That cooperation may be essential given the scope of some of the detectors planned for a South Dakota mine shaft: 40 kilotons of liquid argon in one detector and the prospect of building a second, water-filled one. These enormous detectors are needed to get results up to a useful statistical significance. To feed them with enough neutrinos, the production facility at Fermilab will need to be upgraded with a high-energy, high-throughput linear proton accelerator.
Explore the unknown: New particles, interactions, and physical principles. That proton beam is meant to feed additional experiments housed at Fermi itself as part of an effort toward what’s being called the “intensity frontier.” By producing many events with a high-intensity proton beam, scientists can examine things that are otherwise rare events in machines like the LHC.
One of these events involves the prospect that other particles undergo the identity-changing oscillations we’ve seen in neutrinos; specifically, the Mu2e project will try to determine if, under the right conditions, muons can ever shift identities, converting to electrons. Separately, the Muon g-2 experiment will measure the magnetic properties of muons, which preliminary work suggests deviate from Standard Model predictions. Both of these projects are ready to build, which is why the report recommends shifting money toward construction over the next several years.
Identify the new physics of dark matter Dark matter hasn’t made its presence known in the collisions of the LHC. But colliders aren’t the only option for detecting it. Under many theoretical models, dark matter interacts with normal matter, albeit rarely and very weakly. We’ve built what the report considers the first generation of detectors designed to pick up these weak interactions, and it recommends a second generation of follow-up experiments, as well as preparing to build a third generation.
There’s also the possibility that dark matter particles can collide with each other, resulting in high-energy photons. Currently, those photons have been studied with space-based observatories, but the report recommends following up on pioneering ground-based gamma-ray observatories, building ones tuned to pick up dark matter annihilations.