Precision measurement of $\ddot{I}ƒ(e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}{\hat{I}}^3)/\ddot{I}ƒ(e^{+}{e}^{-}\to \hat{I}{¼}^{+}\hat{I}{¼}^{-}{\hat{I}}^3)$ and determination of the $\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ contribution to the muon anomaly with the KLOE detector

Abstract

We have measured the ratio $\ddot{I}ƒ(e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}{\hat{I}}^3)/\ddot{I}ƒ(e^{+}{e}^{-}\to \hat{I}{¼}^{+}\hat{I}{¼}^{-}{\hat{I}}^3)$, with the KLOE detector at DA$\hat{I}¦$NE for a total integrated luminosity of $\sim$ 240 pb${}^{-1}$. From this ratio we obtain the cross section $\ddot{I}ƒ(e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-})$. From the cross section we determine the pion form factor $|F_{\ddot{I}}€{|}^2$ and the two-pion contribution to the muon anomaly $a_{\hat{I}}¼$ for $0.592<M_{\ddot{I}€\ddot{I}€}<0.975$ GeV, $\hat{I}{”}^{\ddot{I}€\ddot{I}€}{a}_{\hat{I}}¼$= $(385.1\pm 1.1_{\mathrm{stat}}\pm 2.7_{\mathrm{sys}+\mathrm{theo}})\times 10^{-10}$. This result confirms the current discrepancy between the Standard Model calculation and the experimental measurement of the muon anomaly.

18 pages, 8 figures, minor text corrections, one table added, version to appear on Physics Letters B