Hadronic Light-by-Light Scattering Contribution to the Muon Anomalous Magnetic Moment from Lattice QCD

Blum, Thomas; Christ, Norman H.; Hayakawa, Masashi; Izubuchi, Taku; Jin, Luchang; Jung, Chulwoo; Lehner, Christoph

doi:10.1103/physrevlett.124.132002

Cited by 357 publications

(207 citation statements)

References 64 publications

(75 reference statements)

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“…With recent advances in constraining the contribution from hadronic light-by-light scattering (including evaluations [33][34][35]37,38,[55][56][57] based on dispersion relations in analogy to Eq. (1), short-distance constraints [39][40][41], and lattice QCD [36,42]) as well as higher-order hadronic corrections [30,31,43,58], this data-driven determination of HVP has corroborated the ðg − 2Þ μ tension at the level of 3.7σ. Nevertheless, since by far the largest hadronic correction arises from HVP, requirements for the relative precision are extraordinary, with a HVP μ ¼ 693.1ð4.0Þ × 10 −10 [20, [25][26][27][28][29][30] as currently determined from e þ e − → hadrons cross sections corresponding to less than 0.6%.…”

supporting

confidence: 66%

Hadronic Vacuum Polarization:(g−2)μversus Global Electroweak Fits

et al. 2020

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Hadronic vacuum polarization (HVP) is not only a critical part of the standard model (SM) prediction for the anomalous magnetic moment of the muon ðg − 2Þ μ , but also a crucial ingredient for global fits to electroweak (EW) precision observables due to its contribution to the running of the fine-structure constant encoded in Δα ð5Þ had. We find that with modern EW precision data, including the measurement of the Higgs mass, the global fit alone provides a competitive, independent determination of Δα ð5Þ had j EW ¼ 270.2ð3.0Þ × 10 −4. This value actually lies below the range derived from e þ e − → hadrons cross section data, and thus goes into the opposite direction as would be required if a change in HVP were to bring the SM prediction for ðg − 2Þ μ into agreement with the Brookhaven measurement. Depending on the energy where the bulk of the changes in the cross section occurs, reconciling experiment and SM predictions for ðg − 2Þ μ by adjusting HVP would thus not necessarily weaken the case for physics beyond the SM (BSM), but to some extent shift it from ðg − 2Þ μ to the EW fit. We briefly explore some options of BSM scenarios that could conceivably explain the ensuing tension.

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confidence: 66%

Hadronic Vacuum Polarization:(g−2)μversus Global Electroweak Fits

et al. 2020

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“…The simplified connection to model estimates enables our work to provide a valuable cross-check for the predictions of hadronic models and dispersive methods; this work is thereby complementary to lattice calculations directly aiming at a hlbl μ for physical quark masses [16]. At the same time, this study allows us to learn about the size of various sources of systematic error, particularly the finite-size effects, and how well we are able to correct for them semi-analytically.…”

Section: (): V-volmentioning

confidence: 92%

Hadronic light-by-light contribution to $$(g-2)_\mu $$ from lattice QCD with SU(3) flavor symmetry

et al. 2020

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We perform a lattice QCD calculation of the hadronic light-by-light contribution to $$(g-2)_\mu $$ ( g - 2 ) μ at the SU(3) flavor-symmetric point $$m_\pi =m_K\simeq 420\,$$ m π = m K ≃ 420 MeV. The representation used is based on coordinate-space perturbation theory, with all QED elements of the relevant Feynman diagrams implemented in continuum, infinite Euclidean space. As a consequence, the effect of using finite lattices to evaluate the QCD four-point function of the electromagnetic current is exponentially suppressed. Thanks to the SU(3)-flavor symmetry, only two topologies of diagrams contribute, the fully connected and the leading disconnected. We show the equivalence in the continuum limit of two methods of computing the connected contribution, and introduce a sparse-grid technique for computing the disconnected contribution. Thanks to our previous calculation of the pion transition form factor, we are able to correct for the residual finite-size effects and extend the tail of the integrand. We test our understanding of finite-size effects by using gauge ensembles differing only by their volume. After a continuum extrapolation based on four lattice spacings, we obtain $$a_\mu ^{\mathrm{hlbl}}= (65.4\pm 4.9 \pm 6.6)\times 10^{-11}$$ a μ hlbl = ( 65.4 ± 4.9 ± 6.6 ) × 10 - 11 , where the first error results from the uncertainties on the individual gauge ensembles and the second is the systematic error of the continuum extrapolation. Finally, we estimate how this value will change as the light-quark masses are lowered to their physical values.

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“…For the HLbL contribution, new analytic approaches [39][40][41][42][43] as well as the first ab-initio lattice QCD calculation [32] building on multi-year methodology development [44][45][46][47][48][49] so far show consistent results and rule out the HLbL contribution as an explanation for the current * christoph.lehner@ur.de † ameyer@quark.phy.bnl.gov tension between theory and experiment. For the HVP contribution, however, tensions exist within lattice QCD calculations [50] as well as between lattice QCD calculations and R-ratio results [27,50].…”

Section: Introductionmentioning

confidence: 94%

“…In the near future, we also look forward to results from the methodologically independent experimental program at J-PARC [5]. These results are highly anticipated and are accompanied by a concerted effort of the theory community to improve upon and scrutinize the existing standard model results, most importantly for the hadronic vacuum polarization (HVP) [1, and hadronic light-by-light (HLbL) [31,32] contributions, which currently limit the precision of the theory result. The Muon g − 2 Theory Initiative, a multi-year community effort [33][34][35][36][37], is now in the final stages of writing a whitepaper summarizing the current theory status [38].…”

Section: Introductionmentioning

confidence: 97%

Consistency of hadronic vacuum polarization between lattice QCD and the R ratio

2020

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There are emerging tensions for theory results of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment both within recent lattice QCD calculations and between some lattice QCD calculations and R-ratio results. In this paper we work towards scrutinizing critical aspects of these calculations. We focus in particular on a precise calculation of Euclidean position-space windows defined by RBC/UKQCD that are ideal quantities for cross-checks within the lattice community and with R-ratio results. We perform a lattice QCD calculation using physical up, down, strange, and charm sea quark gauge ensembles generated in the staggered formalism by the MILC collaboration. We study the continuum limit using inverse lattice spacings from a −1 ≈ 1.6 GeV to 3.5 GeV, identical to recent studies by FNAL/HPQCD/MILC and Aubin et al. and similar to the recent study of BMW. Our calculation exhibits a tension for the particularly interesting window result of a ud,conn.,isospin,W µ from 0.4 fm to 1.0 fm with previous results obtained with a different discretization of the vector current on the same gauge configurations. Our results may indicate a difficulty related to estimating uncertainties of the continuum extrapolation that deserves further attention. In this work we also provide results for a ud,conn.,isospin µ , a s,conn.,isospin µ , a SIB,conn. µ for the total contribution and a large set of windows. For the total contribution, we find a HVP LO µ = 714(27)(13)10 −10 , a ud,conn.,isospin µ = 657(26)(12)10 −10 , a s,conn.,isospin µ = 52.83(22)(65)10 −10 , and a SIB,conn. µ = 9.0(0.8)(1.2)10 −10 , where the first uncertainty is statistical and the second systematic. We also comment on finite-volume corrections for the strong-isospin-breaking corrections.

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Hadronic Light-by-Light Scattering Contribution to the Muon Anomalous Magnetic Moment from Lattice QCD

Cited by 357 publications

References 64 publications

Hadronic Vacuum Polarization:(g−2)μversus Global Electroweak Fits

Hadronic Vacuum Polarization:(g−2)μversus Global Electroweak Fits

Hadronic light-by-light contribution to $$(g-2)_\mu $$ from lattice QCD with SU(3) flavor symmetry

Consistency of hadronic vacuum polarization between lattice QCD and the R ratio

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