6533b872fe1ef96bd12d3777

RESEARCH PRODUCT

Precision of a data-driven estimate of hadronic light-by-light scattering in the muong−2: Pseudoscalar-pole contribution

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Within a dispersive approach to hadronic light-by-light scattering in the muon g-2, the evaluation of the numerically dominant pseudoscalar-pole contribution involves the pseudoscalar-photon transition form factor FPγ*γ*(-Q12,-Q22) with P=π0,η,η′ and, in general, two off-shell photons with spacelike momenta Q1,22. We show that for π0(η,η′), the region of photon momenta below about 1(1.5) GeV gives the main contribution to hadronic light-by-light scattering. We then discuss how the precision of current and future measurements of the single- and double-virtual transition form factor in different momentum regions impacts the precision of a data-driven estimate of this contribution to hadronic light-by-light scattering. Based on Monte Carlo simulations for a planned first measurement of the double-virtual form factor at BESIII, we find that for the π0,η,η′-pole contributions a precision of 14%, 23%, 15% seems feasible. Further improvements can be expected from other experimental data and also from the use of dispersion relations for the different form factors themselves.