A new measurement of antineutrino oscillation with the full detector configuration at Daya Bay

TL;DR

This paper presents a precise measurement of electron antineutrino disappearance at Daya Bay, utilizing full detector data, improved calibration, and background reduction to refine neutrino oscillation parameters.

Contribution

The study provides the first measurement of antineutrino oscillations using the complete detector setup at Daya Bay with enhanced calibration and background suppression techniques.

Findings

Measured  0.084 b1 0.005 for  0.084 b1 0.005 for  0.084 b1 0.005 for  0.084 b1 0.005 for  0.084 b1 0.005 for  0.084 b1 0.005 for  0.084 b1 0.005 for  0.084 b1 0.005 for  0.084 b1 0.005 and |m^2_{ee}|= (2.42 b1 0.11) imes 10^{-3} eV^2.

The measurement reduced uncertainties in oscillation parameters by half.

Abstract

We report a new measurement of electron antineutrino disappearance using the fully-constructed Daya Bay Reactor Neutrino Experiment. The final two of eight antineutrino detectors were installed in the summer of 2012. Including the 404 days of data collected from October 2012 to November 2013 resulted in a total exposure of 6.9$\times$10$^5$ GW$_{\rm th}$-ton-days, a 3.6 times increase over our previous results. Improvements in energy calibration limited variations between detectors to 0.2%. Removal of six $^{241}$Am-$^{13}$C radioactive calibration sources reduced the background by a factor of two for the detectors in the experimental hall furthest from the reactors. Direct prediction of the antineutrino signal in the far detectors based on the measurements in the near detectors explicitly minimized the dependence of the measurement on models of reactor antineutrino emission. The uncertainties in our estimates of $\sin^{2}2\theta_{13}$ and $|\Delta m^2_{ee}|$ were halved as a result of these improvements. Analysis of the relative antineutrino rates and energy spectra between detectors gave $\sin^{2}2\theta_{13} = 0.084\pm0.005$ and $|\Delta m^{2}_{ee}|= (2.42\pm0.11) \times 10^{-3}$ eV$^2$ in the three-neutrino framework.