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arXiv · 2605.01085

Comparing RM123 and non-perturbative QCD+QED approaches to the HVP with C-periodic boundary conditions

Anian Altherr·Isabel Campos·Alessandro Cotellucci·Roman Gruber·Tim Harris·Javad Komijani·Francesca Margari·Marina K. Marinkovic·Letizia Parato·Agostino Patella·Sara Rosso·Nazario Tantalo·Paola Tavella
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Abstract

Isospin-breaking corrections to the HVP are among the leading sources of uncertainty in the Standard Model prediction of the muon $g-2$. In recent work by the RC$^{\star}$ collaboration, we compute the intermediate window contribution for a flavour non-singlet current using two strategies to include isospin-breaking corrections: the RM123 approach and a fully non-perturbative dynamical QCD+QED simulation. In both computations, we use $C$-periodic spatial boundary conditions to ensure that locality, gauge invariance, and translational invariance are preserved throughout the calculation. At fixed lattice spacing and volume with $N_f =1+2+1$ dynamical fermions, and fully including sea-quark effects in both computations, we find that simulating the full QCD+QED distribution yields smaller uncertainties for a fixed statistics. We summarize the comparison of the two approaches and discuss the implications for future lattice QCD+QED computations.

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Anian Altherr, Isabel Campos, Alessandro Cotellucci, Roman Gruber, Tim Harris, Javad Komijani, Francesca Margari, Marina K. Marinkovic, Letizia Parato, Agostino Patella, Sara Rosso, Nazario Tantalo, Paola Tavella. 2026-05-01. Comparing RM123 and non-perturbative QCD+QED approaches to the HVP with C-periodic boundary conditions. https://arxiv.org/abs/2605.01085

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