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تسجيل مستخدم جديدNew measurement of the K+ => pi+,nu,nubar branching ratio
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E949 Collaboration
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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.
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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 measur
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The results and goals of experiments E787, E949, CKM and KOPIO on the measurement of the branching fractions of K+ -> pi+,nu,nubar and K0L -> pi0,nu,nubar are presented.
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.
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