is the energy of the $\overline{\nu}_{e}$ in MeV, and $L$ is the distance in meters from the production point.

Pinning down $\theta_{13}$ by performing a relative measurement with a set of near and far detectors was suggested at the beginning of this millennium [@mikaelyan]. This method allows cancellation of most systematic uncertainties due to the reactor and the detector that previous experiments suffered. Since 2002, eight reactor experiments were proposed [@whitepaper]; three of them, Daya Bay [@dybcdr], Double Chooz [@doublechooz], and RENO [@reno], were finally constructed.

Among the eight proposals, the Daya Bay experiment is most sensitive for measuring $\theta_{13}$. The nuclear-power complex is among the top five most powerful in the world, providing a very intense flux of antineutrinos. In addition, it is very close to a mountain range in which an array of horizontal tunnels can be built, providing sufficient overburden to attenuate cosmic rays and space to accommodate a relatively large-scale experiment.

The Daya Bay nuclear-power complex is located on the southern coast of China, 55 km to the northeast of Hong Kong and 45 km to the east of Shenzhen. As shown in Fig. 1, the nuclear complex consists of six reactors grouped into three pairs 