6 research outputs found
Sharpening Low-Energy, Standard-Model Tests via Correlation Coefficients in Neutron Beta-Decay
The correlation coefficients a, A, and B in neutron beta-decay are
proportional to the ratio of the axial-vector to vector weak coupling
constants, g_A/g_V, to leading recoil order. With the advent of the next
generation of neutron decay experiments, the recoil-order corrections to these
expressions become experimentally accessible, admitting a plurality of Standard
Model (SM) tests. The measurement of both a and A, e.g., allows one to test the
conserved-vector-current (CVC) hypothesis and to search for second-class
currents (SCC) independently. The anticipated precision of these measurements
suggests that the bounds on CVC violation and SCC from studies of nuclear
beta-decay can be qualitatively bettered. Departures from SM expectations can
be interpreted as evidence for non-V-A currents.Comment: 4 pages, REVTeX, intro. broadened, typos fixed, to appear in PR
Induced pseudoscalar coupling of the proton weak interaction
The induced pseudoscalar coupling is the least well known of the weak
coupling constants of the proton's charged--current interaction. Its size is
dictated by chiral symmetry arguments, and its measurement represents an
important test of quantum chromodynamics at low energies. During the past
decade a large body of new data relevant to the coupling has been
accumulated. This data includes measurements of radiative and non radiative
muon capture on targets ranging from hydrogen and few--nucleon systems to
complex nuclei. Herein the authors review the theoretical underpinnings of
, the experimental studies of , and the procedures and uncertainties
in extracting the coupling from data. Current puzzles are highlighted and
future opportunities are discussed.Comment: 58 pages, Latex, Revtex4, prepared for Reviews of Modern Physic