Absolute $\overline{\nu}_e$ Detection Efficiency of the Daya Bay Experiment

The Daya Bay reactor $\overline{\nu}_e$ experiment has provided the most sensitive measurement of the neutrino mixing parameter $\theta_{13}$ ever recorded, sin$^2 2\theta_{13}=0.090\pm0.009$, by measuring relative differences in neutrino interaction rates between near and far detectors. In addition to measuring relative differences between detectors, the Daya Bay experiment can also make high-statistics measurements of the absolute reactor $\overline{\nu}_e$ flux and spectrum with its near site detectors. An essential input to any absolute measurement of the reactor flux normalization is the absolute efficiency in detecting $\overline{\nu}_e$ inverse beta decay interactions in the detector targets. The absolute efficiency of the Daya Bay inverse beta decay analysis utilizing neutron capture on Gadolinium has been precisely re-calculated using tuned Monte Carlo simulations of the Daya Bay detectors, with cross-checks and systematic uncertainties provided by data-Monte Carlo comparisons of various relevant calibration and inverse beta decay datasets.