Limit on the Fierz Interference Term b from a Measurement of the Beta Asymmetry in Neutron Decay

Heiko Saul , Christoph Roick , Hartmut Abele , Holger Mest , Michael Klopf , Alexander Petukhov (1) , Torsten Soldner (1) , Xiangzun Wang , Dominik Werder , Bastian Märkisch

1 ILL - Institut Laue-Langevin

In the standard model of particle physics, the weak interaction is described by vector and axial-vector couplings only. Nonzero scalar or tensor interactions would imply an additional contribution to the differential decay rate of the neutron, the Fierz interference term. We derive a limit on this hypothetical term from a measurement using spin-polarized neutrons. This method is statistically less sensitive than the determination from the spectral shape but features much cleaner systematics. We obtain a limit of b=0.017(21) at 68.27% C.L., improving the previous best limit from neutron decay by a factor of four.

Mots clés: Nuclear Physics; n: decay; n: decay rate; coupling: axial-vector; interaction: tensor; interference; weak interaction; asymmetry; spectral; spin

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

Heiko Saul, Christoph Roick, Hartmut Abele, Holger Mest, Michael Klopf, et al.. Limit on the Fierz Interference Term b from a Measurement of the Beta Asymmetry in Neutron Decay. Phys.Rev.Lett., 2020, 125 (11), pp.112501. ⟨10.1103/PhysRevLett.125.112501⟩. ⟨hal-02394741⟩