Speaker
Description
Nuclear reactors are copious sources of antineutrinos. This is the main reason why reactors have played a key role in the discovery of the neutrino and in the study of neutrino oscillation phenomena. The comparison of the neutrino flux measurements performed at short baselines with the improved conversion procedure by Huber [1] and Mueller [2] led to the discovery of the so-called reactor antineutrino anomaly [3], a surplus in the number of predicted antineutrinos compared with the measured, and more recently, to the finding of a spectrum distortion around 5 MeV [4]. There is another alternative for the prediction of the antineutrino spectrum, the summation calculation method, which has recently achieved a precision comparable to the conversion procedure [5].
Both methods of calculations of the antineutrino spectrum require assumptions on the shape of the beta transitions. In [6,7] it was argued that not taking into account the shape of first forbidden transitions could itself explain a large part of the discrepancy related to the anomaly.
With this motivation in mind, we have developed a new setup to measure the beta shape of the beta spectrum of relevant decays for the calculation of the antineutrino spectrum. In this presentation, the new setup, and some preliminary measurements performed at Jyväskylä with pure isotopic beams will be presented. The possible impact of the measurements in the calculations will be discussed.
[1] P. Huber, Phys. Rev. C 84, 024617 (2011).
[2] Th. A. Mueller, et al., Phys. Rev. C 83, 054615 (2011).
[3] G. Mention, et al., Phys. Rev. D 83, 073006 (2011).
[4] Double Chooz and Reno Collaborations in Proceedings of the Neutrino 2014 Conference, http://neutrino2014.bu.edu/; Daya Bay Collaboration in Proceedings of the ICHEP 2014 Conference, http://ichep2014.es/.
[5] M. Estienne, et al., Phys. Rev. Lett. 123, 022502 (2019).
[6] A. C. Hayes, et al., Phys. Rev. Lett. 112, 202501 (2014).
[7] L. Hayen, et al., Physical Review C 100, 054323 (2019).