Report urges major effort to site collider in US

A National Research Council committee, charged with charting the course of US particle physics over the next 15 years, has released its report. Because particle physics is a costly business requiring broad support within the intellectual community—not to mention the government—several of the committee’s 22 members, including its chair, economist Harold Shapiro, biologist Harold Varmus, and former Lockheed–Martin CEO Norman Augustine, were not physicists.

Entitled Revealing the Hidden Nature of Space and Time, the 125-page report (available from the National Academies Press at http://www.nap.edu/catalog/11641.html ) contrasts the undeniable excitement and promise of particle physics at the start of the new century with the unmistakable downward trend of experimental facilities and programs in the US. The Superconducting Super Collider was cancelled in 1993 in mid-construction. With the Large Hadron Collider (LHC) about to start operation at CERN, Fermilab’s Tevatron is unlikely to outlive the decade. Neither is the PEP-II asymmetric electron–positron collider at SLAC nor the Relativistic Heavy Ion Collider at Brookhaven National Laboratory.

Why should that matter? “Particle physics plays an essential role in the broader enterprise of the physical sciences,” says the report. “It inspires US students, attracts talent from around the world, and drives intellectual and technological advances in other fields.” As particle physics and its connection with cosmology enter “an era of unprecedented potential, the US should remain globally competitive … by playing a leading role in the worldwide effort to aggressively study terascale physics,” that is, accelerator-based experiments at collision energies of order 10¹² electron volts (1 TeV).

To that end, the report makes three principal recommendations to US funding agencies: They should undertake a “comprehensive program to [make the US] the world-leading center” for developing the science and technology of the International Linear Collider—a proposed TeV e⁺e^– collider—and “do what is necessary to mount a compelling bid to build the proposed ILC on US soil.” Furthermore, they should “fully exploit the opportunities afforded by the LHC” by adequately supporting US groups that will soon be taking data at the 14-TeV proton–proton collider. Finally, lest these programs at the terascale frontier cause neglect of very important particle physics at lower energies, the report urges the expansion of particle-astrophysics programs and the pursuit of “an internationally coordinated, staged program in neutrino physics.”

The ILC is the highest-priority facility on the US particle-physics community’s wish list. After the LHC has surveyed the first rough outline of the terra incognita beyond 1 TeV, an e⁺e^– collider would carry out the precision measurements that are thought to be essential for extracting the full meaning of the LHC discoveries. The report does not quote an explicit cost for building the ILC. But with an estimated price tag on the order of $10 billion, the 30-km collider would obviously have to be thoroughly international from the start. Two years ago, a panel of the International Committee for Future Accelerators settled on superconducting RF acceleration technology for the ILC (see Physics Today, October 2004, page 34 ).

It is expected that the host country would have to pay about half the ILC’s construction cost. But the alternative to bearing that expense would require a generation of US particle physicists to do their experiments abroad. More important, says committee member Jonathan Bagger of Johns Hopkins University, would be the consequent loss of US leadership in this field. The committee’s report urges a concerted effort to avoid that prospect. “What we’ve recommended,” says Sally Dawson, a committee member from Brookhaven, “is the thoughtful pursuit of a high-risk, high-reward strategy.” But even riskier, thinks chairman Shapiro, would have been “to continue on the current trajectory without doing anything.”