Measurement of the Weak Axial-Vector Coupling Constant in the Decay of Free Neutrons Using a Pulsed Cold Neutron Beam

We present a precision measurement of the axial-vector coupling constant g(A) in the decay of polarized free neutrons. For the first time, a pulsed cold neutron beam was used for this purpose. By this method, leading sources of systematic uncertainty are suppressed. From the electron spectra we obtain lambda = g(A)/g(V) = -1.27641 (45)(stat)(33)(sys), which confirms recent measurements with improved precision. This corresponds to a value of the parity violating beta asymmetry parameter of A(0) = -0.11985 (17)(stat)(12)(sys). We discuss implications on the Cabibbo-Kobayashi-Maskawa matrix element V-ud and derive a limit on left-handed tensor interaction.