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Martin Perl awarded 1995 Nobel Prize in physics

STANFORD -- Martin L. Perl, a professor at the Stanford Linear Accelerator Center (SLAC), has been awarded the 1995 Nobel Prize in physics. He will receive the award in Stockholm, Sweden in December for his 1975 discovery of a new elementary particle known as the tau lepton.

Perl, 68, will share the prize with Frederick Reines of the University of California-Irvine.

The SLAC physicist received the news of his selection from a reporter who tracked him down at his home in San Francisco. "We were sleeping soundly when the phone began to ring. We tried to ignore it, but it kept on ringing," he said.

"I'm very pleased. I'm pleased for my colleagues. I'm pleased for SLAC, for Stanford and for the Department of Energy. As you know, funding for this kind of research is less than it used to be. I hope this will help DOE maintain its funding for basic research," Perl said.

SLAC Director Burton Richter, recipient of the 1976 Nobel Prize for physics, said, "All of us at Stanford are elated at the news. Perl's discovery came as a complete surprise to the physics world. This is a well deserved award."

The tau lepton is a superheavy cousin of the electron, the carrier of electrical current in household appliances. The two particles are identical in all respects except that the tau is more than 3,500 times heavier than the electron and survives less than a trillionth of a second, whereas the electron is stable.

In the mid-1970s, working at the Stanford Positron-Electron Asymmetric Ring (SPEAR) in collaboration with 30 other physicists from SLAC and Lawrence Berkeley National Laboratory, Perl began to find events recorded by the detector that could not be explained by any of the known subatomic particles. After more than a year of analysis, Perl was able to convince the rest of his research team that they were in fact observing a new and different type of elementary particle, which he named the 'tau'.

In the standard model of particle physics, the elementary building blocks of matter appear in families, with two leptons and two quarks in each. Until Perl's discovery there were only two such families known to exist.

The tau turned out to be the first-discovered member of a third quark-lepton family. In 1976, the second particle in the family, the bottom quark, was discovered by scientists at Fermi National Accelerator Laboratory. It was not until 1995 that Fermi scientists discovered the third member, the top quark.

Addressing the question of the usefulness of the discoveries like that of the tau lepton, Perl said, "The use of the discovery of basic particles is indirect. We have found that everything of a complicated nature is made from three basic families of particles. Eventually, this will lead to an improved understanding of energy and time. From that we hope will come new ideas that lead to applications like a source of cheap energy which is truly safe."

Scientists have produced the experimental data upon which such improved understanding may come, but the theory to go with it is not yet firm, he continued. "It will take a young woman or young man to find that out. We need young, fresh brains and the research funding to support them," he said.

Perl was awarded the Wolf Prize for his discovery of the tau in 1982. He is a member of the National Academy of Sciences and a fellows of the American Physical Society.

Perl received his Ph.D. in 1955 from Columbia University, where he studied under Professor I.I. Rabi, winner of the 1944 Nobel Prize in physics. Perl has been on the faculty at SLAC since 1963.

The mission of the Stanford Linear Accelerator Center is to design, construct and operate highly advanced electron accelerators and experimental facilities for high energy physics and synchrotron radiation research and to engage in fundamental science. The Stanford Linear Accelerator Center is a national user facility managed for the Department of Energy by Stanford University. -jer-


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