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Monday, March 27, 2023

Explaining Anomalies in Reactor Antineutrinos

• Physics 16, s10

A brand new evaluation finds that discrepancies between reactor neutrino experiments and idea could also be the results of errors within the evaluation of electron information that type the idea of the neutrino predictions.

R. Kaltschmidt/Lawrence Berkeley Nationwide Laboratory

A number of experiments have been arrange exterior nuclear reactors to report escaping antineutrinos. The information usually agrees with idea, however at sure energies, the antineutrino flux is 6–10% above or under predictions. These so-called reactor antineutrino anomalies have excited the neutrino neighborhood, as they may very well be signatures of a hypothetical sterile neutrino (see Viewpoint: Attending to the Backside of an Antineutrino Anomaly). However a brand new evaluation by Alain Letourneau from the French Atomic Power Fee (CEA-Saclay) and colleagues has proven that the discrepancies might come from experimental biases in related electron measurements [1].

The supply of reactor antineutrinos is beta decay, which happens in all kinds of nuclei (greater than 800 species in a typical fission reactor). To foretell the antineutrino flux, researchers have sometimes used beforehand recorded information on electrons, that are additionally produced in the identical beta decays. This conventional technique takes the noticed electron spectra from nuclei, akin to uranium-235 and plutonium-239, and converts them into predicted antineutrino spectra. However Letourneau and colleagues have discovered motive to doubt the electron measurements.

The staff calculated antineutrino spectra—in addition to the corresponding electron spectra—utilizing a basic idea of beta decay. This technique works for some nuclei, however not all, so the researchers plugged the gaps utilizing a phenomenological mannequin. They had been in a position to deal with all 800-plus reactor beta decays, discovering “bumps” within the antineutrino flux that agree with observations. Related options are predicted for electron spectra, however they don’t present up within the information. The outcomes counsel that an experimental bias in electron observations causes the reactor antineutrino anomalies. To substantiate this speculation, the researchers name for brand spanking new precision measurements of the fission electrons.

–Michael Schirber

Michael Schirber is a Corresponding Editor for Physics Journal based mostly in Lyon, France.


  1. A. Letourneau et al., “Origin of the reactor antineutrino anomalies in mild of a brand new summation mannequin with parametrized

    transitions,” Phys. Rev. Lett. 130, 021801 (2023).

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