ICFA Seminar on Future Perspectives in High-Energy Physics

by Mike Perricone

Can the accelerator-building nations of the world join forces to take a global next step in high-energy physics?

Or will daunting economic, political and historical obstacles block the kind of transworld collaboration that most physicists and many policymakers agree will be critical for new machines at the advancing energy frontier?

These were the questions that a high-powered group of the world's high-energy physicists gathered to discuss at a workshop of the International Committee on Future Accelerators, held at Fermilab, Oct. 5-8, 1999. Perspectives differ on what form the next accelerator after the LHC should take; when design decisions should be made; andóespeciallyówhere it should be built.

"If it could be built in space," said Albrecht Wagner, head of Deutsches Elektronen-Synchrotron (DESY) in Hamburg, Germany, "it would already be built. But it has to come down to earth somewhere."

Not in space but in cyberspace, an Internet search under "ICFA," turns up the ëInternational Cemetery and Funeral Association' as its first entry John Peoples, ICFA chairman and Fermilab director emeritus told delegates."

But proceedings were anything but funereal at the four-day workshop on Future Perspectives in High-Energy Physics. The directors of all the world's high-energy physics labs, representatives of many of the world's funding agencies, and scientists from every branch of HEP, grappled with how to move beyond the current nation- or region-centered paradigm, to a new model of world collaboration.

Many of those present clearly believed that an earth-bound consensus is growing, if far from achieved, on a 20-mile long, high-energy (1-1.5 Trillion Electron Volts) electron-positron Next Linear Collider as the next major step in particle physics. The linear collider concept also appears to be gaining momentum outside physics, as Burton Richter declared during a panel discussion of laboratory directors.

Richter, Director Emeritus of the Stanford Linear Accelerator Center, spoke from the audience to warn that a decision could be made among participating countries without advice from the scientific community.

"The governments all know that we (in particle physics) are heading for a multibillion-dollar linear collider," Richter said. "They are going to start talking to each other. It's important for us to get involved with the governments, so that they take science advisers to these meetings, which are going to happen anyway. They must hear the voice of science, and not just the voices of geopolitics and geofinance."

The "voice of science" could be heard clearly in a talk on Perspectives of High Energy Physics: LHC and Beyond, by Jonathan Ellis of CERN. At the top of the list of physics goals, Ellis said, is measurement of the Higgs boson, postulated as the source of mass; the Higgs should be found in the NLC's energy range. The NLC could also open a window on supersymmetry, by viewing weakly interacting particles which can't be seen at LHC.

The influences of geopolitics and geofinance cannot be ignored, because there is virtually no doubt that the next big machine--NLC or otherwise--can be built only by an international collaboration to share the considerable expenses. As Fermilab Director Michael Witherell stated, the high-energy physics community "must envision the linear collider as much as possible with a worldwide view."

Working from just such a viewpoint, Wagner outlined a "Proposal for a Global Linear Collider Laboratory." The envisioned accelerator complex would be built at an undetermined location, but operated remotely from several laboratories around the world. Physicists would in effect be taking their shifts from their home labs via remote electronic communications. The accelerator would operate with a small onsite crew, built with global funding, with experimenters from far and wide.

Wagner cited the example of a synchrotron accelerator in Hiroshima, Japan, operated by remote control from Tokyo. He also noted the many successful remote operations in astronomy and space science, and urged ICFA to set up a task force to study the possibility.

In contrast to Wagner's readiness, there were also voices urging deliberation and caution, including that of Hirotaka Sugawara, Director of KEK, the accelerator laboratory in Tsukuba, Japan.

"I would urge us not to be hasty in solving our problem," Sugawara said in the directors' panel discussion. "I'm afraid of making premature decisions."

The issue of time brought voices calling for both quick and delayed decisions, from both the directors' panel and the audience. Results offering insights into the energy thresholds of new particles are years away, both at Fermilab and at the LHC at CERN, the European particle physics laboratory in Geneva, Switzerland. Meanwhile, the growing scope and expense of high-energy physics machines means a long wait from proposals to operationsóas much as 20 years. The hourglass is seen as both half-full and half-empty in terms of decision-making.

Half-empty, according to Richter: "We won't have new information until Fermilab Run II, and until the LHC is operating for a few years. But we can't wait that long to make a decision. We need to ask, what is the right expansion?"

Half-full, according to audience member Alvin Tollestrup of Fermilab (himself a proponent of muon storage rings and colliders): "The NLC would sit for a year looking at one point for events. I think it's a mistake not to wait until the LHC sets a new mass scale. If we decide before that and we're wrong, it will be a waste of money and a disservice to our field."

Rutherford Appleton Laboratories (U.K.) Director Ken Peach pointed out that "money is an intensely political issue, and politicians want `the Big Idea.'" He was reinforced by a comment from the audience by John O'Fallon, Director of the High Energy Physics Division of the U.S. Department of Energy.

"It's enormously hard to sell modest increases in energy for large amounts of money to politicians," said O'Fallon. "We're talking about billions of dollars."

Also in the category of billions of dollars is the Very Large Hadron Collider, postulated as the machine to move the high-energy frontier beyond the scale of the LHC. There were several references during the conference to the 1996 meeting in Snowmass, Colorado, where the NLC was envisioned as complementary to the LHC at CERN, while VLHC would achieve a 10 TeV center of mass energy with superconducting magnet technology. VLHC would also require a circular ring at least 50 miles in circumference and possibly larger, depending on the kind of magnet technology selected. By comparison, Fermilab's Tevatron is four miles in circumference; the LHC at CERN is 27 kilometers, or about 16 miles in circumference.

As Michael Harrison of Brookhaven National Laboratory said in his presentation, VLHC (indeed, any large-scale project) would require long-term planning to decide on the concept, establish a sense of direction, launch research and development, guide the magnet development, and attempt to minimize the cost of big-ticket items.

"The VLHC could almost be built today," Harrison said. "The technical issues are less difficult than other issues."

As with any large-scale project, those "other issues" clearly are economic and political.

While ICFA adjourned without an endorsement of a specific machine, many of the participants will be heading next to an international conference lending credence to a sense of momentum for NLC: The 8th International Workshop on Linear Colliders, held from Oct. 21-26 at Frascati National Laboratory in Rome, Italy. Jonathan Dorfan, Director of Stanford Linear Accelerator Center, summed up the importance of reaching an international consensus on the direction of high-energy physics.

"No matter which accelerator we eventually build," said Witherell, "we will have to use the world's existing laboratories as resources. All the labs will have to organize to build a big, complicated project. The laboratories are our assets. In any international collaboration, we must keep in mind that we need to maintain healthy national laboratories while we build a new global facility."

Dorfan concluded: "We must try to write a global road map, and address regional balances over time. Intense regionalism is an invitation to extinction."