Neutrinos—fundamental particles most often produced in the fiery hearts of stars—are both famously elusive and tremendously abundant. While neutrinos endlessly bombard every inch of the Earth’s surface at nearly the speed of light, they seldom interact with any matter. This ability to sail unhindered and unnoticed through almost anything earned neutrinos the nickname “ghost” particles. But despite their imperceptibility, neutrinos could be the key to understanding how our universe evolved just after the Big Bang and why the world is made of matter.
The Long-Baseline Neutrino Experiment will use the expertise of Fermi National Accelerator Laboratory’s existing accelerator complex to supply its neutrinos. Fermilab’s Main Injector Ring will smash energetic protons into a fixed target—this collision produces short-lived and exotic particles called pions and kaons. These particles then pass through a “decay pipe,” transforming into an intense beam composed of densely packed neutrinos.
From Fermilab’s location just outside Chicago, IL, the intense neutrino beam will travel 800 miles (1300 kilometers) through the Earth’s mantle before striking its target at the Homestake Mine in Lead, South Dakota. This distance, not much more than a blink for speedy neutrinos, gives the particles time to exhibit one of their strangest and most exciting quirks: flavor transformations.
Neutrinos oscillate between three distinct flavors: muon, tau, and electron. The discovery of this behavior, also called mixing, resulted in one of Brookhaven Lab’s Nobel Prizes, and it continues to be one of the most promising puzzles in Physics.
Most of the neutrinos sent from Fermilab will begin as the muon type, and LBNE will measure these particles as they cross state lines, transforming and passing through the far detector in South Dakota. This 10-kiloton technological marvel will be filled with super-cold liquid argon. As the neutrinos interact with the argon atoms, they create ionized electrons. These newly minted electrons are then manipulated by an electric field, causing interactions with custom-designed wire planes that provide clear evidence of the traveling neutrinos.