4: Explore the Fundamental Interactions of Energy, Matter, Time, and Space

Understand the unification of fundamental particles and forces and the mysterious forms of unseen energy and matter that dominate the universe, search for possible new dimensions of space, and investigate the nature of time itself.

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Executive Summary: With next-generation accelerators, we will test and extend our views of the most basic constituents of matter, and perhaps see the validation of a grand unifying theory of the fundamental forces that govern our world — the goal of particle physics for decades. On the cosmological scale, we hope to reveal the nature and behavior of the enigmatic dark matter and dark energy that we believe account for the bulk of the mass of our universe, and that are responsible for the very startling recent discovery that the expansion of our universe is accelerating. Detailed Commentary: Led by great physicists like Galileo, Einstein, and Heisenberg, we have learned much about the universe. In the early 20th Century, we learned that it is expanding and that space-time is curved. We discovered the quantum nature of matter, a profound advance with many practical benefits. We learned that all matter is built of just 12 types of particles interacting by four basic forces. Nevertheless, we are continually humbled by what we do not understand. For example, we learned recently that the expansion of the universe is accelerating, not slowing down as we had thought. This astonishing fact is attributed to “dark energy” that accounts for nearly three-quarters of the energy of the universe. Nearly a quarter of the energy is made up of another mysterious substance dubbed “dark matter.” Only around 4% is ordinary matter. These are a few of the basic questions yet to be answered: • How were the patterns of particles and forces we see today unified in the early universe? • What is the nature of dark energy? Of dark matter? Why do they make up most of the universe? • Are there more than four dimensions of space-time? If so, how can we detect them? Answering these questions will reveal much about the creation and fate of our universe. Computing resources that dwarf current capabilities will be unleashed on challenging calculations of subatomic structure, while new accelerators will be needed to investigate unification at high energies. Understanding unification and the cosmos is a challenge, but one that is well suited to the large-scale research teams and international partnerships that we bring together. As an integral part of this Strategic Plan, and in Facilities for the Future of Science: A Twenty-Year Outlook, we have identified the need for four future facilities to realize our High Energy Physics vision and to meet the science challenges described in the following pages. Two of the facilities are near-term priorities: the Joint Dark Energy Mission (JDEM) and the BTeV. JDEM is a space-based probe, developed in partnership with NASA, designed to help understand the recently discovered mysterious “dark energy,” which makes up nearly three quarters of the universe and evidently causes its accelerating expansion. BTeV (“Bparticle physics at the TeVatron”) is an experiment designed to use the Tevatron proton-antiproton collider at the Fermi National Accelerator Laboratory (currently the world’s most powerful accelerator) to make very precise measurements of several aspects of fundamental particle behavior that may help explain why so little antimatter exists in the universe. All four facilities are included in our High Energy Physics Strategic Timeline at the end of the chapter and in the facilities chart in Chapter 7 (page 93), and they are discussed in detail in the Twenty-Year Outlook. Our Strategies: In developing strategies to pursue these exciting opportunities, the Office of Science has been guided by long-range planning reports: The Way to Discovery (2002), High Energy Physics Advisory Panel (HEPAP); and Connecting Quarks with the Cosmos (2003), National Research Council. Our Timeline and Indicators of Success Our commitment to the future, and to the realization of Goal 4: Explore the Fundamental Interactions of Energy, Matter, Time, and Space, is not only reflected in our strategies, but also in our Key Indicators of Success, below, and our Strategic Timeline for High Energy Physics (HEP), at the end of this chapter. Our HEP Strategic Timeline charts a collection of important, illustrative milestones, representing planned progress within each strategy. These milestones, while subject to the rapid pace of change and uncertainties that belie all science programs, reflect our latest perspectives on the future— what we hope to accomplish and when we hope to accomplish it— over the next 20 years and beyond. Following the science milestones, toward the bottom of the timeline, we have identified the required major new facilities. These facilities, described in greater detail in the DOE Office of Science companion report, Facilities for the Future of Science: A Twenty-Year Outlook, reflect time-sequencing that is based on the general priority of the facility, as well as critical-path relationships to research and corresponding science milestones. Additionally, the Office of Science has identified Key Indicators of Success, designed to gauge our overall progress toward achieving Goal 4. These select indicators, identified below, are representative long-term measures against which progress can be evaluated over time. The specific features and parameters of these indicators, as well as definitions of success, can be found on the web at www.science.doe.gov/ measures. Key Indicators of Success: • Progress in measuring the properties and interactions of the heaviest known particle (the top quark) in order to understand its particular role in the Standard Model. • Progress in measuring the matter-antimatter asymmetry in many particle decay modes with high precision. • Progress in discovering or ruling out the Standard Model Higgs particle, thought to be responsible for generating the mass of elementary particles. • Progress in determining the pattern of the neutrino masses and the details of their mixing parameters. • Progress in confirming the existence of new supersymmetric (SUSY) particles, or ruling out the minimal SUSY “Standard Model” of new physics. • Progress in directly discovering or ruling out the existence of new particles that could explain the cosmological “dark matter.”

Objective(s):

4.1: Unification Phenomena

4.2: The Cosmos

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