May 7, 2004  




What’s a Nice Field Like Particle Physics Doing in a Universe Like This?

By Judy Jackson

The quarks. The leptons. The bosons, the mesons, the hadrons, the so-forth-and-so-ons.

The committee unveiled the report ‘Quantum Universe’ at the April HEPAP meeting in Washington D.C. (Image Courtesy of Judy Jackson)

Particle physicists spent the 20th century discovering, in incredible depth and with amazing precision, the particles that make up the world and the forces that determine how it works. The result was the Standard Model, the theory that answered the question “What is the Universe made of?”

Then they went and changed the Universe.

Recent astrophysical and cosmological discoveries have revealed the astonishing fact that the Universe we thought we knew is only about five percent of what’s out there. The rest is....well, we don’t know what it is. We call it dark matter and dark energy, for lack of better terminology. Dark matter is what’s holding the Universe together. Dark energy is some unknown force that is driving it farther and farther apart.

Some have compared this revolution to Copernicus’ 16th century recognition that we aren’t at the center of the solar system. We have realized that we do not really know what our Universe is made of.

“Nothing’s bigger than the Universe,” wrote Science Editor-in-Chief Donald Kennedy. “The question is what it’s made of.” Science magazine called the confirmation of a dark Universe the Breakthrough of the Year for 2003.

Where Particle Physics Comes In

A High Energy Physics Advisory Panel (HEPAP) committee, appointed by Chair Fred Gilman and led by Persis Drell (RD), spent the past five months working on a report that explains what the field that brought you the Standard Model is doing in a Universe of matter and energy unlike any we have ever seen before.

“Recent scientific discoveries at the energy frontier and in the far reaches of the Universe have redefined the scientific landscape for cosmology, astrophysics and high energy physics, and revealed new and compelling mysteries,” wrote the DOE and NSF officials responsible for U.S. particle physics research. “We are writing to ask the High Energy Physics Advisory Panel to take the lead in producing a report which will illuminate the issues, and provide the funding and science policy agencies with a clear picture of the connected, complementary experimental approaches to the truly exciting scientific questions of this century.”

Drell said the report articulates a set of questions that define the science of 21st century particle physics and discusses how both current and future particle physics experiments can address those questions.

“This has been a great committee,” Drell said. “The opportunity to collaborate with people from many different branches of physics has been a privilege. We have worked hard but also had a lot of fun. It is an exciting time in particle physics, and we hope that our report will help serve as a guide to where the search for understanding has taken us so far, and to where it is going.”

“It’s been an interesting process,” said theorist Joe Lykken, one of four Fermilab members of the committee. “We wanted to make clear that the questions particle physics has always asked have not changed, but that they have a revolutionary new meaning in the context of these recent discoveries about the nature of the Universe.”

The Quantum Universe report is available on-line at:

Article excerpted from FermiNews, Vol. 27, April 2004, No 4.


The Stanford Linear Accelerator Center is managed by Stanford University for the US Department of Energy

Last update Tuesday May 04, 2004 by Emily Ball