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Register a new userKATRIN: an experiment to measure the neutrino mass
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R. G. H. Robertson
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KATRIN is a very large scale tritium-beta-decay experiment to determine the mass of the neutrino. It is presently under construction at the Forschungszentrum Karlsruhe, and makes use of the Tritium Laboratory built there for the ITER project. The combination of a very large retarding-potential electrostatic-magnetic spectrometer and an intense gaseous molecular tritium source makes possible a sensitivity to neutrino mass of 0.2 eV, about an order of magnitude below present laboratory limits. The measurement is kinematic and independent of whether the neutrino is Dirac or Majorana. The status of the project is summarized briefly in this report.
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The KArlsruhe TRItium Neutrino (KATRIN) experiment is designed to measure tritium $beta$-decay spectrum with enough precision to be sensitive to neutrino mass down to 0.2eV at 90$%$ Confidence Level. After an initial first tritium run in the summer of 2018, KATRIN is taking tritium data in 2019 that should lead to a first neutrino mass result. The $beta$ spectral shape of the tritium decay is also sensitive to four countershaded Lorentz Violating (LV), oscillation-free operators within the Standard-Model Extension that may be quite large. The status and outlook of KATRIN to produce physics results, including in the LV sector, are discussed.
We propose a beta decay experiment based on a sample of ultracold atomic tritium. These initial conditions enable detection of the helium ion in coincidence with the beta. We construct a two-dimensional fit incorporating both the shape of the beta-spectrum and the direct reconstruction of the neutrino mass peak. We present simulation results of the feasible limits on the neutrino mass achievable in this new type of tritium beta-decay experiment.
We studied the effects of the absolute neutrino mass scale in the scotogenic radiative seesaw model. From a scan over the parameter space of this model, a linear relation between the absolute neutrino mass and the dark sector-Higgs coupling $lambda_5= 3.1times10^{-9} m_{ u_e}/$eV has been established. With the projected sensitivity of the KATRIN experiment nearing cosmologically favored values, a neutrino mass measurement would fix the value of $lambda_5$. Subsequent correlations between the DM mass and the Yukawa coupling between DM and the SM leptons can probe the fermion DM parameter space, when lepton flavor violation constraints are also considered. The results are independent of the neutrino mass hierarchy and the CP phase.
The assessment of neutrino absolute mass scale is still a crucial challenge in today particle physics and cosmology. Beta or electron capture spectrum end-point study is currently the only experimental method which can provide a model independent measurement of the absolute scale of neutrino mass. HOLMES is an experiment funded by the European Research Council to directly measure the neutrino mass. HOLMES will perform a calorimetric measurement of the energy released in the electron capture decay of the artificial isotope $^{163}$Ho. In a calorimetric measurement the energy released in the decay process is entirely contained into the detector, except for the fraction taken away by the neutrino. This approach eliminates both the issues related to the use of an external source and the systematic uncertainties arising from decays on excited final states. The most suitable detectors for this type of measurement are low temperature thermal detectors, where all the energy released into an absorber is converted into a temperature increase that can be measured by a sensitive thermometer directly coupled with the absorber. This measurement was originally proposed in 1982 by A. De Rujula and M. Lusignoli, but only in the last decade the technological progress in detectors development has allowed to design a sensitive experiment. HOLMES plans to deploy a large array of low temperature microcalorimeters with implanted $^{163}$Ho nuclei. In this contribution we outline the HOLMES project with its physics reach and technical challenges, along with its status and perspectives.
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.
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