Experimental evidence for neutrino mass was presented on June
5 at the International Neutrino Conference, a biannual meeting that was
held this June in Takayama, Japan. The experiment, called
For years, physicists have sought to measure the neutrino mass. But, until now, it has proved elusive. Hints that the neutrino might have mass were provided by a number of earlier experiments, including the earlier "Kamiokande."
Super-Kamiokande's announcement was heralded because it was the first to have strong evidence that ruled out all known alternative interpretations at a sufficiently high significance level to make it extremely unlikely that the results were an experimental artifact.
The collaboration had been working hard on the papers to be presented at Takayama and, as the meeting approached, knew there would be considerable media as well as professional interest. The word had inevitably gotten out. So a carefully-worded press release was prepared. It was embargoed until the hour that Takaaki Kajita, who was presenting the result to the meeting, would be finished with his talk.
Still, rather overblown statements about the discovery's significance were picked up by the media from unofficial U.S. sources and blown up even further. The effect was that all the major national newspapers, news magazines, and TV networks tended to greatly underestimate the Japanese contributions and left a distorted impression with their readers that the result was highly revolutionary.
Super-Kamiokande is a $100 million project 94-97 percent funded by Japan and located in Japan. Of the 121 scientists authoring the paper, approximately 70 are from Japan and 50 from the U.S. (including foreigners working at U.S. institutions). The spokesman is Yoji Totsuka of Tokyo University .
In an article a few days after the announcement, Atsuko Tsuji,
a reporter for the Washington bureau of
Totsuka and his colleagues did not get the attention they merited in this first round of heavy publicity. However, later reports have been better balanced and I understand they are getting plenty of Japanese media attention now, with Totsuka frequently mentioned as a Nobel candidate. The Japanese are fast learners, and quickly learned the importance of media hype.
And what about the results themselves? First, the claim that the discovery of neutrino mass overthrows the standard model of elementary particles and forces is an overstatement. The standard model assumed zero mass for the neutrinos, since that was what was measured at the time the model was developed, just as it assumed the non-zero measured masses of the electron and proton. The model is now being modified, but nothing in existing theory forbids neutrinos from having mass. The new measurement is important because it points to places to look for extensions beyond the standard model. But it may not require the Kuhnian paradigm-shift that the stories implied.
Second, the neutrino mass was not itself directly measured, just evidence that neutrinos have mass. The most likely interpretation of the results is that one of the three types of neutrinos has a mass on the order of ten million times less than that of the electron. This is about a hundred times smaller than the mass needed for neutrinos to provide enough mass to close the universe. Massive neutrinos have some cosmological importance, but are not likely the major component of the missing matter.
Will this measurement stand the test of time? Only time will tell. Many skilled people have worked long hours checking out all the possible sources of error, and others have checked their work. If the observation should turn out not to be neutrino mass, then it will be something else of still considerable interest. What is the lesson for skeptics? Let me be the first to tell you: don't believe everything you read in the papers. Perhaps the media hype in this event was not as egregious as what has occurred in other recent instances, but we still could have done without it.