Abstract The neutrino mass experiment KATRIN requires a stability of 3 ppm for the retarding potential at − 18.6 kV of the main spectrometer. To monitor the stability, two custom-made ultra-precise ...high-voltage dividers were developed and built in cooperation with the German national metrology institute Physikalisch-Technische Bundesanstalt (PTB). Until now, regular absolute calibration of the voltage dividers required bringing the equipment to the specialised metrology laboratory. Here we present a new method based on measuring the energy difference of two $$^{83{\mathrm{m}}}$$ 83m Kr conversion electron lines with the KATRIN setup, which was demonstrated during KATRIN’s commissioning measurements in July 2017. The measured scale factor $$M=1972.449(10)$$ M=1972.449(10) of the high-voltage divider K35 is in agreement with the last PTB calibration 4 years ago. This result demonstrates the utility of the calibration method, as well as the long-term stability of the voltage divider.
The primary objective of the KATRIN experiment is to probe the absolute neutrino mass scale with a sensitivity of 200 meV (90% C.L.) by precision spectroscopy of tritium beta-decay. To achieve this, ...a low background of the order of 10^(-2) cps in the region of the tritium beta-decay endpoint is required. Measurements with an electrostatic retarding spectrometer have revealed that electrons, arising from nuclear decays in the volume of the spectrometer, are stored over long time periods and thereby act as a major source of background exceeding this limit. In this paper we present a novel active background reduction method based on stochastic heating of stored electrons by the well-known process of electron cyclotron resonance (ECR). A successful proof-of-principle of the ECR technique was demonstrated in test measurements at the KATRIN pre-spectrometer, yielding a large reduction of the background rate. In addition, we have carried out extensive Monte Carlo simulations to reveal the potential of the ECR technique to remove all trapped electrons within negligible loss of measurement time in the main spectrometer. This would allow the KATRIN experiment attaining its full physics potential.
The KArlsruhe TRItium Neutrino (KATRIN) experiment is a next generation, model independent, large scale tritium beta-decay experiment to determine the effective electron anti-neutrino mass by ...investigating the kinematics of tritium beta-decay with a sensitivity of 200 meV/c2 using the MAC-E filter technique. In order to reach this sensitivity, a low background level of 0.01 counts per second (cps) is required. This paper describes how the decay of radon in a MAC-E filter generates background events, based on measurements performed at the KATRIN pre-spectrometer test setup. Radon (Rn) atoms, which emanate from materials inside the vacuum region of the KATRIN spectrometers, are able to penetrate deep into the magnetic flux tube so that the alpha-decay of Rn contributes to the background. Of particular importance are electrons emitted in processes accompanying the Rn alpha-decay, such as shake-off, internal conversion of excited levels in the Rn daughter atoms and Auger electrons. While low-energy electrons (< 100 eV) directly contribute to the background in the signal region, higher energy electrons can be stored magnetically inside the volume of the spectrometer. Depending on their initial energy, they are able to create thousands of secondary electrons via subsequent ionization processes with residual gas molecules and, since the detector is not able to distinguish these secondary electrons from the signal electrons, an increased background rate over an extended period of time is generated.
The focal-plane detector system for the KArlsruhe TRItium Neutrino (KATRIN) experiment consists of a multi-pixel silicon p-i-n-diode array, custom readout electronics, two superconducting solenoid ...magnets, an ultra high-vacuum system, a high-vacuum system, calibration and monitoring devices, a scintillating veto, and a custom data-acquisition system. It is designed to detect the low-energy electrons selected by the KATRIN main spectrometer. We describe the system and summarize its performance after its final installation.
The fact that neutrinos carry a non-vanishing rest mass is evidence of physics beyond the Standard Model of elementary particles. Their absolute mass bears important relevance from particle physics ...to cosmology. In this work, we report on the search for the effective electron antineutrino mass with the KATRIN experiment. KATRIN performs precision spectroscopy of the tritium \(\beta\)-decay close to the kinematic endpoint. Based on the first five neutrino-mass measurement campaigns, we derive a best-fit value of \(m_\nu^{2} = {-0.14^{+0.13}_{-0.15}}~\mathrm{eV^2}\), resulting in an upper limit of \(m_\nu < {0.45}~\mathrm{eV}\) at 90 % confidence level. With six times the statistics of previous data sets, amounting to 36 million electrons collected in 259 measurement days, a substantial reduction of the background level and improved systematic uncertainties, this result tightens KATRIN's previous bound by a factor of almost two.
The Karlsruhe Tritium Neutrino (KATRIN) experiment is designed to measure a high-precision integral spectrum of the endpoint region of T2 beta decay, with the primary goal of probing the absolute ...mass scale of the neutrino. After a first tritium commissioning campaign in 2018, the experiment has been regularly running since 2019, and in its first two measurement campaigns has already achieved a sub-eV sensitivity. After 1000 days of data-taking, KATRIN's design sensitivity is 0.2 eV at the 90% confidence level. In this white paper we describe the current status of KATRIN; explore prospects for measuring the neutrino mass and other physics observables, including sterile neutrinos and other beyond-Standard-Model hypotheses; and discuss research-and-development projects that may further improve the KATRIN sensitivity.
Some extensions of the Standard Model of Particle Physics allow for Lorentz invariance and Charge-Parity-Time (CPT)-invariance violations. In the neutrino sector strong constraints have been set by ...neutrino-oscillation and time-of-flight experiments. However, some Lorentz-invariance-violating parameters are not accessible via these probes. In this work, we focus on the parameters \((a_{\text{of}}^{(3)})_{00}\), \((a_{\text{of}}^{(3)})_{10}\) and \((a_{\text{of}}^{(3)})_{11}\) which would manifest themselves in a non-isotropic beta-decaying source as a sidereal oscillation and an overall shift of the spectral endpoint. Based on the data of the first scientific run of the KATRIN experiment, we set the first limit on \(\left|(a_{\text{of}}^{(3)})_{11}\right|\) of \(< 3.7\cdot10^{-6}\) GeV at 90\% confidence level. Moreover, we derive new constraints on \((a_{\text{of}}^{(3)})_{00}\) and \((a_{\text{of}}^{(3)})_{10}\).
In this work we present a keV-scale sterile-neutrino search with the first
tritium data of the KATRIN experiment, acquired in the commissioning run in
2018. KATRIN performs a spectroscopic ...measurement of the tritium $\beta$-decay
spectrum with the main goal of directly determining the effective electron
anti-neutrino mass. During this commissioning phase a lower tritium activity
facilitated the search for sterile neutrinos with a mass of up to $1.6\,
\mathrm{keV}$. We do not find a signal and set an exclusion limit on the
sterile-to-active mixing amplitude of down to $\sin^2\theta < 5\cdot10^{-4}$
($95\,\%$ C.L.), improving current laboratory-based bounds in the
sterile-neutrino mass range between 0.1 and $1.0\, \mathrm{keV}$.
We report on the direct cosmic relic neutrino background search from the first two science runs of the KATRIN experiment in 2019. Beta-decay electrons from a high-purity molecular tritium gas source ...are analyzed by a high-resolution MAC-E filter around the kinematic endpoint at 18.57 keV. The analysis is sensitive to a local relic neutrino overdensity of 9.7e10 (1.1e11) at a 90% (95%) confidence level. A fit of the integrated electron spectrum over a narrow interval around the kinematic endpoint accounting for relic neutrino captures in the Tritium source reveals no significant overdensity. This work improves the results obtained by the previous kinematic neutrino mass experiments at Los Alamos and Troitsk. We furthermore update the projected final sensitivity of the KATRIN experiment to <1e10 at 90% confidence level, by relying on updated operational conditions.
We present the results of the light sterile neutrino search from the second KATRIN measurement campaign in 2019. Approaching nominal activity, \(3.76 \times 10^6\) tritium \(\beta\)-electrons are ...analyzed in an energy window extending down to \(40\,\)eV below the tritium endpoint at \(E_0 = 18.57\,\)keV. We consider the \(3\nu+1\) framework with three active and one sterile neutrino flavor. The analysis is sensitive to a fourth mass eigenstate \(m_4^2\lesssim1600\,\)eV\(^2\) and active-to-sterile mixing \(|U_{e4}|^2 \gtrsim 6 \times 10^{-3}\). As no sterile-neutrino signal was observed, we provide improved exclusion contours on \(m_4^2\) and \(|U_{e4}|^2\) at \(95\,\)% C.L. Our results supersede the limits from the Mainz and Troitsk experiments. Furthermore, we are able to exclude the large \(\Delta m_{41}^2\) solutions of the reactor antineutrino and gallium anomalies to a great extent. The latter has recently been reaffirmed by the BEST collaboration and could be explained by a sterile neutrino with large mixing. While the remaining solutions at small \(\Delta m_{41}^2\) are mostly excluded by short-baseline reactor experiments, KATRIN is the only ongoing laboratory experiment to be sensitive to relevant solutions at large \(\Delta m_{41}^2\) through a robust spectral shape analysis.
PDF