Abstract

The Reactor Experiment for Neutrino Oscillation (RENO) experiment has been taking data using two identical liquid scintillator detectors since August 2011. The experiment has observed the disappearance of reactor neutrinos in their interactions with free protons, followed by neutron capture on hydrogen (n-H). Based on 1500 live days of data taken with 16.8 GWth reactors at the Hanbit Nuclear Power Plant in Korea, the near (far) detector observes 567690 (90747) electron antineutrino candidate events with the n-H data. This provides an independent measurement of neutrino mixing angle θ13 and a consistency check on the validity of the result obtained from the data with neutron capture on Gadolinium (n-Gd). Furthermore, it provides an important cross-check on the systematic uncertainties of the n-Gd measurement. Based on a rate-only analysis, we obtain sin2 2θ13 = 0.086 ± 0.008(stat.) ± 0.014(syst.). The combination of this result with that of n-Gd is also reported.

Highlights

  • Background uncertaintyThe background uncertainty is an essential part in determining the error of θ13

  • This provides an independent measurement of neutrino mixing angle θ13 and a consistency check on the validity of the result obtained from the data with neutron capture on Gadolinium (n-Gd)

  • We present the Reactor Experiment for Neutrino Oscillation (RENO)’s first measured values of θ13 from the reactor νe disappearance observed in the inverse beta decay (IBD) interactions with neutron capture on hydrogen (n-H) in the near and far detectors based on ∼1500 live days of data taken from 11 August 2011 to 23 April 2017

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Summary

Vertex reconstruction

The event vertex information is used to distinguish the target and GC signals. In addition, the difference in distance between prompt and delayed candidates is useful for eliminating and measuring accidental backgrounds. The event vertex is reconstructed using the observed charge information of individual PMT. A basic algorithm of position reconstruction finds an event charge centroid. The event vertex is reconstructed by calculating a charge weighted average using hit PMTs rvtx. Where rvtx is a reconstructed vertex of each event, i is an index of each PMT, Qi is the charge collected by the i-th PMT, and ri is a position vector of the PMT. This method works well in spherical, fully symmetric detectors [19]. The vertex resolution is less than ∼17 cm at 1 MeV, and improves at higher energies

Energy reconstruction
Muon energy estimation
Accidental background
Fast neutron background
Detection efficiency uncertainty
Background uncertainty
Reactor related uncertainty
Results and summary
Full Text
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