6 research outputs found
Measurement of the Beta-Asymmetry in the Decay of Free Polarized Neutrons with the Spectrometer Perkeo III
The charged current in Weak Interaction, mediated by the W-boson, is maximally parity violating in the Standard Model of particle physics. Studies of neutron decay are very suitable to get access to this property of the Standard Model due to the absence of a nuclear structure, compared with nuclear beta decay. High precision experiments in this field are intended to test the Standard Model and the extensions. In this thesis the first asymmetry measurement with the new neutron decay spectrometer Perkeo III is described. During a nine-month beamtime at the Institute Laue Langevin the beta-asymmetry A in the decay of free polarized neutrons was measured. For the first time, a pulsed neutron beam was used. This significantly improved the experimental systematics. The data analysis confirmed the clean systematics, resulting in new values and improved uncertainties on the beta-asymmetry A and the ratio of axialvector to vector coupling lambda. Compared to the current world average given by the Particle Data Group (PDG), the uncertainty of this measurement is smaller by a factor of 5
Limit on the Fierz Interference Term b from a Measurement of the Beta Asymmetry in Neutron Decay
In the standard model of particle physics, the weak interaction is described
by vector and axial-vector couplings only. Non-zero 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.Comment: Phys. Rev. Lett., https://journals.aps.org/prl
Design of the Magnet System of the Neutron Decay Facility PERC
The PERC (Proton and Electron Radiation Channel) facility is currently under
construction at the research reactor FRM II, Garching. It will serve as an
intense and clean source of electrons and protons from neutron beta decay for
precision studies. It aims to contribute to the determination of the
Cabibbo-Kobayashi-Maskawa quark-mixing element from neutron decay data
and to search for new physics via new effective couplings. PERC's central
component is a 12m long superconducting magnet system. It hosts an 8m long
decay region in a uniform field. An additional high-field region selects the
phase space of electrons and protons which can reach the detectors and largely
improves systematic uncertainties. We discuss the design of the magnet system
and the resulting properties of the magnetic field.Comment: Proceedings of the International Workshop on Particle Physics at
Neutron Sources PPNS 2018, Grenoble, France, May 24-26, 201
Limit on the Fierz Interference Term from a Measurement of the Beta Asymmetry in Neutron Decay
In the standard model of particle physics, the weak interaction is described by vector and axial-vector couplings only. Non-zero 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
Design of the magnet system of the neutron decay facility PERC
The PERC (Proton and Electron Radiation Channel) facility is currently under construction at the research reactor FRM II, Garching. It will serve as an intense and clean source of electrons and protons from neutron beta decay for precision studies. It aims to contribute to the determination of the Cabibbo-Kobayashi-Maskawa quark-mixing element Vud from neutron decay data and to search for new physics via new effective couplings. PERC's central component is a 12 m long superconducting magnet system. It hosts an 8 m long decay region in a uniform field. An additional high-field region selects the phase space of electrons and protons which can reach the detectors and largely improves systematic uncertainties. We discuss the design of the magnet system and the resulting properties of the magnetic field