Jiangmen Underground Neutrino Observatory

Coordinates: 22°07′06″N 112°31′07″E / 22.11827°N 112.51867°E / 22.11827; 112.51867[1]

"JUNO" redirects here. For other uses, see Juno.

The Jiangmen Underground Neutrino Observatory (JUNO) is a medium baseline[2][3] reactor neutrino experiment under construction at Kaiping, Jiangmen in Southern China. It aims to determine the neutrino mass hierarchy and perform precision measurements of the Pontecorvo–Maki–Nakagawa–Sakata matrix elements. It will build on the mixing parameter results of many previous experiments. The collaboration was formed in July 2014[4] and construction began January 10, 2015.[5] Funding is provided by the Chinese Academy of Sciences, but the collaboration is international.

Planned as a follow-on to the Daya Bay Reactor Neutrino Experiment, it was originally planned for the same location, but the construction of a third nuclear reactor (the planned Lufeng nuclear power plant) in that area would disrupt the experiment, which depends on maintaining a fixed distance to nearby nuclear reactors.[6]:9 Instead it was moved to a loation 53 km from both of the planned Yangjiang and Taishan nuclear power plants.[6]:4

Detector

The main detector consists of a 35.4 m (116 ft) diameter transparent sphere containing 20,000 tons of linear alkylbenzene liquid scintillator, surrounded by approximately 17,000 photomultiplier tubes, a water pool, and a muon veto. Deploying this 700 m (2,300 ft) underground will detect neutrinos with excellent energy resolution.[3] The overburden includes 270 m of granite mountain, which will reduce cosmic muon background.[7]

The much larger distance to the reactors (compared to less than 2 km for the Daya Bay far detector) makes the experiment better able to distinguish neutrino oscillations, but requires a much larger, and better-shielded, detector to detect a sufficient number of reactor neutrinos.

Physics

Predicted oscillation probability of electron neutrinos (black) oscillating to muon (blue) or tau (red) neutrinos, as a function of distance from source. Existing short-baseline experiments measure the first small dip in the black curve at 500 km/GeV; JUNO will observe the large dip at 16000 km/GeV. For reactor neutrinos with an energy of ≈3 MeV, the distances are ≈1.5 m and ≈50 km, respectively. This plot is based on assumed mixing parameters; the measured shape will differ and allow the actual parameters to be computed.

The main approach of the JUNO Detector in measuring neutrino oscillations is the observation of electron-antineutrinos (
ν
e) coming from two future nuclear power plants at approximately 53 km distance.[7] Since the expected rate of neutrinos reaching the detector is known from processes in the power plants, the absence of a certain neutrino flavor can give an indication of transition processes.[7]

Although not the primary goal, the detector is sensitive to atmospheric neutrinos, geoneutrinos and neutrinos from supernovae as well.

Expected Sensitivity

Daya Bay and RENO measured θ13 and determined it has a large non-zero value. Daya Bay will be able to measure the value to ≈4% precision and RENO ≈7% after several years. JUNO is designed to improve uncertainty in several neutrino parameters to less than 1%.[8]

See also

References

  1. ↑ He, Miao (9 September 2014). Jiangmen Underground Neutrino Observatory (JUNO) (PDF). Neutrino Oscillation Workshop. Conca Specchiulla (Otranto, Lecce, Italy). Page 9 shows a topographical overview of the complex, with a distinctive C-shaped lake near the top of the figure. The lake is clearly the one at 22°07′30″N 112°30′34″E / 22.1250°N 112.5095°E. Scaling and aligning the image with a map places the experiment at the stated coordinates.
  2. ↑ Ciuffoli, Emilio; Evslin, Jarah; Zhang, Xinmin (August 2013). "The Neutrino Mass Hierarchy from Nuclear Reactor Experiments". Physical Review D. 88 (3): 033017. arXiv:1302.0624Freely accessible. Bibcode:2013PhRvD..88c3017C. doi:10.1103/PhysRevD.88.033017.
  3. 1 2 Li, Yu-Feng; Cao, Jun; Wang, Yifang; Zhan, Liang (16 July 2013). "Unambiguous determination of the neutrino mass hierarchy using reactor neutrinos". Phys. Rev. D. 88 (1): 013008. arXiv:1303.6733Freely accessible. doi:10.1103/PhysRevD.88.013008.
  4. ↑ "JUNO International Collaboration established". Interactions NewsWire. 30 July 2014. Retrieved 12 January 2015.
  5. ↑ "Groundbreaking at JUNO" (Press release). IHEP. 10 January 2015. Retrieved 12 January 2015 – via Interactions NewsWire.
  6. 1 2 Wang, Yifang (24 June 2014). JUNO Experiment (PDF). International Meeting for Large Neutrino Infrastructures. Paris.
  7. 1 2 3 "Introduction to JUNO". JUNO at IHEP. 2013-09-12. Retrieved 2015-01-12.
  8. ↑ Li, Yu-Feng (25 Feb 2014). "Overview of the Jiangmen Underground Neutrino Observatory (JUNO)". arXiv:1402.6143Freely accessible [physics.ins-det].

External links

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