The massive effort to find the particle that is most likely the source of all the mass in the universe
Tamara Traubman
In the "clean room" in the laboratory at the Weizmann Institute - which is only allowed to be entered with hats and nylon robes that prevent hair or clothing fibers from falling - stands Meir Shua, the director of the laboratory, preparing panels of detectors. The detectors will be sent to Saran, the European Laboratory for Particle Physics Research in Geneva, and will be installed in "Atlas", a huge particle detector as tall as a ten-story tower. Physicists hope that in about five years, when "Atlas" starts working, they will discover a mysterious particle called the Higgs boson, which they believe is the source of all mass in the universe and the reason that humans, stars, and in fact all matter in the universe have weight. Leon Lederman, winner of the Nobel Prize in Physics, thought that the role of the Higgs in the creation of the universe was crucial, and called it the "God particle".
"Atlas" will be one of two giant detectors in the world's most powerful particle accelerator, the Large Hadron Collider (LHC). "The LHC is the largest and most complicated machine ever built on Earth," says Prof. Ehud Duchovni, a physicist at the Weizmann Institute, who was previously the head of the Higgs group in one of the experiments at Saran and today is a partner in the construction of the detector.
The Higgs is not the only thing physicists hope to discover in the accelerator; They also hope to find there hints of super theories that predict that there are hidden additional dimensions in the world, and especially evidence of a super theory called "super-symmetry", which predicts that all particles in the universe have partners, which may constitute the "dark matter". "If these particles really exist," says Prof. Giora Mickenberg from the Weizmann Institute, head of the Israeli group in the experiment, "with the new accelerator we will be able to discover them."
When the Higgs is created, assuming it does exist, it will exist for a very short time; Physicists will not be able to observe it directly. The detectors being built at the institute were designed to be able to detect the "golden seal" that the Higgs will leave behind: four isolated muon particles that will travel at very high energy. The detectors undergo quality control by physicists from Tel Aviv University and the Technion. At the Technion, a control system is also being produced, "which will allow physicists above ground to visit and control the detector located about a hundred meters underground," says Dr. Shlomit Terem, coordinator of the "Atlas" activity at the Technion.
At the beginning of the week, Meir Shua went to Geneva to start dismantling LEP, an 11-year-old accelerator in which the circular canal (27 kilometers long) where it lies will begin to build the new accelerator. For the physicists who worked at LEP, these days are the end of a period full of discoveries, which culminates precisely at the time when, according to advance planning, LEP is supposed to close.
About a month before work on it was supposed to stop, the particle detectors at the accelerator began to pick up data that suggested that scientists might have caught a glimpse of the Higgs boson. They implored the laboratory's management to delay the construction of the new accelerator by a year, so that they could collect additional data that would refute or confirm their observations. But after many discussions, Sarnan's CEO decided not to give them such an extension. "Some of the people directly involved in the search for the Higgs felt that they were missing the opportunity of their lives," says Prof. Elam Gross from the Weizmann Institute, who until recently was the head of the Higgs working group in one of the experiments at Saran and today is a partner in building the new project. "But it must be admitted that the evidence for the existence of the particle was not convincing enough to invest the time and money necessary to run LEP for another year, thereby delaying the operation of the new machine." "If the signs we saw were correct, we could discover it in another 6-5 years," says Prof. Mickenberg, "it will be a matter of patience."
However, in March 2001 another accelerator, "Tevatron", located in the Fermi National Laboratory in Chicago (Permilab) will start operating in the arena. "Tevatron" has been renovated, but "it will still be much less powerful than the LHC", says Dr. Marcela Karna, a physicist involved in the search for the Higgs at Paralab.
The theory accepted by most physicists to describe the particles of matter and the forces acting between them is known as the standard model. This model allows physicists to explain all the properties of the known matter in the universe, and its predictions have proven over the years to be very accurate. There is only one problem with the model: it does not explain why particles have mass and why their mass distribution is the way it is. To get the Standard Model out of this impasse, physicists hypothesized that there is an entity called the Higgs boson, which gives particles mass. According to the theory, the Higgs clings to other particles and thus gives them mass. The greater the friction of a particular particle in the Higgs field, the greater its mass.
The answer to the question of who will get the first glimpse of the Higgs depends in part on its mass. The heavier the Higgs, the more powerful an accelerator is needed to produce it.
The standard model does not predict the Higgs mass. According to the theory of supersymmetry, says Dr. Karna, the Higgs mass should be less than 130 GeV. The tevatron at Primilab has a good chance of finding a Higgs at such a mass. If the tevatron fails to collect enough evidence for the existence of a Higgs at a mass of 130 GeV, it will be sad not only for its scientists, but also for the followers of supersymmetry.
In his book "The Legacy of Lucifer: The Meaning of Asymmetry", the physicist Frank Close tells about a trip he took to the Tutelary Gardens in Paris. After wandering the paths and marveling at the precision with which each side of the path—each garden, fountain, or statue—mirrored the other, he was surprised to come across a broken statue of Lucifer. His broken head was lying on the ground. Perhaps, Close suggests, instead of calling the Higgs the God particle it would be better to call it the Satan particle: a particle that confounds physicists the world over, and constantly destroys a world that would otherwise be too perfect to exist.
{Appeared in Haaretz newspaper, 5/12/2000}
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