A comment on the impact of CMD-3 $e^+e^- \to \pi^+\pi^-$ cross section measurement on the SM $g_\mu-2$ value

, in presence of comparably precise ISR measurements of the cross section by BaBar and KLOE experiments being in significant tension with the CMD-3. Assuming that all the experiments are affected by yet unidentified systematic effects, to account for the latter, we scaled the experimental uncertainties following the PDG prescription, thus facilitating a consistent joint fit of the world data on the

e^+e^- \to \pi^+\pi^-

total cross section. The same procedure was applied in all

e^+e^- \to hadrons

channels contributing to the dispersive estimate of

a_\mu^{had,LO}

. Despite an inclusion of the new CMD-3

\pi^+\pi^-

data, our estimate

a_\mu^{had,LO}(e^+e^-) = (696.2 \pm 2.9) \times 10^{-10}

is consistent with

a_\mu^{had,LO}(e^+e^-)

values obtained by other authors before publication of the CMD-3 result. Including our

a_\mu^{had,LO}

value into the SM prediction for

a_\mu

, we obtain

a_\mu^{SM} = (11~659~184 \pm 4_{\mathrm{tot}}) \times 10^{-10}

which is by

4.7\sigma

smaller than the world average for the experimental value

a_\mu^{exp} = (11~659~205.9 \pm 2.2) \times 10^{-10}

. We confirm the observation by the CMD-3 authors that their

\sigma(e^+e^- \to \pi^+\pi^-)

measurement, when taken alone, implies the

a_\mu^{SM}

prediction consistent with the

a_\mu^{exp}

at

\sim 1\sigma

level.

Note:

The note contains a comprehensive bibliography on the total e+e- --> hadrons cross section measurements at sqrt(s) < 12 GeV

muon: magnetic moment
higher-order: 0
total cross section
tension
GeV
dispersion
KLOE
BaBar
hadron

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A comment on the impact of CMD-3 e+e−→π+π−e^+e^- \to \pi^+\pi^-e+e−→π+π− cross section measurement on the SM gμ−2g_\mu-2gμ​−2 value

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A comment on the impact of CMD-3 $e^+e^- \to \pi^+\pi^-$ cross section measurement on the SM $g_\mu-2$ value