What are the most basic building blocks of the universe? What are the forces that enable these elementary constituents to form all that we see around us? What unknown properties of these particles and forces drive the evolution of the universe from the Big Bang to its present state, with its complex structures that support life—including us? These are the questions that particle physics seeks to answer.
Particle physics has been very successful in creating a major synthesis, the Standard Model. At successive generations of particle accelerators in the US, Europe and Asia, physicists have used high-energy collisions to discover many new particles. By studying these particles they have uncovered both new principles of nature and many unsuspected features of the universe, resulting in a detailed and comprehensive picture of the workings of the universe.
Recently, however, revolutionary discoveries have shown that this Standard Model, while it represents a good approximation at the energies of existing accelerators, is incomplete. They strongly suggest that new physics discoveries beyond the Standard Model await us.
A set of interrelated questions defines the path ahead:
The three frontiers of research in particle physics -- the energy frontier, the intensity frontier and the cosmic frontier -- form an interlocking framework that addresses fundamental questions about the laws of nature and the cosmos. These three approaches ask different questions and use different techniques, but they are ultimately aimed at the same transformational science. Discoveries on one frontier will have much greater impact taken together with discoveries on the other frontiers. For example, the discovery of new particles at the energy frontier, combined with discoveries from the intensity frontier about neutrinos and rare processes, may explain the dominance of matter over antimatter. Synthesizing discoveries from all three frontiers creates the opportunity to understand the most intimate workings and origins of the physical universe.
New accelerator and detector technologies bring within reach the discoveries that may transform our understanding of the physical nature of the universe. The Particle Physics Project Prioritization Panel (P5) has recommended an R&D program to design a multi-megawatt proton source at Fermilab. This proton source, known as Project X, would open a path to discovery in neutrino science and in precision experiments with charged leptons and quarks.