Abstract
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 $\beta$-decay kinematics of molecular tritium. The source is highly pure, cryogenic T$_2$ gas. The $\beta$ electrons are guided along magnetic field lines toward a high-resolution, integrating spectrometer for energy analysis. A silicon detector counts $\beta$ 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.
Highlights
The absolute mass scale of the neutrino remains a key open question in contemporary physics, with far-reaching implications from cosmology to elementary particle physics
[14,15] is further improving this approach to target a neutrino-mass sensitivity of 0.2 eV (90% C.L.) after five years of measurement time; note the change to 90% confidence level. This goal requires an improvement of about two orders of magnitude in the m2ν observable. To accomplish this challenging measurement, Karlsruhe Tritium Neutrino (KATRIN) relies on the proven technology of the magnetic adiabatic collimation with an electrostatic filter [(MAC-E filter), developed for neutrino-mass measurements by the Mainz and Troitsk groups [16,17] ] and a large β-decay luminosity provided by a gaseous molecular tritium source
Analog-to-digital converter Confidence level counts per second Data-acquisition system degree(s) of freedom electron gun molecular final-state distribution Focal-plane detector High voltage KATRIN neutrino mass run 1 LAser RAman spectroscopy system Λ cold-dark matter model Magnetic adiabatic collimation with electrostatic filter Monte Carlo part per million Probability of achieving a result as extreme as the one found, through statistical fluctuation Kinetic energy released in tritium β decay Region of interest Time of flight Windowless gaseous tritium source and their characteristics
Summary
The absolute mass scale of the neutrino remains a key open question in contemporary physics, with far-reaching implications from cosmology to elementary particle physics. After commissioning and characterizing the complex 70 m-long electron beam line, initially with monoenergetic calibration sources [19] and subsequently with first-tritium β electrons [20], the KATRIN Collaboration has recently reported an improved upper limit on the neutrino mass of mν < 1.1 eV (90% C.L.) based on an initial four-week science run [21] This result yields an improvement of about a factor of 2 with respect to the best previous direct bound. Analog-to-digital converter Confidence level counts per second Data-acquisition system degree(s) of freedom electron gun molecular final-state distribution Focal-plane detector High voltage KATRIN neutrino mass run 1 LAser RAman spectroscopy system Λ cold-dark matter model (cosmological standard model) Magnetic adiabatic collimation with electrostatic filter Monte Carlo part per million Probability of achieving a result as extreme as the one found, through statistical fluctuation Kinetic energy released in tritium β decay (for zero neutrino mass) Region of interest Time of flight Windowless gaseous tritium source and their characteristics.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
