Speaker: Vladimir Gudkov (University of South Carolina)

NEW GENERATION OF NEUTRON DECAY EXPERIMENTS AND RADIATIVE CORRECTIONS

Neutron beta-decay experiments provide the most precise value of nucleon axial-vector coupling constant. The best values of vector coupling constant and the largest Cabibbo-Kobayashi-Maskawa (CKM) matrix element $V_{ud}$ are obtained from the measurements of Fermi transitions in nuclear beta-decay. Increasing the accuracy of neutron decay experiments can lead to the opportunity to obtain the matrix element $V_{ud}$ within the accuracy comparable to nuclear beta-decay data. Therefore, we can approach the solution of the unitarity problem of the CKM matrix in nuclear model independent way. The opportunity to solve the unitarity problem and the sensitivity to the possible manifestations of deviations from the Standard Model change the status of neutron beta-decay experiments, ranking them closely to the most fundamental experiments in physics. However, radiative corrections for neutron decay have the same order of magnitude as a desirable accuracy of the experiments. In that connection, the current status and a new approach for calculations of radiative corrections, and suggestions for analysis of neutron beta-decay experiments are discussed.