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تسجيل مستخدم جديدSearch for B -> h(*) nu nubar with the full Belle Y(4S) data sample
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We report a search for the rare decays B -> h(*) nu nubar, where h(*) stands for K+, Ks0, K*+, K*0, pi+, pi0, rho+, rho0 and phi. The results are obtained from a 711 fb-1 data sample that contains 772 million BB pairs collected at the Y(4S) resonance with the Belle detector at the KEKB e+e- collider. We search for signal candidates by fully reconstructing a hadronic decay of the accompanying B meson and requiring a single h(*) meson left on the signal side. No significant signal is observed and we set upper limits on the branching fractions at 90% confidence level. The measurements of B+ -> K*+ nu nubar, B+ -> pi+ nu nubar, B0 -> pi0 nu nubar and B0 -> rho^0 nu nubar provide the worlds currently most restrictive limits.
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We search for the decay B+ -> l+ nu gamma with l+ = e+ or mu+ using the full Belle data set of 772 x 10^6 BBbar pairs, collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We reconstruct one B meson in
a hadronic decay mode and search for the B+ -> l+ nu gamma decay in the remainder of the event. We observe no significant signal within the phase space of E_gamma^sig > 1 GeV and obtain upper limits of BR(B+ -> e+ nu gamma) < 6.1 x 10^-6, BR(B+ -> mu+ nu gamma) < 3.4 x 10^-6, and BR(B+ -> l+ nu gamma) < 3.5 x 10^-6 at 90 % credibility level.
A search for additional evidence for the rare kaon decay K^+ --> pi^+ nu nubar has been made with a new data set comparable in sensitivity to the previous exposure that produced a single event.
The first search for the decay K^+ -> pi^+ pi^0 nu nubar has been performed with the E787 detector at BNL. Based on zero events observed in the kinematical search region defined by 90 MeV/c < P_{pi^+} < 188 MeV/c and 135 MeV < E_{pi^0} < 180 MeV, an
upper limit B(K^+ -> pi^+ pi^0 nu nubar) < 4.3 x 10^{-5} at 90% confidence level is established.
We report measurements of the decays B- -> Ds(*)+ K- l- nubar in a data sample containing 657x10^6 BBbar pairs collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. We observe a signal with a significance of 6 sigma for the c
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We present a search for the decays B+ -> mu+ nu_mu and B+ -> e+ nu_e in a 253 fb-1 data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy B factory. We find no significant evidence for a signal and se
t 90% confidence level upper limits of B(B+ -> mu+ nu_mu) < 1.7 x 10^{-6} and B(B+ -> e+ nu_e) < 9.8 x 10^{-7}.
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