An Experimental Measurement of the Gyromagnetic Ratio of the Free Electron

Louisell, W. H.; Pidd, R. W.; Crane, H. R.

doi:10.1103/physrev.94.7

Cited by 54 publications

(21 citation statements)

References 21 publications

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“…(9) where M = Λ is an UV cut-off characterizing the scale of new physics. At that time a e was already well measured by Crane et al [59], but it was clear that the anomalous magnetic moment of the muon would be a much better probe for possible deviations from QED. But how to measure a µ ?…”

Section: Historymentioning

confidence: 85%

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The muon g−2

2009

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The muon anomalous magnetic moment is one of the most precisely measured quantities in particle physics. In a recent experiment at Brookhaven it has been measured with a remarkable 14-fold improvement of the previous CERN experiment reaching a precision of 0.54ppm. Since the first results were published, a persisting "discrepancy" between theory and experiment of about 3 standard deviations is observed. It is the largest "established" deviation from the Standard Model seen in a "clean" electroweak observable and thus could be a hint for New Physics to be around the corner. This deviation triggered numerous speculations about the possible origin of the "missing piece" and the increased experimental precision animated a multitude of new theoretical efforts which lead to a substantial improvement of the prediction of the muon anomaly aµ = (gµ − 2)/2. The dominating uncertainty of the prediction, caused by strong interaction effects, could be reduced substantially, due to new hadronic cross section measurements in electron-positron annihilation at low energies. Also the recent electron g − 2 measurement at Harvard contributes substantially to the progress in this field, as it allows for a much more precise determination of the fine structure constant α as well as a cross check of the status of our theoretical understanding.In this report we review the theory of the anomalous magnetic moments of the electron and the muon. After an introduction and a brief description of the principle of the muon g − 2 experiment, we present a review of the status of the theoretical prediction and in particular discuss the role of the hadronic vacuum polarization effects and the hadronic light-by-light scattering correction, including a new evaluation of the dominant pion-exchange contribution. In the end, we find a 3.2 standard deviation discrepancy between experiment and Standard Model prediction. We also present a number of examples of how extensions of the electroweak Standard Model would change the theoretical prediction of the muon anomaly aµ. Perspectives for future developments in experiment and theory are briefly discussed and critically assessed. The muon g − 2 will remain one of the hot topics for further investigations.

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Section: Historymentioning

confidence: 85%

“…2 IV = 121.8431 (59) . The sum of the results from the different groups thus reads A small contribution to A…”

Section: -Loop: Light Lepton Insertionsmentioning

confidence: 99%

The muon g−2

2009

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“…For the muon (g -2) the story starts in 1956 when the magnetic anomaly a --(g-2)/2 of the electron was already well measured by Crane et al [1]. Berestetskii et el.…”

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confidence: 85%

“…Professor Crane at Ann Arbour [1] was the first to note that at low velocities the orbit frequency coc = eB/mc of an electron (or muon) in a magnetic field B is almost the same as its spin frequency ~;s Eq. (2).…”

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confidence: 99%

The 46 years of Muon g − 2

Farley¹

2004

Nuclear Physics B - Proceedings Supplements

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“…On a historical note, our device is essentially a solid-state analogue of experiments performed in the 1950s that were used to determine the g-factor of the free electron in vacuum using Mott scattering as the spin polarizer and analyser and spin precession in a solenoid [90]. In our case, we already know the g-factor (from e.g.…”

Section: Ballistic Hot Electron Injection and Detection Devicesmentioning

confidence: 99%

Introduction to spin-polarized ballistic hot electron injection and detection in silicon

Appelbaum

2011

Phil. Trans. R. Soc. A.

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Ballistic hot electron transport overcomes the well-known problems of conductivity and spin lifetime mismatch that plague spin injection attempts in semiconductors using ferromagnetic ohmic contacts. Through the spin dependence of the mean free path in ferromagnetic thin films, it also provides a means for spin detection after transport. Experimental results using these techniques (consisting of spin precession and spin-valve measurements) with silicon-based devices reveals the exceptionally long spin lifetime and high spin coherence induced by drift-dominated transport in the semiconductor. An appropriate quantitative model that accurately simulates the device characteristics for both undoped and doped spin transport channels is described; it can be used to recover the transit-time distribution from precession measurements and determine the spin current velocity, diffusion constant and spin lifetime, constituting a spin 'HaynesShockley' experiment without time-of-flight techniques. A perspective on the future of these methods is offered as a summary.

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An Experimental Measurement of the Gyromagnetic Ratio of the Free Electron

Cited by 54 publications

References 21 publications

The muon g−2

The muon g−2

The 46 years of Muon g − 2

Introduction to spin-polarized ballistic hot electron injection and detection in silicon

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