A national panel of high-energy physicists, co-chaired by Jonathan Bagger, a professor of physics in the Krieger School of Arts and Sciences, has recommended that the United States get ready to make a bid to host the world’s next great particle collider.
The recommendation was included in a report on the future of high-energy physics commissioned by the High Energy Physics Advisory Panel, or HEPAP, an advisory organization for high-energy physicists jointly sponsored by the U.S. Department of Energy and the National Science Foundation. Bagger says the goal of the report, “A Long-Range Plan for High-Energy Physics,” was to create a “20-year vision for the future.”
Bagger notes that the report isn’t just a simple path for getting from point A now to point B 20 years in the future. There is too much uncertainty inherent in two decades of future research, he says, for scientists to lay out that kind of path.
“Instead, we set out to make a roadmap to lay out all the opportunities,” he explains. “We know we can’t pursue all of them. And this roadmap will help us know the costs and interrelationships of the choices we make.”
The subpanel that created the report was composed of 21 physicists and the co-chairs, Bagger and Barry Barrish, a professor of physics at Caltech. Bagger says the panel included a representative sample of researchers from the various subspecialties of high-energy physics. Also included were European and Asian physicists.
The group held a series of town meetings and receptions at Department of Energy laboratories over the course of a year, and also participated in an American Physical Society meeting on the future of high-energy physics last summer. That meeting, held in Snowmass, Colo., drew approximately 1,000 participants.
Among the report’s most prominent recommendations were the creation of a national panel to prioritize the selection of “midsize” physics projects, which range from $50 million to $500 million; and the formation of a national committee to represent the interests of U.S. scientists and funding agencies in the linear collider, a project that physicists have proposed internationally as the world’s next high-energy particle collider.
Endorsed by Asian, European and American physicists, the linear collider project proposes that several governments pool their resources to create a new electron-positron collider capable of smashing subatomic particles together at unprecedented energies. Increasing the energy level at which they can work is key for high-energy physicists because breaking matter down into its most fundamental constituents means slamming the particles together harder and harder.
Bagger says scientists envision the project initially achieving energies of 500 gigaelectronvolts, a level about 2.5 times that of the most comparable collider currently in use. And they’re hoping it will be possible to scale the new collider up to twice that level, or about 1 teraelectronvolt.
Borrowing a metaphor from another science, Bagger says, “At those levels, we may be able to reveal the very DNA of matter.”
Scientists are hoping that the linear collider and another collider already under construction in Switzerland, the Large Hadron Collider, or LHC, will provide them with a complementary blend of just the right tools needed for putting together a unified theory of fields and particles, an achievement that’s been their holy grail for decades. In the course of getting there, Bagger says, physicists may reveal new dimensions, connect inner and outer space, and make significant advances in understanding dark matter and energy, two phenomena that have puzzled cosmologists for many years.
Physicists are hoping that the United States will try to host the new linear collider, particularly in light of the cancellation of the last U.S. attempt to build a major high-energy physics research facility. Bagger and others take care to emphasize the differences between the linear collider proposal and that earlier project, the superconducting supercollider. One of the biggest changes is the fact that the superconducting supercollider was solely funded by the United States, while the linear collider is proposed to be a multinational project. Another change is the suggestion from physicists that currently existing high-energy physics research funding be redirected toward the new project.
The subpanel members were in the process of writing their report on Sept. 11, 2001. In their final draft, released on Jan. 28, 2002, they stressed the importance of continued investment in the nation’s scientific and technical base as a component of maintaining national security. Panel members quoted passages from a U.S. Commission on National Security/21st Century that called inadequacies in education and research a greater threat to national security “than any potential conventional war that we might imagine.”
“Particle physics is highly collaborative,” Bagger says, “and we can’t say what the future will be like. But facilities like these do take a long time to build, so if we want to have something up and running not too long after the LHC comes online, we have to start identifying our priorities.”