Neutrino Physics with JUNO (1507.05613v2)

Abstract: The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multi-purpose underground liquid scintillator detector, was proposed with the determination of the neutrino mass hierarchy as a primary physics goal. It is also capable of observing neutrinos from terrestrial and extra-terrestrial sources, including supernova burst neutrinos, diffuse supernova neutrino background, geoneutrinos, atmospheric neutrinos, solar neutrinos, as well as exotic searches such as nucleon decays, dark matter, sterile neutrinos, etc. We present the physics motivations and the anticipated performance of the JUNO detector for various proposed measurements. By detecting reactor antineutrinos from two power plants at 53-km distance, JUNO will determine the neutrino mass hierarchy at a 3-4 sigma significance with six years of running. The measurement of antineutrino spectrum will also lead to the precise determination of three out of the six oscillation parameters to an accuracy of better than 1\%. Neutrino burst from a typical core-collapse supernova at 10 kpc would lead to ~5000 inverse-beta-decay events and ~2000 all-flavor neutrino-proton elastic scattering events in JUNO. Detection of DSNB would provide valuable information on the cosmic star-formation rate and the average core-collapsed neutrino energy spectrum. Geo-neutrinos can be detected in JUNO with a rate of ~400 events per year, significantly improving the statistics of existing geoneutrino samples. The JUNO detector is sensitive to several exotic searches, e.g. proton decay via the $p\to K^++\bar\nu$ decay channel. The JUNO detector will provide a unique facility to address many outstanding crucial questions in particle and astrophysics. It holds the great potential for further advancing our quest to understanding the fundamental properties of neutrinos, one of the building blocks of our Universe.

• The paper demonstrates JUNO’s goal to resolve the neutrino mass hierarchy with a 3-4σ significance over six years using reactor antineutrinos.
• It details the use of a 20 kton liquid scintillator detector designed to measure oscillation parameters with better than 1% precision.
• It outlines JUNO’s capability to detect various neutrino sources and search for exotic physics beyond the Standard Model.

Overview of "Neutrino Physics with JUNO"

The paper "Neutrino Physics with JUNO" summarizes the significant research goals and anticipated outcomes associated with the Jiangmen Underground Neutrino Observatory (JUNO), a major experiment designed to refine our understanding of neutrino physics. JUNO aims to address several critical aspects of neutrino properties, including the determination of neutrino mass hierarchy, precise measurements of neutrino oscillation parameters, and exploration of exotic phenomena. This comprehensive document outlines JUNO's experimental setup, scientific motivations, and potential contributions to the field.

Key Scientific Goals

1. Neutrino Mass Hierarchy: One of JUNO's primary objectives is to determine the neutrino mass hierarchy—whether the third neutrino mass eigenstate is heavier (normal hierarchy) or lighter (inverted hierarchy) than the first two. The experiment is expected to achieve 3-4$\sigma$ significance in determining the hierarchy using antineutrinos from nuclear reactors over six years of operation. This determination is crucial as it influences our understanding of neutrino mass generation and the potential for related CP violation effects.
2. Neutrino Oscillation Parameters: JUNO promises high precision in measuring neutrino oscillation parameters, such as $\sin^2\theta_{12}$, $\Delta m^2_{21}$, and $|\Delta m^2_{ee}|$. A precision of better than 1% is anticipated, which is vital for validating the unitarity of the 3x3 Maki-Nakagawa-Sakata-Pontecorvo (MNSP) mixing matrix, a cornerstone of the standard model of particle physics.
3. Detection of Various Neutrinos: JUNO's design facilitates the detection of not only reactor antineutrinos but also cosmic and atmospheric neutrinos. This capability opens avenues for probing supernova neutrinos, neutrinos from known geological sources (geoneutrinos), and potential new physics phenomena.
4. Exotic Physics Searches: JUNO is also equipped to look for signals of physics beyond the standard model, such as proton decay, interactions related to dark matter, and possible violations of Lorentz invariance. These searches expand the scope of JUNO's scientific inquiry, addressing broader questions in fundamental physics.

Technical and Experimental Aspects

• Detector Design: The central detector of JUNO is a large liquid scintillator with a 20 kton fiducial mass, offering superb energy resolution and substantial volume for neutrino interaction. This setup is crucial for achieving the necessary sensitivity in mass hierarchy determination and oscillation parameter measurements.
• Site Selection: The detector is strategically located in Jiangmen, Guangdong province, China, equidistant from the Yangjiang and Taishan nuclear power plants, ensuring optimal sensitivity for mass hierarchy measurements. Its underground placement and shielding are essential for minimizing background noise and enhancing detection precision.
• Collaborations and Contributions: JUNO represents a collaborative international effort, involving numerous institutions and researchers. The sharing of data and coordination with existing experiments in neutrino physics will be key to maximizing JUNO's impact.

Implications and Future Prospects

The findings from JUNO will extend the boundaries of our understanding in both particle physics and astrophysics. By resolving the neutrino mass hierarchy, JUNO will significantly influence theoretical models of neutrino mass generation and provide insights necessary for the next generation of neutrino experiments. Moreover, the experiment's results will refine our understanding of the role of neutrinos in the cosmos, from supernova dynamics to elemental synthesis, thus offering broader implications for cosmology and earth sciences.

In summary, the JUNO experiment is set to make transformative contributions to neutrino physics, serving as a pivotal resource in resolving outstanding questions about the fundamental properties of neutrinos. This endeavor stands to corroborate and refine current models, or potentially indicate new physics, rendering it a cornerstone project in the ongoing quest to elucidate the universe at its most fundamental level.