Three-pion contribution to hadronic vacuum polarization

Jul 2, 2019
24 pages
Published in:
  • JHEP 08 (2019) 137
  • Published: Aug 26, 2019
e-Print:
DOI:
Report number:
  • INT-PUB-19-030

Citations per year

20032009201520212025020406080100120
Abstract: (Springer)
We address the contribution of the 3π channel to hadronic vacuum polarization (HVP) using a dispersive representation of the e+^{+}e^{−} → 3π amplitude. This channel gives the second-largest individual contribution to the total HVP integral in the anomalous magnetic moment of the muon (g − 2)μ_{μ}, both to its absolute value and uncertainty. It is largely dominated by the narrow resonances ω and ϕ, but not to the extent that the off-peak regions were negligible, so that at the level of accuracy relevant for (g − 2)μ_{μ} an analysis of the available data as model independent as possible becomes critical. Here, we provide such an analysis based on a global fit function using analyticity and unitarity of the underlying γ^{∗} → 3π amplitude and its normalization from a chiral low-energy theorem, which, in particular, allows us to check the internal consistency of the various e+^{+}e^{−} → 3π data sets. Overall, we obtain aμ3π {a}_{\mu}^{3\pi } |1.8GeV_{≤1.8 GeV} = 46.2(6)(6) × 1010^{−10} as our best estimate for the total 3π contribution consistent with all (low-energy) constraints from QCD. In combination with a recent dispersive analysis imposing the same constraints on the 2π channel below 1 GeV, this covers nearly 80% of the total HVP contribution, leading to aμHVP {a}_{\mu}^{\mathrm{HVP}} = 692.3(3.3) × 1010^{−10} when the remainder is taken from the literature, and thus reaffirming the (g−2)μ_{μ} anomaly at the level of at least 3.4σ. As side products, we find for the vacuum-polarization-subtracted masses Mω_{ω} = 782.63(3)(1) MeV and Mϕ_{ϕ} = 1019.20(2)(1) MeV, confirming the tension to the ω mass as extracted from the 2π channel.
Note:
  • 24 pages, 1 figure; Appendix B added; version published in JHEP
  • Chiral Lagrangians
  • Effective Field Theories
  • Nonperturbative Effects
  • Precision QED
  • vacuum polarization: hadronic
  • muon: magnetic moment
  • dispersion relation
  • quantum chromodynamics
  • analytic properties
  • low-energy theorem