Fermi Lab May Have Discovered New Particle or Force

schleprock63 writes "Physicists at Fermi Lab have found a 'suspicious bump' in their data that could indicate they've found a new elementary particle or even a new force of nature. The discovery could 'be the most significant discovery in physics in half a century.' Physicists have ruled out that the particle could be the standard model Higgs boson, but theorize that it could be some new and unexpected version of the Higgs. This discovery comes as the Tevatron is slated to go offline sometime in September."

Comments

It has now been named....

[levell]

It shall henceforth be known as the pleaseExtendOurFunding-ion.

OK, I jest. On a more serious (but related) note, back in 2000, when the LEP at CERN was shutting down, there were possible "hints" of the Higgs' Boson and pleas to extend the running time (which were ultimately denied so that the LHC would not be delayed).

Re:I know it's petty...

[AshtangiMan]

"Physicists at Fermi Lab have found a 'suspicious bump' in that there data that could indicate they've found a new elementary particle or even a new force of nature."

Fixed

Do they account for hypothesis-mining?

[Rich0]

When I read things like "In about 250 times more cases than expected, the total energy of the jets clustered around a value of about 144 billion electron volts" I get nervous.

This is like saying that in a series of 1M coin tosses the sequence HTTHHTTTTHHTTHHH came up 100x more often than would be expected by chance. Does that mean that any particular sequence of 8 tosses should come up 1/65536th of the time, and this one came up 1/655th of the time, or does it mean that some random sequence of results should come up 100% of the time in a random series of 16 coin tosses, and we happened to pick the random series that came up the most often in that particular set of data?

If I mine a big set of data against 100 random hypothesis I'll be able to find about 5 that I can show to be true with 95% confidence, despite the fact that there is nothing really going on.

The real test is to come up with the hypothesis first, then collect the data.

Now, these guys are probably smart, and hopefully control for this. If you want to test for 100 hypotheses and REALLY have 95% confidence, then you need to target a confidence of 1-0.05^100 for each test - at least that is how I see it (being a complete novice at statistics).

Re:Do they account for hypothesis-mining?

[The_Wilschon]

They did take into account the look-elsewhere effect, as is standard in bump-search type papers. This bump has a 3.2 sigma significance _after_ the look-elsewhere significance reduction and other systematic uncertainties.

Re:Do they account for hypothesis-mining?

[radtea]

The real test is to come up with the hypothesis first, then collect the data.

That's not the way the vast majority of science is done. Popper was a philosopher speaking in ignorance (but I repeat myself).

The challenge for these guys is not in the hypothesis testing, but in the cuts. You have to come up with some set of criteria for selecting "good" events in complex detectors of this kind. There is always a degree of arbitrariness in how you do that, and there have been cases in the past (the so-called 'GSI particle') where people tweaked and tuned multi-dimensional cuts to maximize peaks in the data.

In the present case it is clear their cuts are physics-based--they are described in the paper--and that the peak structure is consistent with the resolution one would expect (the GSI particle required some very weird physics to make the narrow peak widths plausible.)

However, the peak is also precisely in the region where their background spectra are varying most rapidly, and this is a huge red flag. It makes them sensitive to any number of minor mis-calibrations. It does NOT mean the phenomenon is not real, but if I had to make a bet on it being physics beyond the standard model or an instrumental artefact, my money would not be on new physics.

Re:If it's not the God particle, it's Salvia.

[Fibe-Piper]

A person who smoked salvia said that a black hole in reality opened up and their soul was sucked into it. Meanwhile physicists claim that black holes suck in matter and light and it can never escape.

Maybe if more physicists smoked Salvia they'd have a better natural understanding of the universe. They would understand that salvia is an alien lifeform, a plant brought to the earth by the http://en.wikipedia.org/wiki/Greys to consume our souls. They would understand that our reality is an illusion and that this force they just discovered is the salvia force, the ultimate proof of alien life. The universe and existence is fake, accept it. You don't have consciousness, you are just a biological machine, please accept it.

Oddly enough, your post is as worth reading as the 40+ posts that came after it. You may have proved a point. God know what it is (maybe on some quantum scale you are proving that insanity is sanity at the same time) but, well done old chap.

Re:If it's not the God particle, it's Salvia.

[TheCRAIGGERS]

Slashdot has just opened up to a new demographic I think.

Who, crazy people? No, they've been here for years.

A useful link

[jd]

...to the paper, as opposed to the commentary by PopSci on the article written by NYT by someone who really didn't know what the hell they were talking about.

Re:If it's not the God particle, it's Salvia.

[kyuubiunl]

You sir, need to find a more competitive source for LSD.

Re:Sad to lose the Tevatron

[The_Wilschon]

FWIW, earlier drafts of the paper were much more sensationalistic than the final draft that the collaboration approved. A large contingent of the collaboration, myself included, would have removed our names from the paper if it had done something as insane as claim discovery of a new particle. So, we specifically pushed to make the paper more scientifically honest and less effective as a "ploy to keep the funds flowing." That said, the NYT article and all the other mainstream news reports on the issue are far, far more sensationalistic than anything the analyzers ever even considered producing...

Some interesting things to note:

• This search was done with a very tight event selection designed to get a relatively pure diboson sample. Loosening up the selection increases the number of data events involved in the analysis by (IIRC) about a factor of 8, and in this looser sample, the significance of the bump decreases to about 1 sigma, which is wholly uninteresting.
• The feeling among the members of my particular group (one of the member institutions of the CDF collaboration) is that this is a very interesting result, but that it should be interpreted more as exposing the difficulties of / our inability to model the very large W+jets background accurately; the Monte Carlo generators are simply insufficient or are slightly incorrectly tuned. We do not really feel that this is likely to be an indication of new physics at all.

So, long story short, there is certainly something here to be interested in. Both the theorists who write the Monte Carlo generators and the experimentalists analyzing data from the LHC experiments are paying close attention to this result, as it affects their work. We will know more after further study and work, both to improve the Monte Carlos and to look for similar effects in the ATLAS and CMS data.

Re:Sad to lose the Tevatron

[The_Wilschon]

I would strongly advise reading the actual paper (can be found on the arxiv) instead of the NYT article, which, as I mentioned, is sensational and largely content-free. There is plenty of information in the paper about how they determined the significance of the result and how the analysis (event selection etc) was done. It should answer your questions in this regard. As far as being "new", the data from these experiments is analyzed in scientifically and statistically rigorous ways all the time. It in no way involves "massaging" the data, which you can see if you read the hundreds of papers that have come out of high energy physics experiments.

I really can't comment professionally on the sterile neutrino re dark matter. I've heard of the MiniBOONE result, and think it is very interesting, but the viability of a sterile neutrino as dark matter is pretty far afield for me. Perhaps a passing cosmologist can comment?