Not happy with the mobile phone network? Neutrinos are the way to go! A group of American scientists have achieved the transfer of information using a beam of neutrinos. The process is highly inefficient at the moment, though, with a transfer speed of merely 1 bit/s and the test being over very short distances.
The experiment is ongoing at the NuMI facility at Fermilab. This facility produces some of the most energetic neutrino beams. This teams up with the Minerva detector kept 1km away from the source! The current experiment was performed on this setup
But why neutrino communication?
Neutrinos are very weakly interacting particles in nature. They have often been describes as ‘ghostly’, owing to the difficulty in detecting them. They are uncharged and thus do not interact with the electromagnetic field. Having no mass means that gravity is out of the question, although, even with a small mass, it wouldn’t have played a role.
Neutrinos can pass through hundreds of lightyears of solid lead! It’s not surprising that they should be able to tunnel through the Earth itself. It is due to this unwillingness to interact that neutrinos can be made into effective communication devices. There would be very little disturbance that would pour into the signal.
The problem is this: Neutrinos being very difficult to detect, are also extremely difficult to control. They cannot be collimated (i.e. made parallel) as easily as lightwaves. Similarly, we need a large flux of neutrinos from the source and a very good detector at the receiving end. The detector is not portable. In fact, neutrino detectors are HUGE! (Pic above)
“Neutrinos” using neutrinos
The idea is to modulate the neutrino beam so that a proper piece of information is transmitted. What is the first message to be tranferred? Simple: “Neutrinos”. The modulation bitrate was 0.1 bit/s, which is WAY slower than today’s communication devices. However, the information was transmitted over a few kilometers and the error was less than 1%.
Much work needs to be done! But, Wolfgang Pauli, the father of the neutrino, would be proud.
Neutrinos seem to be travelling at speed of light once more! A different experimental group – the Icarus group, tried out the same experiment as the OPERA group in the same lab, but using different equipment and found that the speed of the neutrinos was very much compatible with the speed of light within experimental error bounds! The Icarus group have found that neutrinos travel at the speed of light, not faster. The OPERA result, already fraught by reports of device malfunctions, has received another jolt.
The experimental findings of the Icarus group, also based in Gran Sasso just like OPERA, and also receiving neutrinos from the same CERN source, were published in a paper which is available online here.
A second opinion
The Icarus group intends on studying the different properties of neutrinos and also aspects of any proton decay. They use a Liquid Argon Detector – the T600 – which uses 600 tonnes of liquid nitrogen to detect the presence of neutrinos and also measure their direction and momentum. They have been tweaking their experiment so as to be able to re-check OPERA’s claim.
Of course, OPERA itself has been in a soup with its own problems. We reported the initially reported error of an optical fibre delay here and then followed up with yet another error that might have influenced the speed. With so much at stake, the littlest things might compromise the findings of the biggest experimental groups.
Icarus says that there are more tests to come – as many as four more experiments intend to verify OPERA. The entire physics community is expecting negative results, akin to Icarus’, but to be sure of such a thing would be prejudice.
The supposedly greatest anomaly ever detected in physics, capable of undoing a hundred years of physics, may turn out to be a mere computer glitch. There are rumours that the anomaly may be due to a faulty connection between a GPS unit and a computer receiving signals from it.
We had reported the faster-than-light neutrino results in great detail in several posts earlier. The physics group at Gran Sasso laboratory, near CERN, had detected that neutrinos arrives 60 nanoseconds before they are expected to, if they travelled at light speed. This means that they travelled faster than light, violating the cosmic speed limit imposed by Einstein’s Special Theory of Relativity, by a factor of full one-ten thousandth, which is a huge number when it comes to Lorentz violations.
The rumour is that sources inside Gran Sasso say that when a connection between a GPS receiver and the optic fibre was adjusted, the time of flight comes out exactly 60 seconds longer than measured, exactly cancelling the seen anomaly.
New data from independent experiments is still needed to confirm the non-violation of the cosmic speed limit. If this rumour is true, it is face-saving time for the Gran Sasso scientists.
The fantastic results still stay! The sensational OPERA experiment, which gave us the faster-than-light neutrino results, have repeated the experiment and have found similar results. Neutrinos continue to travel faster than light and the amount by which they break the speed barrier is also the same. The experiment was carried out during 30th October to 2nd November.
The latest results give a 60.7 ns advance for the neutrinos with a 7.4 ns error for the systematic and 6.9 ns statistical error. This means that the previous results are not discredited. The difference between the previous experiment and this present one is the proton bunch size.
Scientists are still skeptical and not willing to accept this result yet. Even OPERA and CERN scientists say that the experiment has to be repeated by MINOS or T2K and only then can the experimental results verified.
Detecting one neutrino at a time
This time, the beam of neutrinos has been bunched in 3 ns bins separated by 520 ns. This means that each bunch in the beam consists of basically one neutrino. The experiment has, thus, been repeated with essentially single neutrinos. The number of events is much less than the last time. While OPERA used 16111 events last time, this time they have stuck to merely 20 events. This has led to many people questioning the statistics of the experiment. OPERA, however, claims that the accuracy is just as good, if not better.
The paper of the repeated experiment is already on ArXiv. Here’s the link to the short paper.
Repeat Experiment Needed!
This experiment re-run proves that the beam bunching has nothing to do with the observed results. The effects have not gone away, but that might depend on the CNGS (Cern Neutrino to Gran Sasso) beam structure as well as the systematics of the OPERA detector. A repeat of the experiment in some other part of the world is the need of the day.
Special Relativity may have saved itself from disaster. According to a scientist, the OPERA collaboration overlooked a crucial correction to the result, which exactly matches the discrepancy observed. It involved the effect of time dilation of the clocks aboard the GPS satellite.
Ronald Van Elburg says that the two frames of reference the Gran Sasso laboratory on the ground and the clocks on the GPS satellite in orbit around the Earth – are in relative motion with respect to each other and thus special relativity effects come into the picture. The time of flight, thus, needs to be corrected for this factor too.
From the perspective of the clock, the detector is moving towards the source and consequently the distance travelled by the particles as observed from the clock is shorter
Magnitude of the Effect
Now, for the crucial magnitude of this effect. Van Elburg presents the analysis which shows that this timing should account for 32 ns for the time of flight. Further, this happens at CERN as well as the Gran Sasso Lab in Italy and thus, the number has to be doubled, yielding 64 ns, which exactly compensates the noticed discrepancy of 60 ns.
This solution has recently been released and is yet to be verified properly. The effect seems too obvious and it seems unlikely that OPERA has not taken it into account. OPERA has not responded as yet.
A theoretical attack on the results
Recently, there has been a theoretical attack on the experimental result by Sheldon Glashow (Nobel Laureate, Physics) and his Boston University colleague, Andrew Cohen. They dismiss the results by showing that if the result were true, no high energy neutrino would reach the detector at Gran Sasso. The fact that they detect high energy neutrino (above 12.5 GeV) means that the neutrinos are not travelling faster than light. This is not an experimental result, but a theoretical bound.
We’ll just have to wait and watch. The van Elburg paper is a pre-print and is not yet peer-reviewed.
Particles travelling faster than the speed of light have been found. This startling claim comes from a source as respectable as CERN. This was supposedly observed in a neutrino experiment carried out by CERN. However, it is too early to confirm this startling result.
UPDATE: The ‘discovery’ was made by the OPERA experiment while the neutrinos were beamed from Geneva to a lab in Gran Sasso in Italy. The pre-print of the report, prepared by CERN and published today (23rd September) can be found here: http://arxiv.org/abs/1109.4897
Faster Than The Speed of Light? Real Life Tachyons?
Albert Einstein and his Special Theory of Relativity taught us that nothing having mass can travel at the speed of light or above. Massless particles can travel only at the speed of light. Thus, nothing can travel faster than the speed of light.
CERN’s scientists have now found that neutrinos, one of the most enigmatic particles, have breached this barrier. Neutrinos have nearly no mass, no charge and interact negligibly with ordinary matter. It is due to these properties that they cannot be easily detected. The scientists claim that a neutrino beam fired near Geneva to a lab 730 kilometers away in Italy reached its destination 60 nanoseconds earlier than expected. The experimental and statistical errors combine to deduct 10 nanoseconds, which still leaves 50 nanoseconds unexplained and makes this result significant. There are obvious checks and re-checks being performed.
CERN is now depending on the colliders in America and the T2K neutrino experiment in Japan to reinforce its findings. The findings may need many runs and checks to be confirmed. Once confirmed, it raises many questions, including why such an effect wasn’t noticed before. The big question would be this: What happens to Special Relativity, which is an extremely reliable theory?
John Ellis, a theoretical physicist at CERN, gauges the magnitude of the find, if found true:
This would be such a sensational discovery if it were true that one has to treat it extremely carefully.
About the implication for Special Relativity, Ellis says that It has worked perfectly till now”.
Jury Out On Relativity? Not Really!
A knee-jerk reaction would provoke statements about revolutionizing the whole of physics, since stars to elementary particles, all rely on the Special Theory of Relativity. It has been wonderfully accurate, especially when combined with Quantum Mechanics to form Quantum Field Theory. Personally, at this moment, I don’t think this will throw Relativity out, even if the result is correct – Relativity is too beautiful and has been proved too correct in too many situations for that drastic step. I would even stick my neck out and add that this observation is some sort of experimental glitch and that faster-than-light particles have not really been detected. However, only more tests will testify to that.
The grand old man of physics has been challenged by a tiny, nearly massless particle.
One of the greatest scientific questions of all times may soon have an answer and the key might be one of the lightest, most elusive particles known to science. Scientists claim to have got a signature a hint of the answer to the question Where did all the matter of the Universe come from?’ from looking at oscillations of a mysterious particle known as the neutrino.
Here’s the deal about neutrinos
Neutrinos are extremely light, neutral particles. They are generally found in nature moving close to the speed of light. They are extremely weakly interacting particles, and you have a million million million neutrinos going right through your body at this moment per minute. You need not care they are not harmful, interacting with other atoms extremely rarely.
They come in three types or, as scientists call it, flavors: electron, muon and taon. The electron neutrino is the lightest of the lot, with the muon being a bit heavier and the taon topping the charts. Due to its mass, the tao neutrino is hardly seen in nature and we shall be concerned with the electron and muon neutrino only.
In the long neutrino story, there were many crucial junctions, which we shall not be able to get into here. A debate as to whether neutrinos have mass was resolved when a proposed hypothesis neutrino oscillation was observed. Neutrinos did have mass and they did something akin to magic: an electron neutrino could turn into a muon neutrino.
The Kamiokande and the Super-Kamiokande are two of the experiments designed to measure this oscillation. This is where out story begins.
The T2K Experiment
A new experimental project on this called the T2K was setup in Japan. One of the aims of this was to see whether muon neutrinos became electron neutrinos. The experiment ran from January 2010 till it was rudely interrupted on 11th March 2011 by the Japanese Earthquake. The facility came to no harm and the data is significant enough to analyze. The results came out on the 15th of June, just a couple of days back.
What scientists found was startling. Not only could electron neutrinos turn into muon neutrinos, they could go the other way too something that was only speculated, not confirmed in an experiment. In a muon beam, they found as many as six events of electron neutrinos, while only about 1.5 was expected on average. This is an event rarer than one-in-a-hundred. However, for a discovery, the doubts have to go below the one-in-a-million level and, thus, we can call this nothing more than a signature’. However this is tantalizing.
What’s so tantalizing?
This possibility opens up new avenues of interaction, especially the possibility of asymmetric interactions between neutrinos and the anti-neutrinos (their anti-particles). If the interaction of neutrinos and anti-neutrinos are different on a fundamental scale, then this gives scientists an example of, what is known as, CP violation.
One of the longest outstanding questions of physics is why matter should outnumber anti-matter particles, while physics gives no hint of such an asymmetry at even the most fundamental levels. (That is to say, if we worked with anti-particles rather than particles, we’d use the same physics. Particles’ and anti-particles’ are just labels as far as laws of physics are concerned, just like matter’ and anti-matter’ and there is no unique way to differentiate between them.) CP violation provides the answer, hypothesizing that Nature preferentially creates one more matter particle for every billion or so pairs of matter-antimatter particles. After annihilation, one matter particle out of a billion is left behind and this can account for all the known matter in the universe. (So now, CP violation gives us a unique way to differentiate between matter and antimatter. Just call those particles matter particles’ that are produced in slight excess.)
Journey of a neutrino through to a T2K detector
Here’s the journey a neutrino would have to undertake in order to make it to the last detector in the massive T2K experiment:
Muon neutrinos are produced at the Japan Proton Accelerator Research Center in Tokai, Japan.
They pass through to a series of near detectors so that their composition can be known before they oscillate.
They then fly off and travel for 295 km across Japan to the Super-Kamiokande neutrino detector (which is a huge detector filled with more than 50,000 tons of ultra-pure water and lined with extremely sensitive optical detectors to detect the faintest of flashes). Here we can detect the composition of the beam after the neutrinos have oscillated.
Prof. Dave Wark, head of the UK group for the experiment gave a gem of a statement:
People sometimes think that scientific discoveries are like light switches that click from ‘off’ to ‘on’, but in reality it goes from ‘maybe’ to ‘probably’ to ‘almost certainly’ as you get more data. Right now we are somewhere between ‘probably’ and ‘almost certainly’.
The studies and the data obtained are not confirmatory, but they do provide tantalizing hints to what the answer to the big question of where all the matter in the Universe came from.