Melvin Schwartz, 73; Shared the 1988 Nobel in Physics for Neutrino Work
Melvin Schwartz, who shared the 1988 Nobel Prize in physics for developing the first high-energy neutrino beam and thereby producing one of the most useful tools for experimental nuclear physics, died Monday at his home in Twin Falls, Idaho. He was 73.
Schwartz had battled Parkinson’s disease for several years.
His experiments, performed with co-Nobelists Leon Lederman and Jack Steinberger, made it possible for the first time to study the so-called weak force, one of the four fundamental forces that control the universe.
They also demonstrated conclusively that there were two distinct types of neutrinos, ghostlike particles that have negligible mass and no electrical charge.
The research “opened entirely new opportunities for research into the innermost structure and dynamics of matter,” according to the Nobel citation, and was the birth of a new way of doing high-energy physics.
Both the weak force and the neutrino were considered mysterious in the late 1950s, when the three researchers began their collaboration.
The weak force, which plays a critical role in the form of radioactive disintegration known as beta decay, is very feeble -- only a fraction as strong as the electromagnetic force that pulls protons and electrons together and less than 1% as powerful as the strong nuclear force that binds the atomic nucleus.
The neutrino’s lack of an electrical charge made it seemingly impossible to manipulate, and its ability to pass unscathed through virtually all matter -- including lead walls conceivably light-years thick -- made it difficult to detect.
The inspiration for the team’s work came in November 1959 at a daily coffee hour in the physics department at Columbia University, where all three men worked. Visiting Nobel laureate T.D. Lee asked the assembled group, “Is there any way to study the weak interactions at high energy?”
The group talked about several possibilities, but none seemed feasible, Schwartz said 29 years later when the Nobel was awarded. In any kind of high-energy interaction they could envision, the effects of the weak force would be totally overwhelmed by the other forces and particles generated.
“So I came home still thinking about it, and in a crazy way it just hit me: Use neutrinos!” If someone could shine a beam of high-energy neutrinos on a target, it would produce weak interactions uncontaminated by any other processes.
His solution was to use the Alternating Gradient Synchrotron at Brookhaven National Laboratory on New York’s Long Island to accelerate protons into a beryllium target. Through a series of disintegrations, that process led to a stream of neutrinos.
“It was a really simple idea,” Schwartz told the journal Science. “I called T.D. Lee that night and told him I had a way to do it.”
But implementing it was a little more difficult.
To isolate the neutrinos from all the other particle debris produced in the initial collisions, the trio built a 40-foot-thick wall of steel using armor plate from the battleship Missouri, which had been decommissioned and was being cut up for scrap.
The detector also was problematic. Ultimately, they constructed a 10-ton spark chamber filled with sheets of aluminum separated by narrow gaps. When a neutrino struck an atom in the aluminum, it generated a charged particle that created a visible spark, which could be photographed and analyzed.
The neutrino’s ability to pass through matter with ease was partially counterbalanced by the intensity of the neutrino beam generated in the accelerator. Nonetheless, in the eight months that they bombarded the target with billions of neutrinos, the team observed only 50 spark events. But that was enough to prove that the concept was viable.
One of their first goals was to determine if there was only one type of neutrino or two.
Scientists knew that a neutrino was produced when an electron underwent beta decay. They also knew that a neutrino was produced when a muon -- a particle with a negative charge and a weight 200 times that of an electron -- underwent pion decay. What they didn’t know was whether the electron and muon neutrinos were identical.
The results of their experiments were unequivocal. The Columbia team showed that electron and muon neutrinos were clearly different, shocking the physics community, whose members mostly believed that the two were identical. As a result of their experiments, it soon became clear that the elementary particles belonged in families whose properties were identical but whose masses were different.
The lightest family is composed of the electron, the electron neutrino, and two quarks, known as “up” and “down.” The next lightest family consists of the muon, the muon neutrino, and two quarks known as “strange” and “charmed.” This family structure became a central tenet of the unified theories of physics developed in the 1970s and 1980s.
“We started a sort of cottage industry in identifying basic particles, the quarks and so on,” Lederman said when the Nobel was announced. “Now there are hot- and cold-running neutrinos all over the place.”
Schwartz said he had given up on receiving the Nobel.
“I had thought of it in the 1960s, and I thought of it a lot less in the 1970s, and not at all in the 1980s,” he said. “But I was pretty well known for what I did back in [1961]. It didn’t matter to me if I had a prize or no prize.”
Schwartz was born Nov. 2, 1932, in New York City. His interest in physics began at age 12 when he entered the Bronx High School of Science. “The four years I spent there were among the most exciting and stimulating of my life,” he later wrote.
He enrolled at Columbia University in 1949, beginning a lifelong association that continued even when he moved to other laboratories. “Mel lived and bled Columbia blue,” said physicist William Zajc. “He was willing to question anything and was always trying to do experiments in front of the crowd, not follow it.”
Schwartz became a full professor at Columbia but left in 1966 to accept a position in the physics department at Stanford University. While there, he founded Digital Pathways Inc., a Mountain View-based company that provided computer network management services and security.
Schwartz “didn’t like the trend toward larger and larger collaborations in physics,” Zajc said, and he left Stanford in 1983 to work full time at the company.
The siren call of physics proved too strong, however, and he returned to Columbia in 1991, simultaneously accepting a position as associate director for high energy and nuclear physics at Brookhaven National Laboratory.
In that position, he decided almost single-handedly which proposed projects would be carried out on the Relativistic Heavy Ion Collider, which began operation in 2000. In the collider, beams of energetic gold ions were fired at each other to simulate the conditions that occurred in the very early universe.
Those experiments ultimately showed that the matter in the universe at that early stage was not a gas, as had been previously believed, but a fluid or a liquid. Those findings were considered the physics story of the year in 2005.
Plagued by Parkinson’s disease, Schwartz retired in 2000.
Survivors include his wife of 52 years, the former Marilyn Fenster, and three children, David, Diane and Betty.
