By Eugenie Samuel Reich of Nature magazine
The claim that neutrinos can travel faster than light has been given a knock by an independent experiment.
On 17 October, the Imaging Cosmic and Rare Underground Signals (ICARUS) collaboration submitted a paper to the preprint server arXiv.org, in which it offered a rebuttal of claims to have clocked subatomic particles called neutrinos traveling faster than the speed of light. The original results were published on 22 September by the Oscillation Project with Emulsion-Tracking Apparatus (OPERA) experiment.
Both experiments are based at Gran Sasso National Laboratory near L'Aquila, Italy, and detect neutrinos coming in a beam from CERN, Europe's high-energy particle physics laboratory near Geneva in Switzerland, about 730 kilometers away. Unlike OPERA, ICARUS does not measure the neutrinos' speed directly. Instead, it has shown that the energy spectrum of the neutrinos does not exhibit an effect predicted last month by Andrew Cohen and Sheldon Glashow, theoretical physicists at Boston University in Massachusetts.
If the Cohen-Glashow effect is a valid prediction, "neutrinos are not superluminal," says Sandro Centro, a physicist at the University of Padua in Italy, deputy spokesman for ICARUS and a co-author of the latest paper.
Cohen says that an energy spectrum provided by OPERA showed the same inconsistency, and that the spectrum from ICARUS has added to the problem. "There's always value to having things checked independently," says Cohen. "I think it's great ICARUS has done this so quickly."
Too much momentum
The Cohen-Glashow effect is an extension of another phenomenon, well known to physicists. The speed of light traveling through materials such as water is lower than that in a vacuum, and charged particles such as electrons are able to exceed this lower speed when traveling through the medium. When they do, they have excess energy for their momentum and radiate some away in the form of photons, or 'Čerenkov radiation'.
Cohen and Glashow concluded that neutrinos traveling faster than light would behave similarly, although as neutral particles they would radiate pairs of electrons and positrons rather than photons. This would reduce the energy of neutrinos traveling long distances.
Such an energy reduction is not seen in the neutrinos from CERN at their destination in Gran Sasso. Indeed, Dario Autiero, a physicist at the Institute of Nuclear Physics in Lyons, France, and OPERA's physics coordinator, says that measurements of the neutrino energies by OPERA, reported in a February 2011 paper4, already failed to show signs of the effect later predicted by Cohen and Glashow. "It is very well known, and it has been presented in tens of OPERA talks at conferences," he says, "it is not something that we learn today because of ICARUS."
Autiero adds that the assumptions made by Cohen and Glashow may not be universally valid. Giacomo Cacciapaglia, a theoretical physicist at King's College London, agrees, saying that not all models of faster-than-light neutrinos have to respect the assumptions of Cohen and Glashow. For example, neutrinos might be able to travel faster than light by taking a shortcut through extra dimensions, in which case they might not radiate.
But Jorge Páramos, a theoretical physicist at the Higher Technical Institute in Lisbon, says that tinkering with the theory in this way is a dangerous game. "It requires you to choose from the available range of theoretical concepts, and could also lead to disagreement with other well established experimental results (not related to the speed of light)," he says.
More than 80 papers have been posted on arXiv discussing OPERA's result. Most try to explain it theoretically, but a small minority claim to find problems. Autiero thinks that despite the huge interest from the public and the media, the debate will have to play out at the normal pace of science, "which is necessarily slow". The experimental work that was the basis for OPERA's claim took almost six years. "Further developments will be quicker but cannot happen on a few days' timescale," he says.
Two experiments are planning to try to test OPERA's measurement of neutrino velocity: the Main Injector Neutrino Oscillation Search (MINOS) experiment based at Fermilab in Batavia, Illinois, and the Tokai to Kamioka (T2K) experiment in Japan. Neither is likely to have results for some months.
This article is reproduced with permission from the magazine Nature. The article was first published on October 20, 2011.
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18 Comments
Add CommentIf all you needed was an interpretation of a theory to disprove this (as opposed to actual measurement) then wouldn't Einstein's theory have done just fine? After all which has had more proof up to now.
Reply | Report Abuse | Link to thisSo, according to Giacomo Cacciapaglia, a theoretical physicist at King's College London, the headlines should have read: 'Neutrinos faster than light and extra dimensions discovered!' That would have been even more fun...
Reply | Report Abuse | Link to thisIn theory the galaxies should fly apart - they don’t. In theory the expansion of the universe should be slowing down - it isn’t. In theory the vacuum should blow apart with 10^120 times the force it actually is. In theory a muon and an electron should measure the same proton charge radius - they don’t. In theory nothing can exceed the speed of light…
Reply | Report Abuse | Link to thisI can postulate that muon neutrinos will emit p(ositrons)ink ele(ctrons)phants when they exceed c . But what I cannot do is use the failure to observe pink elephants as proof that the muon neutrinos are in fact not exceeding the speed of light. Not in PHYSICS.
In RELIGION, if the high priest (Dr. Glashow) insists that the failure to observe pink elephants is proof that the muon neutrinos are in fact not exceeding the speed of light - then the muon neutrinos are not exceeding the speed of light. But this is PHYSICS not RELIGION.
In POLITICS, if the consensus is that the failure to observe pink elephants is proof that the muon neutrinos are in fact not exceeding the speed of light - then the muon neutrinos are not exceeding the speed of light. But this is PHYSICS not POLITICS.
In PHYSICS one cannot use a theory to dismiss experimental results. Only further experiments, utilizing high energy muon neutrinos timed over a distance (just as they were in the CERN/OPERA observations) can be used to falsify the results. Otherwise, why pretend, we don’t need Dr. Glashow’s pink elephants, just re-publish Einstein’s 1905 paper and say case closed!
This article has in fact the opposite conclusion than its title suggests. The observed energy spectrum just shows IMO that the theories about superluminal neutrino instability find no confirmation.
Reply | Report Abuse | Link to thisPresently, no calculations (even the best ones) can prove any impossibility of superluminal speed for at least two independent reasons:
(1) they must rely on theories which were tested for luminal and infraluminal speeds only;
(2) we do not know of any particles into which a tiny neutrino could break up.
Effectively, much of what can be said against superluminal speed amounts to the following statement:
"Extrapolating the theories asserting that no domestic animal can run faster than 100km/h, the cheetah cannot run faster than 100km/h, because if it could, it would break up into a yeti and a unicorn."
There is nothing wrong with the above true statement (and its proof may contain great ideas) except that it tells us nothing about the cheetah's speed.
The CERN-LNGS experiment was just the latest and strongest in a series of evidence confirming the neutrino's superluminal speed.
Disregarding the title of this news report, the research report upon which it is based supports this news report's conclusions. Please see:
Reply | Report Abuse | Link to thisThe ICARUS Collaboration, (2011), "A search for the analogue to Cherenkov radiation by high energy neutrinos at superluminal speeds in ICARUS.", http://arxiv.org/abs/1110.3763
Its abstract states:
"Our results therefore refute a superluminal interpretation of the OPERA result according to the Cohen and Glashow prediction [2] for a weak currents analog to Cherenkov radiation."
Exist many scientists who study this, many theorys.
Reply | Report Abuse | Link to thisThis is one opinion but i think In our human intelligent we dont discover the true about the universe!
If the scientists dont fighting each other we have more techonology for discover more news of universe.
Perhaps one day we find the true...
But the point is a rather a bit different.
Reply | Report Abuse | Link to this(1) The reasearch report you quote only *asserts* to refute the earlier 6-sigma-sure (and other) findings by *assuming* the renowned scientists' *prediction*. Just IMHO, you can't surely predict the cheetah's speed based on earlier observations of domestic animals. The report you quote concludes that the beam would have been "dispersed or depleted" *if* the quoted prediction had been valid. Isn't it building castles on the sand?
(2) The above SA article itself quotes Autiero, who "adds that the assumptions made by Cohen and Glashow may not be universally valid" - and don't you agree with that reasonable statement? Experiment always trumps theory. I do appreciate much of the contents of this article.
There is nothing to worry about. The whole Kingdom of Relativity does not have to fall since (to my knowledge) its domain is largely disjoint with the neutrino sector. And, if these latest theoretical refutations of superluminal speed were so clear and simple, why weren't they found *before* the CERN experiment?
The best news in this article is that there will be 2 other readings at various distances, one in Japan and one in Illinois. If they calculate the same speed over these different distances they validate the results.
Reply | Report Abuse | Link to thisIf they get the speed of light plus the same 60 nanosecond lead time we will know with certainty that something is wrong with the measurement even without knowing what.
I am guessing that it will be the 2nd result and that they will ultimately find that the neutrinos are being emitted at CERN 60 nanoseconds earlier than they are calculating.
Yes. And a mathematical formulas prove bumblebees and humming bees can't fly and locomotives can't pull trains.
Reply | Report Abuse | Link to thisI don't see where Einstein's assumptions have been proved. The time dilation experiments did not show independent effects of magnetic and electric fields upon an atomic clock. Nor has the measurement of the speed of the wave front for light been proven to be equal to Lambda Nu. For instance, we need a signal sent from a rocket traveling to and from the earth. The signal should contain a time stamp. The time of reception should also be stamped. This should be done with as much precision as we can muster. The signal should be sent from a known position.
Reply | Report Abuse | Link to thisNeither have we shown that gravity is not a coulomb force. So if we bump into some freaky measurements that show the earth is not flat, do we change our erroneous theory? Come on, an axiom is taken without proof, this does not mean it is correct because we say it is so without rigorous truth. Einstein built his theory upon an assumption without rigorous experiment. We must realize that we can get correct results even with the wrong theory, but we get truth from truthful theory. The key is finding truth. The faster than light neutrino might be truth.
DISLIKE
Reply | Report Abuse | Link to thisThere is a report in Science indicating that the OPERA Collaboration will conduct a new set of tests as early as next week to eliminate the necessity statistically identify a presumed 'emission time' for each detected neutrino from a 10,500 ns pulse of protons. The 10,500 ns proton beam pulses will be replaced by a 1-2 ns beam pulse, which should allow the definitive identification of a neutrino emission start time with a precision of 1-2 ns.
Reply | Report Abuse | Link to thisIt's expected that this new short duration test will allow detection of ~12 neutrinos, allowing some confirmation or denial of previous results. Please see: http://news.sciencemag.org/scienceinsider/2011/10/faster-than-light-result-to-be.html?ref=em&elq=1c69590856da4b2b86118c4d41bfde3f
BTW, the research report I referenced IS the primary subject of this SA news article.
Reply | Report Abuse | Link to thisThe best way to disprove superluminal neutrinos is not by showing they violate theories but by showing the error in the experiment. If they cannot find any error, the result should be repeatable and they need a new theory to explain the result.
Reply | Report Abuse | Link to thisSo, eventually, the Neutrino don't run faster than light,right?
Reply | Report Abuse | Link to thisIt is rather odd to try to use a theory to prove that an experimental result is wrong.
Reply | Report Abuse | Link to thisNeutrinos may really be faster than photons probably because if we were to assume that the vacuum impedance of light is 1 unit, the vacuum impedance of neutrinos may be less than 1 unit.
It is rather odd to use a theory to prove that the result of a carefully done experiment is wrong.
Reply | Report Abuse | Link to thisThe neutrino may actually be faster than light probably because its vacuum impedance is less than that of photons.
Although I still feel that neutrinos can go faster than light because their vacuum impedance is less than that of light photons, here is another possibility that needs to be considered:
Reply | Report Abuse | Link to thisWhat if I pretend that I am an innocent little boy who knows nothing much, but who thinks that neutrinos can go faster than light because neutrinos do not really exist as such, but are actually nothing more than just pulses of energy that is transmitted along an almost infinitely strong and rigid "needle" of length which varies from a few microns to billions of miles and which is incredibly thin.
These "needles" could be made of stacks of Higgs Bosoms and fill up throughout the universe to form the so-called Higgs Field.
Since the needles are almost infinitely stiff, if energy is applied to one end of these needles, the energy pulse ("neutrinos thus created") would be transmitted almost instantly to the other end and if the other end is associated with an electron in the detector material, the energy would be converted into matter and appears as an electron neutrino. If the other end is associated with a muon or tau particle, the energy pulse ("neutrino") would be converted into a muon or tau neutrino.
If we have a bundle which is made up of these needles of varying lengths, and if we have "neutrino" detectors along the whole length of the bundle we will be detecting neutrinos of different types along the length of the bundle. This could explain why neutrinos appear to change flavours or oscillate as they move along. And this could also explain why neutrinos can pass though a large mass like planet earth as the earth is already being pierced by trillions upon trillions of these almost infinitely stiff needles that form the fabric of space.