SCHWARTZ, MELVIN

born Nov. 2, 1932, New York, N.Y., U.S. American physicist and entrepreneur who, along with Leon M. Lederman and Jack Steinberger, received the Nobel Prize for Physics in 1988 for their research concerning neutrinos (subatomic particles that have no electric charge and virtually no mass). Schwartz studied physics at Columbia University, New York City, and received his Ph.D. there in 1958. He taught at Columbia from 1958 to 1966 and then was a professor of physics at Stanford University, Calif., from 1966 to 1983. From 1970 he was president of Digital Pathways, Inc., a company that he founded to design computer-security systems. Schwartz received the Nobel Prize for research he and his Columbia colleagues Lederman and Steinberger performed at Brookhaven National Laboratory in 196062. Neutrinos almost never interact with matter, and consequently it had been extremely difficult to detect them in laboratory research. (It was estimated that from a sample of 10 billion neutrinos traveling through the Earth, only one neutrino would interact with a particle of matter during the entire passage.) Acting on Schwartz's suggestion, the three researchers devised a way to increase the statistical probability of neutrino interactions by producing a beam consisting of hundreds of billions of neutrinos and sending the beam through a detector of solid matter. To achieve this, the scientists used a particle accelerator to generate a stream of high-energy protons, which were then fired at a target made of the metal beryllium. The bombardment produced a stream of different particles, including those called pions (pi mesons) that, as they traveled, decayed into muons (mu mesons) and neutrinos. The stream of particles exiting from the beryllium target then passed through a steel barrier 13.4 m (44 feet) thick that filtered out all other particles except neutrinos. This pure neutrino beam subsequently entered a large aluminum detector in which a few neutrinos interacted with the aluminum atoms. In analyzing these interactions, the three physicists discovered a new type of neutrino, which came to be known as the muon neutrino.