Characterization of large area and thick silicon detectors for neutron beta decay experiments
A. Salas Bacci 1*
1 Department of Physics, University of Virginia, USA
The “Nab” collaboration will measure the electron-neutrino correlation parameter “a”, and the Fierz interference term “b” that are found in the triple differential neutron decay rate equation from neutron decay (n->p+e- + ν-e). These parameters will be measured using unpolarized neutrons at SNS in Oak Ridge National Laboratory. The importance of the measurement of the parameter “a” to 1E-3 accuracy level relies in the fact that this parameter is related to the ratio of the axial-vector to vector coupling constant, λ, which in turn and in combination with the neutron lifetime allow a determination of Vud, the u-d CKM matrix element; meanwhile the Fierz term will provide and independent limit on the tensor weak coupling.
In the “Nab” experiment, both the electron and proton will be accelerated in a 4π-field spectrometer, and detected by a novel detector design consisting of two opposite large area and thick silicon detectors segmented in 127 pixels per detector, and operated at ~100 Kelvin. During the last year we have successfully completed the first phase of detector characterization, operating 0.5, 1.0, and 1.5 mm thick Silicon detectors of 11 cm in diameter for neutron decay experiments at Los Alamos National Laboratory. We will present the status of Silicon detector characterization for 30 keV proton detection.