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Register a new userResult of T-violating muon polarization measurement in the $K^+ to pi^0 mu^+ u$ decay
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J. Imazato
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A search for T-violating muon polarization in the $K^+ to pi^0 mu^+ u$ decay has been performed at KEK using stopped kaons. A new improved limit was obtained, $P_T= -0.0017 pm 0.0023 (stat) pm 0.0011 (syst)$, corresponding to a 90 % confidence limit of $| P_T| < 0.0050$. The T-violating parameter was also determined to be Im$xi = -0.0053 pm 0.0071 (stat) pm 0.0036 (syst)$, and $|{rm Im}xi| < 0.016$ (90 % CL).
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A search for T-violating transverse muon polarization ($P_T$) in the $K^{+}to pi^{0}mu^{+} u$ decay was performed using kaon decays at rest. A new improved value, $P_T= -0.0017pm 0.0023 (stat)pm 0.0011 (syst)$, was obtained giving an upper limit, $| P_T | < 0.0050$. The T-violation parameter was determined to be Im$xi = -0.0053 pm 0.0071(stat)pm 0.0036(syst)$ giving an upper limit, $|$Im$xi| <0.016$.
The K^+ to pi^0 mu^+ u gamma ($K_{mu 3 gamma}$) decay has been measured with stopped positive kaons at the KEK 12 GeV proton synchrotron. A $K_{mu 3 gamma}$ sample containing 125 events was obtained. The partial branching ratio $Br(K_{mu 3 gamma}, E_{gamma}>30 {rm MeV}, theta_{mu^+ gamma}>20^{circ})$ was found to be $[2.4 pm 0.5(stat) pm 0.6(syst)]times 10^{-5}$, which is in good agreement with theoretical predictions.
Using data collected by the fixed target Fermilab experiment FOCUS, we present several first measurements for the semileptonic decay $D^0 to bar{K}^0pi^-mu^+ u$. Using a model that includes a $bar{K}^0 pi^-$ S-wave component, we measure the form factor ratios to be r_v= 1.706+-0.677+-0.342 and r_2= 0.912+-0.370+-0.104 and the S-wave amplitude to be A=0.347+-0.222+-0.053 GeV^-1. Finally, we measure the vector semileptonic branching ratio $frac{Gamma(D^0 to K^{*}(892){-}mu^+ u)}{Gamma(D^0 to bar{K}^0pi^-pi^+)}= 0.337+-0.034+-0.013.
We present a new result on the K^+ --> pi^+ pi^0 gamma decay measurement using stopped kaons. The best fit to the decay spectrum comprised of 10k events gives a branching ratio for the direct photon emission of [3.8+-0.8(stat)+-0.7(syst)] times 10^{-6} in the pi^+ kinetic energy region of 55 to 90 MeV. This result has been obtained with the assumption that there is no component due to interference with the inner bremsstrahlung.
More than 400 $K^{+}topi^{+}mu^+mu^-$ events were observed in a rare $K^+$ decay experiment at the AGS. Normalized to the $K^{+}topi^{+}pi^+pi^-$ decay, the branching ratio is determined to be $(9.22 pm 0.60 (stat) pm 0.49 (syst))times 10^{-8}$. This branching ratio and the $mumu$ mass spectrum is in very good agreement with the measurement of the $K^{+}topi^{+}e^+e^-$ decay, but deviates significantly from the previous measurement.
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