Total Absorption Spectroscopy Study of $^{92}$Rb Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape

TL;DR

This study uses total absorption spectroscopy to investigate the decay of $^{92}$Rb, a key contributor to reactor antineutrino spectra, revealing new beta feeding data that impacts spectral calculations and addresses existing discrepancies.

Contribution

It provides the first detailed decay data for $^{92}$Rb using total absorption spectroscopy, improving the accuracy of reactor antineutrino spectrum models.

Findings

Unobserved beta feeding in the 4.5-5.5 MeV region.

$^{92}$Rb ground state to ground state feeding of 87.5%.

Implications for reactor antineutrino spectrum calculations.

Abstract

The antineutrino spectra measured in recent experiments at reactors are inconsistent with calculations based on the conversion of integral beta spectra recorded at the ILL reactor. $^{92}$Rb makes the dominant contribution to the reactor spectrum in the 5-8 MeV range but its decay properties are in question. We have studied $^{92}$Rb decay with total absorption spectroscopy. Previously unobserved beta feeding was seen in the 4.5-5.5 region and the GS to GS feeding was found to be 87.5(25)%. The impact on the reactor antineutrino spectra calculated with the summation method is shown and discussed.