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M. Shaevitz: Daedalus and IsoDAR

March 4, 2015

IsoDar is a cyclotron for a very short baseline search for sterile neutrinos, working at 60 MeV as a source.

There are many experimental hints for sterile neutrinos. One way to look for them is to use a very short baseline and study oscillations, possibly within the detector (a variation of interaction rate in the longitudinal direction).

Using a 600kW proton beam one can impinge on a 9Be target, and study the electron antineutrinos at a distance of the order of 16 meters. One can thus have a high-statistics, compact source, a well-understood energy spectrum dominated by beta decay of 8Li.

The experiment can run at a number of places, like KamLAND, but JUNO and others are possible. With KamLAND laser surveys have been going on. The sensitivity to antineutrino disappearance, coming from wiggles in the flux, should get to 5-sigma in one year, seeing a signal where the anomaly was observed in the sin^2 2theta vs delta m^2 plane. Coupled with KamLand, IsoDAR’s high statistics and good L/E resolution has the potential to distinguish the 3+1 from the 3+2 oscillation modes.

Coupled to Juno, which has excellent energy and verted resolution, one can completely cover the LSND signal region with a disappearance experiment, which would conclusively rule it out.

DaeDalus is a search for CP violation using electron antineutrino appearance. The L/E dependence of the muon antineutrino to electron antineutrino oscillation is studied. One can use multiple neutrino sources at different distances to map out the appearance rate. One would have three sites. Pion decays at rest are the source. At 1.5 km one would constrain the initial flux, at 8km one would see the rise of the probability wave, and at 20km one would observe the oscillation maximum. This requires a single ultra-large detector with free protons where to do inverse beta decay, constituted e.g. by oil on water.

The possibilities for DaeDalus are Hyper-K (or, initially, Super-kamiokande), and LENA. Liquid argon is not an option for this kind of experiment. In Hyper-K there would be good CP sensitivity as a stand-alone experiment, with small cross section, flux, and efficiency uncertainties. Long baseline experiments have trouble obtaining good statistics for electron antineutrino appearance, which Daedalus can provide.

In summary, high-power-class cyclotrons (1MW) are becoming a reality, offering physics potential as high intensity neutrino sources; they of course have also important industrail interest for medical isotope production. They can help establishing the existence of sterile neutrinos, and study CP violation in the neutrino sector.

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