We describe the method of measuring the integrated luminosity of the e+e- collider DAΦNE, the Frascati φ-factory. The measurement is done with the KLOE detector selecting large angle Bhabha ...scattering events and normalizing them to the effective cross section. The e+e-→e+e-(γ) cross section is calculated using different event generators which account for the \(\mathcal{O}(\alpha)\) radiative initial and final state corrections, and the φ resonance contribution. The accuracy of the measurement is 0.6%, where 0.3% comes from systematic errors related to the event counting and 0.5% from theoretical evaluations of the cross section.
Using a sample of over 400 million φ→KSKL decays produced during the years 2001 and 2002 at the DAΦNE e+e- collider, the ratio RSπ=Γ(KS→π+π-(γ))/Γ(KS→π0π0) has been measured with the KLOE detector. ...The result is RSπ=2.2555±0.0012stat±0.0021corr-stat±0.0050syst, which is in good agreement with the previously published result based on the KLOE data sample from the year 2000. The average of the KLOE results is RSπ=2.2549±0.0054, reducing the total error by a factor of three, to 0.25%.
We have measured the cross section σ(e+e−→π+π−γ(γ)) at DAΦNE, the Frascati ϕ-factory, using events with initial state radiation photons emitted at small angle and inclusive of final state radiation. ...We present the analysis of a new data set corresponding to an integrated luminosity of 240 pb−1. We have achieved a reduced systematic uncertainty with respect to previously published KLOE results. From the cross section we obtain the pion form factor and the contribution to the muon magnetic anomaly from two-pion states in the mass range 0.592<Mππ<0.975 GeV. For the latter we find Δππaμ=(387.2±0.5stat±2.4exp±2.3th)×10−10.
We have searched with the KLOE detector for the P and CP violating decay η→π+π− in a sample of 1.55×107η's from the decay ϕ→ηγ of ϕ-mesons produced in e+e− annihilations at DAΦNE. No signal is found. ...We obtain the upper limit BR(η→π+π−)<1.3×10−5 at 90% confidence level.