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Register a new userA Measurement of the Branching Ratio and Form Factor of K_L->mu mu gamma
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M. B. Spencer et. al
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We report on a measurement of the decay $K_Lrightarrowmu^+mu^-gamma$ from Fermilab experiment E799. We observe $207$ candidate signal events with an estimated background of $10.5 pm 4.0$ events and establish $B(K_Lrightarrowmu^+mu^-gamma) = (3.23pm 0.23(stat) pm 0.19(sys))times 10^{-7}$. This provides the first measurement of the $Kgammagamma^*$ form factor in the muonic Dalitz decay mode of the $K_L$.
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We study the prospects of measurement of the branching ratio of $h to mu ^+ mu ^-$ at the International Linear Collider (ILC). The study is performed at center-of-mass energies of 250 GeV and 500 GeV, using fully-simulated MC samples with the International Large Detector (ILD) model. For both center-of-mass energies, the two final states $qoverline{q}h$ and $ u overline{ u}h$ have been analyzed. For an integrated luminosity of 2000 fb$^{-1}$ at 250 GeV and 4000 fb$^{-1}$ at 500 GeV, corresponding to the H20 running scenario as well as its staged version, the precision on $sigma times mathrm{BR}(h to mu ^+ mu ^-)$ is estimated.
From the 2002 data taking with a neutral kaon beam extracted from the CERN-SPS, the NA48/1 experiment observed 97 $Xi^{0}rightarrow Sigma^{+} mu^{-} bar{ u}_{mu}$ candidates with a background contamination of $30.8 pm 4.2$ events. From this sample, the BR($Xi^{0}rightarrow Sigma^{+} mu^{-} bar{ u}_{mu}$) is measured to be $(2.17 pm 0.32_{mathrm{stat}}pm 0.17_{mathrm{syst}})times10^{-6}$.
We present a measurement of form-factor independent angular observables in the decay mbox{$B^0to K^{*}(892)^{0}mu^+ mu^-$}. The analysis is based on a data sample corresponding to an integrated luminosity of 1.0fb$^{-1}$, collected by the LHCb experiment in $pp$ collisions at a center-of-mass energy of 7TeV. Four observables are measured in six bins of the dimuon invariant mass squared, $q^2$, in the range $0.1<q^2<19.0$GeV$^{2}$/c$^{4}$. Agreement with Standard Model predictions is found for 23 of the 24 measurements. A local discrepancy, corresponding to $3.7$ Gaussian standard deviations, is observed in one $q^2$ bin for one of the observables. Considering the 24 measurements as independent, the probability to observe such a discrepancy, or larger, in one is $0.5%$.
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.
A precise measurement of the vector and axial-vector form factors difference $F_V-F_A$ in the $K^+rightarrow{mu^+}{ u_{mu}}{gamma}$ decay is presented. About 95K events of $K^+rightarrow{mu^+}{ u_{mu}}{gamma}$ are selected in the OKA experiment. The result is $F_V-F_A=0.134pm0.021(stat)pm0.027(syst)$. Both errors are smaller than in the previous $F_V-F_A$ measurements.
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