Over two years of work and 180 tons of baby oil went into an effort to catch something very light.
Interestingly, the research, conducted by scientists at Los Alamos National Laboratory, may have indicated the presence of something very heavy: the missing 90 percent of the entire cosmos.
If further research confirms the findings, the "signature" that was captured in the oil may help account for some of the invisible "dark matter" that provides enough gravity to help form the enormous structures found in the universe.
Neutrinos, which lack an electrical charge, have long been suspected to be this "matter." They come in three "flavors" (electron neutrinos, muon neutrinos and tau neutrinos) which are able to alter during their travels as they go in and out of phase. They barely interact with ordinary matter; only one in every ten billion of them actually hits an atom when passing through the planet Earth. The new experiments, however, show that, contrary to earlier theory, they probably have a small mass (.5 to 5 electron volts). William Louis, a physicist at Los Alamos, explicates what this means. He states that "even half an electron volt is a lot of mass" considering that these "are the dominant particles in number in the universe."
The Los Alamos experiment was designed to generate an antimuon neutrino, which would oscillate into another form. To facilitate this, a beam of protons was fired into a one foot long water container (with a diameter also of one foot). According to theory, after three feet the resultant pions hit a three-cubic foot block of copper. One of the particles which resulted, a heavy electron-like muon, broke down into electron neutrinos, low-energy electrons and antimuon neutrinos. If the latter had any mass, it, through oscillation, became an antielectron neutrino. It was this which hit the 28 foot by 12 foot tank of baby oil (which also contained a few grams of a chemical that amplified such light as was created by any collision). The tank was lined with 1,220 phototubes to detect this light, which they did.
Other laboratories have designed experiments to evaluate Los Alamos's preliminary findings. Both Brookhaven National Laboratory in New York and Fermilab in Illinois have proposed elaborate experiments, the apparatus of which would cover many miles, to confirm or deny them.
However, the present results only may account for 10 to 20 percent of the missing mass, still leaving many questions unanswered.
Source: Curt Suplee, "Oscillating Particle May Illuminate Universe's Dark Matter," The Washington Post, 2/6/95