Light new particles generate asymmetries in e+e- to tau+tau- that allow model-dependent constraints on tau dipole moments, including non-zero effects without electron polarization via imaginary parts.
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Dispersion relation for hadronic light-by-light scattering: two-pion contributions
Canonical reference. 71% of citing Pith papers cite this work as background.
abstract
In this third paper of a series dedicated to a dispersive treatment of the hadronic light-by-light (HLbL) tensor, we derive a partial-wave formulation for two-pion intermediate states in the HLbL contribution to the anomalous magnetic moment of the muon $(g-2)_\mu$, including a detailed discussion of the unitarity relation for arbitrary partial waves. We show that obtaining a final expression free from unphysical helicity partial waves is a subtle issue, which we thoroughly clarify. As a by-product, we obtain a set of sum rules that could be used to constrain future calculations of $\gamma^*\gamma^*\to\pi\pi$. We validate the formalism extensively using the pion-box contribution, defined by two-pion intermediate states with a pion-pole left-hand cut, and demonstrate how the full known result is reproduced when resumming the partial waves. Using dispersive fits to high-statistics data for the pion vector form factor, we provide an evaluation of the full pion box, $a_\mu^{\pi\text{-box}}=-15.9(2)\times 10^{-11}$. As an application of the partial-wave formalism, we present a first calculation of $\pi\pi$-rescattering effects in HLbL scattering, with $\gamma^*\gamma^*\to\pi\pi$ helicity partial waves constructed dispersively using $\pi\pi$ phase shifts derived from the inverse-amplitude method. In this way, the isospin-$0$ part of our calculation can be interpreted as the contribution of the $f_0(500)$ to HLbL scattering in $(g-2)_\mu$. We argue that the contribution due to charged-pion rescattering implements corrections related to the corresponding pion polarizability and show that these are moderate. Our final result for the sum of pion-box contribution and its $S$-wave rescattering corrections reads $a_\mu^{\pi\text{-box}} + a_{\mu,J=0}^{\pi\pi,\pi\text{-pole LHC}}=-24(1)\times 10^{-11}$.
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representative citing papers
A lattice QCD+QED strategy is outlined for calculating isospin-breaking effects in inclusive tau decays to support high-precision HVP contributions to muon g-2.
Disperon QED is a new technique that feeds experimental data into higher-order QED loop calculations in Monte Carlo generators via dispersion relations and threshold subtraction.
This work provides a comprehensive analysis of light new physics contributions to tau lepton dipole moments, detailing interpretations of asymmetry measurements for spin-0 and spin-1 bosons, their decoupling to the EFT limit, and a case study of a tauphilic vector boson at Belle II.
A new model with SU(2)_D symmetry and vector-like muons mediates vector dark matter, simultaneously addressing relic abundance and muon g-2 while identifying an off-resonance suppression mechanism for light DM and deriving collider bounds.
A general framework quantifies correlation-induced uncertainties in precision data combinations and applies it to e+e- to hadrons cross sections for muon g-2 HVP determinations.
The analysis selects the negative E1 phase solution for 0++-2++ amplitudes in J/ψ → γπ⁰π⁰ as consistent with Omnès phases from f0 resonances without large extra phases, and normalizes amplitudes via the branching fraction for future use.
Updated SM predictions yield Br(η→e⁺e⁻)=5.37(4)(2)[4]×10⁻⁹, Br(η→μ⁺μ⁻)=4.54(4)(2)[4]×10⁻⁶, Br(η'→e⁺e⁻)=1.80(2)(3)[3]×10⁻¹⁰, and Br(η'→μ⁺μ⁻)=1.22(2)(2)[3]×10⁻⁷, with a mild 1.6σ tension in the η→μ⁺μ⁻ channel.
The updated SM prediction for the muon anomalous magnetic moment is 116592033(62)×10^{-11}, showing no tension with the experimental average of 38(63)×10^{-11}.
Global analysis constrains fermionic DM to 120-350 GeV and CP-odd scalar to 350-600 GeV in a scotogenic extension, with DESI potentially ruling out inverted neutrino hierarchy and Z invisible width compatible with data at 3 sigma.
The paper provides an overview of theoretical calculations for lepton anomalous magnetic moments arising from quantum corrections in the Standard Model.
The Standard Model value for the muon anomalous magnetic moment is 116591810(43)×10^{-11}, 3.7σ below the Brookhaven experimental measurement.
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Light new particles generate asymmetries in e+e- to tau+tau- that allow model-dependent constraints on tau dipole moments, including non-zero effects without electron polarization via imaginary parts.
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Isospin-breaking effects in inclusive hadronic $\tau$ data for the muon $(g-2)$ from first principles
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Dispersive analysis of the $\boldsymbol{J/\psi \to \gamma \pi^0 \pi^0}$ process
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Improved Standard-Model predictions for $\eta^{(\prime)}\to \ell^+ \ell^-$
Updated SM predictions yield Br(η→e⁺e⁻)=5.37(4)(2)[4]×10⁻⁹, Br(η→μ⁺μ⁻)=4.54(4)(2)[4]×10⁻⁶, Br(η'→e⁺e⁻)=1.80(2)(3)[3]×10⁻¹⁰, and Br(η'→μ⁺μ⁻)=1.22(2)(2)[3]×10⁻⁷, with a mild 1.6σ tension in the η→μ⁺μ⁻ channel.
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The anomalous magnetic moment of the muon in the Standard Model: an update
The updated SM prediction for the muon anomalous magnetic moment is 116592033(62)×10^{-11}, showing no tension with the experimental average of 38(63)×10^{-11}.
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Global analysis of a minimally extended scotogenic model
Global analysis constrains fermionic DM to 120-350 GeV and CP-odd scalar to 350-600 GeV in a scotogenic extension, with DESI potentially ruling out inverted neutrino hierarchy and Z invisible width compatible with data at 3 sigma.
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Lepton anomalous magnetic moments: Theory
The paper provides an overview of theoretical calculations for lepton anomalous magnetic moments arising from quantum corrections in the Standard Model.
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The anomalous magnetic moment of the muon in the Standard Model
The Standard Model value for the muon anomalous magnetic moment is 116591810(43)×10^{-11}, 3.7σ below the Brookhaven experimental measurement.