# Reactor Experiment for Neutrino Oscillation

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±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.

## References

1. ^ a b c Joo, Kyung Kwang (5 July 2016). Results from RENO and prospects with RENO-50. XXVII International Conference on Neutrino Physics and Astrophysics. London. Video available at Neutrino Conference 2016 - Tuesday (part 1) on YouTube.
2. ^ RENO Collaboration (2012-04-03). "Observation of electron-antineutrino disappearance at RENO". Physical Review Letters. 108 (18): 191802. arXiv:1204.0626. Bibcode:2012PhRvL.108s1802A. doi:10.1103/PhysRevLett.108.191802. PMID 23003027.
3. ^ RENO Collaboration (2012-04-04). "Announcement of the First Results from RENO: Observation of the Weakest Neutrino Transformation". Interactions NewsWire.
4. ^ Seon-Hee Seo (for the RENO Collaboration) (2013). "New Results from RENO". arXiv:1312.4111 [physics.ins-det].
5. ^ Seo, Seon-Hee (3 June 2014). New Results from RENO. XXVI International Conference on Neutrino Physics and Astrophysics. Boston.