When physicists announced in September that they had observed neutrinos traveling faster than the speed of light, the scientific community was justifiably skeptical.
Now, the scientists, with collaborators, have completed a second, fine-tuned version of their experiment — and the team's findings still stand. What happens now?
The new results have been published on arXiv's preprint server. In the weeks following September's FTL announcement, one of the most common criticisms to emerge was that the proton pulses used in the original experiments were too long for the researchers to accurately measure the flight time of individual neutrinos.
In response, the researchers agreed to re-run their investigation, this time with shorter pulses. And according to research group OPERA's physics coordinator Dario Autiero, the new data do more than just confirm the team's original findings, they're actually "better than the previous result."
"With the new type of beam produced by CERN's accelerators we've been able to to measure with accuracy the time of flight of neutrinos one by one," said Autiero. He continues:
The 20 neutrinos we recorded provide comparable accuracy to the 15,000 on which our original measurement was based. In addition their analysis is simpler and less dependent on the measurement of the time structure of the proton pulses and its relation to the neutrinos production mechanism.
According to Nature, Dario also claims that "most of" the 15 members of the 180-member OPERA collaboration who declined to sign the original arXiv paper (published back in September) have now "come on board."
It is worth pointing out, however, that the latest arXiv preprint lists 179 authors, while the original lists 174. Would you ever classify five people as "most of" 15? To make things more confusing, a source from within the collaboration claims that "about four" of the 15 members who balked at signing the September preprint have since signed a journal submission to the Journal of High Energy Physics, while "four new people" have decided not to sign, according to Science.
Now, none of the above numbers may match up, but they do help illustrate the upshot of all this news: namely that there is still plenty of uncertainty swirling around this whole FTL neutrino debate, and the search for errors is far from over. Like we've said before, the most telling and important tests will come in the form of cross-checks performed by an independent research team.
Such an experiment is slated to begin soon at Fermilab's MINOS, and results could be in as soon as early 2012.