A NEW METHOD FOR THE DETERMINATION OF THE Vud QUARKMIXING MATRIX ELEMENT.

This project aims at a new measurement of the Vud CKM matrix element in order to search for new physics beyond the Standard Model. According to the Standard Model (SM) of elementary particles the CKM matrix should be unitary. Deviations from unitarity point to new physics beyond the SM. Unitarity can be verified experimentally by measuring the 3 upper-row matrix elements, who’s values squared should add up to 1. This has now been verified to a precision of 0.05%, and the error on the Vud and Vus matrix elements contribute equally to this current precision [Har09, Dow13]. Therefore new independent and precise measurements of Vud and Vus are being considered in order to further reduce their error bars. A recent survey on the beta-decay properties of five T=1/2 mirror decays, decaying though a mixed F/GT branch, has revealed that Vud can be determined to a precision of 0.17% from these data, although none of these studies where aiming at a high precision [Nav09]. Here we propose a dedicated high-precision measurement of the Vud matrix element through a dedicated high-precision study of the beta-asymmetry parameter in the 35Ar ground state mirror decay. The current relative precision on this asymmetry parameter is about 5%. We aim at improving this value with a factor of 10, yielding a precision on Vud of 0.04%, which is just a factor of 2 higher than the most precise value known today, as derived from dedicated measurements on 13 superallowed beta-decaying isotopes.