Perhaps appropriately for the Land of the Bible, Israeli researchers played a significant part in Wednesday’s breakthrough on what scientists call the “God particle,” properly known as the Higgs boson, the missing link in Einstein’s Standard Theory.
Researchers at the Weizmann Institute in Rehovot, Hebrew University, and the Technion have been active in the search for the elusive particle for years, as well as in the development of the CERN particle accelerator that scientists have been using in the experiments that led to Wednesday’s announcement.
Scientists have been on the trail of Higgs boson since 1964, when British physicist Peter Higgs theorized that elementary particles gained mass by interacting with a special quantum field that permeates space (the Higgs field), and leads to the development of quarks and electrons, the elementary particles of matter.
In essence, the Higgs boson is considered the final building block that has been missing from the “Standard Model,” which describes the structure of matter in the universe. An essential part of the theory, a boson that would provide the basic material for the development of matter (converting mass to matter and giving it different properties), was missing, and the search for the boson (called the Higgs boson), which could only be done in a proton accelerator (because of its size, scientists say), was under way.
That search was one of the reasons for the construction of the Large Hadron Collider (LHC), the world’s largest and highest-energy particle accelerator, which lies in a tunnel 27 kilometers (17 miles) in circumference and as deep as 175 meters (574 feet) beneath the Franco-Swiss border near Geneva, Switzerland. The LHC was first activated in 2008, and is the largest machine in the world, accelerating beams of protons up to 99.999998% the speed of light. According to the theory of relativity, this increases their mass by 7,500 times that of their normal resting mass. The accelerator aims the beams straight at each other, causing collisions that release so much energy, the protons themselves explode — a situation scientists believe was extant immediately after the Big Bang.
The Higgs boson has been popularly called the “God particle” after a book on the nature of matter and the Higgs boson by physicist Leon Lederman used the term because it was “so central to the state of physics today.” Physicists, however, were never happy with that term, and a British newspaper once ran a contest seeking a better popular name for the particle. Lederman himself was quoted as joking that he called it the God particle because “the publisher wouldn’t let us call it the Goddamn Particle, though that might be a more appropriate title, given its villainous nature and the expense it is causing.”
On Wednesday, CERN, the European Center for Nuclear Research, which operates the LHC, announced that scientists had discovered a new particle that seemed to fit the theoretical characteristics of the Higgs boson. The newly discovered particle was a boson, said Joe Incandela, a spokesman for one of the experiments, and it was the heaviest boson ever found, as Higgs’s theories would have indicated.
Nevertheless, Incandela said, investigations were still ongoing. “The implications are very significant and it is precisely for this reason that we must be extremely diligent in all of our studies and cross-checks,” he said in a statement. “This is a preliminary result, but we think it’s very strong and very solid.”
Higgs, 83, had tears in his eyes as the announcement was made. “It is an incredible thing that it has happened in my lifetime,” he told members of the organization and guests at a press conference at CERN headquarters outside Geneva Wednesday.
Also excited, if not near tears himself, was Professor Eilam Gross of the Weizmann Institute. Gross is the convener of the statistical data analysis forum of the ATLAS detector, which measures the results of experiments in the LHC.
“This is the biggest day of my life,” said Gross. “I have been searching for the Higgs boson since I was a student in the 1980s. Even after 25 years, it still came as a surprise. No matter what you call it — we are no longer searching for the Higgs but measuring its properties. Though I believed it would be found, I never dreamed it would happen while I was holding a senior position in the global research team.”
Indeed, if Higgs is the father of the boson that bears his name, scientists at the Weizmann Institute are at least uncles. Weizmann scientists have made strong contributions to bringing CERN researchers to the point where they felt comfortable making Wednesday’s announcement. The boson was discovered by intensive use of the LHC to collide particles and examination of the resulting data from the breakup of the protons into ever-smaller particles.
But it’s a laborious task; the likelihood of creating the Higgs boson in a single collision is similar to that of randomly extracting a specific living cell from the leaf of a plant, out of all the plants growing on Earth, say Weizmann scientists. A Weizmann team, headed by Professor Giora Mikenberg, developed unique particle detectors which were manufactured at the institute, as well as in Japan and China. The detectors were adapted to detect muon particles, which are an indication that a Higgs particle is present.
Mikenberg was for many years head of the research group that sought the Higgs boson in CERN’s OPAL experiment. He was then leader of the ATLAS Muon Project — one of the two experiments that eventually revealed the particle. In addition, Weizmann Professor Ehud Duchovni heads the institute team that examines other key questions at CERN. In the Weizmann team three scientific generations are represented: Mikenberg was Duchovni’s supervisor, who was, in turn, Professors Eilam Gross’s supervisor.
Weizmann scientists are not the only Israeli scientists involved in the search for Higgs boson. Hebrew University Professor Eliezer Rabinovici is Israel’s representative to the governing CERN council, and director of the Israel Institute for Advanced Studies at Hebrew University. In addition, Technion Professor Shlomit Tarem, who has been working on the Higgs boson project for well over a decade, oversees detector control for several of the research groups. And Technion Professor Yoram Rozen helped design the 2008 CERN “Big Bang” experiment.
In addition to actual work on the Higgs boson project, Israeli researchers were key to building the LHC particle accelerator. The system includes the world’s largest superconducting electromagnets, built in conjunction with Israeli companies. The entire structure includes 10,000 radiation detectors spaced just one millimeter apart, has a volume of 25,000 cubic meters, and features half a million electronic channels. Most of the muon radiation detectors were built from components produced in Israel. A unique laser system tracks the exact location of the detectors with an accuracy of 25 microns (half the thickness of a human hair).
In addition, part of the ATLAS detector, the largest detector in the world, was made in Israel. The detector boards for ATLAS were made at the Weizmann Institute and tested at the Technion. On every board, there are thin, gold-plated electric wires, each one 50 microns in diameter. The overall area of the detector being built in Israel is six dunams and the total length of the electric wires inside equals the circumference of the Earth. Inside each one of the boards is an electronic circuit that was built at the Technion’s Faculty of Physics.
Israel was invited to join CERN last year. That, Rabinovici said, was a milestone for Israeli science, which has generally not been identified with the “big science” of particle acceleration. The invitation “is recognition for the fact that Israeli high-energy physicists, experimental and theoretical, have made significant contributions to the field in general over the years, and at CERN in particular,” Rabinovici said. “I think this is a badge of honor, and a recognition of everything [we’ve] done.”