Fast Neutrinos: Still Fast

One of the more reasonable criticisms of the OPERA result showing neutrinos apparently moving faster than light was that they were claiming 20-nanosecond resolution on the timing of a neutrino pulse that was 10000 nanoseconds long. They got their timing by doing fits to the shape of the whole pulse, as described in that link, and there’s always a little bit of alchemy in that sort of process, but they had big long pulses because that’s what the accelerator at CERN that served as the source of the neutrino beam provided.

After the original annoucnement, they got the neutrino beam reconfigured to produce much, much shorter pulses– less than 10ns. And while they’ve only been running this way for a few weeks, they’ve already got 20 neutrino detections from the shorter pulses, and they see exactly the same timing anomaly. Tommaso Dorigo has more details, with graphs.

Now, this isn’t a solid proof of anything– it’s the same people using the same apparatus, so all it really shows is that their results are self-consistent. In other words, they’re not idiots getting confused by curve-fitting anomalies. There’s still the possibility of some subtle systematic effect in the apparatus throwing everything off– indeed, that remains the most likely explanation. All this really does is require that the systematic-error explanation be a little more subtle than it was before.

16 comments

  1. Tommaso Dorigo’s mention of the possibility of a systematic from changes in the 8-km-long light guide is very interesting. That sounds like it’s definitely the next thing to look into.

  2. I still fail to see why this, if it gets confirmed in the long run, has to be such a big deal. It’s not like the neutrinos seem to be order of magnitude faster than the established value of C. C was defined at some point based on the most accurate measurements at the time, having to revise the value by a minute fraction based on new measurements shouldn’t result in having to redo Einstein. GR is dependent on the concept of C, not the absolute value.
    In deed, I’m wondering how many physicists silently adjusted their error estimates over the last decades when their measurements didn’t agree with C, because they “knew” the value of C.

  3. @Mu: The problem is that c has been measured by a variety of other techniques, and to very high precision. So high, in fact, that uncertainties in the definition of the meter came to dominate uncertainties in the value of c, a problem which was solved by defining the meter to be the distance light travels in 1/299792458 s. So the fact that the neutrinos are apparently arriving 60 +/- 10 ns earlier than they would if they were traveling at c is a Big Deal. If that’s a real result rather than an artifact of some not-yet-found systematic error, there is a fair amount of physics that breaks–not just GR, but a big chunk of classical E&M and some quantum stuff.

  4. There would naturally be the possibility that our assumption that a dark matter filled universe has the same refractive index as the “vacuum universe” Einstein assumed.

  5. Sooo…..maybe c is not a constant, then?

    Isn’t there already another unknown affecting the conclusions that can be drawn from this experiment: the mass of a neutrino?

  6. Mu: then there is a lot of other problems.

    Like why there is no dispersion? I.e. why gamma rays travel as fast as radiowaves?

  7. Whether it’s about method, instrumentation or properties of particles, something of real value is going to be learned soon. This is cool.

  9. I’m no physicist, but the whole thing is fascinating.

    A question for those in the know … is this the first time neutrinos have had their speed checked?

    I say they’re moving through a slippery neutrino conduit which affords them the luxury of a faster trip; and we should all be so lucky. By the way, if all this turns out to be true and they indeed are moving a bit faster, then I’d like credit for the term “slippery neutrino”.

  11. Forgive the amateur question, but I am curious about this. It is mentioned above that the speed of light is now known with great accuracy, citing how light was used to determine the length of a meter. Is it problematic using light (somewhat indirectly) to measure the speed of light?

  12. I’ve studied physics and quarks at a-level but I can’t seem to find a reason why neutrino’s breaking the speed of light would change anything. Because if they are travelling at that speed now then they’ve always being travelling at that speed? It wouldn’t change calculations massively if the chance is only nanoseconds… just seems like a revised C. What would the effect of the change in C mean?

  13. @ Cllio #11

    Maybe you should take a refresher course then :)? If they are in fact faster than light that would make e=mc^2 less relevant if not even irrelevant (I say less relevant because it might only be a quantum thing). The theory revolves around light being the absolute top speed in the universe.

    It would theoretically make travelling back in time possible.

  14. I’ve studied physics and quarks at a-level but I can’t seem to find a reason why neutrino’s breaking the speed of light would change anything.

    Allow me to answer in the form of a limerick!

    If you go from Point A to Point B
    With a d/t faster than c
    The trip is the same
    (In another man’s frame)
    As a trip back in time. QED.

  15. アジア杯の上の惨敗は私達を中国ugg ショップのサッカーの立ち後れることがはっきり見timberland アウトレットえさせて、日本のサッカーはすでにみごとに世界に向かいました。アジア杯の(以)後で、pumaは日の本文で霊感の2足のサッカーシューズに変わることを出しました――PWR-C1.10 TokyoとV1.10 Kanji。PWR-C1.10 Tokyoは東京街頭の文アウトドアシューズ スニーカー特価化を霊感にして、下手な字を書く方法は日本語の“東京”の印を白色の靴の表面の上にあります。V1.10 Kanjiの中Kanjiは日本語サッカー ユニフォーム 通販の“漢字”の意味です。設計者は漢字の“高速”の印を靴の表面の上で、際立っているV1.10のスピードは思います。哀れみを誘うのは中国の文化の代表の漢字にするのが意外にも日本の文化の元オーストラリア　ブーツ素にして今回の付けてはいけない設計の霊感の出所になったのなのです。見たところサッカーシューズの領域にもっと多い発言権を持ちたくて、中国のサッカーの後れているレベルは最大の妨害です。

  16. アジア杯の上の惨敗は私達を中国ugg ショップのサッカーの立ち後れることがはっきり見timberland アウトレットえさせて、日本のサッカーはすでにみごとに世界に向かいました。アジア杯の(以)後で、pumaは日の本文で霊感の2足のサッカーシューズに変わることを出しました――PWR-C1.10 TokyoとV1.10 Kanji。PWR-C1.10 Tokyoは東京街頭の文アウトドアシューズ スニーカー特価化を霊感にして、下手な字を書く方法は日本語の“東京”の印を白色の靴の表面の上にあります。V1.10 Kanjiの中Kanjiは日本語サッカー ユニフォーム 通販の“漢字”の意味です。設計者は漢字の“高速”の印を靴の表面の上で、際立っているV1.10のスピードは思います。哀れみを誘うのは中国の文化の代表の漢字にするのが意外にも日本の文化の元オーストラリア　ブーツ素にして今回の付けてはいけない設計の霊感の出所になったのなのです。見たところサッカーシューズの領域にもっと多い発言権を持ちたくて、中国のサッカーの後れているレベルは最大の妨害です。

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