Determination of the weak axial vector coupling \lambda = g_A/g_V from a measurement of the \beta-asymmetry parameter A in neutron beta decay

D. Mund, B. Märkisch, M. Deissenroth, J. Krempel, M. Schumann, H. Abele, A. Petoukhov, and T. Soldner

Accepted Thursday Feb 21, 2013

We report on a new measurement of the neutron b-asymmetry parameter A with the instrument . Main advancements are the high neutron polarization of P = 99.7(1)% from a novel arrangement of super mirror polarizers and reduced background from improvements in beam line and shielding. Leading corrections were thus reduced by a factor of 4, pushing them below the level of statistical error and resulting in a significant reduction of systematic uncertainty compared to our previous experiments. We derive the b-asymmetry parameter A0 = -0.11972(45)stat(+32-44)sys = -0.11972(+53-65), and the ratio of the axial-vector to the vector coupling constant l = gA/gV = -1.2761(12)stat(+9-12)sys = -1.2761(+14-17).