Yu. A. Mostovoi

Measurement of the Antineutrino Escape Asymmetry With Respect to the Spin of the Decaying Neutron

The result of a new run of measurements of the antineutrino escape asymmetry with respect to the spin of the decaying neutron is presented. The asymmetry coefficient is B=0.9821±0.0040, which is consistent with the prediction of the standard model of weak interactions. The prospects for increasing the accuracy of the measurements are discussed.

Experimental value of GA/GV from a measurement of both P-odd correlations in free-neutron decay

A new experimental value of the fundamental weak-interaction parameter λ=GA/GV (−1.2686±0.0046) is obtained for the first time by an original method that consists in measuring both P-odd correlations in free-neutron decay.

The upper limit of the branching ratio for radiative beta decay of free neutrons

We conducted an experiment on radiative neutron beta decay on an intensive cold-neutron beam at ILL during April and May 2002. This work is dedicated to the analysis of the methodology and the results of the study. The main outcome of this experiment is the branching ratio (BR) for the rare neutron-decay mode in the gamma-ray quanta energy region from 35 to 100 keV. The limit obtained is BR<6.9×10−3 (90% C.L.), which is only a few permilles greater than the theoretical BR value calculated within the standard weak-interactions model.

Search for Radiative β-Decay of the Free Neutron

Results of the first experiment to search for the radiative decay mode of the free neutron are reported. The γ-spectrum was studied in the energy region from 35 keV to 100 keV in six Cs(Tl) scintillators, each set at an angle of 35° to, and shielded from, a central plastic scintillator electron detector. Triple coincidences were recorded with recoil protons detected in a micro-channel plate. A limit for the branching ratio BR < 6.9 × 10−3 (90 % confidence level) was obtained, which is greater that the theoretical prediction by not more than a few tenths of a percent.

Estimation of scalar and tensor weak-interaction constants on the basis of recent neutron experimental data

The contributions of scalar and tensor interactions associated with right-handed neutrinos to the effective hadron-lepton Hamiltonian are estimated on the basis of modern measurements of the neutron lifetime and correlations in the beta decay of a free neutron.