New bounds of right-handed currents from a polarization asymmetry correlation measurement with 107In

The first measurement of the longitudinal positron polarization for polarized nucleus beta decay has been made for cryogenically polarized 107In. Time‐resolved decay of positronium hyperfine states was used to measure the positron polarization. Our preliminary result is in agreement with V‐A and sets a new semi‐leptonic limit on the mass of a possible right‐handed gauge boson.