Leading-order hadronic contribution to the electron and muon<i>g</i>− 2

Jegerlehner, F.

doi:10.1051/epjconf/201611801016

Cited by 70 publications

(107 citation statements)

References 77 publications

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“…The long-standing (3)(4)σ discrepancy between the experimental value of the muon anomalous magnetic moment a μ = (g − 2)/2 and the Standard Model (SM) prediction, a μ (Exp − SM) ∼ (28 ± 8) × 10 −10 [1,2], has been considered during these years as one of the most intriguing indications of physics beyond the SM. However, the accuracy of the SM prediction, 5 × 10 −10 , is limited by strong interaction effects, which cannot be computed perturbatively at low energies.…”

Section: Introductionmentioning

confidence: 99%

Measuring the leading hadronic contribution to the muon g-2 via $$\mu e$$ μ e scattering

et al. 2017

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We propose a new experiment to measure the running of the electromagnetic coupling constant in the spacelike region by scattering high-energy muons on atomic electrons of a low-Z target through the elastic process μ e → μ e. The differential cross section of this process, measured as a function of the squared momentum transfer t = q 2 < 0, provides direct sensitivity to the leading-order hadronic contribution to the muon anomaly a HLO μ . By using a muon beam of 150 GeV, with an average rate of ∼1.3 ×10 7 muon/s, currently available at the CERN North Area, a statistical uncertainty of ∼0.3% can be achieved on a HLO μ after two years of data taking. The direct measurement of a HLO μ via μe scattering will provide an independent determination, competitive with the time-like dispersive approach, and consolidate the theoretical prediction for the muon g-2 in the Standard Model. It will allow therefore a firmer interpretation of the measurements of the future muon g-2 experiments at Fermilab and J-PARC. a

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Section: Introductionmentioning

confidence: 99%

Measuring the leading hadronic contribution to the muon g-2 via $$\mu e$$ μ e scattering

et al. 2017

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“…For an alternative up-todate analysis that leads to a larger 4.0 σ discrepancy see ref. [18]. On the theory side, there is a fairly general consensus that hadronic loop uncertainties alone cannot explain such a large discrepancy.…”

Section: Introductionmentioning

confidence: 99%

Contributions of axionlike particles to lepton dipole moments

et al. 2016

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Contributions of a spin 0 axion-like particle (ALP) to lepton dipole moments, g-2 and EDMs, are examined. Barr-Zee and light-by-light loop effects from a light pseudoscalar ALP are found to be capable of resolving the long-standing muon g-2 discrepancy at the expense of relatively large ALP-γγ couplings. The compatibility of such large couplings with direct experimental constraints and perturbative unitarity bounds is discussed. Future tests of such a scenario are described. For CP violating ALP couplings, the electron EDM is found to probe much smaller, theoretically more easily accommodated ALP interactions. Future planned improvement in electron EDM searches is advocated as a way to not only significantly constrain ALP parameters but also, to potentially unveil a new source of CP violation which could have far reaching ramifications.

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“…The BNL result differs with the theoretical calculation by about 3.5σ , which has sparked extensive research from investigating missing systematic effects to looking for new physics beyond the Standard Model to account for the discrepancy. On the theoretical side, in addition to investigating physics beyond the Standard Model, work is ongoing [8,11,12,13] to improve the uncertainty on the Standard Model calculations. On the experimental side, a new experiment is being constructed at Fermi National Accelerator Laboratory (FNAL) [8] to address the discrepancy, and intends to measure the anomalous magnetic moment to a precision of 140 ppb-a four-fold improvement on the BNL result.…”

Section: The Anomalous Magnetic Momentmentioning

confidence: 99%

Precision Magnetic Field Calibration for the Muon $g-2$ Experiment at Fermilab

Flay¹

2017

Proceedings of 38th International Conference on High Energy Physics — PoS(ICHEP2016)

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The Muon g − 2 Experiment at Fermilab (E989) has been designed to determine the muon anomalous magnetic moment to a precision of 140 parts per billion (ppb), a four-fold improvement over the Brookhaven E821 measurement. Key to this precision goal is the absolute determination of the magnetic field of the experiment's muon storage ring to better than 70 ppb. The magnetic field will be measured and monitored by nuclear magnetic resonance (NMR) probes, which are mounted on a trolley and pulled through the muon storage region when muons are not being stored. These trolley probes will be calibrated in terms of the free-proton Larmor precession frequency ω p by a specially-constructed NMR absolute calibration probe. In E821, the uncertainty in the field measurement was 170 ppb, of which 50 ppb was due to the absolute probe. In E989, these uncertainties will be reduced to 70 ppb and 35 ppb, respectively. To meet these stringent requirements, a new calibration probe has been designed and is currently under construction, along with a so-called plunging probe. This plunging probe will be used to transfer the calibration to the trolley probes. This poster will present the design, fabrication, and testing of the absolute and plunging probes, along with the calibration procedure.

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Leading-order hadronic contribution to the electron and muong− 2

Cited by 70 publications

References 77 publications

Measuring the leading hadronic contribution to the muon g-2 via $$\mu e$$ μ e scattering

Measuring the leading hadronic contribution to the muon g-2 via $$\mu e$$ μ e scattering

Contributions of axionlike particles to lepton dipole moments

Precision Magnetic Field Calibration for the Muon $g-2$ Experiment at Fermilab

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