The mission of the High Energy Physics program is to understand how our universe works at its most fundamental level. We do this by discovering the most elementary constituents of matter and energy, exploring the basic nature of space and time itself, and probing the interactions between them. These fundamental ideas are at the heart of physics and hence all of the physical sciences. To enable these discoveries, HEP supports theoretical and experimental research in both elementary particle physics and fundamental accelerator science and technology. HEP underpins and advances the DOE missions and objectives through this research, and by the development of key technologies and trained manpower needed to work at the cutting edge of science.
The Office of High Energy Physics promotes a broad, long term particle physics program at three interrelated frontiers of particle physics. The office supports current operations and experiments and research and development for future facilities and experiments.
- The Energy Frontier directly explores the fundamental constituents and architecture of the universe. Here accelerators produce the highest-energy particles ever made by man; collisions of these particle beams produce unusual and new particles. Sophisticated detectors observe the final state particles, providing insight into the fundamental interactions and windows to the conditions of the early universe.
- The Intensity Frontier, accessed with a combination of intense particle beams and highly sensitive detectors, offers a second, unique investigation of fundamental interactions. Neutrinos, though ubiquitous in the universe, are elusive and require populous beams and vast detectors to observe. Measurements of the mass and other properties of neutrinos have profound consequences for understanding the evolution of the universe. Observations of rare processes, that require exquisitely sensitive detectors as well as intense beams, also explore high energies, providing an alternate, powerful window to the nature of fundamental interactions.
- The Cosmic Frontier reveals the nature of dark matter and dark energy by using particles from space to explore new phenomena. Cosmic rays in the earth’s atmosphere, neutrinos from the sun, and gamma rays from deep space, are some of the known natural sources. Searches are also underway for alternate explanations of dark matter and energy. Observations of the cosmic frontier reveal a universe far stranger than ever thought possible. The new techniques at the cosmic complement the accelerator-based research of the other frontiers.
These scientific frontiers form an interlocking framework that addresses fundamental questions about the laws of nature and the cosmos.
High Energy Physics Enablers
One can’t build a house without a hammer and a saw. Likewise, you can’t construct the edifice of particle physics without accelerators, detectors, and computers. These are the tools of the physicist, the foundations upon which scientific discovery rests.
Accelerators—Without accelerators able to collide ions and electrons together to make new particles that haven’t existed since the early universe, the Standard Model of Particle Physics would not have coalesced in the late 20th C. Over the years, accelerators have gotten more and more powerful—and more expensive to build--as we probe deeper into the fundamental nature of matter and energy. Today we search for physics beyond the Standard Model, and the challenge for accelerator physics is how to attain even higher energies and greater beam intensities so that whole new worlds of physics swing into view.
Detectors—Many high energy physics detectors are monumental in size. They need to be in order to stop, track, and record the energetic particles that pass through them. Other detectors need to be large in order to catch rare or difficult to detect particles. Their size increases the probability of an event and its detection. Many detectors also need to be radiation resistant and to work in harsh environments all the while returning useful data. And still others require technological developments to reduce size and cost or improve efficiency or are required to develop a technology to detect particles not yet proven to exist. Like accelerators, detectors and detector R&D are cornerstones of modern physics
Computers—Modern high energy physics experiments produce massive amounts of data. And sometimes what the physicist is looking for is a needle in a haystack. The data must be captured and stored and distributed to end users who search through the mountains of data for telltale signatures of physics events of interest. Higher energy accelerators, and bigger and better detectors, increase the rate in which data are accumulated. Advances in computers must keep pace with the all the developments in the field.
A Path Forward
Scientific progress at the Energy, Intensity, and Cosmic Frontiers is dependent not only upon the enablers of high energy physics experiments but also upon the intersection of another three spheres, those of Theory, Simulations, and Experiments. How these three spheres interact provides a path forward that increases our scientific understanding of physical reality.
Theory—A theory provides a framework to explain what we observe. It takes what seem to be unrelated observations (for example, galaxy red shifts and cosmic microwave background) and shows how they are related (the Big Bang). The theoretician works at the boundary between what is experimentally known and unknown. Any good theory must be able to make predictions that are verifiable. And so the theoretician and experimentalist work hand in hand: the experimentalist provides data and either confirms or refutes a theory, and the theoretician points the experimentalist where to look and for what.
Simulations—Between Theory and Experiment lay Simulations. They can be used to help calibrate a detector or they can embody a theory and generate simulated data that can be compared with experimental data. If the simulated data compares well with experimental data, we say that the theoretical model accurately depicts physical reality. Sometimes, various theories are used to simulate data to understand the differences in their expectations. They make manifest where the experimentalist should look to find a signature to help decide between competing theories.
Experiment—HEP’s scientific experiments provide validation of our understanding of the world about us. Without this validation-- this hard data--our ideas about the physical world remain conjecture and speculative. At their best experiments supply new and unexplained data or allow us to decide between competing theories. Experimental results increase our knowledge of the universe and lead the theoretician to dream new possibilities that, if true, would require further experimental confirmation at the frontiers of our knowledge.