Bonn 2020 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 61: Astroparticle Physics II

HK 61.1: Group Report

Friday, April 3, 2020, 11:00–11:30, J-HS L

Measurement of weak couplings in neutron beta decay — •Bastian Märkisch¹, Hartmut Abele², Dirk Dubbers³, Holger Mest³, Michael Klopf², Alexander Petoukhov⁴, Christoph Roick¹, Heiko Saul¹, Torsten Soldner⁴, Xiangzun Wang², and Dominik Werder³ — ¹Physik-Department, Technische Universität München, Germany — ²Technische Universität Wien, Atominstitut, Austria — ³Physikalisches Institut, Universität Heidelberg, Germany — ⁴Institut Laue-Langevin, Grenoble, France

We present the most precise determination of the nucleon axial coupling from a measurement of the beta asymmetry in the decay of polarized neutrons. The instrument Perkeo III was installed at the PF1b beamline at the Institut Laue-Langevin, Grenoble, France. Leading sources of systematic error are eliminated or controlled by using a pulsed cold neutron beam. This measurement confirms previous results by Perkeo II and UCNA with improved precision. From it we determinate the CKM matrix element V_ud, and derive constraints on tensor interactions and a best limit on the Fierz interference term b from neutron decay. We conclude by presenting the status of the follow-up facility PERC at the FRM II, Garching.