Mott polarimeter for electrons from neutron decay in BRAND experiment

The BRAND experiment aims at the search of Beyond Standard Model (BSM) physics via measurement of exotic components of week interaction. For this purpose the eleven correlation coefficients of the neutron β decay will be measured simultaneously. Seven of them: H, L, N, R, S, U and V, are sensitive to the transverse polarization of electrons from free neutron decay. The correlation coefficients will be derived using Mott polarimetry and completely determined kinematics of products from the polarized neutron β decay. For this aim the beam of cold polarized neutrons available at the PF1B facility of the ILL, Grenoble will be utilized. The electron detection system features both the tracking and energy measurement capability as well as the Mott polarimetry for determination of the electron spin orientation. The 3D tracking is performed with the use of low density, helium based drift chamber with hexagonal cell structure which is optimised for β-particles. The Mott polarimeter is an integral part of the tacker. It consists of a thin Pb foil installed inside the drift chamber and two plastic scitillators, providing trigger and scattered electron energy measurement. The results of the first pilot run of the BRAND experiment performed in September'20 are reported with the emphasis on the description and the performance of the electron detection system and the Mott polarimeter.