(ADs) are installed in the three halls, with two in EH1, two in EH2, and four in EH3. Each AD has 20-ton target mass to catch the reactor antineutrinos. The sensitivity to $\sin^22\theta_{13}$ was designed to be better than 0.01 at 90% confidence level in 3 years.

History of the Daya Bay Experiment {#history}
==================================

The idea of determining $\theta_{13}$ using the Daya Bay reactor complex was proposed in 2003. The first dedicated workshop for the Daya Bay experiment was held in the University of Hong Kong in November 2003 [@hk2003]. It was immediately followed by the second one in January 2004 at the Institute of High Energy Physics [@ihep2004], at which a preliminary experimental design was presented, including the unique multiple-detector scheme and the reflective panel design for light collection. In response to the recommendation of measuring $\sin^22\theta_{13}$ to the level of 0.01 by the APS Neutrino Study [@numatrix] and NuSAG [@nusag], the target mass of the detectors was enlarged from 8 ton to 20 ton. The Conceptual Design Report (CDR) was released at the end of 2006 [@dybcdr].

The Daya Bay Collaboration with international participation was formed in February 2006. The project was approved by the Chinese Academy 