Report on LBNF/DUNE-US Project Plan

The mission of the High Energy Physics (HEP) program is to support exploration of the physical universe through the discovery and study of the elementary constituents of matter and energy and the nature of space and time. These areas of research are an integral component for the advancement of all science and technology and an expression of society's timeless intellectual quest to understand the universe. The Standard Model of particle physics represents an unprecedentedly successful description of the elementary particles and their interactions; however, we know this model is incomplete and our - present understanding indicates the existence of a more fundamental underlying theory. Elucidating this deeper theory requires a broad research program at the complementary and interrelated Energy, Intensity, and Cosmic Frontiers of particle physics. At the Intensity Frontier, intense particle beams are utilized to investigate the properties of neutrinos and rare processes, both probes of new physics. Results from the last decade conclusively demonstrate that the three known neutrinos have nonzero mass, mix with one another, and oscillate between generations-properties which represent tantalizing hints of physics beyond the Standard Model. Cosmology indicates that the neutrino mass is less than one-millionth that of the electron, yet oscillation studies from experiments find tiny, but nonzero, mass differences between neutrino generations and large values for two of the three mixing angles. Currently, the individual masses are unknown and only an upper limit exists for the third angle. The recent progress in neutrino physics has laid the basis for new discovery opportunities. As a fundamental physical constant, measurement of the unknown third mixing angle is of great interest and will influence the direction and evolution of an international neutrino program. Determining the relative masses and mass ordering of the three known neutrinos will give guidance and constraints to theories beyond the Standard Model. The study and observation of the different behavior of neutrinos and antineutrinos traversing matter will offer insight into the dominance of matter over antimatter in our universe and, therefore, the very structure of our universe. The only other source of the matter-antimatter asymmetry, in the quark sector, is too small to account for the observed matter dominance. A popular hypothesis asserts that the asymmetry arises from neutrino interactions and is the subject of intense research. to deep underground location for possible future enhancements) and potential for attracting additional resources external to DOE to support possible future enhancements and a broader based physics program in support of mission need. Based on the above considerations, the alternative, Construct a new low energy neutrino beamline with a 10 kton liquid LAr-TPC surface detector at Homestake site in South Dakota, at a 1,300 km baseline distance from Fermilab, is the recommended alternative for LBNE. This preference is driven by the scientific advantages of a longer distance baseline between the neutrino source and detector afforded by siting the detector on the Homestake site. This alternative requires a new neutrino beamline to meet the necessary beam directional, energy and long-term operability requirements needed to initiate and sustain the LBNE program. This