title: Determination of the weak axial vector coupling λ = gA/gV from a measurement of the β-asymmetry parameter A in neutron beta decay.
abstract: We report on a new measurement of the neutron β-asymmetry parameter A with the instrument Perkeo II. The main enhancements are the high neutron polarization of P = 99.7(1)% from a novel arrangement of supermirror polarizers and reduced background from improvements in beam line and shielding. The 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 β-asymmetry parameter A0 = -0.11972(45)(stat)((-44)(+32))(sys) = -0.11972((-65)(+53)) and the ratio of the axial vector to the vector coupling constant λ = gA/gV = -1.2761(12)(stat)((-12)(+9))(sys) = -1.2761((-17)(+14)).
authors.affiliation: Physikalisches Institut, Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Mund
authors.forename: B
authors.initials: B
authors.lastname: Märkisch
authors.forename: M
authors.initials: M
authors.lastname: Deissenroth
authors.forename: J
authors.initials: J
authors.lastname: Krempel
authors.forename: M
authors.initials: M
authors.lastname: Schumann
authors.forename: H
authors.initials: H
authors.lastname: Abele
authors.forename: A
authors.initials: A
authors.lastname: Petoukhov
authors.forename: T
authors.initials: T
authors.lastname: Soldner