  Precision measurements in nuclear beta decay offer a sensitive window to
search for new physics beyond the standard electroweak model and allow also the
determination of the fundamental weak vector coupling in processes involving
the lightest quarks. Searches for new physics are also a strong motivation for
experiments carried out at the high energy frontier reached at the most
powerful particle colliders. It is instructive to confront results from the low
energy and the high energy frontiers in order to look for possible
complementarities and orient new avenues for experiments at low energies. We
review here the status of constraints on new physics obtained from nuclear and
neutron decays and compare them to those from other semi-leptonic processes and
from the LHC. We stress the requirements of new precision experiments in beta
decay in order to impact the search for new physics at the light of current and
projected LHC results. We describe recent experimental results and ongoing
developments in nuclear and neutron beta decay, with emphasis on their planned
goals to improve present limits on exotic weak couplings.
