Martin Perl, 87, Is Dead; Nobel-Winning Physicist
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Martin Perl, in his lab at Stanford in 1995, after learning that he had won the Nobel.John G. Mabanglo/Agence France-Presse — Getty Images
Martin Perl, who was awarded the1995 Nobel Prize in Physics for discovering a new subatomic particle, one of the building blocks of the universe, died on Tuesday in Palo Alto, Calif. He was 87.
The cause was a heart attack, said his son Jed Perl, an author and art critic for The New Republic.
Dr. Perl was a professor emeritus at the SLAC National Accelerator Laboratory at Stanford, the particle physics laboratory where he did his epochal work.
The discovery of the subatomic particle, the tau lepton, as it is formally known, was a crucial step in figuring out the jigsaw puzzle of elementary particles that form the bedrock of material reality.
The evidence emerged slowly, over three years of particle collisions at SLAC in the 1970s.
“Every month or so we would get another handful — 10 to 20 — of these funny (particle collision) events,” Dr. Perl recalled in 2013, according to a statement released by SLAC.
His colleagues urged caution, his son said, but eventually “he very consciously went out on a limb.”
“He decided it was better that he stand by what he thought he was seeing, even at the risk of being wrong, than to be afraid to take the leap,” his son said.
Martin Lewis Perl was born on June 24, 1927, in Brooklyn, the son of Jewish immigrants from what was then the Polish part of Russia. The family struggled to stay in the middle class, his father running a printing business and his mother working as a secretary and bookkeeper for a wool merchant firm.
As a young man, Martin enjoyed building things, and one of the disappointments of his early years, he said, was that his parents never bought him an Erector Set or a chemistry set. Luckily, his cousin had an Erector Set.
Martin graduated from James Madison High School in Brooklyn in 1942 at 16. Although he was a good student and even won a physics prize, he never thought about being a scientist, for practical reasons. “We did not know that it was possible for a man to earn a living as a scientist,” he wrote in an autobiographical sketch for the Nobel committee.
Instead, he enrolled in the Polytechnic Institute of Brooklyn with the aim of becoming a chemical engineer. With the onset of World War II, he left to attend the United States Merchant Marine Academy and was then drafted into the Army. He spent a year doing desk work in Washington.
After the war, he resumed his studies and graduated in 1948. Hired by General Electric, he became interested in a new technology, television, particularly in how television tubes worked.
“At the age of 23,” he wrote, “I finally decided to begin the study of physics.”
He earned a Ph.D. at Columbia, studying the nuclei of sodium atoms under the Nobel laureate Isidor Isaac Rabi. After a stint at the University of Michigan, he was offered at job at the new Stanford Linear Accelerator Center (now known as SLAC).
Dr. Perl saw the new lab as a place where he could dig into a longstanding puzzle. In the 1930s, physicists had discovered a new particle they called the mu meson (it is now called the muon), which was identical to an electron but 200 times more massive. Where this particle fit in the scheme of things was a mystery. “Who ordered that?” Dr. Rabi is said to have asked.
Burton Richter, a former director of SLAC, said in an interview that when he first met him, “Martin was already fascinated by the quest for the brotherhood of the mu mesons: Why there was only one mu meson? Why weren’t there more? Could there be more?”
Dr. Perl thought that finding an even heavier electron might answer some of these questions and help explain the muon’s role in the scheme of things. He and his group figured out that such particles might be detected in a new collider being planned called Spear, forStanford Positron Electron Accelerating Ring. The particles would decay radioactively immediately but would leave behind a distinctive trail of subatomic debris.
In the official proposal for the Spear collider, the heavy lepton search was left for last, and allotted just three pages. As Dr. Perl wrote, “to most others it seemed a remote dream.”
The Spear machine started up in 1973, colliding electrons and their antimatter opposites, positrons, to produce tiny fireballs. By virtue of Einstein’s equivalence of matter and energy, these little clouds of energy could condense into anything, including the muons and their heavier brothers, if any existed. Dr. Richter recalled that by 1975 it was clear that there was something there.
At a conference and in a paper in 1975, Dr. Perl and his colleagues announced that they had discovered a new particle, but that they were not sure yet what it was.
“We have no conventional explanation for these events,” they wrote in their paper. At first they called the particle “U,” for unknown. It took two more years of collecting data to convince the rest of the physics world that this was the long-lost brother of the electron, joining the muon to make a triad.
The tau, as it came to be called, after Greek for “the third,” is 3,500 times as massive as the electron. But it lives only a third of a trillionth of a second before decaying into a spray of its lighter brethren and the ghostly particles known as neutrinos.
To this day the tau is the heaviest of the electron brothers. In the Standard Model that now rules physics, all matter in the universe is divided into two sets of six particles each: six so-called leptons, which include the three electron brothers and three types of neutrinos that are associated with them, and six quarks, which make up the innards of particles like protons and neutrons. Nobody knows why there are six of each.
It was fitting that in 1995 when Dr. Perl won the Nobel Prize, he shared it with Frederick Reines, who had discovered the neutrino. The Royal Swedish Academy of Sciences cited them for discovering “two of nature’s most remarkable subatomic particles.”
Dr. Perl went on to investigate the nature of quarks. He continued to visit the SLAC lab long after retirement, most recently to collaborate on an investigation of dark energy.
A lifelong liberal and opponent of the Vietnam War, he helped found a group called Scientists and Engineers for Social and Political Action, which opposed the war.
Besides his son Jed, he is survived by two other sons, Joseph and Matthew; a daughter, Anne Bernard; eight grandchildren and one great-grandchild.
Dr. Perl took particular delight in the gritty mechanical and physical details of doing experiments, an interest he traced to his boyhood joy in playing with construction toys like Lincoln Logs. To make up for his lack of an Erector Set while growing up, he later amassed a large collection of them and other construction toys.
“He really saw those toys as the germ out of which experimental creativity could come,” Jed Perl said.
In recent years, Mr. Perl said, his father traveled in India and Japan lecturing about creativity and his concern that science education was becoming too rigid. He urged students to keep a journal and write down crazy ideas. But he also urged them and his colleagues not to get too far ahead of the fundamental truth of experiment in science.
In a blog post last year he wrote: “The time scale for physics progress is a century not a decade. There are no decade-scale solutions to worries about the rate of progress of fundamental physics knowledge. My advice is (a) study calculus and machine shop in high school and (b) have a long life as advised in the old song by buttoning up your overcoat and eating an apple every day.
“On the other hand,” he continued, “occasional scanning of the obituaries in The New York Times indicates that financiers live longer than physicists, so perhaps start a hedge fund in high school.”
http://www.nytimes.com/2014/10/04/science/martin-perl-physicist-who-discovered-electrons-long-lost-brother-dies-at-87.html?_r=0
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