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Register a new userK+/-e2 search and Lepton Flavor Violation at KLOE
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B. Sciascia
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This paper is devoted to the first analyses based on the complete data sample collected by the KLOE detector at DAPHNE, the Frascati phi-factory. The result for the BR(K_S -> gammagamma) and the search for the decay K_S->e+e- are presented. Particular emphasis is put on the measurement of the ratio of Ke2 and Kmu2 BRs.
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A search for lepton flavor violating decays, kmmp, keep, kpem, kmep and pizem, was performed using the data collected in E865 at the Brookhaven Alternating Gradient Synchrotron. No signal was found in any of the decay modes. At the 90% confidence level, the branching ratios are less than $3.0times10^{-9}$, $6.4times10^{-10}$, $5.2times10^{-10}$, $5.0times10^{-10}$ and $3.4times10^{-9}$ respectively.
We present a precise measurement of the ratio R_K = Gamma(Ke2(gamma))/Gamma(Kmu2(gamma)) performed with the KLOE detector. The results are based on data collected at the Frascati e^+e^- collider DAFNE for an integrated luminosity of 2.2 fb^{-1}. We find R_K = (2.493pm0.025_{stat}pm0.019_{syst})times 10^{-5}, in agreement with the Standard Model expectation. This result is used to improve constraints on parameters of the Minimal Supersymmetric Standard Model with lepton flavor violation.
We present measurements of the branching fractions for the decays $Bto K mu^{+}mu^{-}$ and $Bto K e^{+}e^{-}$, and their ratio ($R_{K}$), using a data sample of 711 $fb^{-1}$ that contains $772 times 10^{6}$ $Bbar{B}$ events. The data were collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. The ratio $R_{K}$ is measured in five bins of dilepton invariant-mass-squared ($q^{2}$): $q^{2} in (0.1, 4.0), (4.0, 8.12), (1.0, 6.0)$, $(10.2, 12.8)$ and ($>14.18) GeV^{2}/c^{4}$, along with the whole $q^2$ region. The $R_{K}$ value for $q^{2} in (1.0, 6.0) GeV^{2}/c^{4}$ is $1.03^{+0.28}_{-0.24} pm 0.01$. The first and second uncertainties listed are statistical and systematic, respectively. All results for $R_{K}$ are consistent with Standard Model predictions. We also measure $C!P$-averaged isospin asymmetries in the same $q^{2}$ bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the $q^{2}in(1.0,6.0) GeV^{2}/c^{4}$ bin in the mode with muon final states. The measured differential branching fractions, ${dcal B}/{dq^{2}}$, are consistent with theoretical predictions for charged $B$ decays, while the corresponding values are below the expectations for neutral $B$ decays. We have also searched for lepton-flavor-violating $B rightarrow Kmu^{pm}e^{mp}$ decays and set $90%$ confidence-level upper limits on the branching fraction in the range of $10^{-8}$ for $B^{+} rightarrow K^{+}mu^{pm}e^{mp}$, and $B^{0} rightarrow K^{0}mu^{pm}e^{mp}$ modes.
The Mu2e experiment at Fermilab will search for the charged lepton flavor violating process of neutrino-less $mu to e$ coherent conversion in the field of an aluminum nucleus. About $7 cdot 10^{17}$ muons, provided by a dedicated muon beam line in construction at Fermilab, will be stopped in 3 years in the aluminum target. The corresponding single event sensitivity will be $2.5cdot 10^{-17}$. In this paper a brief overview of the physics explored by the $mu to e$ conversion is given, followed by a description of the Mu2e experimental apparatus and the expected detector performance.
We search for the lepton-flavor-violating decay of the $J/psi$ into an electron and a muon using $(225.3pm2.8)times 10^{6}$ $J/psi$ events collected with the BESIII detector at the BEPCII collider. Four candidate events are found in the signal region, consistent with background expectations. An upper limit on the branching fraction of $mathcal{B}(J/psi to emu)< 1.5 times 10^{-7}$ (90% C.L.) is obtained.
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