The Reactor Experiment for Neutrino Oscillation (RENO) is a short baseline reactor neutrino oscillation experiment in South Korea. The experiment was designed to either measure or set a limit on the neutrino mixing matrix parameter θ₁₃, a parameter responsible for oscillations of electron neutrinos into other neutrino flavours. RENO has two identical detectors, placed at distances of 294 m and 1383 m, that observe electron antineutrinos produced by six reactors at the Hanbit Nuclear Power Plant (the old name: the Yeonggwang Nuclear Power Plant) in Korea.

Each detector consists of 16.5 t of gadolinium-doped liquid scintillator (LAB), surrounded by an additional 450 tons of buffer, veto, and shielding liquids.^[1]: 6

On 3 April 2012, with some corrections on 8 April, the RENO collaboration announced a 4.9σ observation of θ₁₃ ≠ 0, with

${\displaystyle \sin ^{2}2\theta _{13}=0.113\pm 0.013({\rm {stat.}})\pm 0.019({\rm {syst.}})}$^[2][3]

This measurement confirmed a similar result announced by the Daya Bay Experiment three weeks before and is consistent with earlier, but less significant results by T2K, MINOS and Double Chooz.

RENO released updated results^[4] in December 2013, confirming θ₁₃ ≠ 0 with a significance of 6.3σ:

${\displaystyle \sin ^{2}2\theta _{13}=0.100\pm 0.010({\rm {stat.}})\pm 0.015({\rm {syst.}})}$

In 2014, RENO announced the observation of an unexpectedly large number of neutrinos with an energy of 5±1 MeV.^{[5]: 14–15} This has since been confirmed by the Daya Bay and Double Chooz experiments,^{[1]: 14–17} and the cause remains an outstanding puzzle.

Expansion plans, referred to as RENO-50, will add a third medium-baseline detector at a distance of 47 km. This distance is better for observing neutrino oscillations, but requires a much larger detector due to the smaller neutrino flux. The location, near Dongshin University, has a 450 m high mountain (Mt. Guemseong), which will provide 900 m.w.e. shielding for the detector. If funded, this will contain 18000 t of scintillator,^[1]: 31 surrounded by 15000 photomultiplier tubes.

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