Neutron sensitivity of the endcap RPC modules in Belle detector

In recent Belle experiment at KEK B factory, an increase in noise rate due to beam backgrounds is observed in the endcap KLM detector. Accompanying the increased noise rate, lower detection efficiency was also observed. To study what the sources of noises in the endcap KLM detector are, we performed simulations of sensitivities of neutrons and γs as the sources of noises in the endcap KLM detector using a Geant4 simulation toolkit. We present comparisons of the simulations with the experimental data and propose a candidate for the noise source in the endcap KLM detector.