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 ${\mathrm{m}}^2$ 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) × ${10}^{-8\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\mathrm{s}}^{-1\mathrm{}}$ ${\mathrm{sr}}^{-1\mathrm{}}$ at 2090 m of water equivalent (mwe) to (4.57±1.37) × ${10}^{-9\mathrm{}}$ ${\mathrm{cm}}^{-2\mathrm{}}$ ${\mathrm{s}}^{-1\mathrm{}}$ ${\mathrm{sr}}^{-1\mathrm{}}$ at 4157 mwe.