C.C. Chang, et al., A percent-level determination of the nucleon axial coupling from Quantum Chromodynamics, Nature 558 (2018) 91-94 

The neutron lifetime has profound consequences on the composition of the universe. This lifetime can be predicted from the Standard Model, and is dependent on the nucleon axial coupling g_A.   Determining this fundamental parameter is very challenging as the underlying theory of quantum chromodynamics (QCD) is non-perturbative, precluding the use of known analytic methods.  A team led LBNL staffers has recently performed the first ever percent-level determination of g_A using lattice QCD, a rigorous numerical implementation of QCD.  Critical to their success was the use of an innovative method to perform the calculations, as well as access to powerful supercomputers.  The results are statistics limited, signifying a straightforward path to improving the precision to a level commensurate with the experimental precision.  This may eventually lead to the resolution of the discrepancies in different neutron lifetime measurements.

Figure: A comparison of previous lattice QCD determinations of g_A with the present work and the experimental determination, from the Particle Data Group, 2018.