Remarks by
Dr. Raymond L. Orbach
Director, Office of Science
U.S. Department of Energy

Second International Conference on
Particle and Fundamental Physics in Space (SpacePart '03)
December 10, 2003
Washington, D.C.

Abstract

The Office of Science is the single largest supporter of basic research in the physical sciences in the United States. It is the principal federal funding agency of the Nation’s research programs in high-energy physics, nuclear physics, and fusion energy science. Our high energy and nuclear physics programs are increasingly relevant to astrophysics and cosmology. We have long collaborated with other U.S. agencies and with other nations on research questions of common interest and this collaboration is increasing. Research facilities are an important Office of Science resource and our recently released “Facilities for the Future of Science: A Twenty-Year Outlook” has profound implications for investigations of the very small and the very large.

Introduction

From their earliest days, humans have taken things apart to see what they were made of, and looked at the moon and stars and wondered what they were.

We still look and we still wonder, but now with more powerful instruments and deeper understanding. My audience today includes some who take things apart and others who look up at the sky. Yet we all realize how closely these two lines of investigation are connected. To understand stars, supernovae, and the evolution of the universe, we must understand the elementary forms of matter and energy, nuclear matter, and their interactions. To understand these elements, we must study the universe, from its genesis to stars and galaxies and to dark matter and dark energy.

We have come a long way since early man, but we still have a long way to go. For example, just five years ago, we learned that most of the energy density in the universe consists of a new form called dark energy, which pushes the universe apart at an accelerating rate. The next largest part of its energy density is in the form of dark matter, which affects the motion of galaxies. Ordinary matter amounts to less than five percent.

We have a long way to go, but we have excellent vehicles for the journey. Astronomers and high energy and nuclear physicists are working together to understand our universe and the matter and energy it contains. Today I would like to tell you about some of these ways the Office of Science supports these explorations.

Key Questions at the Intersection

High energy and nuclear physics try to understand the fundamental constituents of matter, the fields that affect them, and the nature of nuclear matter. We have learned much, but still have important questions. For example, what is the origin of mass? Are matter constituents and forces related? Can the Standard Model be combined with gravity? Do nuclei dissolve into a quark-gluon plasma at high energies? What is the full significance of neutrino mass? Can we understand the dominance of matter over anti-matter in the universe?

Astronomers, astrophysicists, and cosmologists have also made great progress and yet have equally fascinating questions. How did the large scale structure of the universe form? How do black holes decay? How did the universe begin, why is it now expanding at an accelerating rate, and how will it end?

Physics and astronomy research programs are substantially independent. However, they do have some major intersecting interests, which were the subject of a study begun in 2000 by the National Research Council of the National Academies of Science. A special committee chaired by Michael Turner produced an excellent report last spring: Connecting Quarks with the Cosmos: Eleven Science Questions for the New Century. The report poses eleven key questions at the intersection of physics and astronomy. To answer these questions, those who look outward and those who look inward must work together.

Facilities Outlook

For both outer-directed and the inner-directed researchers, powerful facilities are essential: particle accelerators, underground detectors, astronomical observatories, powerful computing facilities. For accelerators, underground detectors, and computing, SC plays a leading role. To place an observatory in orbit requires the unique capabilities of NASA but DOE is involved in the instruments. NSF is leading on a possible national underground science laboratory, but DOE plays a leading role on detectors. The three agencies are working together and global collaborations are becoming more important.

In this context, it is imperative that the Office of Science fully operate its current facilities and plan for the future. We need a facilities plan that looks well ahead, setting priorities and considering feasible schedules for construction. With the help and advice of our six advisory panels, we have recently prepared such a plan.

Office of Science research facilities span a wide range of science: biology, chemistry, materials science, computer science, nuclear fusion, and physics. Some 18,000 researchers from universities, laboratories, private industry, and foreign nations use our facilities every year. We are the single largest supporter of the physical sciences in the United States, providing about 40 percent of all federal funds in this area. As Secretary of Energy Spencer Abraham often says, “The Department of Energy could just as well be named the Department of Energy and Science.” Indeed, science is one of DOE’s four Strategic Goals, as you can see in the DOE Strategic Plan released in September.

On November 10, Secretary Abraham released Facilities for the Future of Science: A Twenty-year Outlook. It describes 28 facility projects that we believe will be needed in the next two decades. They are listed in three groups according to when they would be needed: near-term, mid-term, and far-term. Obviously, decisions to carry out any of these projects will be made by the Administration and the Congress. With the Facilities Outlook, we have tried to think ahead and be prepared to follow where science leads.

At the top of our list for the near term is ITER, an international collaboration to build the first fusion science experiment capable of producing a self-sustaining fusion reaction, “burning plasma.” Our second near-term priority is to create an UltraScale Scientific Computing Capability to meet the exciting scientific opportunities across the Office of Science that require a 100- to 1,000-fold increase in computational capability. Two good examples are simulations of supernova explosions and black hole mergers. (http://www.pnl.gov/scales/)

Many SC facilities now operating are helping us to answer some of the eleven key questions, and with the facilities projected in our Facilities Outlook, we could address most of them. I will now speak to some of the ways that DOE’s Office of Science is involved in answering these questions.

What is the Nature of Dark Energy?

As you know, studies of Type Ia supernovas carried out by two teams of astronomers, one of them collaborating with high energy physicists at the Lawrence Berkeley National Laboratory (LBNL), recently unveiled a major surprise about the universe. Its expansion is speeding up rather than slowing down! The cause of this acceleration is attributed to a dark energy in the vacuum of space that causes an outward gravitational pull on the universe. The nature of the dark energy has not yet been explained, but it seems to make up more than 70% of the total energy content of the universe. This is one of the most important discoveries of the twentieth century.

To answer this question, a joint SC-NASA facility is now being planned. Called the Joint Dark Energy Mission (JDEM), it is high on the near-term list in our Facilities Outlook. JDEM will launch a dedicated wide-angle supernova telescope into space to investigate the question of dark energy much more thoroughly. By using such supernovas to map the history of the expansion of the universe we can learn about the ends of time – both its earliest birth pangs of inflation and its future destiny. JDEM is tied for third on the list of SC near-term facility priorities with three other projects.

Are There Additional Space-Time Dimensions?

A promising, if challenging, theoretical approach to unification is string theory, which represents elementary particles as “musical notes” of tiny loops of energy, called strings, and which requires extra dimensions of space-time. These could have such small extent that they don’t affect us, but might explain why gravity is so much weaker than the other basic forces: perhaps its effect is spread over more than three dimensions. Experimenters are already searching for evidence of extra dimensions; for example, a loss of energy from high energy particle collisions.

To include fermions (matter constituents) as well as bosons (force carriers) among the elementary particles it describes, a string theory must obey supersymmetry. This theory adds a boson partner for each fermion and a fermion partner for each boson and thus doubles the number of elementary particles.

Most of the superpartners are expected to be too massive to produce with the energies available at today’s accelerators, but some may be within their reach. Energy frontier accelerators like the Tevatron and the LHC may discover some of the lighter superpartners and provide good evidence that physics is supersymmetric at very high particle energies, like those that prevailed in the early universe.

The first item on our mid-term list of projects in the Facilities Outlook is a major new accelerator project, the Linear Collider (LC), which would be a substantial help in addressing the questions of unification, extra dimensions, and the early universe. The LC would collide electrons and positrons at high energies and allow investigations of these topics with remarkable power and precision. Because of the cost and worldwide appeal of the LC, it would be an international project from the outset.

What is Dark Matter?

The search for superpartners mentioned above also connects strongly with Dark Matter. A leading candidate for the dark matter is the lightest, stable supersymmetric particle (LSP). Superpartners should have been produced in the early universe and some may have survived until now. The fermionic partner of a neutral gauge boson is called a neutralino and may be the LSP. The neutralino is considered the best candidate for dark matter because of its high mass, perhaps about 100 times that of a proton. The Tevatron, LHC, or Linear Collider may discover the neutralino, or it may be seen in cosmic ray experiments like the Cryogenic Dark Matter Search (CDMS-II). This experiment, located in a deep mine, looks for the nuclear recoils when a WIMP interacts in cryogenic germanium or silicon detectors.

What Are the Masses of the Neutrinos, and How Have They Shaped the Evolution of the Universe?

Another weakly interacting particle, the neutrino, is abundant. Its mass is so small, however, that it can only account for a small fraction of the dark matter. The neutrino is very important in other ways, though. Its mass may help set the energy scale for unification and it plays an important role in the explosions of stars, where many of the atomic nuclei are formed. Neutrinos are created in specific types or “flavors” but oscillate among all three flavors as they travel through space. Experiments are underway to study neutrino oscillations using neutrinos from accelerators, nuclear reactors, and the sun.

Other experiments are planned to search for neutrinoless double beta decay and could measure neutrino mass if the neutrino is its own antiparticle (a Majorana neutrino). A double beta decay underground detector is a mid-term item in our Facilities Outlook.

Neutrinos were important in determining how many protons, deuterons, and lithium nuclei were formed in the early universe, because of their ability to change a neutron to a proton or vice versa. Neutrinos play an important role in supernovae, where some heavy nuclei are formed.

Neutrinos could also help explain the existence of any matter at all in the universe today. There seems to be no antimatter, although equal amounts of matter and antimatter must have been produced in the early universe and it should all have annihilated by now. DOE is helping to fund an experiment, the Alpha Magnetic Spectrometer (AMS), led by Professor Sam Ting, scheduled for the International Space Station looking for anti-matter if it exists in the universe today. A small asymmetry called CP violation that occurs in some weak processes could help explain how an excess of matter developed. The amount of CP violation observed in quark decays, however, does not appear to be sufficient to account for the observed amount of matter. If CP is also violated in the neutrino sector, it might be enough to resolve this mystery. A super neutrino beam is a far-term item in our Facilities Outlook and would be valuable for exploring this key question.

What Are the New States of Matter at Exceedingly High Density and Temperature?

Until the universe was a few microseconds old, it was hot enough that quarks and gluons were free particles, part of hot primordial plasma. A little later, it had cooled enough to condense into baryons, where they have been imprisoned by the strong nuclear force (QCD) ever since. This QCD phase transition may have left its signature in a gravitational wave signal; LISA will begin a search for such a signal. Quark-gluon plasma may also play a role in the interiors of neutron stars, and x-ray observations of them could shed light on its behavior. Meanwhile, nuclear physicists using the Relativistic Heavy Ion Collider at Brookhaven National Laboratory are colliding high energy beams of gold nuclei to see if they can form brief samples of quark-gluon plasma. An upgrade of the RHIC facility is one of the mid-term items in our Facilities Outlook.

How Were the Elements from Iron to Uranium Made?

Nuclei of the lightest elements were formed within the first few seconds of the universe, but heavier nuclei were not formed until much later (a billion years), when the nuclear furnaces called stars were formed. In stars and supernovae, nuclei up to iron were created, but we still don’t know where and exactly how heavier nuclei were formed. Supernovae or neutron stars are thought to be likely sites. To answer this question, we’ll need to work on several avenues at once. Full three-dimensional calculations of supernova explosions will need the ultrascale computation capability that I mentioned earlier. Neutrino parameters will be needed because neutrinos play an important role in supernovae. Experimental data on the r-process and r-p process nuclei far from stability will also be needed. A new accelerator called the Rare Isotope Accelerator (RIA), a near-term project in our Facilities Outlook, will use beams of short-lived nuclei to obtain these data. By combining RIA results with x-ray and gamma-ray observations of newly formed elements in supernovae, it may be possible to determine the source of the elements from iron to uranium.

How Do Cosmic Accelerators Work and What Are They Accelerating?

Extremely high energy (1019-1020 eV) cosmic rays have been observed, far beyond the highest energies we can produce with accelerators (1012 eV), and their origins are a mystery. They may be relics of the early universe. These mysterious rays are very rare, no more than one per square kilometer per year. To study them, a 3,000 square kilometer array of shower detectors called the Pierre Auger Observatory is being assembled in Argentina. About the size of Rhode Island, it uses Cerenkov light detectors, a technology developed for high energy physics experiments.

An international collaborative project called the Gamma Ray Large Area Space Telescope (GLAST), with strong participation by NASA and SC, is now being prepared to investigate the gamma ray sky. To be launched into earth orbit in 2006, it will look at high energy gamma ray bursts with energies from 10 MeV to more than 100 GeV, using a Large Aperture Telescope (LAT) that we are providing. Gamma rays emitted by active galactic nuclei are believed to be powered by accretion onto super massive black holes. GLAST could also detect gamma rays from annihilation of light supersymmetric particles in the galactic halo, thus helping physicists discover supersymmetry and helping astronomers explain dark matter.

Concluding Remarks

We live in an exciting era of fundamental science, with quantitative studies underway that will tell us about the origin and fate of our universe. There has been a fusion of sciences, so that for many important questions, it’s hard to see the boundaries that once separated physics, astrophysics, and cosmology. Quarks are indeed connected to the cosmos.

The same kind of fusion is taking place among federal agencies, with DOE’s Office of Science, NSF, and NASA now working closely together on important questions at the intersections of these fields of science. Secretary Abraham made a major policy speech for DOE when he unveiled our new Facilities Outlook for the next twenty years of science. In this unique presentation, the Secretary put science first and foremost. You can see his speech at the Web site given above.

I am optimistic and very excited about what we can learn in the coming years by working together and using ever more powerful research facilities. This is a great time to be a scientist!