvis in front of the town hall. People got to arguing over whether it was tasteful or not, whether the government had authority to do it or not, and so on, but then one side said "And it really, really matters, because we could have eliminated the federal deficit and even funded a whole extra war with what was left over from that 20,000 dollars." and somehow, that claim was never questioned by a great many.
I see this same sort of thing now in so many areas. Casey Anthony's trial. A forensic pathologist with an exceptionally good reputation testifies, and since he is making a machine that can identify traces of human remains decay, the defence argues that he is biased towards saying anything that might help possible sales of that machine. Never mind that his working for a national laboratory, developing just such devices, is some sort of evidence he is an exceptionally good expert witness - try to make it so a mark of his high quality instead becomes a reason to distrust his testimony, and see if the jury will bite.
Or John Kerry gets three purple hearts. Raise questions about one of them, and see how many of the public will automatically believe that all three were tainted. The more military medals a person gets, the easier it is to find one that sounds a little fishy, so any time somebody runs for office with a Medal of Honor and half a dozen other awards for extreme valor, it will be a piece of cake to find something about at least one, relentlessly attack whichever award sounds weakest, and prove the public should vote for your candidate, who maybe next time this trick is tried, doesn't have a record of this type at all to be challenged. Turn what should normally be an asset into a liability.