We present a measurement of the K–π vector current form-factor parameters for the decay KL→π±e∓ν. We use 328 pb−1 of data collected in 2001 and 2002, corresponding to ∼2 million Ke3 events. ...Measurements of semileptonic form factors provide information about the dynamics of the strong interaction and are necessary for evaluation of the phase-space integral IKe needed to measure the CKM matrix element |Vus| for KL→π±e∓ν decays. Our result is λ+=(28.6±0.5±0.4)×10−3 for a linear fit, and λ+′=(25.5±1.5±1.0)×10−3, λ+″=(1.4±0.7±0.4)×10−3 for a quadratic fit.
We measured, with the KLOE detector, the spectrum of π+π− invariant mass in a sample of 6.7×105e+e−→π+π−γ events with the photon at large polar angle (θγ>45°) at a centre of mass energy s around the ...ϕ mass. We observe in this spectrum a clear contribution from the intermediate process ϕ→ f0(980)γ. A sizeable effect is also observed in the distribution of the pion forward–backward asymmetry. We use different theoretical models to fit the spectrum and we determine the f0 mass and coupling constants to the ϕ, to π+π− and to KK¯.
We have measured the fully inclusive K+→μ+ν(γ) absolute branching ratio with the KLOE experiment at DAΦNE, the Frascati ϕ-factory. From some 865 283 K+→μ+ν(γ) decays obtained from a sample of ...∼5.2×108, ϕ-meson decays, we find BR(K+→μ+νμ(γ))=0.6366±0.0009stat.±0.0015syst., corresponding to an overall fractional error of 0.27%. Using recent lattice results on the decay constants of pseudoscalar mesons one can obtain an estimate for the CKM mixing matrix element |Vus|=0.2223±0.0026.
Using a large sample of pure, slow, short lived
K
0
mesons collected with KLOE detector at DAΦNE, we have measured the
K
S
lifetime. From a fit to the proper time distribution we find
τ
(
K
S
...)=(89.562±0.029
stat
±0.043
syst
) ps. This is the most precise measurement to date of the short lived
K
0
meson lifetime, in good agreement with the world average derived from previous measurements. We observe no dependence of the lifetime on the direction of the
K
S
in galactic coordinates.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).We present a measurement of eta meson production in photon-photon interactions produced by electron-positron beams ...colliding with ... GeV. The measurement is done with the KLOE detector at the -factory DA Phi NE with an integrated luminosity of 0.24 fb super(-1). The e super(+) e super(-) arrow right e super(+) e super(-) eta cross section is measured without detecting the out-going electron and positron, selecting the decays eta arrow right pi super(+) pi super(-) pi super(0) and eta arrow right pi super(0) pi super(0) pi super(0). The most relevant background is due to e super(+) e super(-) arrow right eta gamma when the monochromatic photon escapes detection. The cross section for this process is measured as sigma (e super(+) e super(-) arrow right eta gamma ) = (856 plus or minus 8 sub(stat) plus or minus 16 sub(syst)) pb. The combined result for the e super(+) e super(-) arrow right e super(+) e super(-) eta cross section is sigma (e super(+) e super(-) arrow right e super(+) e super(-) eta ) = (32.72 plus or minus 1.27 sub(stat) plus or minus 0.70 sub(syst)) pb. From this we derive the partial width Gamma ( eta arrow right gamma gamma ) = (520 plus or minus 20 sub(stat) plus or minus 13 sub(syst)) eV. This is in agreement with the world average and is the most precise measurement to date.
We have studied the vector to pseudoscalar conversion decay phi -> eta e(+)e(-), with.. eta -> pi(0)pi(0)pi(0), with the KLOE detector at DA phi NE. The data set of 1.7 fb(-1) of e(+)e(-) ...collisions at root s similar to M-phi contains a clear conversion decay signal of similar to 31,000 events from which we measured a value of BR(phi -> eta e(+)e-) = (1.075 +/- 0.007 +/- 0.038) x 10(-4). The same sample is used to determine the transition form factor by a fit to the e(+)e(-) invariant mass spectrum, obtaining b(phi eta)=( 1.28 +/- 0.10(-0.08)(+0.09)) GeV-2, that improves by a factor of five the precision of the previous measurement and is in good agreement with VMD expectations.
We present a measurement of the KL lifetime using the KLOE detector. From a sample of ∼4×108KSKL pairs following the reaction e+e−→ϕ→KSKL we select ∼15×106KL→π0π0π0 decays tagged by KS→π+π− events. ...From a fit of the proper time distribution we find τL=(50.92±0.17stat±0.25syst) ns. This is the most precise measurement of the KL lifetime performed to date.
We report the first observation of the rare η→e+e−e+e−(γ) decay based on 1.7 fb−1 collected by the KLOE experiment at the DAΦNE ϕ-factory. The selection of the e+e−e+e− final state is fully inclusive ...of radiation. We have identified 362±29 events resulting in a branching ratio of (2.4±0.2stat+bckg±0.1syst)×10−5.
We have searched for a light vector boson U, the possible carrier of a "dark force", with the KLOE detector at the DA Phi NE e(+)e(-) collider, motivated by astrophysical evidence for the presence of ...dark matter in the Universe. Using e(+)e(-) collisions collected with an integrated luminosity of 239.3 pb(-1), we look for a dimuon mass peak in the reaction e(+)e(-) -> mu(+)mu(-)gamma, corresponding to the decay U -> mu(+)mu(-). We find no evidence for a U vector boson signal. We set a 90% CL upper limit for the mixing parameter squared between the photon and the U boson of 1.6 x 10(-5) to 8.6 x 10(-7) for the mass region 520 < m(U) < 980 MeV.
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