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Register a new userMeasurement of the charge asymmetry for the $K_S rightarrow pi e u$ decay and test of CPT symmetry with the KLOE detector
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Using 1.63 fb$^{-1}$ of integrated luminosity collected by the KLOE experiment about $7times 10^4$ $K_S rightarrow pi^{pm}e^{mp} u$ decays have been reconstructed. The measured value of the charge asymmetry for this decay is $A_S = (-4.9 pm 5.7_{stat} pm 2.6_{syst}) times 10^{-3}$, which is almost twice more precise than the previous KLOE result. The combination of these two measurements gives $A_S = (-3.8 pm 5.0_{stat} pm 2.6_{syst}) times 10^{-3}$ and, together with the asymmetry of the $K_L$ semileptonic decay, provides significant tests of the CPT symmetry. The obtained results are in agreement with CPT invariance.
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Based on a sample of 300 million $K_S$ mesons produced in $phi to K_L K_S$ decays recorded by the KLOE experiment at the DA$Phi$NE $e^+e^-$ collider we have measured the branching fraction for the decay $K_S to pi mu u$. The $K_S$ mesons are identified by the interaction of $K_L$ mesons in the detector. The $K_S to pi mu u$ decays are selected by a boosted decision tree built with kinematic variables and by a time-of-flight measurement. Signal efficiencies are evaluated with data control samples of $K_L to pi mu u$ decays. A fit to the reconstructed muon mass distribution finds $7223 pm 180$ signal events. Normalising to the $K_S to pi^+ pi^-$ decay events the result for the branching fraction is $mathcal{B}(K_S to pi mu u) = (4.56 pm 0.11_{rm stat} pm 0.17_{rm syst})times10^{-4}$.
We present the result of a direct search for the decay K_S -> e+e-, obtained with a sample of e+e- -> phi -> K_S K_L events produced at DAFNE, the Frascati phi-factory, for an integrated luminosity of 1.9 fb^-1. The search has been performed using a pure K_S beam tagged by the simultaneous detection of a K_L interaction in the calorimeter. Background rejection has been optimized by using both kinematic and particle identification cuts. We find BR(K_S -> e+e-) < 9x10^-9 at 90% CL, which improves by an order of magnitude on the previous best limit.
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.
We present the current status of the analysis of about 1.7 billion KSKL pair events collected at DAFNE with the KLOE detector to determine the branching ratio of KS -> pi e nu decay and the lepton charge asymmetry. This sample is ~4 times larger in statistics than the one used in a previous KLOE analysis, allowing us to improve the accuracy of the measurement and of the related tests of CPT symmetry and Delta S = Delta Q rule.
The recent interest in a light gauge boson in the framework of an extra U(1) symmetry motivates searches in the mass range below 1 GeV. We present a search for such a particle, the dark photon, in ${rm e^+ e^-}rightarrow {rm U}gamma$, U$rightarrow pi^+pi^-$ based on 28 million $mathrm{e^+ e^-} rightarrow pi^+ pi^-gamma$ events collected at DA$Phi$NE by the KLOE experiment. The $pi^+ pi^-$ production by initial-state radiation compensates for a loss of sensitivity of previous KLOE ${rm U} rightarrow mathrm{e^+ e^-}$, $mu^+mu^-$ searches due to the small branching ratios in the $rho-omega$ resonance region. We found no evidence for a signal and set a limit at 90% CL on the mixing strength between the photon and the dark photon, $varepsilon^2$, in the U mass range between $527$ and $987$~MeV. Above 700 MeV this new limit is more stringent than previous ones.
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