/ Maggie Koerth-Baker / 12 pm Mon, Oct 31 2011
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  • Faster-than-light neutrino update: What's going on behind the scenes?

    Faster-than-light neutrino update: What's going on behind the scenes?

    The publication process for a research paper about physics works a little differently than other subjects. That's because of arXiv. Funded by Cornell University, this site posts research papers, before they're formally published in a scientific journal. Unlike most scientific journals, which charge big fees for subscriptions or even to view a single paper, arXiv is free and open to the public. You can read everything published there—more than 700,000 papers about physics, math, computer science, and more. The other big difference: arXiv isn't peer reviewed. At least, not ahead of time.

    A lot of the time, when you read a newspaper article about a new study in one of those fields, the study hasn't actually yet been published in a peer-reviewed journal. It's just been posted to arXiv, which sort of becomes a crowd-sourced peer review peer review of its own. Especially for headline-grabbing research making big, bold claims.

    That's the background you need to understand what's going on right now with the study that claimed to find neutrinos traveling faster than the speed of light. That announcement was made in an arXiv paper. Putting those results on arXiv was as much a way of saying, "Woah, we just found something crazy, please tell us if you see something we've done wrong," as it was a formal declaration of scientific discovery.

    Since that paper was published in September, there have been more than 80 follow-up papers, also published on arXiv, offering criticism of the original research or proposing theoretical explanations of how that seemingly crazy finding could fit into physics as we know it. And all of this is happening before anybody has gone through the peer-review publishing process.

    That's why it's not terribly weird that you're now hearing all sorts of criticism of the original FTL neutrino findings. That's what was supposed to happen. It's also not terribly weird that the original researchers have announced that they're going to re-do the experiment themselves, taking into account some of the big criticisms brought up on arXiv. The BBC explains what will be done differently this time:

    The neutrinos that emerge at Gran Sasso start off as a beam of proton particles at Cern. Through a series of complex interactions, neutrino particles are generated from this beam and stream through the Earth's crust to Italy.

    Originally, Cern fired the protons in a long pulse lasting 10 microseconds (10 millionths of a second). The neutrinos showed up 60 nanoseconds (60 billionths of a second) earlier than light would have over the same distance.

    However, the time measurement is not direct; the researchers cannot know how long it took an individual neutrino to travel from Switzerland to Italy. Instead, the measurement must be performed statistically: the scientists superimpose the neutrinos' "arrival times" on the protons' "departure times", over and over again and taking an average.

    But some physicists say that any wrong assumptions made when relating these data sets could produce a misleading result. This should be addressed by the new measurements, in which protons are sent in a series of short bursts - lasting just one or two nanoseconds, thousands of times shorter - with a large gap (roughly 500 nanoseconds) in between each burst. This system, says Dr Bertolucci, is more efficient: "For every neutrino event at Gran Sasso, you can connect it unambiguously with the batch of protons at Cern," he explained.

    By taking these criticisms into account now, the FTL neutrino researchers are doing sort of a pre-peer-review peer review. If their new experiment yields the same results, it makes the claim stronger and makes a traditional journal more likely to publish the results. As a bonus: Those results will already have been tested against the most obvious criticisms. If FTL neutrinos make it to a peer-reviewed journal, there will be a much greater likelihood that what's being published is actually worth paying attention to. If they don't, there's a well-established record of how smart people got something wrong—valuable to future researchers, even though it wouldn't be likely to pass muster in a journal.

    Meanwhile, because none of these papers had to go through the lengthy (and costly) traditional publishing process, we've been able to see both the weird finding and the critical evaluations far faster than we otherwise would have. And because the weird finding was made available sooner, there will be independent researchers trying to replicate it sooner. In fact, there's a good chance that, if the FTL neutrino researchers decide to go ahead and publish their results in a peer-reviewed journal, several other, independent teams will be well on their way to replicating the results (or not) by the time that paper is printed.

    So if there's one thing you should be taking away from all the fuss over FTL neutrinos, it's this: Science benefits when scientists have more than one way to share information with each other.

    Image: Science Centre at CERN, a Creative Commons Attribution Share-Alike (2.0) image from johnjobby's photostream

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