Saul H, Roick C, Abele H, Mest H, Klopf M, Petukhov A K, Soldner T, Wang X, Werder D, Märkisch B
Physik-Department ENE, Technische Universität München, James-Franck-Straße 1, 85748 Garching, Germany.
Technische Universität Wien, Atominstitut, Stadionallee 2, 1020 Wien, Austria.
Phys Rev Lett. 2020 Sep 11;125(11):112501. doi: 10.1103/PhysRevLett.125.112501.
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.
