The detectors are susceptible to noise signals. Occasionally muons produced by the cosmic-ray pass through the detector and produce unwanted signals, decreasing the accuracy and precision of the experiment.

Each antineutrino detector is enclosed by 2.5 m of water to shield energetic neutrons produced by cosmic-ray muons and gamma-rays from the surrounding rock.

In order to study the background generated by cosmic-ray muons, a modified Gaisser parametrization is used for the cosmic-ray flux at the surface. Then a software code called MUSIC is used to estimate the muon intensity and energy at the underground halls based on the mountain profile.

Below is an example of muon system:

Sources: U, Th, K, Rn, neutron

1. Single gamma rate @ 0.9MeV < 50Hz/antineutrino detector

2. Single neutron rate < 1000/day/antineutrino detector

1. Fast Neutrons: double coincidence

2. ⁸He/⁹Li: beta-neutron emitting decays