9-14 September 2018
University of Ferrara
Europe/Rome timezone

Reduced hadronic uncertainty in the determination of $V_{ud}$

11 Sep 2018, 16:40
A10 (Polo degli Adelardi - Via Adelardi, 33)


Polo degli Adelardi - Via Adelardi, 33

Parallel Sessions Low Energy Spin Physics with Lepton, Photon and Hadron Probes Low Energy Spin Physics with Lepton, Photon and Hadron Probes


Dr Mikhail Gorshteyn (Mainz University)


We propose a novel dispersion relations-based evaluation of the $\gamma W$-box correction to the universal radiative correction $\Delta_R^V$ to the neutron and nuclear $\beta$ decay. This correction is the main source of the theoretical uncertainty in extracting the value of $V_{ud}$ from those decay processes. We relate the needed input into the dispersion integral to the data on neutrino and antineutrino scattering. This leads to a significant shift in the central value accompanied by a reduction of the uncertainty due to hadronic structure. Applied to the superallowed nuclear $\beta$ decays, these two effect create a tension in the first row CKM unitarity if assuming all other ingredients remain unchanged, $|V_{ud}|^2+|V_{us}|^2+|V_{ub}|^2=0.9983(4)$. We discuss further ways to improve the precision of the calculation of the $\gamma W$-box, and point out that dispersion relations provide a unified formalism for hadronic and nuclear corrections to nuclear beta decay.

Primary author

Dr Mikhail Gorshteyn (Mainz University)

Presentation Materials