Highest-Intensity Neutrino Beam on the Planet

thumbnail Graphical rendering of Fermilab's Main Injector accelerator (cyan and magenta magnets at bottom) and the extraction region for the LBNF primary beamline (magnets at top) as the LBNF beam exits through the (green) wall, and begins its arc up and over the apex of the hill (not shown) in which the beam is pointed in the right direction.

Supplying neutrinos to DUNE

A neutrino is an elementary particle that is at least a million times lighter than an electron and has no electric charge. Neutrinos are harmless particles that are among the most abundant — yet least understood — in the universe; they are a billion times more abundant than the particles that make up stars, planets and people. These tiny particles have no electric charge and mostly pass right through the empty space in the atoms that make up ordinary matter, very rarely interacting with it. Therefore, not only are they harmless, but very challenging to observe!

Experiments carried out over the past half century have revealed that neutrinos are found in three states, or flavors, and can transform from one flavor into another. These results offer the most compelling evidence to date for physics beyond the Standard Model. In a single experiment enabled by LBNF's high-intensity neutrino source, generated from a megawatt-class proton accelerator, DUNE will conduct a broad exploration of the three-flavor model of neutrino physics with unprecedented detail. The 800 mi (1,300 km) separation ("baseline") between the neutrino source and the far detector delivers optimal sensitivity to this physics.

The Long-Baseline Neutrino Facility (LBNF) will build on an already extensively developed plan for a beamline and related facilities to support this world-class experiment. How do you make a neutrino beam?

Why neutrinos?

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Neutrinos were created in vast numbers just after the Big Bang and were virtually alone in their ability to penetrate the early dense universe. These tiny particles are therefore crucial to understanding the origins of our universe. The discovery that neutrinos have mass, contrary to what was previously thought, has revolutionized our understanding of neutrinos in the last two decades while raising new questions about matter, energy, space and time. Neutrinos may play a key role in solving the mystery of how the universe came to consist of matter rather than antimatter. They could also unveil new, exotic physical processes that have so far been beyond our reach.

The Neutrino Beam

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Using Fermilab's Main Injector accelerator as a proton source, the Long-Baseline Neutrino Facility's beamline is expected to make the highest-intensity neutrino beam in the world – i.e., the most highly concentrated beam of these particles that travel at nearly the speed of light.

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Cartoon of planned LBNF Beamline

The Proton Improvement Plan-II (PIP-II), a proposed facility for Fermilab that would significantly increase the number of protons the Main Injector could supply, would provide increased intensity for LBNF's neutrino beam.

Through the Earth

thumbnail Courtesy Homestake Adams Research and Cultural Center

The neutrinos will travel 1,300 km from Illinois (the near site) to South Dakota (the far site) through the earth's mantle. The newly formed DUNE science collaboration will provide massive underground detectors at the far site to record neutrinos and study their properties with unprecedented precision. Smaller detectors at the near site will collect data that will enhance the performance of the overall experiment as well as make independent measurements and conduct sensitive searches for new physics.

How do you make a neutrino beam?

Watch this short video that explains the neutrino-making process.

The processs starts by extracting a proton beam from an accelerator complex and smashing the protons into a target. The protons' interactions with the protons and neutrons in the target material produce new, short-lived particles such as pions and kaons. These particles travel a short distance (about 200 m) through a "decay pipe," and as they do, a good fraction of them decays into neutrinos that continue on in the same direction, forming a neutrino beam. Of the three known neutrino types, a beam produced in this manner contains mostly muon neutrinos.

Using Fermilab's Main Injector accelerator as a proton source, the proposed LBNF beamline will be able to make the highest-intensity neutrino beam in the world.

Like the beam of light produced by a flashlight, the beam of neutrinos produced by an accelerator widens over distance. To make sure that a sufficiently large number of neutrinos hits the particle detector, located hundreds of miles away, the beam must be highly concentrated, highly focused and aimed precisely in the right direction. Because neutrinos have no electric charge, there is no way to change the direction of a neutrino once it has been created.