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Measurement of K^{-}_{e3} branching ratio

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 Added by Vladimir Romanovsky
 Publication date 2007
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and research's language is English




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The branching fraction for the decay $K^{-} to pi^{0} e bar u$ is measured using in-flight decays detected with {bf ISTRA+} setup working at the 25 GeV negative secondary beam of the U-70 PS:linebreak $Br_{K_{e3}}= (5.124 pm 0.009 (stat) pm 0.029(norm) pm 0.030(syst))%$. From this value the $|V_{us}|$ element of the CKM matrix is extracted, using previously measured $f_{+}(t)$ form factor: $|V_{us}|=0.227 pm 0.002$. The results are in agreement with recent measurements by BNL E865, FNAL KTeV, KLOE.



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214 - E949 Collaboration 2008
Three events for the decay K+ => pi+,nu,nubar have been observed in the pion momentum region below the K+ => pi+,pi0 peak, 140 < P_pi < 199 MeV/c, with an estimated background of 0.93+-0.17(stat.)+0.32-0.24(syst.) events. Combining this observation with previously reported results yields a branching ratio of B(K+ => pi+,nu,nubar) = (1.73+1.15-1.05)e-10 consistent with the standard model prediction.
239 - E. Frlev{z} 2008
The PEN Collaboration is conducting a new measurement of the pi+ -> e+ nu branching ratio at the Paul Scherrer Institute, with the goal uncertainty of delta B/B(pie2)=5E-4 or lower. At present, the combined accuracy of all published pie2 decay measurements lags behind the theoretical calculation by a factor of 40. In this contribution we report on the PEN detector configuration and its performance during two development runs done in 2007 and 2008.
71 - A.A. Poblaguev 2004
E865 at the Brookhaven National Laboratory AGS collected about 70,000 K+(e3) events to measure the K+(e3) branching ratio relative to the observed K+ -> pi+ pi0, K+ -> pi0 mu+ nu, and K+ -> pi+ pi0 decays. The pi0 in all the decays was detected using the e+e- pair from pi0 -> e+e-gamma decay and no photons were required. Using the Particle Data Group branching ratios for the normalization decays we obtain BR(K+(e3(gamma))=(5.13+/-0.02(stat)+/-0.09(sys)+/-0.04(norm))%, where $K+(e3(gamma)) includes the effect of virtual and real photons. This result is 2.3 sigma higher than the current Particle Data Group value. The implications of this result for the $V_{us}$ element of the CKM matrix, and the matrixs unitarity are discussed.
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08 ^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical, the second systematic and the third is associated to the ratio of fragmentation fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/- 0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be (3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.
The process e+e-->mu+mu- has been studied by SND detector at VEPP-2M e+e- collider in the phi(1020)-resonance energy region. The measured effective phi meson leptonic branching ratio: B(phi->l+l-)=sqrt{B(phi->e+e-)*B(phi->mu+mu-)}=(2.89+-0.10+-0.06)*10^{-4} agrees well with the PDG value B(phi->e+e-)=(2.91+-0.07)*10^{-4} confirming mu-e universality. Without additional assumption of mu-e universality the branching ratio B(phi->mu+mu-)=(2.87+-0.20+-0.14)*10^{-4} was obtained.
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