N. A. Titov

Direct search for neutrino mass and anomaly in the tritium beta-spectrum: Status of “Troitsk neutrino mass” experiment

Abstract Results of the “Troitsk ν-mass” experiment on search for the neutrino rest mass in the tritium beta-decay are presented. New data on the time dependence of the anomalous, bump-like structure at the end of the beta spectrum reported earlier are discussed. Possible systematics is considered in view of contradiction of “Troitsk nu-mass” observation with those of “Mainz neutrino” set-up. An upper limit for electron antineutrino rest mass remains at m ν 2.5eV c 2 at 95% C.L.

Results of the troitsk experiment on the search for the electron antineutrino rest mass in tritium beta-decay

Abstract The end-point region of the β-spectrum of tritium has been measured with an integral electrostatic spectrometer with adiabatic magnetic collimation and gaseous tritium source. The search for the neutrino rest mass has resulted in m ν 2 = − 22 ± 4.8 eV 2 / c 4 . It is shown that the negative m ν 2 effect may be explained by the local enhancement in the region 7–15 eV below the end point with an integral B.R. of about 10 −10 . After accounting for this anomaly one is able to deduce that m ν

Neutrino mass and anomaly in the tritium beta-spectrum. Results of the “Troitsk ν-mass” experiment

Abstract Results of the “Troitsk ν-mass” experiment on the search for the neutrino rest mass in the tritium beta-decay are presented. Study of time dependence of anomalious, bump-like structure at the end of beta spectrum reported earlier gives indication of periodic shift of the position of the bump with respect to end-point energy with period of 0.5 year. New upper limit for electron antineutrino rest mass m ν eV / c 2 is derived after accounting for the bump. Possible variants of more sensitive facility are discussed.

Neutrino rest mass and anomaly in the tritium β spectrum

The results of the “Troitsk ν -mass” experiment on the search for the neutrino rest mass in the tritium β -decay are presented. The study of the time dependence of an anomalous, bump-like structure at the end of β -spectrum reported earlier, gives an indication of a periodic shift of the position of the bump with respect to the end-point energy with a period of 0.5 year. A new upper limit for the electron antineutrino rest mass m ν 2 2 is derived after taking into account the effect of the bump.

Effects of plasma phenomena on neutrino mass measurements process using a gaseous tritium β-source

In the paper the ionization state of molecular tritium and electric potentials in a Windowless Gas Tritium Source (WGTS) of tritium β-decay experiment KATRIN are considered. The ionization processes in WGTS are sustained by β-electrons and so-called “secondary electrons”, arising from inelastic and ionization collisions of “primary” β-electrons with tritium molecules. As a result in the WGTS tritium gas volume acts as a low-temperature and slightly ionized gas steady state close to quasi neutrality (the Debye length is small in comparison with the setup characteristical sizes). On the basis of an one-dimensional self-consistent model the WGTS plasma steady state is described and the influence of plasma phenomena on neutrino mass measuring process is discussed. It is found that electric potentials in a main plasma volume can not significantly make worse the measurement process. At the same time the nonequilibrium electron spectrum and fast plasma flow at the end of the tube can result in instabilities which are able to spoil slightly the β-electron spectrum endpoint. This problem must be carefully investigated further. For more reliable conclusions more detailed consideration is required that will include kinetic effects in the WGTS plasma.

Direct search for mass of neutrino and anomaly in the tritium beta-spectrum

Abstract Results of the “Troitsk ν-mass” experiment on the search for the neutrino rest mass in the tritium beta-decay are presented. Study of time dependence of anomalious, bump-like structure at the end of beta spectrum reported earlier gives indication of periodic shift of the position of the bump with respect to end-point energy with period of 0.5 year. New upper limit for electron antineutrino rest mass m ν eV c 2 is derived after accounting for the bump.

Parity violation in p-p scattering: the TRIUMF experiment

Parity violation in proton-proton elastic scattering provides a unique window on the hadronic weak interaction. At low and intermediate energies, the coupling constants of an effective meson exchange model provide an appropriate parametrization. Measurements at different beam energies permit the lowest partial wave amplitudes to be determined in a model independent framework. The TRIUMF cyclotron provides a unique opportunity to measure the 3P2−1D2 contribution to proton-proton parity violation at 221 MeV beam energy. This partial wave in turn isolates the weak ρ meson exchange contribution, which is only known to within a factor of 2 from theoretical estimates. An experiment underway for many years at TRIUMF completed data taking in 1999, and the analysis is now nearing completion. Preliminary results, based on half of the acquired data sample, are consistent with the meson exchange model prediction at this beam energy.

Neutrino rest mass and anomaly in the tritium beta-spectrum

Abstract The end point region of the tritium beta-spectrum has been studied on the “Troitsk ν -mass” set-up during 1993–1997. Fits to the data give evidence for the existence of a bump-like structure placed 5–12 eV below end point with a relative intensity about 10 −10 . The comparison of the anomaly region of the spectrum measured at different time reveals a movement of the bump position back and forth with respect to end point energy. After accounting for the bump and a correction for effect of electron trapping in the source the shape of all the measured part of the beta spectrum agree with m ν 2 about zero thus eliminating the problem of “negative m ν 2 ”. An upper limit for the neutrino mass including only data of 1994–1996 runs is: m ν eV / c 2 at 95% C.L.