RESUMO
The absolute scale of the neutrino mass plays a critical role in physics at every scale, from the subatomic to the cosmological. Measurements of the tritium end-point 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^{3}-scale physical detection volume, a limit of m_{ß}<155 eV/c^{2} (152 eV/c^{2}) is extracted from the background-free measurement of the continuous tritium beta spectrum in a Bayesian (frequentist) analysis. Using ^{83m}Kr calibration data, a resolution of 1.66±0.19 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.
RESUMO
It has been understood since 1897 that accelerating charges must emit electromagnetic radiation. Although first derived in 1904, cyclotron radiation from a single electron orbiting in a magnetic field has never been observed directly. We demonstrate single-electron detection in a novel radio-frequency spectrometer. The relativistic shift in the cyclotron frequency permits a precise electron energy measurement. Precise beta electron spectroscopy from gaseous radiation sources is a key technique in modern efforts to measure the neutrino mass via the tritium decay end point, and this work demonstrates a fundamentally new approach to precision beta spectroscopy for future neutrino mass experiments.
RESUMO
For the neutrino mass determination experiment KATRIN, the long-term stability of the spectrometer voltage is of crucial importance. Therefore, it is planned to control the voltage continuously in a smaller spectrometer, which monitors the position of the conversion electron line emitted in the 32 keV transition in the decay of (83m)Kr. Due to the short half-life of (83m)Kr (t(1/2)=1.83h), it has to be supplied by a long-lived (83m)Kr((83)Rb) generator (t(1/2)=86d). Here, a hitherto unexploited method for the efficient production of (83)Rb and its suitability for its application in the KATRIN monitor spectrometer is described.