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More superluminal neutrinos

Sun, 20th Nov 2011

Dave Ansell

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In September results indicating that neutrinos travel faster than the speed of light were released, this week the same group has released further data.

The experiment is spread out between CERN near Geneva and a neutrino detector near Rome called OPERA over 700km away. In CERN groups of protons flying around the LHC ring are redirected down an alternative route and crash into a lump of graphite. This produces a variety of particles but includes a large number of particles called mesons, which have a very short lifetime, they fly down a kilometre long tube where some of them decay to form an electron and a neutrino.        

These neutrinos hardly interact with matter, so they easily pass through the 700km of solid rock, and then a tiny proportion of them interact with plates of lead in the OPERA detector inside a mountain in Italy, producing a signal which can be detected.

The experiment was designed to investigate whether neutrinos change over time, and to measure how much slower than the speed of light they travel, which would give information about their mass and behaviour.

The very surprising result was that they appeared to be travelling the distance about 60ns faster than the speed of light, travelling about 2.5 parts in 100 000 faster. This would indicate fundamentally new physics and extraordinary claims require extraordinary evidence, and they have had a variety of suggestions from the community on how they could improve their results.

So they have gone away and tried to improve the resolution of their results. They have tried to get a more accurate measurement of the relative positions of the two facilities as the time difference could be explained by an error of position of about 180m. They have also made the bunches of protons that create the neutrinos shorter which makes it easier to measure the exact time they arrive. And seem to give the same result.

This is interesting but there is still a lot of evidence to overcome, for example in 1987 there was a supernova in the large magellanic cloud which produced both light and neutrinos and they both arrived here a few hours apart where as with the difference of speeds they were finding at CERN you would expect a difference of a couple of years. These neutrinos were lower energy than the ones produced in this experiment so it is possible they behave differently, but without independent confirmation I wouldn't start ordering your faster than light spacedrives yet.


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I think we should hold a Naked Scientist Forum Sweepstake for the reason that the OPERA Gran Sasso results do not comply with received knowledge.  One guess per member and no duplicates.

My guess is a systematic calculational error between the timing of the proton pulse and the "start" of the neutrino journey imatfaal, Tue, 22nd Nov 2011

I don't know what it might be. It could be something making it possible, Soulsurfers idea of a tunnelling perhaps? Or maybe something else that we still have to understand. What I can't accept would be the idea of mass being faster than light, that makes too little sense. Because that universe would indeed be 'magical'. yor_on, Tue, 22nd Nov 2011

I'm going with an error in accounting for the GPS measurements (probably due to general relativistic effects).  jpetruccelli, Tue, 22nd Nov 2011

I have one other suggestion that is a bit off the wall.  That is, it is a geometrical error caused by the "shape" of the neutrinos.

Consider first a neutrino moving quite slowly at a low energy say around the sort of speeds familiar on the earth.  This particle is extremely light, how light we don't quite know.  The suggestion is that it is considerably less than 1eV.  Now the size of a normal atom is determined by the uncertainty in the position of the electrons i.e. their De Broglie wavelength.  Even with the relatively high momentum of an electron in an orbital, electrons are quite big at normal room temperature (this defines the size of atoms) they are much bigger and the slower things go the bigger they get.  Neutrinos because of their very low mass are at least a million times "bigger" than this and would probably be seriously large in cross section but very thin discs because if their high momentum in one direction  (a classic example of Lorenz contraction).

Remember the colliding lead nuclei in the LHC when it is in heavy particle mode are thin discs because of this effect

The question then is how accurately are the generation and detection areas lined up in angle because with a small angular error there could be a significant distance error.  I am sure that in setting up the beam they checked quite precisely that the neutrinos were going in the right direction so that the beam spread met the detector but they may not have accounted fully for their unusual shape. Soul Surfer, Tue, 22nd Nov 2011

Imatfaal sweepstake

My guess is that photons interact with the sea of virtual particles en route hence travel slightly slower than Neutrinos that do not.
I think we should talk of Neutrinos traveling at the ultimate speed not photons. syhprum, Tue, 22nd Nov 2011

I'll set up a poll. Geezer, Tue, 22nd Nov 2011

Syhprum That is an interesting and reasonably plausible idea but as far as I can see that would mean that the 1987 supernova neutrino pulse was a wrong observation.  although it is quite possible these events are rare and the secondary confirmation is weak. Soul Surfer, Wed, 23rd Nov 2011

But that has same problem as JP brought up to SSurfers tunnelling concept - if photons are interacting then the majority of them should be scattering and they are not imatfaal, Wed, 23rd Nov 2011

This case proves relativity is wrong. simplified, Wed, 23rd Nov 2011

Nope, it just prove that a statistical experiment can get very weird results :)
Lights speed in a vacuum will still be a 'constant'. yor_on, Wed, 23rd Nov 2011

Physics can not be the same. simplified, Wed, 23rd Nov 2011

The funny thing with this approach is that everyone seems keen to mix QM effects with classical observations. This can be cool if we define it such that there must be a strict causality between QM and macroscopic 'reality', but those doing research are not as sure, as far as I've seen. And when it comes to photons/waves 'interacting' then that is QM.

When it comes to the Higgs Boson/sea whatever "An updated assessment, to be discussed at the Lepton Photon Conference in Mumbai, shows the excess events appear to be melting away, and along with them much premature excitement."

Meaning that the probability for it existing "According to Cern, Atlas and CMS have excluded the existence of a Higgs over most of the mass region 145 to 466 GeV with 95% certainty."

It will be much harder to find any for it evidence now "The ranges left after these results suggest that the Higgs is either quite a light particle, below about 145 GeV, or a heavy one, above 466 GeV. A couple of islands in the middle, around 250 GeV, have not been fully excluded yet."

"And now what we're being left with is the harder part; the regions where it's harder for us to see and harder to pick out the signal from the background."

The problem with 'causality chains' is that it somehow bogs down to a statistical method. After all, then we don't have to question and then define what we see, instead we can formulate it in form of probabilities of it existing. A downside to this approach might possibly be that there can't be a 100% probability of anything. That as a statistical approach always will relay on histories of happenings, and only be as true as its 'history'. Another downfall to it is that it it defines a arrow, and draw its implications from the assumption of this being an absolute truth. So a 'time reversibility' giving us a different outcome should then be a thorn in its side.

Although you might put a probability to the arrow of time it should become self-defeating as what you use for defining that probability will be what you doubt there. yor_on, Wed, 23rd Nov 2011

And yes Simplified if mass would be proven to go FTL it sure would change physics. Even though light still would be a constant. So it's wrong :) yor_on, Wed, 23rd Nov 2011

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