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.

• Received 8 December 2000

DOI:https://doi.org/10.1103/PhysRevLett.86.5666