Live Chat: Have Neutrinos Broken the Speed Limit of Light?

Nothing can go faster than light, right? Einstein said so. But last week a group of researchers in Italy announced that they’d measured the speed of thousands of neutrinos (tiny, almost massless particles that were fired at their detector from the CERN particle physics lab 730 kilometers away) and found they were traveling slightly faster than light. Is this the beginning of the end for Einstein’s theory of relativity? Have the researchers simply made a mistake in their measurements? Or are the neutrinos, as some versions of string theory allow, taking a shortcut through a higher dimension and arriving in Italy in double-quick time?
Join us for a live chat on this page at 3 p.m. EDT on Thursday, 29 September, to discuss these and other questions with two experts in the field. You can leave your questions in the comments section below before the chat starts.
Upcoming Event:  Have Neutrinos Broken the Speed Limit of Light?

“Relativity without light”, the answer in the superluminal neutrinos;

Suppose that the result of the OPERA experiment is right and neutrinos travelling faster than light….
This is the end of Einstein’s theory of special relativity and the Lorentz transformations?
Is it possible the special relativity without the second postulation;
The answer is yes.
Read for example:
Simple derivation of the special theory of relativity
without the speed of light axiom
” –
a very simple yet rigorous derivation of the invariance of the space-time interval (and hence the whole special relativity) just from the isotropy, homogeneity and a principle of relativity, without the need of the speed of light axiom.

Potential mistakes in the Opera research

Almost all theoretical oriented physicists including myself seem to feel almost certain that there is a mistake in the Opera paper and the claimed violation of the relativistic speed limit will go away.

On the other hand, I think that many people who like technology etc. were impressed by the precision work that the Opera folks have demonstrated. It’s a complex piece of work in which particle physicists became top metrologists – their work was endorsed by two teams of professional metrologists, too. In some sense, their measurement is also a pioneering work: as far as I know, the propagation of speed-of-light-in-the-vacuum signals between very distant places on Earth has never been tested against GPS metrology before so it shouldn’t be shocking that one gets a 18-meter discrepancy when he tries it for the first time.

There’s a lot of potential for errors. The measurement may be schematically represented as three steps: “measuring the distance”, “bringing the proper universal time to CERN clocks”, and “bringing the proper universal time to Gran Sasso clocks”. So the mistakes may be divided into three basic groups:

  • timing errors at CERN
  • timing errors in Italy
  • errors in the distance measurement

This is just a very rough, “geographic” separation of the possible mistakes. Various numbers in the calculations depend on each other and one should be more specific about the origin of the error, anyway…… Continue reading Potential mistakes in the Opera research

The Phantom of OPERA

Those working in science are accustomed to receiving emails starting with “dear sir/madam, please look at the attached file where I’m proving einstein theory wrong”. This time it’s a tad more serious because the message comes from a genuine scientific collaboration… As everyone knows by now, the OPERA collaboration announced that muon neutrinos produced at CERN arrive to a detector 700 kilometers away in Gran Sasso about 60 nanoseconds earlier than expected if they traveled at the speed of light (incidentally, trains traveling the same route arrive always late)….. Continue reading The Phantom of OPERA

Some Comments on the Faster Than Light Neutrinos

Matt Strassler

The OPERA experiment has now presented its results, suggesting that a high-energy neutrino beam has traveled 730 kilometers at a speed just a bit faster than the speed of light.  It is clear the experiment was done very carefully.  Many cross-checks were performed.  No questions were asked for which the speaker did not have at least a reasonable answer.
Some preliminary comments on the experiment (none of which is entirely well-informed, so caution…)

  • They have to measure times and distances to an accuracy of 1 part in a few hundred thousand. This is hard, not impossible, and they have worked with metrology experts to carry these measurements out.
  • The timing measurement is not direct; it has to be made in a statistical fashion. The proton beam pulses that make the neutrino beam pulses [read more about making neutrino beams here] are not sharp spikes in time, but are distributed in time over ten thousand nanoseconds. (Recall the measured early arrival of the neutrinos is only 60 nanoseconds.) And so one cannot measure, for each arriving neutrino, how long it took to travel. Instead one has to measure the properties of the proton beam pulses carefully, infer the properties of the neutrino pulses, measure the timing of the many arriving neutrinos, and work backwards to figure out how much time on average it took for the neutrinos to arrive. This sounds tricky.[Thanks to Ryan Rohm for calling my attention to this a few days ago.]That said, the experimenters do show some evidence that their technique works.  But this could be a weak point.
  • I am a bit concerned about the way in which statistical and systematic errors are combined. The theory for statistical errors is well-defined; one assumes random fluctuations. In combining two statistical errors E1 and E2, one says that the overall error is the square root of E1-squared + E2-squared.  This is called “adding errors in quadrature.”  But systematic errors are much less well-defined, and it is not clear you should combine them in quadrature, or combine them with statistical errors in quadrature. The OPERA experiment combines all errors in quadrature, and says they have a measurement at 6 standard deviations away from the speed of light. If you instead combined systematic errors linearly with statistical errors (E1+E2 instead of as above) you would get 4 standard deviations. If you combined all the systematic errors with each other linearly, and then with the statistical error linearly, you would get 2 standard deviations (though that is surely too conservative). All this is to say that this result is not yet so significant that different and more conservative treatments of the uncertainties would all give a completely convincing result. This is just something to keep in mind when evaluating such an exceptional claim; we need exceptional confidence……

Read more:

Dimension-hop may allow neutrinos to cheat light speed

What are we seeing here?

A CERN experiment claims to have caught neutrinos breaking the universe’s most fundamental speed limit. The ghostly subatomic particles seem to have zipped faster than light from the particle physics laboratory near Geneva, Switzerland, to a detector in Italy.

Fish that physics textbook back out of the wastebasket, though: the new result contradicts previous measurements of neutrino speed that were based on a supernova explosion. What’s more, there is still room for error in the departure time of the supposed speedsters. And even if the result is correct, thanks to theories that posit extra dimensions, it does not necessarily mean that the speed of light has been beaten.

“If it’s true, it’s fantastic. It will rock the foundation of physics,” saysStephen Parke of Fermilab in Batavia, Illinois. “But we still have to confirm it.”

Neutrinos are nearly massless subatomic particles that are notoriously shy of interacting with other forms of matter. An experiment called OPERA (Oscillation Project with Emusion tRacking Apparatus) sent beams of neutrinos from a particle accelerator at CERN to a detector in the Gran Sasso cavern in Italy, 730 kilometres away.

The neutrinos arrived 60 nanoseconds sooner than they would have if they had been travelling at the speed of light, the team says.

Supernova contradiction

If real, the finding will force a rewrite of Einstein’s theory of special relativity, one of the cornerstones of modern physics (and a theory whose predictions are incorporated into the design of the accelerators at CERN). “It’s not reasonable,” says theorist Marc Sher of the College of William and Mary in Williamsburg, Virginia….. Continue reading Dimension-hop may allow neutrinos to cheat light speed

Measurement of the neutrino velocity with the OPERA detector in the CNGS beam

The OPERA neutrino experiment at the underground Gran Sasso Laboratory has measured the velocity of neutrinos from the CERN CNGS beam over a baseline of about 730 km with much higher accuracy than previous studies conducted with accelerator neutrinos. The measurement is based on high-statistics data taken by OPERA in the years 2009, 2010 and 2011. Dedicated upgrades of the CNGS timing system and of the OPERA detector, as well as a high precision geodesy campaign for the measurement of the neutrino baseline, allowed reaching comparable systematic and statistical accuracies. An early arrival time of CNGS muon neutrinos with respect to the one computed assuming the speed of light in vacuum of (60.7 \pm 6.9 (stat.) \pm 7.4 (sys.)) ns was measured. This anomaly corresponds to a relative difference of the muon neutrino velocity with respect to the speed of light (v-c)/c = (2.48±0.28 (stat.)±0.30 (sys.)) x 10-5……..

…… Conclusions
The OPERA detector at LNGS, designed for the study of neutrino oscillations in appearance mode, has provided a precision measurement of the neutrino velocity over the 730 km baseline of the CNGS neutrino beam sent from CERN to LNGS through the Earth’s crust. A time of flight measurement with small systematic uncertainties was made possible by a series of accurate metrology techniques. The data analysis took also advantage of a large sample of about 16000 neutrino interaction events detected by OPERA.
The analysis of internal neutral current and charged current events, and external νµ CC interactions from the 2009, 2010 and 2011 CNGS data was carried out to measure the neutrino velocity. The sensitivity of the measurement of (v-c)/c is about one order of magnitude better than previous accelerator neutrino experiments.
The results of the study indicate for CNGS muon neutrinos with an average energy of 17 GeV an early neutrino arrival time with respect to the one computed by assuming the speed of light in vacuum:
δt = (60.7 ± 6.9 (stat.) ± 7.4 (sys.)) ns.
The corresponding relative difference of the muon neutrino velocity and the speed of light
(v-c)/c = δt /(TOF’c – δt) = (2.48 ± 0.28 (stat.) ± 0.30 (sys.)) ×10-5.
with an overall significance of 6.0 σ.
The dependence of δt on the neutrino energy was also investigated. For this analysis the
data set was limited to the 5489 νµ CC interactions occurring in the OPERA target. A measurement performed by considering all νµ CC internal events yielded δt = (60.3 ± 13.1 (stat.)± 7.4 (sys.)) ns, for an average neutrino energy of 28.1 GeV. The sample was then split into two bins of nearly equal statistics, taking events of energy higher or lower than 20 GeV. The results for the low- and high-energy samples are, respectively, δt = (53.1 ± 18.8 (stat.).) ± 7.4 (sys.)) ns and (67.1 ± 18.2 (stat.).) ± 7.4 (sys.)) ns. This provides no clues on a possible energy dependence of δt in the domain explored by OPERA within the accuracy of the measurement.
Despite the large significance of the measurement reported here and the stability of the
analysis, the potentially great impact of the result motivates the continuation of our studies in order to investigate possible still unknown systematic effects that could explain the observed anomaly. We deliberately do not attempt any theoretical or phenomenological interpretation of the results.
Read more: