A. Kovalik

Final results from phase II of the Mainz neutrino mass searchin tritium \({\beta}\) decay

Abstract.This paper reports on the improved Mainz experiment on tritium

High precision measurement of the tritium β spectrum near its endpoint and upper limit on the neutrino mass

beta

The Mainz neutrino mass experiment

spectroscopy which yields a 10 times higher signal to background ratio than before. The main experimental effects and systematic uncertainties have been investigated in side experiments, and possible error sources have been eliminated. Extensive data taking took place in the years 1997 to 2001. A residual analysis of the data sets yields for the square of the electron antineutrino mass the final result of

Ultra-stable implanted 83Rb/83mKr electron sources for the energy scale monitoring in the KATRIN experiment

m^2(nu_e) = (-0.6 pm 2.2_{mathrm{{stat}}} pm 2.1_{mathrm{{syst}}})

Newest results from the Mainz neutrino mass experiment

eV2/c4. We derive an upper limit of

Newest results from the Mainz neutrino-mass experiment

m(nu_e)leq 2.3

Results from the Mainz neutrino mass experiment

eV/c2 at 95% confidence level for the mass itself.

New results from the mainz neutrino mass experiment

Abstract The Mainz neutrino mass experiment investigates the endpoint region of the tritium β decay spectrum to determine the mass of the electron antineutrino. By the recent upgrade the former problem of dewetting T2 films has been solved and the signal-to-background-ratio was improved by a factor of 10. The latest measurement leads to m ν 2 =−3.7±5.3 stat ±2.1 sys eV 2 /c 4 , from which an upper limit of m ν eV/c 2 (95% C.L.) is derived. Some indication for the anomaly, reported by the Troitsk group, was found, but its postulated half year period is contradicted by our data.

Latest results from the Mainz neutrino mass experiment

The Mainz neutrino mass experiment is investigating the endpoint region of the tritium β decay spectrum to determine the mass of the electron antineutrino. For this purpose we have developed a new type of spectrometer with magnetic adiabatic collimation and subsequent e lectrostatic filter (MAC-E filter) [1]. After finishing an extensive improvement programme in 1997 measurements have been resumed in 1998 with a 5 times higher signal rate and a two times lower background rate (≈ 15 mHz). Also the homogeneous thickness of the evaporated T2 source film could be stabilized by cooling it down to temperatures below 2 K. Thereby, previously observed systematic distortions of the spectrum by an uncontrolled energy loss in a dewetted, recrystalized film could be avoided [2,3]. On the other hand, we have discovered and explained a charging of the T2 film up to a critical field strength of 62 MV/m due to the residual daughter ions after β decay [4]. Until end of 2001, 12 runs (Q1 Q12) covering a total measuring time of one year will have been performed with the upgraded apparatus. Results up to Q5 have been published in ref. [5] with the result mν = (3.7 ± 5.3stat ± 2.1sys) eV/c which corresponds to an upper limit for the neutrino mass of mν ≤ 2.8 eV/c 2 (95 % C.l.). In a recent update [6] runs up to Q8 are included in the analysis yielding (preliminarly) mν = (1.6 ± 2.5stat ± 2.1sys) eV/c and mν ≤ 2.2 eV/c (95 % C.l.).

SCATTERING OF ELECTRONS IN BETA-SPECTROSCOPY SOURCES

The KATRIN experiment aims at the direct model-independent determination of the average electron neutrino mass via the measurement of the endpoint region of the tritium beta decay spectrum. The electron spectrometer of the MAC-E filter type is used, requiring very high stability of the electric filtering potential. This work proves the feasibility of implanted 83Rb/83mKr calibration electron sources which will be utilised in the additional monitor spectrometer sharing the high voltage with the main spectrometer of KATRIN. The source employs conversion electrons of 83mKr which is continuously generated by 83Rb. The K–32 conversion line (kinetic energy of 17.8 keV, natural line width of 2.7 eV) is shown to fulfill the KATRIN requirement of the relative energy stability of ±1.6 ppm/month. The sources will serve as a standard tool for continuous monitoring of KATRINs energy scale stability with sub-ppm precision. They may also be used in other applications where the precise conversion lines can be separated from the low energy spectrum caused by the electron inelastic scattering in the substrate.