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

B Märkisch; H Mest; H Saul; X Wang; H Abele; D Dubbers; M Klopf; A Petoukhov; C Roick; T Soldner; D Werder

doi:10.1103/PhysRevLett.122.242501

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

Phys Rev Lett. 2019 Jun 21;122(24):242501. doi: 10.1103/PhysRevLett.122.242501.

Authors

B Märkisch^{1

2}, H Mest², H Saul^{1

3

4}, X Wang^{1

3}, H Abele^{1

2

3}, D Dubbers², M Klopf³, A Petoukhov⁵, C Roick^{1

2}, T Soldner⁵, D Werder²

Affiliations

¹ Physik-Department, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany.
² Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany.
³ Technische Universität Wien, Atominstitut, Stadionallee 2, 1020 Wien, Austria.
⁴ Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II), Technische Universität München, Lichtenbergstraße 1, 85748 Garching, Germany.
⁵ Institut Laue-Langevin, 71 avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France.

PMID: 31322367
DOI: 10.1103/PhysRevLett.122.242501

Abstract

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 λ=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.