Yesterday, the US Department of Energy released a roadmap for the projects it would like to pursue over the rest of this decade. The report lays out five major priorities for the physics community and lists a set of projects that can be built to meet them. To make sure those projects are completed, it recommends an increased emphasis on funding actual construction (as opposed to technology development or research) over the next several years. All of which sounds good—until you recognize that the report's worst-case budget scenario is better than the Obama administration's budget request for this research.

It's worth going through each of the five points and the projects that serve them.

Use the Higgs boson as a new tool for discovery. For the foreseeable future, the Large Hadron Collider is the only game in town for the Higgs, and the US is already heavily involved. Upgrades have been completed that will allow the LHC to reach its full design energies, and the US is committed to further upgrades that will increase its luminosity—the number of collisions per unit time—and upgrade the detectors to cope with the increased load.

The report calls for the US to contribute to the technology development for the International Linear Collider, which would further characterize the Higgs. But the call is a bit tepid, which suggests that, for now, it involves little money and only focuses on areas where there is strong expertise.

Pursue the physics associated with neutrino mass. Neutrinos could have a lot to tell us about physics beyond the Standard Model, and the report says that the US is poised to be a leader in their study thanks to the Large Baseline Neutrino Experiment. It also says that the project should be expanded to the LBNF, with the "F" standing for "facility." This move would open it up for international cooperation rather than making it a US-centric facility.

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.

Understand cosmic acceleration: Dark energy and inflation. Astronomy is the new particle physics. That's part of the message of the dark matter search and pretty much the whole angle for dark energy, which is driving the accelerating expansion of the Universe. Right now, we don't know enough about dark energy to even know if it makes sense to lump it into particle physics, and the only way we can learn more is to better characterize how it's acting. And that means looking at the expansion of the Universe.

Unfortunately, one of the more promising approaches for doing so, the Dark Energy Spectroscopic Instrument (DESI), is right on the edge of the funding lines considered in the report—accordingly, it's the first to be cut if the funds are tight. DESI would map the motion of all the galaxies within a 10 billion light year sphere centered on Earth. It's not the only instrument that's in the report that will look into dark energy, but it's the only project that will be funded in the high-budget scenario.

Dead on arrival

All of the budget scenarios were undoubtedly intended to seem reasonable, as they included several years of flat spending before a return to weak growth of two to three percent per year. But the present budget request for high energy physics would see spending cut by nearly seven percent. Unless Congress acts to restore the budget, some of the projects that were viewed as guaranteed of funding in this report would take a very heavy hit.

Perhaps that's why the report starts with the following: "Panel reports usually convey their results logically and dispassionately, with no mention of the emotional, soul-searching processes behind them. We would like to break with tradition."

The paragraphs that follow include a number of emotional calls to recognize the importance of high-energy physics:

Our society’s capacity to grow is limited only by our collective imagination and resolve to make long-term investments that can lead to fundamental, game-changing discoveries, even in the context of constrained budgets.

...

Wondrous projects that address profound questions inspire and invigorate far beyond their specific fields, and they lay the foundations for next-century technologies we can only begin to imagine.

There's always the chance that these sorts of appeals will be enough to sway a budget-minded Congress.

The sentence describing DESI was changed to more accurately reflect the considerations of this report.