Abstract:

The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multipurpose underground liquid scintillator detector, was proposed with the determination of the neutrino mass hierarchy at 3σ significance with six years of running of JUNO. The measurement of the antineutrino spectrum with excellent energy resolution will lead to the precise determination of the neutrino oscillation parameters sin²θ₁₂, Δm²₂₁ and Δm²₃₁ to an accuracy of 0.2-0.5%, which will play a crucial role in the future unitarity test of the MNSP matrix. JUNO measures the reactor neutrino signal via the inverse beta decay reaction: v_e+p→e⁺+n. In the liquid scintillator, the energetic cosmic muons and subsequent showers can interact with 12C and produce radioactive isotopes ⁸He/⁹Li with half-lives of 0.178 s and 0.119 s, respectively — the most serious correlated background source to reactor antineutrinos, because they can decay by emitting both a beta and a neutron which mimics as an antineutrino signal. To suppress this type of background, it is necessary to reconstruct muon track direction and exclude the volume around it from the analysis.

At this seminar, the muon reconstruction method in the JUNO detector with the help of spherical functions will be presented. Also, we will review the methods for suppressing the background from ⁸He/⁹Li isotopes in different antineutrino experiments.

(In connection with the re-election to fill the position of senior research scientist)