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| Reactor antineutrino anomaly | |
|---|---|
| Name | Reactor antineutrino anomaly |
| Discovery | 2011 |
| Field | Particle physics |
| Key people | Mentioned in article |
Reactor antineutrino anomaly is a discrepancy between predicted and observed fluxes of electron antineutrinos emitted by nuclear reactors. First highlighted in 2011, the anomaly influenced experimental programs at facilities such as Los Alamos National Laboratory, Oak Ridge National Laboratory, Lawrence Livermore National Laboratory, CERN, and Fermilab. The issue connects to results from historical and modern neutrino experiments including Homestake Experiment, KamLAND, Super-Kamiokande, SNO, and Daya Bay.
The anomaly refers to a roughly 5–7% shortfall in detected reactor electron antineutrino rate compared to updated predictions from reference calculations carried out by groups associated with Institut Laue-Langevin, Saclay, and collaborations tied to International Atomic Energy Agency datasets. Discussion involved stakeholders such as researchers at Argonne National Laboratory, Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, and university teams from Massachusetts Institute of Technology, University of Chicago, University of California, Berkeley, Princeton University, and Harvard University. The topic intersected with work at detector projects including Bugey Nuclear Power Plant experiments, ILL reactor measurements, and reactor monitoring initiatives supported by Department of Energy (United States), National Science Foundation, and European agencies.
Early indications arose from reanalysis of short-baseline data from experiments like Bugey 3, Daya Bay, RENO, Double Chooz, Gösgen Reactor, ILL–Grenoble, and PROSPECT precursor studies. Measurements at facilities correlated with reactor cores operated by corporations and institutions such as Électricité de France, Kernkraftwerk Leibstadt, and university research reactors at University of Illinois Urbana-Champaign and University of Wisconsin–Madison displayed deficits when compared with spectra computed by groups led by researchers from École Polytechnique, CEA, and teams linked to Institut National de Physique Nucléaire et de Physique des Particules. Later short-baseline searches at Nucifer, STEREO, SoLid, NEOS, and PANDA provided additional datasets used in global fits performed by collaborations at Imperial College London, University of Tokyo, Seoul National University, and Korea Advanced Institute of Science and Technology.
Explanations split between new physics and modeling issues. New physics proposals invoked sterile neutrino hypotheses developed in contexts involving LSND experiment and MiniBooNE, and theoretical frameworks discussed in workshops at Perimeter Institute, Institute for Advanced Study, CERN Theory Division, and conferences like Neutrino 2012 and ICHEP. Alternative proposals emphasized nuclear physics: beta decay branch uncertainties studied by groups at Los Alamos National Laboratory, Oak Ridge National Laboratory, Brookhaven National Laboratory, and CEA Saclay; forbidden beta transition treatments explored by researchers affiliated with University of Manchester, Uppsala University, Stockholm University, and University of Jyväskylä. Additional ideas involved reactor operational factors evaluated with contributions from Westinghouse Electric Company, Kraftwerk operators, and modelers at International Atomic Energy Agency and Nuclear Energy Agency (NEA). Cosmological constraints from Planck (ESA) and terrestrial bounds from KATRIN experiment and IceCube Neutrino Observatory informed viability assessments.
Flux predictions relied on beta-conversion methods and ab initio summation techniques developed by teams at Institut Laue-Langevin, CEA, ENEA, Los Alamos National Laboratory, Argonne National Laboratory, Brookhaven National Laboratory, and university groups at University of Strasbourg, University of Paris-Saclay, Columbia University, and University of Michigan. Key inputs included fission yields from isotopes Uranium-235, Uranium-238, Plutonium-239, and Plutonium-241 and beta decay data from nuclear databases curated by National Nuclear Data Center and Joint Institute for Nuclear Research. Studies published by collaborations with members from Harvard University, Yale University, University of California, Davis, Ohio State University, and University of Wisconsin re-evaluated forbidden transition corrections, electron screening, and off-equilibrium effects. Workshops at Institute for Nuclear Theory and reports by Nuclear Energy Agency (NEA) summarized methodological differences between conversion and summation approaches.
If interpreted as oscillations into sterile neutrinos, the anomaly would require extensions of the three-flavor framework developed by Pontecorvo–Maki–Nakagawa–Sakata, affecting global fits combining data from Solar Neutrino Observatory, Atmospheric neutrino experiments, Long Baseline Neutrino Facility, NOvA, T2K, and precision electroweak constraints from LEP. Impacts extend to leptogenesis scenarios discussed at CERN, constraints from Big Bang nucleosynthesis analyses associated with teams at Planck (ESA), and model building at institutions like Perimeter Institute and Institute for Advanced Study. Null results from sterile neutrino searches by Daya Bay, MINOS+, and IceCube narrowed parameter space, while positive hints motivated new proposals from groups at Fermilab and Brookhaven National Laboratory.
Planned and executed experiments target short baselines and high-resolution spectra: PROSPECT at High Flux Isotope Reactor, STEREO at Institut Laue-Langevin, SoLid at BR2 reactor, NEOS in Korea, and projects like JUNO, TAO, SOLID, and successor arrays coordinated by CERN and Fermilab. Proposed upgrades and new detectors involve collaborations with Lawrence Berkeley National Laboratory, Argonne National Laboratory, Oak Ridge National Laboratory, Brookhaven National Laboratory, Korea University, ETH Zurich, and University of Geneva. Results from these experiments, alongside reactor modeling improvements from CEA Saclay, Institut Laue-Langevin, and nuclear data updates by National Nuclear Data Center, aim to resolve whether the anomaly signals new particles or unresolved nuclear physics, with implications for neutrino mass hierarchy programs at JUNO and for nonproliferation monitoring efforts coordinated by International Atomic Energy Agency.
Category:Neutrino physics