First Step Towards A New Proton Decay Experiment In Ice

摘要

Grand Unified Theories (GUTs) predict a finite lifetime for the proton. The most recent limit, reported by0+ e+) correspondsto 1.01 × 1034years. In the supersymmetric extensions of SU(5), the lifetime of the proton is expected to be lowerthan 1036years. To reach 1036years sensitivity to proton decay requires a detector with a volume on the megatonscale sensitive to sub-GeV energy. Where and how such a detector might ever be realized remains an open challenge.Installation of massive detectors underground is presently a technological challenge with costly excavation, engineeringand installation. We consider here the ice cap at the South Pole which might provide an alternative scenario for a megatonring imaging Cherenkov experiment in the search for proton decay. The ice, studied by the IceCube Collaboration, ismeasured to be extremely pure and transparent. Further, IceCube has demonstrated the ability to instrument a detectorvolume at the gigaton scale on-schedule and on-budget. The 86 strings of IceCube photosensors provide sensitivity toparticle interactions with energies between tens of GeV up to extremely high energies. Given the success of the IceCubeproject in instrumenting the world's largest Cherenkov neutrino detector, and the DeepCore sub-array to extend the reachto low-GeV physics, it seems reasonable to consider the question if the same principle of IceCube, using the Cherenkovmedium as the detector support infrastructure, could provide a cost effective and simplified path to instrument megatonscale detectors with sufficient photocathode area to permit a viable proton decay experiment sensitive to 1036 year lifetime and beyond. In this paper we present the very first steps of a developing design study for a proton decay detector to bepotentially deployed in the center of IceCube-DeepCore, based on Geant4 and the IceCube software with realistic opticalproperties of the glacial ice.