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 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.
We present a measurement of the ratio R=Γ(K
0
e3γ
;E
*
γ
> 30 MeV, θ
*
γ
>20
°
)/Γ(K
0
e3
) and a first measurement of the direct emission contribution in semileptonic K
L
decays. The measurement was ...performed at the DA NE φ factory by selecting φ→K
L
K
S
decays with the KLOE detector. We use 328 pb
-1
of data, corresponding to about 3.5 million K
0
e3
events and about 9000 K
0
e3γ
radiative events. Our result is R=(924±23
stat
±16
syst
)×10
-5
for the branching ratio and 〈X〉=-2.3±1.3
stat
±1.4
syst
for the effective strength parameter describing direct emission.
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