Cosmic-ray muons in the deep ocean

A string of seven optical detectors deployed from a ship was used to detect the Cherenkov light from muons at ocean depths ranging from 2000 to 4000 m in intervals of {~}500 m. The flux and angular distributions of cosmic-ray muons were measured. An effective area for fivefold coincidences of 420 m² for downward-going muons was achieved. The results are consistent with those derived from underground observations and theoretical calculations. The measured vertical intensity ranges from (9.84±{}6.5) ×{} 10^-8 cm^-2 s^-1 sr^-1 at 2090 m of water equivalent (mwe) to (4.57±{}1.37) ×{} 10^-9 cm^-2 s^-1 sr^-1 at 4157 mwe.