Speaker
Description
The unitarity of the CKM quark mixing matrix can be tested by measuring the unitarity sum of the f irst row, which requires precision extraction of the first element (V$_\mathrm{ud}$). V$_\mathrm{ud}$ can be measured by combining measurement of the neutron lifetime with the axial-vector weak coupling constant. The Nab experiment, located at the Spallation Neutron Source at Oak Ridge National Lab is intended to measure the weak coupling constant by measuring a, the correlation coefficient between the emitted electron and antineutrino momenta in unpolarized neutron beta decay. Nab’s asymmetric spectrometer permits the full kinematic reconstruction of each decay event and thus the measurement of the energies of the coincident proton and electron from neutron beta decay, in turn permitting the reconstruction of the electron-antineutrino correlation. Pixelated silicon detectors at each end of the magnetic spectrometer permit the direct measurement of the electron energies and the time of flight of the coincident protons. In this talk, we will present the status of the Nab experiment, including preliminary results from early data runs, as well as proposed future use of the Nab spectrometer to measure polarized neutron beta decay correlations.
