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Register a new userMeasurement of the absolute branching ratio of the K+ -> pi+ pi0 (gamma) decay with the KLOE detector
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We have measured the absolute branching ratio of the K+ -> pi+ pi0 (gamma) decay, using about 20 million tagged K+ mesons collected with the KLOE detector at DAFNE, the Frascati phi-factory. Signal counts are obtained from the fit of the distribution of the momentum of the charged decay particle in the kaon rest frame. The result, inclusive of final-state radiation, is BR(K+ -> pi+ pi0 (gamma))=0.2065+/-0.0005_{stat}+/- 0.0008_{syst}.
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We have measured the fully inclusive K+ -> mu+nu(gamma) absolute branching ratio with the KLOE experiment at DAFNE, the Frascati Phi-factory. From some 865,283 K+ -> mu+nu(gamma) decays obtained from a sample of about 5.2x10^8 Phi-meson decays, we find BR(K+ -> mu+ nu (gamma)) = 0.6366 +-0.0009(stat.) +-0.0015(syst.), 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.
We present a study of the reaction e+e- --> pi+pi-pi0 at the phi peak W=M(phi)=1019.4 MeV observed with the KLOE detector at Dafne. The reaction is dominated by phi production and decay, e+e- --> phi --> pi+pi-pi0. From a fit to the Dalitz plot density distribution we obtain the rho-meson parameters for its three charge states. We also find the relative amplitudes for phi --> rhopi and phi -> pi+pi-pi0 and the cross-section for e+e- --> omega pi0 with omega --> pi+pi-.
We have analyzed 1.62 fb$^{-1}$ of $e^{+}e^{-}$ collisions at a center of mass energy $sim M_{phi}$ collected by the KLOE experiment at DA$Phi$NE. This sample corresponds to a production of $sim$ 1.7 billion of $ks$ $kl$ pairs which allowed us to search for the rare $K_Sto gammagamma$ decay. $K_S$ are tagged by the $K_L$ interaction in the calorimeter and the signal is searched for by requiring two additional prompt photons. Strong kinematic requirements reduce the initial 0.5$times 10^6$ events to 2300 candidates from which we extract a signal of 600 $pm$ 35 events. By normalizing to the $ks to 2 pi^0$ decays counted in the same sample, the measured value of BR($ks to gammagamma$) is (2.27 $pm 0.13(stat.) ^{+0.03}_{-0.04} (syst.)) times 10^{-6}$, in agreement with $O(P^4)$ Chiral Perturbation Theory predictions.
In a sample of 5.3x10^7 phi-decays observed with the KLOE detector at the Frascati phi-factory Dafne we find 605 eta pi0 gamma events with eta --> gammagamma and 197 eta pi0 gamma events with eta --> pi+ pi- pi0. The decay phi --> eta pi0 gamma is dominated by the process phi --> a0 gamma. From a fit to the eta pi0 mass spectrum we find BR(phi --> ao(980) gamma)= (7.4 +- 0.7)x10^-5.
We present the current status of the analysis of about 1.7 billion K_S K_L pair events collected at DA{Phi}NE with the KLOE detector to determine the branching ratio of K_S -> {pi}e{ u} decay and the lepton charge asymmetry. This sample is ~4 times larger in statistics than the one used in the previous most precise result, from KLOE as well, allowing us to improve the accuracy on the measurement and related tests of CPT symmetry and Delta S = Delta Q rule.
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