Isospin-breaking corrections to the muon magnetic anomaly in Lattice QCD

Giusti, D.; Martinelli, G.; Sanfilippo, Francesco; Simula, Silvano

doi:10.22323/1.317.0063

Cited by 3 publications

(5 citation statements)

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“…This procedure allows them to extrapolate the vector correlator to the physical pion point both at finite volumes and in the infinite-volume limit. The corresponding estimate of FVEs at the physical pion point turns out to be larger than the NLO ChPT prediction by a factor of ∼ 1.5-2 [373,404]. This is in accord with the NNLO FVEs in Ref.…”

Section: Connected Light-quark Contributionsupporting

confidence: 87%

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The anomalous magnetic moment of the muon in the Standard Model

Aoyama,

Asmussen,

Benayoun

et al. 2020

Preprint

148

296

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We review the present status of the Standard Model calculation of the anomalous magnetic moment of the muon. This is performed in a perturbative expansion in the fine-structure constant α and is broken down into pure QED, electroweak, and hadronic contributions. The pure QED contribution is by far the largest and has been evaluated up to and including O(α 5 ) with negligible numerical uncertainty. The electroweak contribution is suppressed by (m µ /M W ) 2 and only shows up at the level of the seventh significant digit. It has been evaluated up to two loops and is known to better than one percent. Hadronic contributions are the most difficult to calculate and are responsible for almost all of the theoretical uncertainty. The leading hadronic contribution appears at O(α 2 ) and is due to hadronic vacuum polarization, whereas at O(α 3 ) the hadronic light-by-light scattering contribution appears. Given the low characteristic scale of this observable, these contributions have to be calculated with nonperturbative methods, in particular, dispersion relations and the lattice approach to QCD. The largest part of this review is dedicated to a detailed account of recent efforts to improve the calculation of these two contributions with either a data-driven, dispersive approach, or a first-principle, lattice-QCD approach. The final result reads a SM µ = 116 591 810(43) × 10 −11 and is smaller than the Brookhaven measurement by 3.7σ. The experimental uncertainty will soon be reduced by up to a factor four by the new experiment currently running at Fermilab, and also by the future J-PARC experiment. This and the prospects to further reduce the theoretical uncertainty in the near future-which are also discussed here-make this quantity one of the most promising places to look for evidence of new physics.

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Section: Connected Light-quark Contributionsupporting

confidence: 87%

“…[428]. The perturbative expansion was used to calculate QED corrections to HVP by the ETM collaboration [12,17,371,404,429,430] and the RBC/UKQCD collaboration [11,399].…”

Section: Strong and Qed Isospin-breaking Contributionsmentioning

confidence: 99%

The anomalous magnetic moment of the muon in the Standard Model

Aoyama,

Asmussen,

Benayoun

et al. 2020

Preprint

148

296

View full text Add to dashboard Cite

show abstract

“…This procedure allows them to extrapolate the vector correlator to the physical pion point both at finite volumes and in the infinitevolume limit. The corresponding estimate of FVEs at the physical pion point turns out to be larger than the NLO ChPT prediction by a factor of ∼1.5-2 [377,408]. This is in accord with the NNLO FVEs in Ref.…”

Section: Connected Light-quark Contributionsupporting

confidence: 87%

“…[432]. The perturbative expansion was used to calculate QED corrections to HVP by the ETM collaboration [12,17,375,408,433,434] and the RBC/UKQCD collaboration [11,403]. One important issue when including QED in lattice calculations is the treatment of the zero-mode of the photon field, which cannot be constrained by a gauge-fixing procedure (see Ref.…”

Section: Strong and Qed Isospin-breaking Contributionsmentioning

confidence: 99%

The anomalous magnetic moment of the muon in the Standard Model

Hoferichter

2022

Preprint

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Precision measurements of low-energy observables can allow one to derive powerful constraints on physics beyond the Standard Model of particle physics—if the same quantity can be predicted at the same level of precision as experiment. The anomalous magnetic moment of the muon is a prominent example in which the sensitivity to potential contributions beyond the Standard Model crucially depends on the theoretical prediction. In the seminar I will give an overview of the first publication of the Muon g-2 Theory Initiative, Phys. Rept. 887 (2020) 1, which provided a comprehensive review of all sectors contributing to the Standard Model prediction, with focus on the hadronic corrections.

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“…Using the analytic representation the FVEs on a HVP,LO µ (ud) were estimated for the first time in a non-perturbative way directly on the lattice [24] and shown to differ significantly from the prediction of Chiral Perturbation Theory (ChPT) at next-to-leading order (NLO) up to values of M π L ≈ 6 (see also Ref. [53]). Later FVEs on a HVP,LO µ (ud) have been calculated within ChPT at NNLO [54].…”

Section: The Hadronic Input V (T)mentioning

confidence: 99%

Ratios of the hadronic contributions to the lepton $g-2$ from Lattice QCD+QED simulations

Giusti,

Simula

2020

Preprint

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The ratios among the leading-order (LO) hadronic vacuum polarization (HVP) contributions to the anomalous magnetic moments of electron, muon and τ -lepton, a HVP,LO =e,µ,τ , are computed using lattice QCD+QED simulations. The results include the effects at order O(α 2 em ) as well as the electromagnetic and strong isospin-breaking corrections at orders O(α 3 em ) and O(α 2 em (m u − m d )), respectively, where (m u − m d ) is the u-and d-quark mass difference. We employ the gauge configurations generated by the Extended Twisted Mass Collaboration with N f = 2 + 1 + 1 dynamical quarks at three values of the lattice spacing (a 0.062, 0.082, 0.089 fm) with pion masses in the range 210−450 MeV. The calculations are based on the quark-connected contributions to the HVP in the quenched-QED approximation, which neglects the charges of the sea quarks. The quark-disconnected terms are estimated from results available in the literature. We show that in the case of the electronmuon ratio the hadronic uncertainties in the numerator and in the denominator largely cancel out, while in the cases of the electron-τ and muon-τ ratios such a cancellation does not occur. For the electron-muon ratio we get R e/µ ≡ (m µ /m e ) 2 (a HVP,LO e /a HVP,LO µ ) = 1.1478 (70) with an uncertainty of 0.6%. Our result, which represents an accurate Standard Model (SM) prediction, agrees very well with the estimate obtained using the results of dispersive analyses of the experimental e + e − → hadrons data. Instead, it differs by 2.7 standard deviations from the value expected from present electron and muon (g − 2) experiments

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Isospin-breaking corrections to the muon magnetic anomaly in Lattice QCD

Cited by 3 publications

References 48 publications

The anomalous magnetic moment of the muon in the Standard Model

The anomalous magnetic moment of the muon in the Standard Model

The anomalous magnetic moment of the muon in the Standard Model

Ratios of the hadronic contributions to the lepton $g-2$ from Lattice QCD+QED simulations

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