Particle physics below the Earth's surface, an overview of possibilities

Potential subterranean cosmic ray and high energy particle physics experiments of current interest are reviewed. It is argued that most of the experiments may be attempted with instruments that fall generally into two classes: (1) detectors with greater than one thousand ton mass and MeV energy sensitivity, and (2) those with far greater mass, megatons or more, but much higher energy threshold, TeV. Those in class 1 are useful for nucleon decay searches, solar neutrino observations, and monitoring for supernovae in our galaxy. Class 2 detectors are aimed at high energy neutrino astronomy and various cosmic ray muon studies and the nature of interactions at ultra high energies. Both types can do useful muon studies, depending particularly upon depth. Finally the prospects for second generation nucleon decay searches are discussed and it is concluded that a national underground laboratory may be justified sometime in the future, after the results of contemporary endeavors are available, but that at present it is not possible to define the characteristics required of such a national facility. However, it is suggested that studies be undertaken to evaluate the various options, including novel technology, such as TPC-like devices, and to evaluate location options, such as being near a surface cosmic ray installation, or being located in the ocean