Why should the laboratory be situated underground?

Neutrinos, as mentioned before, are notoriously difficult to detect in a laboratory because of their extremely weak interaction with matter. The background from cosmic rays (which interact much more readily than neutrinos) and natural radioactivity will make it almost impossible to detect them on the surface of the Earth. This is the reason most neutrino observatories are located deep inside the Earth's surface. The overburden provided by the Earth matter is transparent to neutrinos whereas most background from cosmic rays is substantially reduced depending on the depth at which the detector is located.

One of the earliest laboratories created to detect neutrinos underground in the world was located more than 2000 m deep at the Kolar Gold Field (KGF) mines in India. The first atmospheric neutrinos were detected at this laboratory in 1965. This laboratory has been closed due to the closure of the mines. Most underground laboratories around the world are located at a depth of a km or more. There are two types of underground laboratories: either located in a mine or in a road tunnel. There are now four major laboratories around the world: in Sudbury in Canada, in Kamioka in Japan, under the Gran Sasso mountains in Italy and in Soudan mines in the USA. Several others are planned including INO which is an attempt to recapture the pioneering studies on neutrinos at KGF.