Researchers had gone to great lengths to remove error sources in the measurements; distances were measured with a very high precision GPS named PolarX, time was measured to an accuracy of one nanosecond using cesium clocks and an accounting was made for tidal motion, Earth’s rotation, variations between day and night and spring and fall, etc, etc. The statistical significance of the result was six-sigma; in other words the probability that the result was a random error was a one in a billion chance. In a meeting with a roomful of physicists on Nov. 2011, Dario Autiero of OPERA was grilled on possible potential errors and he seemed to be able to account for all of them.
Still physicists are skeptical and now the plan is to confirm these findings in separate experiments in other laboratories. If the findings are indeed true, would Special Relativity be violated? Not really as the theory does admit superluminal particles that are known as Tachyons.
Let’s look at this a little closer. Protons have immense power requirements (electrical energy equal to that consumed by a large city for a day) to accelerate them to close to the speed of light. And they cannot attain the speed of light in that it would require infinite energy with the proton’s mass becoming infinite.
However, this cosmic speed limit does not work for all particles (or objects being the sum of many particles). For example, turning on a lamp causes it’s light bulb to emit photons at light speed. Since photons are the mass-less components of light, relativity says they can travel at that speed. Neutrinos are created with a certain speed and they are nearly mass-less particles that can pass through anything so they’re not likely to start at a relatively low speed accelerating to reach a higher one. Because they are so speedy and nearly mass-less it takes a light-year of lead to effectively block a neutrino. Neutrinos don’t slow down either, they just interact with matter eventually via the weak force, ceasing to exist as neutrinos. Special Relativity says that a particle with mass cannot attain or exceed the speed of light barrier. However it does allow for the possibility that the object or particle can be created with a superluminal speed. For this particle, it can’t slow down to drop below the speed-of-light barrier. Therefore if a particle is created subluminal, it has to stay subluminal. If created superluminal, it must remain superluminal.
It should be noted that most physicists are still skeptical about OPERA’s results, many of them referencing the results of data from the 1987 supernova explosion, in which neutrinos were detected here on Earth. It was brought up that if neutrinos are as fast as OPERA’s data indicate, then neutrinos from the supernova at a distance of 168,000 light-years, should have arrived on Earth years before photons from the supernova. Data results were that the supernova neutrinos arrived hours before the light did. The reason given for this lag by astronomers was that the photons were delayed in the collapsing stages of the star, while the neutrinos sped right on through. However, the fact that the neutrinos arrived ahead of the photons does appear to support the superluminal hypothesis. A subsequent experiment was conducted arriving at results confirming those of the initial experiment.
In the initial experiment proton pulses that were used to generate neutrinos via stationary target collisions were relatively long; lasting 10.5 microseconds. Scientific criticism was made that these long pulses may have induced a level of some uncertainty. Therefore OPERA scientists requested that CERN shorten the pulses ( three nanoseconds). The original result was that neutrinos traveling from CERN to Gran Sasso 60 nanoseconds faster than light would have taken in the same 732 kilometers. The standard statistical error was one-sixth as large equating to an extremely significant ‘six sigma’ meaning that its probability of being a fluke was less than one in 3.5 million. The subsequent shorter pulses make the pulse length fall within the standard error, and therefore did not contribute to a possible false finding. More significantly, the new results based on neutrinos generated from the new ultra short pulses, replicated the earlier OPERA result: The neutrinos still appear to travel faster than light.
OPERA scientists are now more confident of their findings and await verification or refutation of by other research teams.
Speaking of other teams; MINOS (Fermi Lab’s Main Injector Neutrino Oscillation Research), physicists are going through the huge data set on neutrino speeds accumulated over years of research. While the GPS used in calculating these speeds is not as accurate as OPERA’s, the amount is still useful in confirming or presenting a challenge of the superluminal findings.
So is the neutrino really a tachyon?