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arXiv · 2212.03877

Indirect new physics effects on $σ_{\rm had}$ confront the $(g-2)_μ$ window discrepancies and the CMD-3 result

Luc Darmé·Giovanni Grilli di Cortona·Enrico Nardi
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Abstract

Recent lattice determinations of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment $a_μ^{\rm HVP}$ have confirmed the discrepancy with the data-driven dispersive method. In the meanwhile the CMD-3 collaboration has reported a result for the $e^+e^-\to π^+π^-$ cross section considerably larger than previous experimental results (and close to the lattice determinations) exacerbating the discordance between different $e^+e^-$ datasets. We explore to what extent these disagreements can be accounted for by some new physics effect altering selectively the individual experimental determinations of $σ(e^+e^- \to\;$hadrons). We find that specific effects of GeV-scale new particles are able to shift upwards the KLOE and BaBar results in the low and intermediate energy windows, while leaving unaffected the CMD-3 energy scan. Although these new physics effects cannot fully explain all the discrepancies among the different $σ(e^+e^- \to\;$hadrons) datasets, they succeed in mitigating the overall tension between data-driven and lattice estimates of $a_μ^{\rm HVP}$. Remarkably, the additional loop corrections involving the new particles concur to solve the residual discrepancy with the experimental value of $(g-2)_μ$.

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Luc Darmé, Giovanni Grilli di Cortona, Enrico Nardi. 2024-01-16. Indirect new physics effects on $σ_{\rm had}$ confront the $(g-2)_μ$ window discrepancies and the CMD-3 result. https://arxiv.org/abs/2212.03877

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