Maximum likelihood reconstruction for the Daya Bay Experiment

The Daya Bay Reactor Neutrino experiment is designed to precisely determine the neutrino mixing angle theta13. In this paper, we report a maximum likelihood (ML) method to reconstruct the vertex and energy of events in the anti-neutrino detector, based on a simplified optical model that describes light propagation. We calibrate the key paramters of the optical model with Co60 source, by comparing the predicted charges of the PMTs with the observed charges. With the optimized parameters, the resolution of the vertex reconstruction is about 25cm for Co60 gamma.