J. Bonn

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

A solenoid retarding spectrometer with high resolution and transmission for keV electrons

\beta

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

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

Improved limit on the electron-antineutrino rest mass from tritium β-decay

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

The Mainz neutrino mass experiment

eV2/c4. We derive an upper limit of

Hyperfine structure and isotope shifts of neutron-rich138–146Cs

m(\nu_e)\leq 2.3

Status and perspectives of the Mainz neutrino mass experiment

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

Measurement of energy resolution and dead layer thickness of LN2-cooled PIN photodiodes

Abstract We have built an electrostatic electron spectrometer combining both high resolution and large luminosity. The instrument consists essentially of two superconducting solenoids separated by a system of ring electrodes of 4 m in length. Source and detector are placed in the high-field regions of the superconducting solenoids, whereas the repellent analyzing electrostatic potential of the ring electrodes peaks at the minimum of the magnetic field in between these solenoids. The magnetic guiding field provides (i) the acceptance of the full foreward solid angle of 2π, (ii) the transformation of the transverse cyclotron motion into longitudinal motion parallel to the magnetic field. The energy resolution of the electrostatic filter is determined by the ratio of the magnetic fields at the source and in the analyzing plane. It is typically 5 × 10 3 in our case. The spectrometer will serve first of all to investigate the limits of the rest mass of the electron antineutrino from 3 H 2 s-decay. It has been tested by measuring conversion lines from a 83m Kr source which yielded an energy of Eγ = 32151.5(11) eV for the corresponding nuclear transition.

Precision measurement of the conversion electron spectrum of83m Kr with a solenoid retarding spectrometer

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.

Half-lives, neutron emission probabilities and fission yields of neutron-rich rubidium isotopes in the mass regionA=96 toA=100

Abstract The endpoint region of the β-spectrum of tritium was remeasured by an electrostatic spectrometer with magnetic guiding field. It enabled the search for a rest mass of the electron-antineutrino with improved precision. The result is m2v=−39±34stat±15syst(eV/c2)2, from which an upper limit of mv m( T )−m( 3 He )=18 591±3 eV /c 2 .