52 research outputs found
Final Measurement of the U235 Antineutrino Energy Spectrum with the PROSPECT-I Detector at HFIR
This Letter reports one of the most precise measurements to date of the
antineutrino spectrum from a purely U235-fueled reactor, made with the final
dataset from the PROSPECT-I detector at the High Flux Isotope Reactor. By
extracting information from previously unused detector segments, this analysis
effectively doubles the statistics of the previous PROSPECT measurement. The
reconstructed energy spectrum is unfolded into antineutrino energy and compared
with both the Huber-Mueller model and a spectrum from a commercial reactor
burning multiple fuel isotopes. A local excess over the model is observed in
the 5MeV to 7MeV energy region. Comparison of the PROSPECT results with those
from commercial reactors provides new constraints on the origin of this excess,
disfavoring at 2.2 and 3.2 standard deviations the hypotheses that
antineutrinos from U235 are solely responsible and non-contributors to the
excess observed at commercial reactors respectively.Comment: The paper has been updated with an improved parametrization of the
observed antineutrino spectrum excess and extended discussion on its
potential isotopic origi
Tritium Beta Spectrum and Neutrino Mass Limit from Cyclotron Radiation Emission Spectroscopy
The absolute scale of the neutrino mass plays a critical role in physics at
every scale, from the particle to cosmological. Measurements of the tritium
endpoint spectrum have provided the most precise direct limit on the neutrino
mass scale. In this Letter, we present advances by Project 8 to the Cyclotron
Radiation Emission Spectroscopy (CRES) technique culminating in the first
frequency-based neutrino mass limit. With only a cm-scale physical
detection volume, a limit of <180 eV is extracted from the
background-free measurement of the continuous tritium beta spectrum. Using
Kr calibration data, an improved resolution of 1.660.16 eV
(FWHM) is measured, the detector response model is validated, and the
efficiency is characterized over the multi-keV tritium analysis window. These
measurements establish the potential of CRES for a high-sensitivity
next-generation direct neutrino mass experiment featuring low background and
high resolution.Comment: 7 pages, 5 figures, for submission to PR
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