SMuK 2023 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 62: Astroparticle Physics I

HK 62.1: Gruppenbericht

Donnerstag, 23. März 2023, 14:00–14:30, SCH/A252

Probing the Standard Model in Free Neutron Decay — •Karina Bernert, Max Lamparth, and Bastian Märkisch — Technische Universität München, Germany

(For the PERKEO and PERC consortia) Measurements of free neutron decay enable a variety of tests of the Standard Model of particle physics. Among the observables are the parity-violationg beta asymmetry A, and the Fierz interference term b. From precision measurements of A and the neutron lifetime, the CKM matrix element V_ud is determined without nuclear corrections. It serves as input for the first-row unitarity test of the CKM matrix and the current Cabibbo-angle anomaly. A non-zero Fierz term b would signal the existence of novel scalar and tensor interactions.

With its unique measurement technique, PERKEO III delivers the currently most precise values of A and b using a polarized neutron beam. We present the status of the data analysis of the most recent campaign at the ILL PF1b beam line in Grenoble, France, with the aim to extract an improved limit for the Fierz term b from the electron spectrum.

Meanwhile, the new PERC (Proton Electron Radiation Channel) facility is being set up at the research reactor FRM II of the Heinz Maier-Leibnitz Zentrum in Garching, with the aim to measure correlation coefficients one order of magnitude more precisely.