The hadronic cross section measurement at KLOE

KLOE uses the radiative return to measure the hadronic cross section e(+)e(-) --> pi(+) pi(-) at DAPhiNE. The emission 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, s(pi), in the whole s(pi) region 2 from threshold to m.. 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 a(mu) in the S-pi range between 0.37 GeV2 and 0.93 GeV2 yields a(mu) = 378.4 +/- 0.8(stat) +/- 4.5(syst) +/- 3-0(theo) 3.8(FSR), consistent with the CMD-2 result and confirming the present discrepancy between e(+)e(-) and tau data

The hadronic cross section measurement at KLOE

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

Highlights on hadronic physics at KLOE

The KLOE experiment has just collected 2.5 fb-1 of e +e- collisions at center of mass energy around the mass. Radiative decays are used to produce large statistical samples of light scala and pseudoscalar mesons. The analysis of the first 450 pb-1 is almost completed. For the scala sector we have investigated the properties of these particles by studying their invariant mass shapes or the event density in the Dalitz plot. With the same data set, the η mass and the ratio BR( → η′γ)/BR( → ηγ) have been measured. From this last quantity we extract the most precise determination of the η/η′ mixing angle, which is strictly related to the η′ gluon content. © 2006 American Institute of Physics