2023/08/31 by Ma, Peng-Xiang, Feng, Xu, Gorchtein, Mikhail +5 · 5 citations
#FOS: Physical sciences #High Energy Physics - Lattice (hep-lat) #High Energy Physics - Phenomenology (hep-ph) #Nuclear Experiment (nucl-ex)
paper · doi:10.48550/arxiv.2308.16755
We present the first lattice QCD calculation of the universal axial γW-box contribution \squareγWVA to both superallowed nuclear and neutron beta decays. This contribution emerges as a significant component within the theoretical uncertainties surrounding the extraction of |Vud| from superallowed decays. Our calculation is conducted using two domain wall fermion ensembles at the physical pion mass. To construct the nucleon 4-point correlation functions, we employ the random sparsening field technique. Furthermore, we incorporate long-distance contributions to the hadronic function using the infinite-volume reconstruction method. Upon performing the continuum extrapolation, we arrive at \squareγWVA=3.65(8)lat(1)PT×10-3. Consequently, this yields a slightly higher value of |Vud|=0.97386(11)exp.(9)RC(27)NS, reducing the previous 2.1σ tension with the CKM unitarity to 1.8σ. Additionally, we calculate the vector γW-box contribution to the axial charge gA, denoted as \squareγWVV, and explore its potential implications.