Abstract:
With more intense sources of cold and ultracold neutrons becoming available and with improved experimental techniques being developed, determination of |Vud| from neutron beta decay with a similar precision to that from from superallowed beta decays is within reach. Determination of |Vud| from neutron beta decay, free from nuclear corrections, hold the most promise for a further improvement of the determination of |Vud|. The current and future neutron beta decay correlation experiments including the UCNA experiment at Los Alamos National Laboratory are reviewed

Abstract:
The matrix element Vud of the CKM matrix can be determined by two independent measurements on neutron decay: the neutron lifetime tau and the ratio of coupling constants lambda, which is most precisely determined by measurements of the beta asymmetry angular correlation coefficient A. We present recent progress on the determination of these values and derive a world average of Vud = 0.9743 (2)RC (8)tau (12)lambda.

Abstract:
Harvey, Hill, and Hill have found that unexpected interactions involving the nucleon, photon, and weak gauge bosons at low energies emerge from gauging the axial anomaly of QCD under the full electroweak symmetry of the Standard Model (SM). In this contribution we consider how such interactions can be isolated through a triple-product momentum correlation in neutron radiative beta-decay. The correlation is both parity- and naively time-reversal-odd, so that it vanishes in the Standard Model save for effects induced by final-state interactions (FSI). Nevertheless, the correlation can be generated by sources of CP violation beyond the Standard Model, and such couplings, being spin-independent, are not constrained by the nonobservation of the neutron electric dipole moment (EDM). We consider the sorts of limits on its strength which can be determined at existing and anticipated facilities, as well as the size of induced correlations from known FSI. We also briefly consider the possibility of nuclear beta-decay studies as well as the prospects for muon-induced reaction studies.

Abstract:
The Vud element of the Cabibbo-Kobayashi-Maskawa matrix can be determined from several different experimental approaches: either 0+-to-0+ superallowed nuclear beta decays, neutron decay, nuclear mirror decays, or pion beta decay. Currently all give consistent results but, because the nuclear superallowed value has an uncertainty at least a factor of seven less than all other results, it dominates the result. A new survey of world superallowed-decay data establishes the Ft values of 14 separate superallowed transitions to a precision of order 0.1% or better; and all 14 are statistically consistent with one another. This very robust data set yields the result Vud = 0.97417(21), the value we recommend.

Abstract:
The best value for Vud comes from superallowed 0+ to 0+ nuclear beta transitions, of which thirteen have now been measured with high precision. The current status of these measurements is described, and the result compared with that of measurements from neutron decay and pion beta decay. Future prospects for improvement are discussed.

Abstract:
The best value for Vud comes from superallowed 0+ to 0+ nuclear beta transitions, of which thirteen have now been measured with high precision. The current status of these measurements is described, and the result compared with that of measurements from neutron decay and pion beta decay. Future prospects for improvement are discussed.

Abstract:
The experimental determination of V_{ud} from neutron beta decay requires accurate values of the neutron lifetime and the ratio of the weak axial-vector to vector coupling constants of the nucleon. The latter is derived from measurements of angular correlation coefficients in the differential decay probability, such as the beta asymmetry parameter A, the neutrino-electron angular correlation coefficient a, or the parameter C of the proton asymmetry. As a probe free from nuclear structure corrections the decay of the free neutron has the potential to provide the most accurate value of V_{ud}. Towards that end however, the experimental sensitivity still needs to be further improved to become competitive with superallowed nuclear beta decays. This contribution briefly reviews the current status of those neutron decay studies relevant for the determination of V_{ud}.

Abstract:
The experimental determination of V_{ud} from neutron beta decay requires accurate values of the neutron lifetime and the ratio of the weak axial-vector to vector coupling constants of the nucleon. The latter is derived from measurements of angular correlation coefficients in the differential decay probability, such as the beta asymmetry parameter A, the neutrino-electron angular correlation coefficient a, or the parameter C of the proton asymmetry. As a probe free from nuclear structure corrections the decay of the free neutron has the potential to provide the most accurate value of V_{ud}. Towards that end however, the experimental sensitivity still needs to be further improved to become competitive with superallowed nuclear beta decays. This contribution briefly reviews the current status of those neutron decay studies relevant for the determination of V_{ud}.

Abstract:
Precision measurements in neutron beta decay serve to determine the coupling constants of beta decay and allow for several stringent tests of the standard model. This paper discusses the design and the expected performance of the Nab spectrometer.