Improved FIFRELIN de-excitation model for neutrino applications

Abstract

The precise modeling of the de-excitation of Gd isotopes is of great interest for experimental studies of neutrinos using Gd-loaded organic liquid scintillators. The FIFRE-LIN code was recently used within the purposes of the STEREO experiment for the modeling of the Gd de-excitation after neutron capture in order to achieve a good control of the detection efficiency. In this work, we report on the recent additions in the FIFRELIN de-excitation model with the purpose of enhancing further the de-excitation description. Experimental transition intensities from EGAF database are now included in the FIFRELIN cascades, in order to improve the description of the higher energy part of the spectrum. Furthermore, the angular correlations between γ rays are now implemented in FIFRELIN, to account for the relative anisotropies between them. In addition, conversion electrons are now treated more precisely in the whole spectrum range, while the subsequent emission of X rays is also accounted for. The impact of the aforementioned improvements in FIFRE-LIN is tested by simulating neutron captures in various positions inside the STEREO detector. A repository of up-todate FIFRELIN simulations of the Gd isotopes

Interpreting Reactor Antineutrino Anomalies with STEREO data

“…A precise modeling of the de-excitation of Gd isotopes af-ter neutron capture is obtained using the FIFRELIN code [54]. New features have been implemented to improve the reliability of the STEREO detector response compared to the previous version [55]: the physics of conversion electrons and the subsequent X-ray emission has been treated more accurately; a better description of the high-energy part of the γ-ray spectrum has been achieved by taking into account available experimental data on primary γ-rays; a complete treatment of angular correlations between γ-rays has been implemented [56].…”

Summary of Session I: Oscillation Parameters, Present

“…Data were collected from the end of 2017 until the end of 2020 and the analysis realized with the full data set was presented. Among the improvements of this new analysis we notice the use of an improved version of the FIFRELIN code [16] for the 𝛾 cascade model for the neutron capture on Gd. Oscillation results exlude most of the RAA allowed region at 95% (for Δ𝑚 2 41 < 4 eV 2 ) and the RAA best fit point is excluded at ∼4𝜎.…”