New precision measurements of free neutron beta decay with cold neutrons

High Precision Neutron Beta-Decay Measurements

Precision Measurements in Neutron Decay

Free neutrons decay with a mean lifetime τn of about 15 minutes in electron, proton, and electron anti-neutrino: n → e p νe. The maximal kinetic energy of the electron is Emax(e) = 782 keV. For the proton, Emax(p) = 780 eV is three orders of magnitude smaller. Neutron decay – involving all particles of the first generation – constitutes an ideally suited laboratory to do particle physics at ver...

Precision Neutron Polarimetry for Neutron Beta Decay

The abBA collaboration is developing a new type of field-expansion spectrometer for a measurement of the three correlation coefficients a, A, and B and the shape parameter b. The measurement of A and B requires precision neutron polarimetry. We will polarize a pulsed cold neutron beam from the SNS using a (3)He neutron spin filter. The well-known polarizing cross section for n-(3)He has a 1/v d...

Measuring Neutron Beta Decay “A” Parameter Using Ultracold Neutrons

The UCNA experiment is designed to measure the neutron decay beta asymmetry (the "A" parameter) to very high precision (<0.5%), using the ultracold neutron (UCN) source at the Los Alamos National Lab. After a successful commissioning run in 2007, data were taken in 2008 which will lead to a 1% measurement of A. In this talk, I will discuss major improvements we made in 2008, and report the stat...

Precision measurements in nuclear –decay with LPCTrap

The experimental achievements and the current program with the LPCTrap device installed at the LIRAT beam line of the SPIRAL1-GANIL facility are presented. The device is dedicated to the study of the weak interaction at low energy by means of precise measurements of the  angular correlation parameter. Technical aspects as well as the main results are reviewed. The future program with new ava...