Daya Bay Reactor Neutrino Experiment Muon System

The search for $\theta_{13}$, the last unknown mixing angle, is extremely important in understanding the lepton flavor mixing matrix, and the CP violation in the lepton sector. Reactor neutrino experiments can provide a clean laboratory for the $\theta_{13}$ measurement via electron antineutrino disappearance. The Daya Bay experiment proposes to measure $\sin^{2}2\theta_{13}$ with a sensitivity better than 0.01 (90\% C.L) in a three-year-run at the Daya Bay reactor power plant in China. To achieve this, the muon-induced backgrounds must be reduced to a low level. The Daya Bay muon system is a dual tagging system with multiple layers of resistive plate chambers (RPCs) above a water-pool (Cherenkov light detector). It detects cosmic ray muons and measures their time and positions relative to signal events with an overall combined efficiency of more than $99.5\%$. In this talk we are going to present details of the muon system along with the current status and estimates of expected background rates.