Photomultiplier tubes can be used to detect Cerenkov radiation produced by these particles interacting with electrons in heavy water and pure water detectors such as the Sudbury Observatory and Super Kamiokande detector.  
Extrasolar ones may be found by the cosmic ray detector AUGER (pron. oh-ZHAY) via horizontal air showers.  Because they were not warmed by electron-positron annihilation, they should have a 2 Kelvin blackbody background spectrum. Photomultiplier tubes can be used to detect Cerenkov radiation produced by these particles interacting with electrons in heavy water and pure water detectors such as the Sudbury Observatory and Super Kamiokande detector.  FTP, name these leptons which can oscillate between three flavors, and have no charge and nearly no mass.
Extrasolar ones may be found by the cosmic ray detector AUGER (pron.
neutrinos