U.S. Department of Energy

Pacific Northwest National Laboratory

Why it Matters

Some of the most compelling questions in modern science fall at the intersection of nuclear physics, particle physics, astrophysics, and cosmology (NPAC). This intersection occurs not only in the intertwined science drivers recognized by the P5 report, but also by the technological means for their pursuit.

Why it matters

Our field is on the cusp of a revolution, perhaps as profound as that encountered in the early 20th century when the Newtonian view crumbled before a new paradigm of Relativity and Quantum Mechanics. Modern physics offers a quantifiable and testable connection between the physics of the very small and the physics of the very large, encompassing the following broad and intertwined questions:

  • How did the Universe originate and evolve to the one we observe today?
  • How are the fundamental forces in Nature unified?

The Standard Model of Particle Physics has been remarkably successful in explaining phenomena in High Energy Physics that we have studied in Earth-bound laboratories over the past decades. It ties together the particles that make up the visible matter and their interactions, as shown above. Yet, it is also known to be incomplete.

It is remarkable to consider that the most elusive particles in Nature, neutrinos and dark matter, could be the reason that the Universe has evolved to the one observed today and ultimately the reason for why we are here! Our Initiative will directly attack fundamental questions integral to this timely challenge:

  • What is the neutrino mass and is the neutrino its own antiparticle? Is CP-symmetry violated in the neutrino sector, driving the matter-antimatter asymmetry of the Universe via leptogenesis? Are there additional states of matter such as sterile neutrinos?
  • What is the dark matter in the Universe and what are its properties? How can these properties be revealed using non-accelerator and accelerator-based experiments?

The quest to elucidate the nature of neutrinos and dark matter naturally couples fundamental physics on the subatomic scale to that on the cosmic scale. The technology to pursue this science necessarily relies on a non-accelerator program using expertise in nuclear and particle physics and the development of novel and ultra- sensitive detectors of the most rare events in Nature. The paradigm of new physics will also require advances in the accelerator physics program using fixed-target neutrino beams and to directly produce new phenomena in high-energy particle collisions. There is physics Beyond the Standard Model and it is available to be discovered.

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