Autiero (pictured here, blue shirt) told Nature that he did not resign because he made mistakes in the measurement. Rather, he and Ereditato (also pictured) "felt that tensions that had always existed within OPERA were becoming impossible to bridge."
The large international collaboration has had to contend not just with the usual personality conflicts, but also with cultural differences between Italian, Northern European, and Japanese scientists. The added scrutiny from the controversial result exacerbated those tensions.
A Question of Cross Checks
Much of the negative reaction, says Conrad, stems from the fact that there were insufficient experimental checks carried out prior to the announcement, which can damage collegial trust. "A [paper in] Physical Review Letters is four pages long. An experiment is vastly more complicated than that," she says. "So we have to rely on our colleagues having done all of their cross checks. We don't expect to make a retraction within a year."
Fermilab's Joseph Lykken concurs. "Precisely because these are big, complicated experiments, the collaborations have a responsibility to both the scientific community and to the taxpayers to perform due diligence checks of the validity of their results," he says. "The more surprising the result, the more time one must spend on validation. Anyone can make a mistake, but scientific collaborations are supposed to catch the vast majority of mistakes through internal vetting long before a new result sees the light of day."
Indeed, several OPERA members refused to add their names to the original paper because they felt the announcement and submission of the results for publication were premature. Extraordinary claims, as the saying goes, require extraordinary evidence.
Faster-than-light neutrinos are the very definition of an extraordinary result. "The theory of relativity is exquisitely well-tested and consistent. Superluminal neutrinos were far, far too much in violation of the rules to be believed, even for a nanosecond," says CERN physicist Alvaro De Rujula. "That ought to have made the OPERA management have everything checked even more carefully. Alas, it turned out not to be a subtle error, but mainly a bad connection, the very first thing one checks when anything misbehaves."
So the unhappiness stems not so much from the fact that the collaboration made a mistake, but that the mistake was not a subtle one. "There is a big difference between a result that goes away because it turns out to be a statistical fluctuation, and a result that goes away because of a technical screw-up that should have been detected early on," says Lykken.
In fact, Lykken recalls running into a veteran neutrino experimentalist shortly after the original announcement, and asked if she believed the results. She did not, opining that it was probably an issue with the cables.
In OPERA's defense, Belgian physicist Pierre Vilain points out that the optical fiber in question was barely visible at the back of an electronic rack. It would be easy to miss a slight unplugging.
Also, the fiber had been calibrated twice, in 2006 and 2007, and the team members had no reason to suspect that the calibration would have changed. A similarly calibrated optical fiber at CERN has remained constant over the years, with no significant variations.
"The fact that a slight unplugging of this fiber could produce a delay as high as 70 nanoseconds was a surprise for everybody," says Vilain. "The imperfect contact of the fiber leads to a reduction of the amount of light hits the photocathode, and only a very deep knowledge of the electronic chip which treats the signal can explain why it leads to such a long and fatal delay."
Conrad notes that it took OPERA five months of round-the-clock work, checking and re-checking every aspect of the experiment, before they found the error. So it was not quite as trivial a mistake as one might think, just from hearing the words "faulty cable."
Still, a premature announcement might have been avoided had the checks completed in December been done earlier, in September. That would have meant turning off the beam in the middle of continued data acquisition - not an easy call for a team leader to make in a culture where taking data is the top priority, given the high expense of beam time.
Don't Believe the Hype
Then there was the way the announcement and press rollout were handled. Ereditato initially refused public comment, but subsequently issued a lengthy statement in which he verified Autiero's version of events, and criticized the media for sensationalizing the results. Autiero, too, told Nature that despite OPERA's caveats, many newspapers "played with the sensationalism of the story."
But press releases and press conferences usually set the tone for subsequent media coverage. "Unfortunately, I think CERN amped it up," says Conrad, adding that those involved should have known that the mere mention of particles moving faster than light would ignite widespread public interest. People leap automatically to dreams of tachyons and time travel.
Conrad receives at least one email a week from someone pushing a superluminal theory ("EINSTEIN WAS WRONG, AND I CAN PROVE IT!"), and most theoretical physicists can say the same. "The press release is pretty vivid, it really pushes forward the idea that neutrinos go faster than light," she says. "The paper is much more circumspect." The press release just fanned the flames.
Conrad is not alone in her assessment. "I was against the way things were communicated," Luca Stanco, leader of the OPERA group at the University of Padovo, told Physics World. "In front of the media, we had a duty to be more careful with our language."
Then again, Marc Sher of William and Mary College doesn't see how avoiding hype would be possible with such a provocative topic: "OPERA gave all the caveats. I don't really know what else they could have done."
De Rujula is a bit more skeptical: "An announcement with many caveats may be interpreted as an attempt to have the cake and eat it, too, which (in this case) proved dangerous."
There is also the question of why OPERA felt the need to make a preliminary announcement at all, when the collaboration had no direct competitor for their experimental "scoop." Conrad, however, sees in this a bigger problem: the trend in US high energy physics away from doubling up on experiments. Fermilab, for instance, had two separate collaborations - D-Zero and CDF - each providing checks and balances to the others analyses.
This is also the case with the Large Hadron Collider at CERN, where two separate experiments are searching for the Higgs boson. It was not the case with OPERA. "Wouldn't it have been nice if another experiment had been in a position to respond immediately [to the OPERA results]?" Conrad says. "This has been a major change in thinking in science, and I think it's a terrible mistake."
To the physics community's credit, while many were skeptical, most took the findings seriously rather than dismissing them out of hand. Conrad says she attended at least three conferences where a great deal of time was devoted to studying the results, pondering different explanations or theories.
In short, the whole debacle stemmed not so much from one single major mistake, but a series of smaller missteps that built up before exploding, with some fairly high-profile fallout. That said, in the end, good science won out. "The fact that the error has been found and recognized and that extra experiments may give a definite answer shows that the field, and basic science, are in good health," says De Rujula.
Image credit: OPERA/CERN