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HK: Fachverband Physik der Hadronen und Kerne

HK 72: Poster

HK 72.46: Poster

Donnerstag, 14. März 2024, 17:15–18:45, HBR 14: Foyer

Status of the Fierz term analysis with PERKEO III — •Anna Schubert for the PERKEO III collaboration — Technical University of Munich, Garching, Germany

Measurements of the free neutron decay enable a variety of tests of the Standard Model of particle physics. Observables of the decay are, among others, the beta asymmetry A and the Fierz interference term b. From precision measurements of A the CKM matrix element V_ud may be determined, while a non-zero Fierz term b would signal the existence of scalar and tensor interactions beyond the Standard Model.

Determinations of these neutron decay parameters were pursued by the PERKEO III experiment by measurements of the electron and/or proton energy spectrum, during multiple runs at the ILL PF1b facility. For these measurements, we used a pulsed beam of cold neutrons to control major systematic effects. This beam is guided into the 2 m long decay volume of the experiment, in which some of the neutrons decay. The charged particles from the decay are guided by a magnetic field towards one of two scintillation detectors with PMT readout. With this measurement technique, PERKEO III delivers the currently most precise values for A and b with a polarized neutron beam.

We present experimental details of the 2019/2020 campaign to measure the electron spectrum from unpolarized neutrons to extract an improved limit for the Fierz interference term and the ongoing analysis, where we currently focus on the characterization of the readout electronics.

Keywords: Neutron decay; Fierz interference; Weak interaction