M. Šefčík | Searcharxiv

arXiv2023

Gamma-ray energies and intensities observed in decay chain $^{83}Rb$/$^{83m}Kr$/$^{83}Kr$

Radioactive sources of the monoenergetic low-energy conversion electrons from the decay of isomeric $^{83m}Kr$ are frequently used in the systematic measurements, particularly in the neutrino mass and dark matter experiments. For this purpose, the isomer is obtained by the decay of its parent radionuclide $^{83}Rb$. In order to get more precise data on the gamma-rays occuring in the $^{83}Rb$/$^{83m}Kr$ chain, we re-measured the relevant gamma-ray spectra, because the previous measurement took place in 1976. The obtained intensities are in fair agreement with this previous measurement. We have, however, improved the uncertainties by a factor of 4.3, identified a new gamma transition and determined more precisely energies of weaker gamma transitions.

nucl-ex↗

arXiv2021

Analysis methods for the first KATRIN neutrino-mass measurement

We report on the data set, data handling, and detailed analysis techniques of the first neutrino-mass measurement by the Karlsruhe Tritium Neutrino (KATRIN) experiment, which probes the absolute neutrino-mass scale via the $β$-decay kinematics of molecular tritium. The source is highly pure, cryogenic T$_2$ gas. The $β$ electrons are guided along magnetic field lines toward a high-resolution, integrating spectrometer for energy analysis. A silicon detector counts $β$ electrons above the energy threshold of the spectrometer, so that a scan of the thresholds produces a precise measurement of the high-energy spectral tail. After detailed theoretical studies, simulations, and commissioning measurements, extending from the molecular final-state distribution to inelastic scattering in the source to subtleties of the electromagnetic fields, our independent, blind analyses allow us to set an upper limit of 1.1 eV on the neutrino-mass scale at a 90\% confidence level. This first result, based on a few weeks of running at a reduced source intensity and dominated by statistical uncertainty, improves on prior limits by nearly a factor of two. This result establishes an analysis framework for future KATRIN measurements, and provides important input to both particle theory and cosmology.

hep-ex↗