We all knew that when the OPERA experiment announced preliminary evidence that neutrinos were traveling faster than the speed of light, the result was so hard to swallow that independent confirmation from other experiments would be necessary before too many people jumped on the bandwagon. In the meantime, a number of theoretical papers pointed out difficulties in accepting the result at face value (probably the cleanest by Cohen and Glashow). And just last month OPERA itself announced that they had located a couple of possible systematic errors in their experiment, without actually backing off the original result. But lets just say things haven’t been looking good.
Now we have what might be the nail in the coffin: another experiment, ICARUS, at the same laboratory in Gran Sasso in Italy, has reported an independent measurement of the neutrino time-of-flight from CERN. (The CERN twitter feed points to an frustratingly vague press release; more useful info from Tommaso Dorigo.) Answer: spot on the speed of light. They even have a paper on the arxiv, from which we get this lovely plot:
Colloquially, we would say “game over, man.” The new measurements sit spot on the speed of light (zero on the plot), and are inconsistent with OPERA. (Actually neutrinos have tiny masses and therefore move just a bit slower than light, but it’s close enough as to be invisible in this plot.) Note that ICARUS had previously “refuted” OPERA, but in a much more indirect way, by checking that the neutrinos hadn’t lost any energy along the way. This new result is a straight-up check of the original claim, and it falls short.
As Tommaso points out, the precision of the ICARUS result is comparable to that of OPERA, so if you live in a mental space free of theoretical priors you could assign 50/50 weight to each one. Those of us in the real world should be ready to accept that the speed of light isn’t just a good idea: it’s the law.
I also believe that these deniers CTF is financed by the oil industry
Sean, there were some quotes in press that the superluminal neutrinos is evidence for string theory.
Now that the this result has been refuted, does that imply that string theory is ruled out?
Both ICARUS n OPERA took into account GR effects.To try to question GR is absolutely absurd.
@Shantanu, both your premise and conclusion are wrong. In the “standard” formulation of string theory, e.g., the formulation found in Polchinski’s books, relativity and the local Lorentz invariance are exact.
When the erroneous OPERA result came out, various people tried to become famous by cooking up all sorts of crazy, but ultimately flawed, models of superluminal behavior. This even included some string theorists, who decided to abandon the basic structure of string theory – that had worked so well – and replace it with some ad hoc dicey construction in a desperate attempt to become famous. Well this turned out to be a waste of time.
So string theory still lives on, by simply recovering relativistic quantum field theory in regimes that are not “too extreme”. But much more importantly: Einstein was right.
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