Measurement of the pion form factor for M_{pipi}^2 between 0.1 and 0.85 GeV^2 with the KLOE detector

TL;DR

This paper reports a precise measurement of the pion form factor in a specific energy range using the KLOE detector, extending previous measurements and confirming the discrepancy in the muon g-2 value.

Contribution

It provides new experimental data on the pion form factor at low energies, improving the understanding of its contribution to muon g-2 and extending the covered energy range.

Findings

Measured the pion form factor between 0.1 and 0.85 GeV^2

Confirmed the discrepancy in muon g-2 calculations

Extended the energy range of previous measurements

Abstract

The KLOE experiment at the phi-factory DA$\Phi$NE has measured the pion form factor in the range between 0.1 < M_{pipi}^2 < 0.85 GeV^2 using events taken at sqrt{s}= 1 GeV with a photon emitted at large polar angles in the initial state. This measurement extends the M_{pipi}^2 region covered by KLOE ISR measurements of the pion form factor down to the two pion production threshold. The value obtained in this measurement of the dipion contribution to the muon anomalous magnetic moment of \Delta a_mu^{pipi} = (478.5+-2.0_{stat}+-4.8_{syst}+-2.9_{theo}) 10^{-10} further confirms the discrepancy between the Standard Model evaluation for a_mu and the experimental value measured by the (g-2) collaboration at BNL.