Measurement of the neutron magnetic moment

arXiv 18 May 2011, extended version of: Reviews of Modern Physics, in print.Experiments with cold and ultracold neutrons have reached a level of precision such that problems far beyond the scale of the present Standard Model of particle physics become accessible to experimental investigation. Due to the close links between particle physics and cosmology, these studies also permit a deep look into the very first instances of our universe. First addressed in this article, both in theory and experiment, is the problem of baryogenesis, the mechanism behind the evident dominance of matter over antimatter in the universe. The question how baryogenesis could have happened is open to experimental tests, and it turns out that this problem can be curbed by the very stringent limits on an electric dipole moment of the neutron, a quantity that also has deep implications for particle physics. Then we discuss the recent spectacular observation of neutron quantization in the earth's gravitational field and of resonance transitions between such gravitational energy states. These measurements, together with new evaluations of neutron scattering data, set new constraints on deviations from Newton's gravitational law at the picometer scale. Such deviations are predicted in modern theories with extra-dimensions that propose unification of the Planck scale with the scale of the Standard Model. These experiments start closing the remaining "axion window" on new spindependent forces in the submillimeter range. Another main topic is the weak-interaction parameters in various fields of physics and astrophysics that must all be derived from measured neutron decay data. Up to now, about 10 different neutron decay observables have been measured, much more than needed in the electroweak Standard Model. This allows various precise tests for new physics beyond the Standard Model, competing with or surpassing similar tests at high-energy. The review ends with a discussion of neutron and nuclear data required in the synthesis of the elements during the "first three minutes" and later on in stellar nucleosynthesis.DOI: xx,xxxx/RevModPhys.xx.xxx PACS number(s): 14.20.Dh,

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“…The proton and the neutron magnetic moments are known very precisely, the latter as a by-product of a neutron EDM search (Greene et al, 1979)…”

Section: Magnetic Dipole Momentmentioning

confidence: 99%

The neutron and its role in cosmology and particle physics

2011

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“…was obtained by combining Greene's measurement [5] of γ n /γ p with the determination of the shielded proton gyromagnetic ratio in pure water γ p . In this letter we report on a measurement of the neutron magnetic moment with an accuracy of better than 1 ppm, using an apparatus that was built to search for the neutron electric dipole moment [7].…”

Section: Introductionmentioning

confidence: 99%

“…The experimental method differs in two essential aspects from the one reported in Ref. [5]. First, we use stored ultracold neutrons (UCNs) rather than a beam of cold neutrons.…”

Section: Introductionmentioning

confidence: 99%

A measurement of the neutron to 199 Hg magnetic moment ratio

et al. 2014

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“…1 Here, γn = −2π × 29.165 MHz/T is the gyromagnetic ratio of the neutron [27]. Detailed theoretical descriptions of the spin flip process, NSE, and NRSE can be found in Ref.…”

Section: Introductionmentioning

confidence: 99%

Neutron phase spin echo

Piegsa

Hautle

Schanzer³

2016

Phys. Rev. C

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A novel neutron spin resonance technique is presented based on the well-know neutron spin echo method. In a first proof-of-principle measurement using a monochromatic neutron beam, it is demonstrated that relative velocity changes of down to a precision of 4 × 10 −7 can be resolved, corresponding to an energy resolution of better than 3 neV. Currently, the sensitivity is only limited by counting statistics and not by systematic effects. An improvement by another two orders of magnitude can be achieved with a dedicated setup, allowing for energy resolutions in the 10 peV regime. The new technique is ideally suited for investigations in the field of precision fundamental neutron physics, but will also be beneficial in scattering applications.

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Measurement of the neutron magnetic moment

Cited by 58 publications

References 33 publications

The neutron and its role in cosmology and particle physics

The neutron and its role in cosmology and particle physics

A measurement of the neutron to 199 Hg magnetic moment ratio

Neutron phase spin echo

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