Determination of $\sigma(e^+e^-\to \pi^+ \pi^-)$ from radiative processes at DA$\Phi$NE

TL;DR

This paper reports a measurement of the $e^+e^- o \pi^+\pi^-$ cross section using radiative processes at DA$\Phi$NE, providing data crucial for calculating the hadronic contribution to the muon anomalous magnetic moment.

Contribution

It introduces a method to extract the $e^+e^- o \\pi^+\\pi^-$ cross section from radiative processes at DA$\Phi$NE, enabling precise determination of the pion form factor and muon anomaly contribution.

Findings

Measured the cross section $\sigma(e^+e^- o\pi^+\pi^-\gamma)$ at $W=1.02$ GeV.

Extracted $\sigma(e^+e^- o\\pi^+\\pi^-)$ for $0.35<m^2(\\pi^+\\pi^-)<0.95$ GeV$^2$.

Provided data for the pion form factor and the hadronic contribution to $a_\\mu$.

Abstract

We have measured the cross section $\sigma(e^+e^-\to\pi^+\pi^-\gamma)$ with the KLOE detector at DA$\Phi$NE, at an energy $W=M_\phi=1.02$ GeV. From the dependence of the cross section on $m(\pi^+\pi^-)=\sqrt{W^2-2WE_\gamma}$, where $E_\gamma$ is the energy of the photon radiated from the initial state, we extract $\sigma(e^+e^-\to\pi^+\pi^-)$ for the mass range $0.35<m^2(\pi^+\pi^-)<0.95$ GeV$^2$. From our result we extract the pion form factor and the hadronic contribution to the muon anomaly, $a_\mu$.