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arXiv · 2112.00878

Leading isospin breaking effects in the HVP contribution to $a_{\mu}$ and to the running of $\alpha$

Andreas Risch·Hartmut Wittig
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Abstract

The anomalous magnetic moment of the muon $a_{\mu}$ and the running of the electromagnetic coupling $\alpha$ play a fundamental role in beyond Standard Model (SM) physics searches. Non-perturbative hadronic contributions to both quantities, which are related to the hadronic vacuum polarization (HVP) function consisting of two electromagnetic currents, are a main source of uncertainty in the SM prediction. We compute the HVP function in lattice QCD+QED applying the time-momentum representation method. We expand the relevant correlation functions around the isosymmetric limit. In particular, we focus on leading isospin breaking effects taking quark-connected contributions into account, which we evaluate on isosymmetric $N_{\mathrm{f}}=2+1$ QCD gauge ensembles generated by the CLS initiative with non-perturbatively $O(a)$-improved Wilson fermions.

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Andreas Risch, Hartmut Wittig. 2021-12-01. Leading isospin breaking effects in the HVP contribution to $a_{\mu}$ and to the running of $\alpha$. https://arxiv.org/abs/2112.00878

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