Precision measurement of reactor antineutrino oscillation at kilometer-scale baselines by Daya Bay

We present a new determination of the smallest neutrino mixing angle ${\theta }_{13}$ and the mass-squared difference $\mathrm{\Delta }{\mathrm{m}}_{32}^2$ using a final sample of $5.55\times {10}^6$ inverse beta-decay (IBD) candidates with the final-state neutron captured on gadolinium. This sample was selected from the complete data set obtained by the Daya Bay reactor neutrino experiment in 3158 days of operation. Compared to the previous Daya Bay results, selection of IBD candidates has been optimized, energy calibration refined, and treatment of backgrounds further improved. The resulting oscillation parameters are ${\mathrm{s}\mathrm{i}\mathrm{n}}^{2}2{\theta }_{13}=0.0851\pm 0.0024$, $\mathrm{\Delta }{\mathrm{m}}_{32}^2=(2.466\pm 0.060)\times {10}^{-3}{\mathrm{e}\mathrm{V}}^2$ for the normal mass ordering or $\mathrm{\Delta }{\mathrm{m}}_{32}^2=-(2.571\pm 0.060)\times {10}^{-3}{\mathrm{e}\mathrm{V}}^2$ for the inverted mass ordering.