Far From Florida, a Cliffhanger Recount in Physics
PARIS, Nov. 12 -Last week, at the leading European particle physics laboratory, CERN, an institution straddling the French-Swiss border far from the superhot center of American politics but well within its sphere of influence, the question arose: is it more important to determine who the next American president will be or to discover why all matter in the universe has mass, rather than weighing nothing?
It could be argued that the answer to only one of those questions explains why the planets do not come unhinged in their orbits and fly off into space. And so, at CERN, that question dominated the discussion as hundreds of physicists fought for the right to continue working on an experiment they said was on the verge of discovering a particle that theorists believe is the key to why matter has mass and weight.
But the physicists also constantly marveled over strange parallels between the fight at CERN and the American elections, which have been heavily covered in Europe. The two battles have been protracted and excruciatingly close, and each has revolved around the subtler points of counting and statistics-involving the Florida ballots in one case and a handful of ambiguous detections within giant particle-counting devices in the other.
The long-sought particle is called the Higgs boson. It is the last undetected particle whose existence is required according to the so-called Standard Model of particle physics, which correctly describes all the known properties of matter as determined by the experiments that have been performed to date. For example, the model accounts for the masses of all the known particles, from electrons to quarks, as well as the ways in which they interact, or exert forces on one another.
Like the role of the presidency in American government, the Higgs has a special and indispensable status within the Standard Model. All particles in the model receive their mass by interacting with a wellspring of energy called the Higgs field, which is thought to permeate all of space, and has probably existed since the universe began in a great explosion known as the Big Bang.
The Higgs field usually cannot be seen, but by smashing ordinary particles together at tremendous energies, a Higgs boson should occasionally be jarred loose by the alchemy of Einstein's famous relativity equation, which relates the equivalency of mass and energy. In that case, the Higgs exists too briefly to be detected directly either, but it decays into a characteristic spray of other particles that can be seen.
That is exactly what CERN physicists believe they saw, starting in July, within a subterranean particle racetrack, 17 miles in circumference, near Geneva.
Year by year and month by month, engineers had been gradually increasing the energy of the accelerator, called the Large Electron-Positron collider, or LEP. It was the physicists' misfortune that the apparent Higgs bosons began turning up only near the highest planned energy of the accelerator, just before it was scheduled to be shut down and demolished in September. A new $4 billion accelerator is supposed to occupy the same tunnel and be completed by 2005.
That machine will be much more powerful and, everyone agrees, will certainly find the Higgs if it is there.
But the precise value of the mass of the apparent Higgs bosons the LEP physicists were seeing caused them to begin a frantic lobbying effort to keep their accelerator open for another year-to confirm their discovery, they hoped-and delay the start of construction for the new machine.
The exact mass of the Higgs is not predicted by the model, but must be measured in experiments. The higher that mass, the more powerful the accelerator that is required to create it. The mass suggested by the results, about 115 times the mass of the proton, was just within reach of the highest LEP energies and should be easy to achieve on the new machine. But it should also be just within reach of an upgraded machine at the Fermi National Accelerator Laboratory, near Chicago, which is scheduled to be finished in the spring and could therefore make the discovery first.
"It's a politically very interesting value," said Dr. Alvaro de Rujula, a CERN theorist, who favored continuing with the existing accelerator. "Precisely for this value of mass, Fermilab comes into play. Even the American community is going to be split." Dr. de Rujula was referring to physicists in the United States who either work at LEP or Fermilab, or have plans to work on the new machine at CERN, called the Large Hadron Collider.
The split was most striking at CERN, where the crucial decision had to be made. From Nov. 3 through Nov. 7, the American Election Day, three separate advisory committees at CERN failed to reach a consensus on which decision to make.
At one point a LEP physicist rushed into the CERN press room and said she had been told that the most influential of those committees, called the Research Board, had split down the middle with nine yeas, nine nays and one abstention. The laboratory would not confirm the report.
The parallels between Florida and Geneva went on. A news conference announcing the final decision by CERN's director general, Prof. Luciano Maiani and his inner circle of advisers, originally scheduled for Nov. 7, was first delayed until the next morning and then until the afternoon. Professor Maiani finally announced that LEP would indeed be shut down-but would not be demolished until yet another vote was taken in December, this time by a quasi-political body called the CERN Council of States.
Some at LEP said they would plead with the council, in the equivalent of acourt challenge, to permit what might amount to a physics recount, allowing the accelerator to run another year to bolster the thin statistical evidence so far-just four especially striking counts that might be Higgs detections.
Even Dr. Lyndon Evans, the Large Hadron Collider's project leader, conceded that if the experiment were a small tabletop device rather than a multinational behemoth, he would have advised a change in plans to keep chasing the Higgs.
Everyone involved seemed to agree that the almost unstoppable, programmatic nature of very big science was always a potential drawback when unexpected discoveries beckoned around corners that only smaller and nimbler projects could take.
Some scientists, like partisans of a candidate who had lost a close recount, took a wistful but resigned view as the discovery-that-might-have-been receded into the distance. Prof. Sau Lan Wu, a University of Wisconsin physicist, worked on the experimental group that collected some of the first evidence that LEP might have been seeing the Higgs. "In my mind, if Fermilab discovered it, I would be happy," she said, before adding, "but if CERN discovered it, I would be happier."