Particle Physics at a Crossroads, Academy Study Finds

This is an exciting time in particle physics, and the United States should increase its investment in the field to maintain leadership, says a National Academy of Sciences report released in April.

The report, titled Revealing the Hidden Nature of Space and Time, said that the field of particle physics is now at a crossroads, as several major experiments are scheduled to end soon. The report identified several priorities for US particle physics in the next 15 years. The main recommendations, in priority order, are:

1. First, support American scientists working at the Large Hadron Collider
2. Second, invest in the necessary research and development in order to make a compelling bid to host the International Linear Collider
3. Third, expand the program in particle astrophysics and pursue an internationally coordinated program in neutrino physics.

Harold Shapiro, an economist and former President of Princeton University, chaired the NRC's Committee on Elementary Particle Physics in the 21^st Century which drafted the report. He announced the panel’s recommendations at a press conference April 26 in Washington.

Several major particle physics experiments will come to an end soon, the committee noted. Fermilab is scheduled to shut down around 2010. Shapiro said he had been disappointed to learn that no plan was in place for the future. “When we looked at the status of high-energy physics in the US, we were sobered,” he said. “We had no compelling follow-on program.”

The report says that the United States should play a leadership role in the worldwide effort to study Terascale physics, and accelerators are an essential component of this effort.

The panel recommends spending $300 to $500 million over the next five years on research and development for the accelerator for the proposed International Linear Collider. The panel also recommends that the US expresses its strong intent that the ILC will be built in the United States.

Shapiro noted that this is a risky strategy, but said that doing nothing would be even riskier. If nothing is done, US particle physicists will be forced to work abroad, and students will lose interest in the field, he said.

Experiments at the Terascale may soon enable physicists to answer some exciting questions, such as where particle masses come from, whether the forces of nature are unified at some energy scale, whether space and time have extra dimensions, and what makes up the dark matter. The LHC, scheduled to begin operation in 2007, could discover the Higgs boson, evidence of supersymmetric particles, or evidence of new physics. The ILC, which will collide electrons and positrons, will be able to clarify and provide more details about any discoveries made by the LHC.

“This might be the most exciting moment in particle physics in a generation” said Shapiro.

In the short run, the panel found, funds could be reallocated from experiments that are ending in the next few years. But an increase in resources will be needed to sustain US leadership in particle physics. The panel says the budget for particle physics needs to increase by at least 2% to 3% per year in real terms.

The committee also discussed how to avoid the kind of problems that led to the cancellation of the SSC by Congress in 1993. Shapiro said that the committee believes the ILC is on a better path because it will be an international collaboration from the very beginning.

The 22-member committee included particle physicists, physicists in other fields, and non-physicists.

This unusual composition of the committee meant that the physicists had to work harder to make the case for why particle physics is important.

Committee member Jonathan Bagger of Johns Hopkins University said that it was clear that American particle physics is at a crossroads, and it was important to have people outside of physics look at the field.

The report is part of the Physics 2010 project, a series of National Research Council studies that will explore opportunities and priorities for many branches of physics.