Science: Window on Mystery

As atom smashers have grown larger and more powerful, the subatomic particles that scientists have been able to find have grown stranger and more elusive. Still, it hardly seemed probable that anyone would ever discover another bit of matter quite so peculiar as the neutrino, first detected near a nuclear reactor in 1956. So light that it weighs nothing at all, the neutrino is free of electric charge and can pass through the heaviest materials as if it were hurtling through empty space. But last week, a team of Columbia University physicists did the improbable: using 5,000 tons of battleship armor along with the most powerful atom cracker yet built, they found another variety of neutrino. Around the world, great laboratories are already planning experiments to exploit the tiny new window opening on the unknown.

Guilty Particles. Hardly had the neutrino become established as a real particle when physicists noticed that pi mesons (middleweight particles, also called pi-ons, that are created by powerful atom smashers) disintegrate into slightly lighter mu mesons (muons) while an unseen particle carries away part of their energy. At first the physicists assumed that ordinary neutrinos were the guilty particles. Then they began to have their doubts. Maybe another kind of neutrino was stealing the pion's energy. But it had been hard enough to trap regular neutrinos; how were scientists to locate and study an even more evasive particle?

They found their answer in the enormous alternating gradient synchrotron at Brookhaven National Laboratory on Long Island. That mighty machine can spin protons up to the energy of 33 billion electron-volts, bounce them off targets and produce all sorts of atomic debris—including neutrinos. Physicists figured that any new type neutrinos created by this monstrous slingshot should have as much as i billion volts of energy. They would not be nearly so numerous as the neutrinos flooding out of a nuclear reactor, but their high energy should allow them many more ways of interacting with matter; as a result they would be more easily detectable.

The team that laid out the momentous experiment was led by Columbia Professors Leon Lederman, Melvin Schwartz and Jack Steinberger, and helped by Brookhaven scientists in charge of the synchrotron. First step was to shoot the machine's high-energy protons at a beryllium target and produce an intense beam of pions—which decay rapidly into muons, neutrinos (perhaps the new type), and other nuclear odds and ends. After shooting across some 70 ft., this beam of mixed particles hit a shield of battleship armor 42 ft. thick that stopped everything but the neutrinos, which sailed on unheeding.