Description
The Reactor Antineutrino Anomalies are a 10-years long standing problem in neutrino physics. They refer to a norm and shape discrepancies between experimental reactor antineutrino data and the state-of-the-art model proposed by Huber and Mueller et al. This model is based on a conversion procedure of the electron energy spectra measured in the 80’s at ILL with the BILL spectrometer. Within this approach, biases due to the conversion procedure or present into the experimental electron data are directly propagated into the antineutrino spectra. Those biases have to be evaluated to see if they may be at the origin of the anomalies.
To address this issue, we have recently revisited the summation method, which consists in summing over all beta-branches of decaying fission products, by implementing a phenomenological beta-decay strength model. This model allows to circumvent the main drawback of the method which is the lack of knowledge of some beta-transitions in the ENSDF nuclear database. Within this approach, we show that the bias due to the conversion method is small and could not explain the anomalies. Then we show that $^{235}$U electron and antineutrino energy spectra are not consistent whereas $^{239}$Pu and $^{241}$Pu are consistent, pointing toward an incorrect normalisation of the $^{235}$U electron energy spectra as the origin of the reactor antineutrino anomaly (RAA). Finally, the model is able to reproduce the measured $^{235}$U antineutrino energy spectra putting in evidence that the shape anomaly (the “5 MeV bump”) could probably find its origin in the measured electron energy spectra for both $^{235}$U, $^{239}$Pu and $^{241}$Pu.
In this contribution, we will present the model and discuss the results.
