Charged kaon lifetime at KLOE

Preliminary result on the charged kaon lifetime, obtained by the KLOE experiment operating at DA$\Phi$NE, the Frascati $\phi$-factory, is presentedComment: 3 pages, 3 figures, to appear in the proceedings of 42nd Rencontres de Moriond on Electroweak Interactions and Unified Theories, La Thuile, Aosta Valley, Italy, 10-17 Mar 200

Determination of CP and CPT violation parameters in the neutral kaon system using the Bell-Steinberger relation and data from the KLOE experiment

We present an improved determination of the CP and CPT violation parameters Re(epsilon) and Im(delta) based on the unitarity condition (Bell-Steinberger relation) and on recent results from the KLOE experiment. We find Re(epsilon) = (159.6 \pm 1.3)10^-5 and Im(delta) = (0.4 \pm 2.1)10^-5, consistent with no CPT violation.Comment: Submitted to JHE

Measurements of the Absolute Branching Ratios for the Dominant KL Decays, the KL Lifetime, and Vus with the KLOE Detector

From a sample of about 10^9 Phi mesons produced at DAFNE, we have selected KL mesons tagged by observing KS->pi+pi- decays. We present results on the major KL branching ratios, including those of the semileptonic decays needed for the determination of Vus. These branching ratio measurements are fully inclusive with respect to final-state radiation. The KL lifetime has also been measured.Comment: Submitted to Phys. Lett.

Hadroproduction of the Chi1 and Chi2 States of Charmonium in 800 GeV/c Proton-Silicon Interactions

The cross sections for the hadroproduction of the Chi1 and Chi2 states of charmonium in proton-silicon collisions at sqrt{s}=38.8 GeV have been measured in Fermilab fixed target Experiment 771. The Chi states were observed via their radiative decay to J/psi+gamma, where the photon converted to e+e- in the material of the spectrometer. The measured values for the Chi1 and Chi2 cross sections for x_F>0 are 263+-69(stat)+-32(syst) and 498+-143(stat)+-67(syst) nb per nucleon respectively. The resulting sigma(Chi1}/sigma(Chi2) ratio of 0.53+-0.20(stat)+-0.07(syst), although somewhat larger than most theoretical expectations, can be accomodated by the latest theoretical estimates.Comment: 4 pages, 4 figure

A direct search for the CP-violating decay Ks->3p^0 with the KLOE detector at DAFNE

We have searched for the decay Ks->3p^0 with the KLOE experiment at DAFNE using data from e^+ e^- collisions at a center of mass energy W= m(phi) for an integrated luminosity L=450 pb^-1. The search has been performed with a pure Ks beam obtained by tagging with Kl interactions in the calorimeter and detecting six photons. We find an upper limit for the branching ratio of 1.2x10^-7 at 90% C.L.Comment: 15 pages, 6 figures. To be submitted to Physics Letter

Study of the decay phi--> f0(980)g --> pi+pi-g with the KLOE detector

We measured, with the KLOE detector, the spectrum of pi+pi- invariant mass in a sample of 6.7 x 10^5 e+e- --> pi+pi-g events with the photon at large polar angle (theta_g>45^o) at a centre of mass energy sqrt(s) around the phi mass. We observe a clear contribution from the intermediate process phi --> f0(980)g. A sizeable effect is also observed in the distribution of the forward-backeard asymmetry. We use different theoretical models to fit the spectrum and we determine the f_0 mass and coupling constants to the phi, to pi+pi- and to KK.Comment: 15 pages, 6 figures, submitted to Phys.Lett.

Measurement of the pseudoscalar mixing angle and η′\eta^{\prime} gluonium content with KLOE detector

We have measured the ratio $R_{\phi}=BR(\phi \to \eta^{\prime} \gamma)/BR(\phi \to \eta \gamma)$ by looking for the radiative decays $\phi \to \eta^{\prime} \gamma$ and $\phi \to \eta \gamma$ in the final states $\pi^+\pi^-$ 7 $\gamma$'s and 7 $\gamma$'s respectively, in a sample of $\sim 1.3\cdot 10^{9}$ $\phi$ mesons produced at the Frascati $\phi$-factory. We obtain $R_{\phi}=(4.77\pm0.09_{stat}\pm0.19_{sys})\cdot 10^{-3}$ from which we derive $BR(\phi \to \eta^{\prime} \gamma)=(6.20\pm0.11_{stat}\pm0.25_{sys})\cdot 10^{-5}$. In the hypothesis of no gluonium content we extract the pseudoscalar mixing angle in the quark-flavor basis $\phi_P=(41.4\pm0.3_{stat}\pm0.7_{sys}\pm0.6_{th})^{\circ}$. Combining the value of $R_{\phi}$ with other constraints, we estimate the gluonium fractional content of $\eta^{\prime}$ meson as $Z^2 = 0.14\pm0.04$ and the mixing angle $\phi_P = (39.7\pm0.7)^{\circ}$.Comment: 13 pages, 8 figure

Measurement of the KL meson lifetime with the KLOE detector

We present a measurement of the KL lifetime using the KLOE detector. From a sample of 4 x 10^8 KS KL pairs following the reaction e+ e- -> phi -> KS KL we select 15 x 10^6 KL -> p0 p0 p0 decays tagged by KS -> pi+ pi- events. From a fit of the proper time distribution we find tau_L = (50.92 +- 0.17{stat} +- 0.25{syst})$ ns. This is the most precise measurement of the KL lifetime performed to date.Comment: 14 pages, 14 figure

Measurement of the Branching Ratio of the KL -> pi+pi- decay with the KLOE Detector

We present a measurement of the branching ratio of the CP violating decay KL->pi+pi- performed by the KLOE experiment at the phi factory DAFNE. We use 328 pb-1 of data collected in 2001 and 2002, corresponding to ~ 150 million tagged KL mesons. We find BR(KL->pi+pi-) = $(1.963 +/- 0.012 +/- 0.017)x 10^-3. This branching ratio measurement is fully inclusive of final-state radiation. Using the above result, we determine the modulus of the amplitude ratio |\eta_{+-}| to be (2.219 +/- 0.013)x 10^{-3} and |\epsilon| to be (2.216 +/- 0.013)x 10^{-3}.Comment: Subitted to Phys. Lett.

First observation of quantum interference in the process phi -> KS KL ->pi+pi-pi+pi-: a test of quantum mechanics and CPT symmetry

We present the first observation of quantum interference in the process phi -> KS KL ->pi+pi-pi+pi-. This analysis is based on data collected with the KLOE detector at the e^+e^- collider DAFNE in 2001--2002 for an integrated luminosity of about 380pb^-1. Fits to the distribution of Delta t, the difference between the two kaon decay times, allow tests of the validity of quantum mechanics and CPT symmetry. No deviations from the expectations of quantum mechanics and CPT symmetry have been observed. New or improved limits on various decoherence and CPT violation parameters have been obtainedComment: submitted to Physics Letter B one number changed old:gamma=(1.1+2.9-2.4)10^-21 GeV new:(1.3+2.8-2.4)10^-21GeV corrected typo