U.S. Department of Energy

Pacific Northwest National Laboratory

Neutrino Physics and Fundamental Symmetries

Modern cosmological theory makes several accurate predictions that have been confirmed by observations. One key prediction, not yet confirmed, is that every cubic centimeter of the universe contains, on average, 336 neutrinos left over as relics of the Big Bang. If true, then neutrinos outnumber particles of “normal” matter in the universe, mostly protons and neutrons by mass, by a billion to one. Neutrinos were long assumed to be strictly massless and are built into the highly successful Standard Model of particle physics as such. However, many recent particle physics experiments have demonstrated that neutrinos do indeed have non-zero mass by observing the phenomenon of neutrino oscillations.  The leaders of the SNO and Super Kamiokande experiments were awarded the 2015 Nobel Prize for that discovery.

It is believed that their extreme lightness, mixing properties, and relationship to antineutrinos is related to the dominance of matter over antimatter in the universe through a process called leptogenesis. It is therefore in the early universe where we find the deep connections between neutrinos and other NPAC efforts.

Implications of the absolute neutrino mass scale in particle physics are profound, as it is probably related to the scale of new physics Beyond the Standard Model. Whatever mechanism is responsible for neutrino mass, it is likely not the Higgs Mechanism that generates the masses of force carriers in the Standard Model, and is thus a new phenomenon.

| Pacific Northwest National Laboratory