Indication for the disappearance of reactor electron antineutrinos in the Double Chooz experiment

TL;DR

The Double Chooz experiment observed a deficit in reactor electron antineutrinos consistent with neutrino oscillations, providing evidence for a non-zero neutrino mixing parameter, through measurements at a nuclear power plant in France.

Contribution

This study provides the first indication of reactor electron antineutrino disappearance consistent with neutrino oscillations using the Double Chooz detector.

Findings

Observed a ratio of 0.944 ± 0.016 (stat) ± 0.040 (syst) in antineutrino events.

Estimated the neutrino mixing parameter 3a0= 0.086 b1 0.041 (stat) b1 0.030 (syst).

Set a 90% confidence level interval for 3a0 between 0.015 and 0.16.

Abstract

The Double Chooz Experiment presents an indication of reactor electron antineutrino disappearance consistent with neutrino oscillations. A ratio of 0.944 $\pm$ 0.016 (stat) $\pm$ 0.040 (syst) observed to predicted events was obtained in 101 days of running at the Chooz Nuclear Power Plant in France, with two 4.25 GW$_{th}$ reactors. The results were obtained from a single 10 m$^3$ fiducial volume detector located 1050 m from the two reactor cores. The reactor antineutrino flux prediction used the Bugey4 measurement as an anchor point. The deficit can be interpreted as an indication of a non-zero value of the still unmeasured neutrino mixing parameter \sang. Analyzing both the rate of the prompt positrons and their energy spectrum we find \sang = 0.086 $\pm$ 0.041 (stat) $\pm$ 0.030 (syst), or, at 90% CL, 0.015 $<$ \sang $\ <$ 0.16.