Precision Measurement of the Hadronic Contribution to the Muon Anomalous Magnetic Moment

TL;DR

This paper presents a highly precise measurement of the $e^+e^- o ext{pi}^+ ext{pi}^-$ cross section using ISR data, leading to an improved estimate of the hadronic contribution to the muon g-2.

Contribution

It provides the most precise determination to date of the $e^+e^- o ext{pi}^+ ext{pi}^-$ cross section in the 0.3-1.0 GeV range, refining the muon g-2 calculation.

Findings

Measured cross section with 0.7% statistical uncertainty.

Calculated hadronic contribution to muon g-2 as (500.4±3.6±7.5)×10^{-10}.

Enhanced precision in the muon anomalous magnetic moment estimate.

Abstract

We report on a precision measurement of the cross section for the reaction $e^+e^-\to\pi^+\pi^-$ in the mass range $0.30<M_{\pi\pi}<1.00$ GeV with the initial state radiation (ISR) method, using 817 pb$^{-1}$ of data at $e^+e^-$ center-of-mass energies near 3.77 GeV and 586 pb$^{-1}$ of data at $e^+e^-$ center-of-mass energies near 4.17 GeV, collected with the CLEO-c detector at the CESR $e^+e^-$ collider at Cornell University. The integrated cross sections in the range $0.30<M_{\pi\pi}<1.00$ GeV for the process $e^+e^-\to\pi^+\pi^-$ are determined with a statistical uncertainty of $0.7\%$ and a systematic uncertainty of $1.5\%$. The leading-order hadronic contribution to the muon anomalous magnetic moment calculated using these measured $e^+e^-\to\pi^+\pi^-$ cross sections in the range $M_{\pi\pi}=0.30$ to 1.00 GeV is calculated to be $(500.4\pm3.6 (\mathrm{stat})\pm 7.5(\mathrm{syst}))\times10^{-10}$.