Standard model radiative corrections in the pion form factor measurements do not explain the aμ anomaly

Abstract

In this letter, we address the question of whether the almost four standard deviations difference between theory and experiment for the muon anomalous magnetic moment aµ can be explained as a higher-order Standard Model perturbation effect in the pion form factor measurements. This question has, until now, remained open, obscuring the source of discrepancies between the measurements. We calculate the last radiative corrections for the extraction of the pion form factor, which were believed to be potentially substantial enough to explain the data within the Standard Model. We find that the corrections are too small to diminish existing discrepancies in the determination of the pion form factor for different kinematical configurations of low-energy BABAR, BESS-III and KLOE experiments. Consequently, they cannot noticeably change the previous predictions for aµ and decrease the deviations between theory and direct measurements. To solve the above issues, new data and better understanding of low-energy experimental setups are needed, especially as new direct aµ measurements at Fermilab and J-PARC will provide new insights and substantially shrink the experimental error.

Hadronic Vacuum Polarization:(g−2)μversus Global Electroweak Fits

“…Traditionally, hadronic vacuum polarization (HVP) has been determined via a dispersion relation from the cross section σðe þ e − → hadronsÞ [ where in the usual conventions for isospin-breaking effects the integral starts at the threshold s thr ¼ M 2 π 0 due to the e þ e − → π 0 γ channel [52] and the kernel functionKðsÞ can be expressed analytically. Global analyses based on a direct integration of cross section data [25,26,29,30] can now also be combined with analyticity and unitarity constraints for the leading 2π [27,29,53] and 3π [28] channels, covering almost 80% of the HVP contribution, to demonstrate that the experimental data sets are consistent with general properties of QCD, and radiative corrections for the 2π channel have been completed at next-to-leading order [54]. With recent advances in constraining the contribution from hadronic light-by-light scattering (including evaluations [33][34][35]37,38,[55][56][57] based on dispersion relations in analogy to Eq.…”

Explaining (g−2)μ,e , the KOTO anomaly, and the MiniBooNE excess in an extended Higgs model with sterile neutrinos

“…Very recently, the lattice calculation for the hadronic light-by-light scattering contribution confirms the Δa μ discrepancy [15]. Recently, the measurement of the radiative corrections to the pion form factor also confirm the need of a beyond SM explanation of a μ [16].…”

Getting chirality right: Single scalar leptoquark solutions to the (g−2)e,μ puzzle

“…This makes anomalies in ðg − 2Þ l , particularly if these differ between lepton flavor, a very strong indication of new physics (NP) effects at loop level [1,2]. For the muon, there is persistent deviation between the SM prediction and the measured value [3,4],…”

“…The important issue to be addressed in this paper is that the discrepancies, Δa μ and Δa e , are of opposite sign, which is a difficulty to be overcome when searching for a common explanation. 2 The leading candidates to explain these deviations involve flavor-dependent, loop-level, NP effects. It has long been established that exotic scalar-only extensions to the SM are capable of generating sizeable corrections to ðg − 2Þ l .…”