Virtual electromagnetic corrections largely cancel radiative-channel contributions in data-driven HVP evaluations for muon g-2, reconciling timelike and spacelike methods via a VMD model.
Alexandrou et al
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abstract
We present an investigation of the electromagnetic pion form factor, $F_\pi(Q^2)$, at small values of the four-momentum transfer $Q^2$ ($\lesssim 0.25$ GeV$^2$), based on the gauge configurations generated by European Twisted Mass Collaboration with $N_f = 2$ twisted-mass quarks at maximal twist including a clover term. Momentum is injected using non-periodic boundary conditions and the calculations are carried out at a fixed lattice spacing ($a \simeq 0.09$ fm) and with pion masses equal to its physical value, 240 MeV and 340 MeV. Our data are successfully analyzed using Chiral Perturbation Theory at next-to-leading order in the light-quark mass. For each pion mass two different lattice volumes are used to take care of finite size effects. Our final result for the squared charge radius is $\langle r^2 \rangle_\pi = 0.443~(29)$ fm$^2$, where the error includes several sources of systematic errors except the uncertainty related to discretization effects. The corresponding value of the SU(2) chiral low-energy constant $\overline{\ell}_6$ is equal to $\overline{\ell}_6 = 16.2 ~ (1.0)$.
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Lattice QCD calculation of pion and kaon unpolarized quark PDFs on a 32^3×64 ensemble with 260 MeV pion mass, using LaMET and SDF matching at boosts up to 2.07 GeV.
An auxiliary function of Q squared is introduced to reformulate the model-independent extraction of meson charge radii, suppressing higher-order finite-volume contributions more effectively than previous methods.
citing papers explorer
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Field-theoretic versus data-driven evaluations of electromagnetic corrections to hadronic vacuum polarization in $(g-2)_\mu$
Virtual electromagnetic corrections largely cancel radiative-channel contributions in data-driven HVP evaluations for muon g-2, reconciling timelike and spacelike methods via a VMD model.
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Pion and Kaon PDFs from Lattice QCD via Large Momentum Effective Theory and Short-Distance Factorization
Lattice QCD calculation of pion and kaon unpolarized quark PDFs on a 32^3×64 ensemble with 260 MeV pion mass, using LaMET and SDF matching at boosts up to 2.07 GeV.
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An improvement of model-independent method for meson charge radius calculation
An auxiliary function of Q squared is introduced to reformulate the model-independent extraction of meson charge radii, suppressing higher-order finite-volume contributions more effectively than previous methods.