KLOE uses the radiative return to measure the hadronic cross section e+e- → π+− at DANE. Theemission of one or more hard photons in the initial state (ISR) reduces the collision energy, otherwise fixed at 1020 MeV, and allows to perform an effective scan of the two pions invariant mass squared, sπ, in the whole sπ, region from threshold to mφ2. An extremely accurate knowledge of experimental systematics, background, luminosity and, on the theoretical side, a precise description of initial state radiation are needed to perform a competitive measurement. We present here the status of the analysis of 140 pb−1 collected in 2001. A preliminary evaluation of the hadronic contribution to aμ in the sπ range between 0.37 GeV2 and 0.93 GeV2 yields aμ = 378.4 ± 0.8stat ± 4.5syst ± 3.0theo ± 3.8FSR, consistent with the CMD-2 result and confirming the present discrepancy between e+e− and τ data.
The hadronic cross section measurement at KLOE
GORINI, Edoardo;PRIMAVERA, Margherita;VENTURA, Andrea;
2004-01-01
Abstract
KLOE uses the radiative return to measure the hadronic cross section e+e- → π+− at DANE. Theemission of one or more hard photons in the initial state (ISR) reduces the collision energy, otherwise fixed at 1020 MeV, and allows to perform an effective scan of the two pions invariant mass squared, sπ, in the whole sπ, region from threshold to mφ2. An extremely accurate knowledge of experimental systematics, background, luminosity and, on the theoretical side, a precise description of initial state radiation are needed to perform a competitive measurement. We present here the status of the analysis of 140 pb−1 collected in 2001. A preliminary evaluation of the hadronic contribution to aμ in the sπ range between 0.37 GeV2 and 0.93 GeV2 yields aμ = 378.4 ± 0.8stat ± 4.5syst ± 3.0theo ± 3.8FSR, consistent with the CMD-2 result and confirming the present discrepancy between e+e− and τ data.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
