Costing about $130 million for the cyclotron pair, the DAEδALUS scheme would be much cheaper and smaller than the LBNE (see ‘Cyclotrons recycled’). The cyclotrons could not match the proton energies of Fermilab’s proton accelerators, but, partly by operating at a higher power, they would generate a comparable number of antineutrinos per second, and so produce a similar amount of data. They would also generate a cleaner beam of antineutrinos than the LBNE could, because the energy levels at which DAEδALUS operates allow the copper in the target to neatly separate out the positively charged pions that in turn generate the desired antineutrinos.
Pairs of cyclotrons could be set up at three different distances, or baselines, around the same detector, which would measure how many antineutrinos from each beam morph into a different type during flight. By operating simultaneously with three baselines, DAEδALUS could map the shape, or waveform, of the antineutrino oscillations. If there is asymmetry between matter and antimatter, the shape of these oscillations would take on a characteristic pattern — and there would be no need for the experiment to run separately with a beam of neutrinos.
The two experiments would both need large liquid detectors, but Conrad notes that Japan is already planning to build a water-based detector for astrophysical neutrinos that could work with DAEδALUS. The DAEδALUS accelerators are cheap and small enough that they could be reproduced and built up around pre-existing detectors, rather than the other way around. “The beauty of DAEδALUS is that you can forget about accelerators being stuck at laboratories,” says Conrad.
Other physicists are impressed. “It’s an imaginative proposal for how to address neutrino oscillations,” says Jonathan Rosner, a particle physicist at the University of Chicago in Illinois who oversees the Snowmass Study as chair of the American Physical Society’s Division of Particles and Fields.
LBNE co-spokesperson Milind Diwan of Brookhaven National Laboratory in Upton, New York, also says that the idea is technically interesting. But he says it is not yet proven or accepted, and that the United States needs to commit to a strong domestic program based around the DOE-approved LBNE in order to draw international funding.
If DAEδALUS features prominently in the Snowmass final report, expected in November, it could find a spot in the agenda set by the Particle Physics Project Prioritization Panel (P5), a group of DOE advisers who will convene shortly after receiving the Snowmass report and begin ranking projects. P5 is likely to recommend some US involvement in high-energy machines, both the LHC and a next-generation machine that Japan hopes to host, the International Linear Collider. The panel could also renew an emphasis, set in its 2008 report, on the intensity frontier, which led to the flagship LBNE proposal.
But some US physicists say that shrinking US budgets mean that projects may end up competing more on scientific merit and cost, rather than what they do for the status of any nation’s program. “We have to tighten our belts,” says Rosner. “It’s not just business as usual.”