Investigating the Reactor Antineutrino Anomaly with Beta Spectroscopy*

The Reactor Antineutrino Anomaly is a discrepancy between the expected flux of antineutrinos from nuclear reactors and the detected flux. This anomaly is often explained by either the existence of a fourth, sterile neutrino or by incorrect calculations of the predicted number of reactor antineutrinos. Calculations of the expected flux assume that all the fission product $\beta$ decays have spectral shapes that are nearly identical to the allowed shape. However, many of the highest energy transitions are first forbidden and may have a different spectral shape, which could alter the predicted antineutrino flux and explain the anomaly. We will perform measurements of the shapes of $\beta$ decay spectra on the isotopes that have the biggest impact on the Reactor Antineutrino Anomaly. Those nuclei, starting with $^{92}$Rb, will be produced at the CARIBU facility at Argonne National Laboratory and the $\beta$ spectra will be measured in plastic scintillators. The energy response of the plastic scintillators will be calibrated by studying the allowed $\beta$ decay of $^{8}$Li.